Post by: Guest on September 11, 2005, 03:02:04 AM
Anyone have any experience with these heat pumps? They sound great..about twice as expensive to start with, but if the savings are up to 40% per year, that should be recovered quickly enough. But in the spirit of TANSTAAFL, I'm wondering about the down sides to them.
One of my biggest questions is how effective they'd be in a cold Mid-western winter.
Post by: Guest on September 11, 2005, 03:32:39 AM
Post by: 280plus on September 11, 2005, 04:58:28 AM
I happen to be a heating contractor in CT
First off, I can't say for sure that a geo thermal heatpump will actually deliver 40% savings. Each installation is different so it's very hard to make and prove that claim. It sounds more like an advertising claim. I do know that they are touted as the most efficient way to heat. Another thing I know is that many people dislike heat pumps because the air coming out of the registers is only around 105* F and while it is more than enough to heat the place it feels cool / cold when it blows on you. People want to feel nice warm air coming out of their heating system. It's what they are used to.
As long as your "heat sink" in the ground is adequately sized (it's good to go 1/3 bigger than the figures tell you to) and deep enough it should be able to keep up in your climate. But only someone familiar with your area can say that for sure. I do not know if a GHP will have "supplemental heat" to make up for when the heat pump CANNOT keep up. In most cases this would be electric heat. Very bad (the worst of all) efficiency. You need to investigate that.
Building a passive solar house with a geothermal supplemental system is probably the best route. So that when the solar has enough sun to work you get a "free ride" but on cloudy or very cold days you'll have the heat pump to back you up. Be aware none of this stuff will be cheap.
FYI What I'm concentrating on right now is putting in high efficiency oil fired boilers combined with radiant "floor warming" under tile floors and forced hot air heated by the hot water from the boiler for the rest of the house. Very comfortable, very efficient. Excluding heat pumps, a high efficiency oil fired boiler will give you the most heat for your fuel dollar. If you wanted to couple the system to a solar array it would probably save you money during the milder days. I have kicked this idea around with a few people but again, it ain't cheap. You would have to put antifreeze in it which opens up a bg can of worms which means $. Plus you have to find a company that's willing AND CAPABLE of doing the job the way you want. Most guys I know are stuck in ther ways and as soon as you start venturing away from what they are comfortable with they get antsy. They do make GHPs that will heat water instead of air which opens up more possibilities.
I need to get going but we can continue the discussion any tme. Feel free to pick my brain.
Maybe some other HVAC people will chime in, I'd love to hear what others have to say on the subject!
I also have a passive solar design in my head to heat your domestic hot water for you. Again, it would only be feasible as a supplement to a conventional hot water heater but would save you fuel $ when the weather is right. Unfortunately, still not cheap because, in effect, you are installing TWO hot water making systems vs the usual one. Then there's the antifreeze thing as well.
Water Furnace is a GHP brand that I know is popular around here. Google them and they should come up.
Post by: thumbody on September 11, 2005, 06:03:22 AM
The heat is kept constant so it runs more often but you don't get the 5 -8 degree temperature fluctuations. The air conditioning is through the same compressor so you dont need a seperate unit. He had fuel oil before and his heating cost dropped dramatically .
Post by: K Frame on September 11, 2005, 07:33:33 AM
The advantages are that they're probably the most economical form of heating and cooling your home over the long run, they don't burn anything, and they're not affected by changes in air temperature like air source heat pumps.
Post by: Guest on September 11, 2005, 08:10:12 AM
Post by: K Frame on September 11, 2005, 09:36:34 AM
Of course, your water supply depends on mother nature not throwing drought your way, too.
Post by: 280plus on September 11, 2005, 01:43:52 PM
Post by: Dave Markowitz on September 11, 2005, 01:52:16 PM
Send a PM to Vern Humphrey over on THR. I believe he has some kind of geothermal HVAC system.
Post by: K Frame on September 11, 2005, 06:41:35 PM
Post by: Gewehr98 on September 11, 2005, 06:43:49 PM
http://www.geocities.com/s_wheaton/
And for folks in the snowbelt, take a look at this residence in Colorado (which was for sale, last I looked, I may make a bid on it next year):
http://www.wagonmaker.com/
How about a wood-fired hot tub?
Post by: 280plus on September 12, 2005, 02:13:17 AM
Barbara, are you planning to have a basement or build on a slab? I don't know how they do it in your area. Either way, heating either the basement floor or the slab with hot water tubes embedded is the most comfortable and efficient way to heat there is. There are GTHPs that produce hot/cold water instead of air. You could, once again, couple it to a solar system as well. The machine will also make domestic hot water (DHW) IIRC. I believe I once talked to a Water Furnace rep on the phone about it. But, I can't recall exactly. I've talked to a few reps around here about it all. Once again, I can't stress it enough, none of this stuff is cheap. I get a lot of people that talk about all the latest technology they found on the net and, don't get me wrong I'd LOVE to sell it to them, but when I show them what it costs they usually choke. I get frustrated because I KNOW they should be willing to make the investment, it's WORTH IT! ESPECIALLY IF YOU PLAN ON STAYING THERE A WHILE!! They'll spend $40K 0n a car every 3 years but balk at the same price for the heating system that will last them for a lifetime, that they can figure into their mortgage. It just doesn't make sense to a logical thinker but in this world, the bottom line rules.
And the old adage applies, "You get what you pay for."
If someone could give me a quick rundown on posting pix I can show you some of my latest project and explain a few things if you'd like. It is NOT a GTHP system though. I get the feeling I need to post them to a website and then reference them from here?
One more thing on open loop. It can/will suck up all kinds of junk from the pond or stream and requires more maintenance than a closed loop which requires viurtually none and it can fail at the most inoportune time because of a clog.
One thing I do NOT like about GTHP is if the power fails, no heat. And it requires a good sized generator if you were to go that way. I could run my fossil fuel heat systems on just a midsized portable generator and have juice leftover for the fridge.
Another advantage of heating the concrete, it gives you ~ 3 days worth of leftover heat if it does fail.
Post by: Guest on September 12, 2005, 04:50:18 AM
It looks like I need to do some more digging on this. For instance, can the GTH be backed up with solar panels, instead of relying completely on outside power? We'd had ice storms here that knock out power for a couple weeks in a time, so I want something that can be used even if that happens.
It will be a couple of years before I can do this..but when I do, I want to have something that is going to last and be as fuel efficient and self-reliant as possible over the next 30-40 years. If that means spending more immediately on energy efficiency, and less on interior froo-froo stuff, I'm good with that. Carpet gets replaced, trim can be upgraded, etc. What I want is a good basic structure and energy systems in place.
Post by: K Frame on September 12, 2005, 05:29:44 AM
In-floor radiant heat is amazing, but I'm not so sure that there are any systems that integrate a geothermal heat pump with in-floor radiant. That's usually a fossile fuel option.
The one drawback to IFR is that if you want air conditioning, you still need ductwork, which adds quite a bit of price to an already pretty expensive system.
As for drafting from a pond, that's generally not how it's done because of the problems you mention. The pond option is almost always a closed loop system with the coils suspended in the pond.
Open loop residential systems are virtually always done with wells, and then only where codes permit.
Here's a good link for information on these systems: http://www.geoexchange.org/about/how.htm
Post by: 280plus on September 12, 2005, 07:46:07 AM
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In-floor radiant heat is amazing, but I'm not so sure that there are any systems that integrate a geothermal heat pump with in-floor radiant. That's usually a fossile fuel option.
Mike, I'm pretty sure water furnace offers a water based system as oppsed to forced air. Someone does, I talked to somebody about it. GTHP is the PERFECT system to couple with IFR due to the low temp of the water produced by the GTHP being in the same neighborhood as the temps needed for IFR. There are no issues with terying to keep the return water temp up as GHTP does not have any flue gas exhaust that could condense water in the chimney and cause premature erosion of the mortar and a boiler's cast iron.Yes a closed loop system is the best option for a pond but I HAVE seen systems that draw and use directly from ponds and streams. A GTHP is really nothing more than a water source heat pump (WSHP) (as opposed to air source) so any way you get water to it works as long as the temperature of the water is within design specs. There is nothing new about WSHPs the newer part is the method of using the earth as a heat sink.
Yes, if you do IFR you indeed must install ductwork anyways in order to cool the home and all along I have been saying "not cheap"
This is where the hybrid design of only "warming" certain floors but then using a hot water coil in the A/C ductwork shines. The overall cost is reduced as you are not tubing the whole place. Just the concrete basement floor and bathrooms, kithcen and any other tile floor. Still I am doing a house this way right now and the price of the system is in the range of $38,000. If we were to tube the whole place and do A/C the price could easily get to $50,000.The thing about any hot water heating system is versatility. With the same hot water system you can heat your DHW, your home, your pool, you can have towel warmers in the bathrooms, anti bathroom mirror fogging, melt the snow on the steps sidewalk and driveway. Again NOT CHEAP! But available. You can always add these niceties later too, as long as you have a big enough source of hot water.
Barbara, you are smart. Most people design and even begin to build a house before they give serious consideration to heating and cooling it. The correct way is to decide how you want to condition the home and then design around that. As far as solar panels, the compressor in a GTHP will draw a good bit of power but as long as your solar electrical system is adequate, it is not a problem.
Post by: Guest on September 12, 2005, 08:34:12 AM
I'm new to all this, and definitely need to do some more reading and work on the options.
I'm really leaning towards some sort of earth-bermed or earth sheltered kind of thing if I can find some options that are affordable, moisture resistant and don't leave me living in a basement.
This looks like the same general idea I'm headed for, if not exactly.
http://www.ourcoolhouse.com/
Post by: K Frame on September 12, 2005, 08:41:31 AM
Water can be used to heat and cool, but depending on the season, its temperature has to be modified somehow, either through the burning of fossile fuels (hot water heating systems) or chilling it (mostly used in commercial buildings, though).
If you're drawing ground water from a well, the water temperature, depending on depth of the well, will remain fairly constant, say at 58 deg. F year round. That's much colder than you want to keep your home in winter, but even 58 F water has a HUGE amount of latent heat in it -- that's what these systems capture, the latent heat.
In summer, you don't capture latent heat from the well water, you exhaust heat removed from the home into it. Again, at 58 deg. F, the water has the ability to absorb a great amount of heat.
You can't, however, cool your home with infloor radiant tubing. Remember, chilled surfaces collect condensation, and a floor that's wet all the time isn't a good thing.
Post by: cfabe on September 12, 2005, 08:59:01 AM
So, if you want to cool with your heat pump as well, you'll need the ductwork and air handler anyway. A nice hybrid system could probably be designed that would heat both the air through the air handler in the winter as well as heat the floors, and then in the summer, just cool through the air handler system. That'd probably be a pretty expensive system though.
This is a great thread, I'm always amazed at the variety of knowledge we have on these forums. I'm not going to be building my house for a few years at least, but this is great information to have.
Post by: 280plus on September 12, 2005, 11:26:25 AM
I agree on the depth of knowledge around here and it's nice to have a forum to discuss non gun related items without getting all in trouble too!
Post by: K Frame on September 12, 2005, 12:41:09 PM
Cold doesn't radiate like heat does, it's much more effective when actually circulated via a fan.
I also can't imagine why you would expend the energy to dehumidify the air (which requires chilled surfaces) and not combine it with a cooling aspect, as well.
Post by: Guest on September 12, 2005, 03:01:47 PM
What do you think about combining the use of a GTHP with either an earth-bermed or earth-sheltered design and some amount of solar energy usage?
Any thoughts on materials?
The construction costs on this would be pretty high with all this. But like I said, I'm willing to go cheap on some cosmetic things to start with if I can get the structure right.
Post by: 280plus on September 12, 2005, 03:42:12 PM
Quote
I can't imagine that cooling the walls and floors would be an effective, or espeically cost effective, means of cooling people. I also can't imagine why you would expend the energy to dehumidify the air (which requires chilled surfaces) and not combine it with a cooling aspect, as well.
You'd have to talk to the Germans, apparently it works. Are you familiar with the term "Cold 70"? The Germans have square pipe too, figure that one out The real story is humidity. If you can dry the air out you will feel cool even at 80* room temp. Vice versa when you heat, 65* will feel warmer at 50% humidity than 30% humidity.I am familiar with two solar heated houses in my area. One is is free standing the other buried into the side of a hill. The buried one is a lot like being in a cave and can feel a bit uhhhhh dank(?) claustrophobic too. Only the front of the house had windows. You do feel like your in a basement. The free standing one had the better design circulating air through panels on the roof and down under the slab where they had put very coarse rock that would allow the air to pass through, thereby heating the rocks and the slab during the day which would hold overnight. They had both a wood stove and a gas funace as backup. Every solar house needs backup heat.
The cave had a wood stove. It was designed with a huge overhang so that in the summer the sun was high and did not get into the house but when it was winter the sun was lower and it would shine on the concrete floor and warm it during the day again holding overnight. So the cave was passive and the free standing was active. It used a fan to circulate the air.
Now that I think about it, the reason I came in contact with the cave is because the new owner did not feel warm enough and had me install a furnace!
Post by: Guest on September 12, 2005, 03:54:59 PM
http://www.ourcoolhouse.com/images/construction/internal.htm
These don't look bad. I'd want to look at different exterior materials, and style, but they've done some neat stuff with the house..including the etched concrete floors inside..the house is bermed on two sides, but doesn't look dungeonish at all, from the photos. As long as the bedrooms had two means of egress, it should be workable.
http://www.ourcoolhouse.com/images/construction/equipment.htm
This is a picture of their heat pump setup. This is where I get in over my head, for sure. I need to do some serious reading in the next year or so.
Post by: 280plus on September 12, 2005, 04:25:24 PM
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This is a picture of their heat pump setup.
That's pretty much all the bells and whistles there! Major dollars!! I have a little issue with the way they use the DHW heater for the slab. Most towns around here won't let you do that because in the summer that water stagnates in the slab abd then can contaminate your fresh hot water (or DHW) tank and make you ill. All you see there is very similar to what I'm doing right now except I'm using an oil fired boiler. Do they mention cost anywhere?
Post by: 280plus on September 12, 2005, 04:35:09 PM
Post by: Guest on September 12, 2005, 04:36:36 PM
On average, a geothermal heat pump system costs about $2,500 per ton of capacity, or roughly $7,500 for a 3-ton unit (typical residential size). In comparison, other systems would cost about $4,000 with air conditioning. When included in the mortgage, the homeowner has a positive cash flow from the beginning. For example, say that the extra $3,500 will add $30 per month to each mortgage payment.
Post by: 280plus on September 12, 2005, 04:46:31 PM
I'm going off now. I'll check back in tomorrow!
Post by: Guest on September 12, 2005, 06:14:22 PM
Quote from: Barbara
What do you think about combining the use of a GTHP with either an earth-bermed or earth-sheltered design and some amount of solar energy usage?
Hi Barbara. You linked to my "OurCoolHouse.com" website and I followed your link back here.Tying Geothermal (GSHP) to Radiant heat (and cool) is EXTREMELY practical and not really that expensive (depending on your land etc).
I have geothermal radiant heat, and geothermal ducted air (heat and cool). My winter heating bills are a fracton of my neighbors (I live in the mounains of Western MD: 80" of snow on average).
I'm also earth sheltered (rear and side walls) and I also have an Energy Recovery Ventilator.
And finally, mine is a passive solar design (no solar cells or a anything like that) which uses the nartual winter/summer sun cycles to heat and cool the house.
These things don't automatically make a house expensive, it's just a matter of giving up some other things to ballance the budget (like granite counter tops and 3-4 bathrooms
Phil.
Post by: Guest on September 12, 2005, 06:26:26 PM
Quote from: Mike Irwin
Cold doesn't radiate like heat does, it's much more effective when actually circulated via a fan.
Actually, cold radiates EXACTLY like heat does. Heat transfer through radiation is dictated by the temperature difference between the two radiating surfaces. You are one surface and the slab/walls/floor are the other. Heat always moves from the hot surface to the cold one.A basement or cave feels cold because the walls are cool.
Radiant cooling can be very effcient, and the only trick to eliminating condensation is to make sure the surface temperature does not get below the dew point of the air. You can do this by 1) monitoring the humidity, and controling the surface temperature, or 2) Dehumidifying the interior air and thereby raising the dew point.
Circulating the water from a ground loop through some air coils is a great way to pull the moisture out at a central location... then the same water can be used to cool a radiant slab. Remeber the slab doesn't have to be "cold" it just needs to be cooler than your body to generate a net heat loss.
I actually can run my GSHP in reverse and cool my slab. It only takes a few degrees to make a difference. Cooling the air and blowing it around the house and hoping it's cool enough by the time it reaches the far side is pretty a indirect way to cool a person.
Phil
www.OurCoolHouse.com
Post by: K Frame on September 12, 2005, 08:10:11 PM
"I have a little issue with the way they use the DHW heater for the slab. Most towns around here won't let you do that because in the summer that water stagnates in the slab abd then can contaminate your fresh hot water (or DHW) tank and make you ill."
They don't.
"This configuration keeps the domestic hot water separate from the radiant slab fluid, which can then contain an additive to prevent freezing."
National plumbing code won't allow hydronic water to be mixed with domestic hot water. The big concern is Legionaire's Disease.
Post by: K Frame on September 12, 2005, 08:15:21 PM
That's an AVERAGE cost. Friends looked into this option in the Springfield, Virginia, area, and were quoted costs of roughly $5,000 per ton, and that didn't include all of the excavation work to plant the loops.
Systems using wells are normally a lot more expensive depending on the number of wells you need.
If you have someone quote you a price, make absolutely certain that it includes all excavation and coverage costs, as well.
Post by: K Frame on September 12, 2005, 08:18:43 PM
I assume that you're not talking about the Igloo 70 quart cooler.
I'd really want to see some installation and usage costs on a system such as that.
I can't imagine that it would be any more effective than using a multi-speed system connected to internal and external thermostats and humidistats, but I can imagine it being a lot more expensive.
Post by: K Frame on September 12, 2005, 08:27:16 PM
Phil,
I said that poorly.
Cold air stratifies much more readily than heated air, and will produce virtually no convection currents. I supposed the best solution to that would be ceiling mounted cooling panels.
I need to read more about this. I'm still very dubious about the concept as a whole.
I found this link from UBerkley: http://www.cbe.berkeley.edu/research/radiant_cooling.htm
I'll read up on it, but I'm still quite dubious.
Post by: Guest on September 12, 2005, 11:48:36 PM
I love your house!
Post by: 280plus on September 13, 2005, 01:31:55 AM
Quote
"I have a little issue with the way they use the DHW heater for the slab. Most towns around here won't let you do that because in the summer that water stagnates in the slab abd then can contaminate your fresh hot water (or DHW) tank and make you ill."
They don't.
Mike, if you look closely at the diagram of the heat pump setup you will see that it DOES show using the DHW for slab heat. You CAN use a DHW heater but CANNOT or SHOULD NOT connect it to the DHW you'll use for drinking, washing etc.They don't.
"cold 70" is a term coined for the phenomenon where the air temp is 70* but all the surrounding surfaces are much colder. Walls, floor, ceiling, furniture etc. Even though a thermometer will indicate the air temp is 70 people feel cold. Best example I can think of is a bank once where they had granite counters and brick walls. They would shut the heat off at night and all that rock in there would achieve something like 56* IIRC. When they turned the heat back on in the A.M. the air would warm to 70* but all the rock would still be 56* even by late afternoon. Those girls were FREEZING even though the air temp was 70*.
Why? Cold does not radiate, heat does. In effect their warm little (some not so little) bodies were radiating their heat to the cold surfaces making them feel chilly. You might look at it as the cold surfaces were pretty much "sucking" the heat out of them.
Anyhow, thats how "radiant cooling" works. As a matter of fact, now that Phil mentions it I DO recall something about cooling the ceiling. Honest, they do it in Germany.
Quote
I can't imagine that it would be any more effective than using a multi-speed system connected to internal and external thermostats and humidistats, but I can imagine it being a lot more expensive.
This is MY contention. Yes GTHP are considered to be the most efficient heat around however, I can't buy 40% savings over a well designed high efficiency oil fired system. I too would like to see hard numbers but unles you build 2 identical houses side by side one with GTHP the other with a good oil system and compare the reults it is nearly impossible to verify any of this. 40% over an old furnace, definitely. 40% over a high efficiency oil fired hydronic system? Not likely. Maybe 20% I'd buy.
They say 40%. %40 over WHAT!? They conveniently leave that part out.
Nice system Phil! I may be drooling...
I'm going to correct myself. While the diagram shows the DHW hooked to the slab I don't have enough info there to determine exactly what's going on. From what I am reading the heat pump heats either one or the other. As long as there is no way for slab water to find it's way back into DHW then it's ok. A DHW heater is another accepted way to heat a radiant system due to it's being designed for low water temps and there are those that use them. There WERE also those who were using them simultaneously for DHW. This was found to be a bad idea for the reasons described above.
Post by: cfabe on September 13, 2005, 03:43:22 AM
In theory these systems are the most efficient, but in practice they may not be, espicially if the implementation is not engineered perfectly. In my area (northeast Ohio) there are more than a few houses built in the early to mid 80s using air source heat pumps. Lots of problems with these because of improper system design. In a heat pump system when the heat pump can't keep up with the heating load in the house, electric resistance backup heating is used. For air-source systems, I believe this usually occurs when the outside temp drops below the mid 30s F. So around here the home with air-source heat pumps have nice low bills in the fall and spring, but tremendous bills if january and feb if we get a cold spell. Geothermal does help this by keeping a more constant temperature heat source, but this is just one example of poor implementation. If these guys with air-source pumps had also had a natural gas backup furnace instead of electric, they'd be much better off.
Post by: 280plus on September 13, 2005, 05:02:37 AM
The reason heat pumps are so efficient is nothing is being burned or consumed to provide the heat. It is simply taking the heat inherently present in the ground (or air), concentrating it (if you will) and transfering it into your house.
Post by: K Frame on September 13, 2005, 08:00:09 AM
The diagram is, at best, nebulous. I'm going by what they're saying, in words, on the website. As I noted, Nat. Plumbing Code won't allow heating and potable water systems to be linked.
There are water heaters available that have a tank for domestic hot water and a coil that sits in the tank. In that sense, it's no different from a boiler with a domestic hot water coil.
That set up is allowed by the code.
Post by: K Frame on September 13, 2005, 08:04:57 AM
Even during the coldest spells, where the temperature doesn't go above freezing during the day, I rarely see my auxilliary heat (the toaster, as I call it) come on.
I used to moan like crazy about a heat pump, because the heat it provides just isn't "warm." However, given the price of gas and oil over the last couple of years, I'm liking my heat pump more and more. I'm not seeing the ENORMOUS spikes in prices that my friends and family are seeing.
Yes, I'd like to have hot water heat, or steam heat (I grew up in a house with steam heat), but I'm comfortable in my house with a heat pump, and spot heating when necessary with a little electric heater.
Post by: mfree on September 13, 2005, 09:47:41 AM
But there is no cold. Consider it like a vacuum or a darkness, it can't radiate as there's nothing really there.
Post by: 280plus on September 13, 2005, 09:54:13 AM
Quote
The diagram is, at best, nebulous.
Yup, the way it appears the slab and DHW look linked but you're right, it could be an indirect water heater and an incorrect diagram.12+ SEER means you took "The High Road"
when you purchased your system and now you reap the benefits. It get's a bit colder up here in CT though so our "toasters" (I like that one) come on much more often. That defrost is a killer. Does yours develop and hold frost on the outside unit when it's cold?? Another killer is an improperly charged system. If It's undercharged the heat will run much more to keep up and use those toasters even more. If it is overcharged OR undercharged it will not cool well either and, once again, run more often and longer than it should. A 12+SEER Air Source Heat pump that switches over to a high efficiency oil fired hydro air system at around 40* (maybe a little lower) would provide very comfortable heat and be miserly on the fuel consumption. Now you're not digging trences or drilling wells either.
Post by: 280plus on September 13, 2005, 09:59:27 AM
Quote
But there is no cold. Consider it like a vacuum or a darkness, it can't radiate as there's nothing really there.
I like that on too! It reminds me of another axiom "Light bulbs don't emit light, they suck in dark."
Then there's "Is it the electrons moving forward or the holes where the electrons go moving backward that creates current flow?"
But I digress...
LOL
Post by: K Frame on September 13, 2005, 11:42:49 AM
The only thing in this universe that truly radiated cold was my exwife.
She'd open her mouth and the heat pump would come on.
Post by: K Frame on September 13, 2005, 11:48:27 AM
Mine has an "intelligent sensor" on it that detects when ice has built up. It's much better than the old systems that were regulated by a timer.
Post by: 280plus on September 13, 2005, 02:03:44 PM
Quote
Any heat pump will develop a frost layer within certain humidity/temperature parameters.
Yes, but if the ODT is far enough above freezing the frost will melt off during the "off" cycle as opposed to needing a defrost.Quote
Mine has an "intelligent sensor" on it that detects when ice has built up. It's much better than the old systems that were regulated by a timer.
Yes, in the "old days" some had a timer that would electrically "ask" the heat pump, by means of a thermostat, every 30 minutes if it wanted a defrost and if the weather was particularly cold or HP was not operating correctly it WOULD go into defrost every 30 minutes and I pity the wallet that's got THAT going on.Others had a pressure switch that sensed a lowering of air pressure between the condenser fan and coil, indicating that the fan was trying to draw against a blocked coil, and trip it into defrost that way. IIRC there was also a brand that used a sail switch in the airstream. As the ice built up the air velocity over the coil would slow to the point where the sail switch would cycle and initiate a defrost.
Another problem with the "toaster" type HP setup was if the HP failed and the system automatically switched itself over to "emergency heat" people would not know this and would be heating their houses with the toasters instead of HP. This too makes for a big electric bill. This caused some loss of popularity as well
Post by: cfabe on September 13, 2005, 03:35:49 PM
In my (future) house I think I'm going to do hot water heat using either in floor or base boards as a baseline heating system that will keep the house at 55-60 and wood heat to supplement. Advantage with hot water is that it's easy for a layman with a little plumbing experience to install. In my area if a house is designed well there's really only a few weeks a year where a/c is necessary/desired, and I'd just get a window unit for the bedroom if necessary.
Post by: Guest on September 13, 2005, 03:39:57 PM
I would plan on the house having a second source of heat anyway, most likely wood for those chilly nights.
Post by: 280plus on September 13, 2005, 05:15:38 PM
Quote
I believe that some/most of the heat pump systems had an indicator light on the thermostat that would illuminate when they were in "emergency heat" mode
yes that's true as long as you physically switch the t'stat to "Emergency heat" if it turns on automatically because the HP is not keeping up MOST will have no indication that you are using the strip heaters. There was at least one that DID give a fault light when things weren't right.Barb, an air source HP In Northern climates DOES need supplemental heat as they are unable to keep up once the outside air temp gets too low. Most automatically shift to a secondary source of heat. Worst case is switching it to electric heat. A ground source should not require any additional heat. Air source means it collects heat from the surrounding outside air. Ground source is your Geothermal collecting heat from the ground. A geo thermal is also what we call a water source HP as it picks up heat from a source of water. There are many ways to put heat back into the water once it has been removed by the HP and transfered to the space. In the case of a GTHP the water is reheated by passing it through the relatively warm ground. if you can expect to be without power for 3 weeks a wood stove and a good supply of wood wouldn't be a bad idea at all regardless of what type you have.
Post by: K Frame on September 13, 2005, 05:40:54 PM
??Here's my original statement: "Any heat pump will develop a frost layer within certain humidity/temperature parameters."
There's no but statement required; my wording makes it abundantly clear that frosting/icing does NOT occur all the time. My unit goes into defrost mode most when the temperature is between about 40 and 45 deg. F and the humidity is in the 50% plus range, which actually occurrs fairly frequently here in DC in the fall.
"I believe that some/most of the heat pump systems had an indicator light on the thermostat that would illuminate when they were in "emergency heat" mode. Of course if you never look at the thermostat, that doesn't help much."
I believe that all thermostats made for use with a heat pump with electric resistance heat have this light.
"Advantage with hot water is that it's easy for a layman with a little plumbing experience to install."
DANGER WILL ROBINSON! DANGER WILL ROBINSON!
Yes, relatively easy to install, but the big question is, who is going to do your design? That's the kicker part.
I have very fond memories of telling a rather arrogant know it all (who for some really really liked me) that he had REALLY screwed up when trying to save a few bucks doing his own heating renovations.
He decided to pull the old, ugly, outdated cast iron radiators out of his house and replace them with baseboard units. Fairly common thing to do, I personally hate to see it, but I like the old CI radiators.
The only problem was, he replaced the radiators with similar lengths of slant fin. The end result? He reduced the amount of heat going into his rooms by anywhere from 2/3 to 3/4ths. His wife as NOT pleased with him, and he wasn't pleased with me when I told him he screwed up, and then proceeded to explain to him how he screwed up.
His poor ego.
Post by: K Frame on September 13, 2005, 05:45:55 PM
Incorrect.
At least that's incorrect if the T-stat is properly installed and is designed for use with a heat pump. And given that you need a heat pump thermostat to run the supplemental heat, chances are pretty good that you're going to have the proper T-stat with the little light.
If the emergency coils switch on for any reason, that little light is supposed to go on on the T-stat. That includes the system being switched to emergency, the system dropping into reversing mode to defrost, or the system requiring more heat than can be extracted from the atmosphere (usually a differential of about 1.5 deg. from the T-stat to registered room temp).
My 12 SEER Trane replaced a 6 SEER Rudd that had been installed when the home was built in 1979. The thermostat was original to the unit, as well, and it had the emergency heat light that lit under all conditions noted.
I decided it was time to upgrade when the reversing valve reversed one evening during a defrost and refused to unreverse.
Post by: K Frame on September 13, 2005, 05:53:17 PM
Yes.
There are propane and natural gas options for the emergency/supplemental heat, possibly oil, as well.
I'm not a big fan.
Why?
Because if you have a fossile fuel supplemental heat, you've got TWO heating systems, and the secondary heating system requires all of the attributes of a fossile fuel system -- chimney, fuel source, etc., with all of the ancillary cost.
If you're going to go for the electric heat pump, I figure just go all of the way. Yes, the electric resistance will cost more to run than a fossile fuel backup, but I SERIOUSLY question whether you'll ever recoup the cost of the fossile fuel system.
If, however, you wanted to go that way, your best bet would probably be a separate gas water heater with a dedicated coil in the plenum and a small circulator pump. An on-demand style heater might actually be best, but it will also be expensive.
All in all, I think it's far better to stick with the electric supplemental heat in the unit and then go to something like wood (if you have it), a pellet or corn stove, etc.
Post by: cfabe on September 13, 2005, 06:01:03 PM
Quote from: Mike Irwin
"Advantage with hot water is that it's easy for a layman with a little plumbing experience to install."
DANGER WILL ROBINSON! DANGER WILL ROBINSON!
Yes, relatively easy to install, but the big question is, who is going to do your design? That's the kicker part.
Don't worry mike, I'm years out from building and the heating system design is just one of the things I'll need to figure out. As I get closer I'll be doing a ton more research. What I meant was that once I have a design figured out, I know I can do a hot water system with my plumbing skills, where I'd have a harder time doing a forced air duct system, and doing a good job of it.
DANGER WILL ROBINSON! DANGER WILL ROBINSON!
Yes, relatively easy to install, but the big question is, who is going to do your design? That's the kicker part.
Post by: Guest on September 13, 2005, 06:36:26 PM
When my system was initially designed (by the HVAC company doing the Geothermal, Radiant heat and ducted air), they were going to configured it with the GSHP heating up water in a storage tank, and that tank being used to deliver DHW and Radaint heat with a tempering valve.
The GSHP was configured to generate Potable water.
So in this configuration, the Hydroninc and DHW were directly mixed in the Storage tank.
However, at that time, I was considering feeding the slab with water directly from the ground loop, which contained anti-freeze (to experiment with passive radiant cooling), so I asked the installers to put a heat exchanger between the hot water storage tank and the hydronic loop to keep them isolated. This is how the system was first installed.
Some of my original web pages may still refer to this configuration. The two fluids (DHW and Hydronic) were totally sepparate.
HOWEVER...
After a year of running the system, and many "active" discussions on my forum, it was decided that this was a very inefficient configuration. A better one would be to directly connect the GSHP to the hydronic loop to get maximum efficiency from the GSHP when generating hot water for the radiant heat.
In this new configuration the GSHP would switch between heating up the DHW OR heating/cooling the radiant slab. So, in this new configuration, the DHW and Hydronic would be physically linked, and there could be occasional bleeding of Hydronic fluid into the same tank that stored DHW (when the system switches between DHW and Radaint Heat).
Since this was doing less mixing of fluids than the original planned configuration, I assumed it would be OK/Safe. Any hydronic fluid that bled through would be heated back up to 120-130 F, which is high enough to kill any nastie bugs. Plus I provided a way to periodically flush the radiant loops.
This is how the system is currently running.
Note: The domestic cold water supply is not exposed to the radiant loops.
So naturally, I am suprized by the comment that this configuration is forbidden by the "National Plumber's code".
Can anyone give me a reference for the appropriate section of the code so I read the specifics. A web link would be great.
Phil.
Post by: K Frame on September 13, 2005, 07:41:17 PM
No, no it's not.
Legionella and other water-born pathogens can survive and remain viable at temperatures well above above that. Britain recommends that boiler water for potable systems be kept above 140 deg. F (http://www.allerdale.gov.uk/downloads/page139/legion.factsheet.pdf)
CDC notes that Legionella has been isolated from water in the 145 deg. F range, as well. (http://www.cdc.gov/ncidod/EID/vol10no3/02-0707.htm)
Granted, water treatment processes will go a long way towards (hopefully) preventing any sort of pathogen in the water, but I'd still be VERY hesitatant of a system that mixed heating water and potable water due to the possibility for stagnation of the heating water allowing free chlorine to bleed off.
I'm looking for the citation that I found regarding the National Plumbing Code and hydronic heating systems. It's been awhile. I don't have a copy of the National Plumbing Code, and I've not found one on-line, either.
Post by: 280plus on September 14, 2005, 01:17:13 AM
It's QUITE possible for a malfunctioning HP to use electric heat all winter without the knowledge of the homeowner. Seen it, many times. The usual call is "Gee, my electric bill is sky high, can you check if my HP is running properly?" DING DING DING!! "Sounds like it's running electric heat instead of HP!" Ka-CHING!$!
What I said in terms of frost and defrost is that if the ODT is high enough the HP may still frost but will melt the frost off during the "off" cycle not needing a defrost. MY opinion is that you should shut the thing off at just ABOVE the ODT at which this ceases to occur and switch to conventional heat. Let me rephrase that, high efficiency conventional heat. You want to eliminate defrost cycles which is where the ASHP loses it's efficiency. This becomes less of an issue as you get farther south. It would be alsmost inane to couple a HP to fossil in FLA for example but up here in the great white north it becomes a more viable option. None of this is necessary with GTHPs, which is why they are so much more efficient. However the ASHP / fossil system may be cheaper on install than the GTHP. Keep thinking like 3 wells or 3 trenches something like 4' x 8' x 75' each and the associated loop hardware. Then, as I've stated earlier an extra trench or well wouldn't be a bad idea at all.
If you are installing A/C anyways there is only a small added expense to put in a HP condenser vs an A/C only. So if your main system was going to be oil fired forced air with A/C, for example, the extra cash outlay to install a HP instead of an A/C condenser is minimal. A few hundred $. Yes it is even LESS expensive to install a HP with electric backup but operation costs are quite high (especially up north here) compared to a mix of HP and fossil fuel systems.
We are talking about trying to squeeze every bit of heat out of our fuel $. HPs with electric backup and gas water heaters to warm our airstream are not the way we do this. Cheaper to install yes, but if one is truly planning on staying in the same house for the next 30 years any added expense by putting in a better system WILL be recouped well before 30 years is up. Is there any way to tell exactly when this happens. Not that I know of. "Rule of Thumb" says 7 to 10 years.
PS, I think arguing the details of operation on these systems is not necessarily what Barbara is looking for.
Phil!! If you are mixing slab water with DHW THAT IS BAD!! I know of no code personally but I DO know most local officials will not let you do it if they are the least bit informed. And in this world, the local official is the final say on everything. Really the only problem is when the water stagnates in the slab circuit over a period of non use, it builds up bacteria that can be discharged to the DHW system upon first start up the following heating season. The cheapest way around this is to add a timer that once a day circulates the water in the slab for a few minutes during the off season to prevent stagnation.
Post by: cfabe on September 14, 2005, 03:59:40 AM
Thread Summary:
An air-source heat pump will not work well in a cold climate, and will need supplemental heat of some sort (fossil or resistance electric). A ground source (geo-thermal) heat pump will work well in sub-freezing temperatures, but is more expensive to install. If you plan on staying in a home for many years, it will probably be a good investment. A GTHP system will me considerably more expensive than a 'normal' heating system, perhaps twice or more as expensive.
A GTHP is the most efficient method of heating we have, other than solar. Passive solar feautres will help but you'll still need the heateing system. However as with any heating system, it needs to be properly designed and installed by someone who knows what they're doing. A poorly done GTHP system may be no better or worse than the cheaper alternatives. GTHP systems are rare compared to "conventional" heating, so you may have a hard time finding a good installer in your area, espicially if you are in a remote area.
Some people dislike heat pumps with air-delivery because the air feels cooler than fossil-fueled furnaces, though it does heat the house. Hot water delivery of the heat is an option, but this eliminates the possibility of using the heat pump to do air conditioning as well, since this requires air-delivery because of the condensation. You can have a hybrid system with both, but it will be more expensive and complicated.
Post by: K Frame on September 14, 2005, 08:08:08 AM
As far as I know, every Honeywell thermostat that is designed for use with a heat pump has those attributes. My rather basic 1979 model from Honeywell had that feature, and my rather advanced programmable Honeywell on the new system has that feature.
As far as I can determine, all major manufacturers of heat pump thermostats use both indicator lights, and have for years. I'd be interested in hearing if you know of any made today that don't.
Every heat pump system made today (again, as far as I know), also has the control circuits necessary to run both lights, and have had for years.
Yes, it's possible that a series of failures could push the heating system over onto strictly electrical heat, and a less than observant homeowner might go weeks, or months, without noticing. But I have to think that if they're that much of a brain dead dullard, they'll also have problems figuring out when their gas or oil systems aren't running optimally and are wasting large amounts of money, as well. You can only design in so much "stupid" factor for people. After that, they are on their own.
"What I said in terms of frost and defrost is that if the ODT is high enough the HP may still frost but will melt the frost off during the "off" cycle not needing a defrost."
Gotcha. Yes. That's often the case unless for some reason the cooling load is unusually high.
Personally, I think in the North, anything much above the Pennsylvania Maryland border, no one should be installing heat pumps in the first place unless, as you note, they're ground source.
Interesting aside...
I was talking about this thread to my Father (a civil engineer in Pennsylvania) and he mentioned that my Grandfather installed some of the first ground source heat pumps to be used in Pennsylvania, in the early 1950s. Grandpa was a mechanical engineer, in charge of the boilers and mechanical maintenance at the American Viscose Plant in Lewistown, PA. They used the Juniata River as the ground source.
As a further aside, Mom and Dad live in the house that Grandma and Grandpa bought in 1943. They bought it from the estate. The boiler is a Burnham Jubilee that Dad and Grandpa installed in 1956 to replace the coal-fired gravity hot water system that was in the house originally.
Dad and I were talking about putting a new boiler in (50 years is a good life for a boiler), but now that his health is getting worse, it will probably be contracted out.
Post by: 280plus on September 14, 2005, 08:10:30 AM
Quote
A GTHP system will me considerably more expensive than a 'normal' heating system, perhaps twice or more as expensive
YES!Quote
so you may have a hard time finding a good installer in your area, espicially if you are in a remote area.
YES! Finding a GOOD installer as well as a GOOD repairer! Very important!
Post by: Guest on September 14, 2005, 01:26:05 PM
Quote from: 280plus
Really the only problem is when the water stagnates in the slab circuit over a period of non use, it builds up bacteria that can be discharged to the DHW system upon first start up the following heating season. The cheapest way around this is to add a timer that once a day circulates the water in the slab for a few minutes during the off season to prevent stagnation.
Just for reference, I did a good year of research while designing my current home. I find it strange that I saw MANY examples (in various literature and online) showing a radiant slab being heated from the DHW tank. I find it strange that this is only the second time I've heard anything negative about this approach.But... I do want to understand (that's why I do research).
What is the actual problem with stagnation? What is the critical factor for causing problems.
Is it really just that the Water doesn't move?... how does moving the water fix the problem?
Can the microbes really tell? Water could sit in city supply lines for quite a while, or move extremely slowly in some conditions... How is that different?
It would be extremely easy for me to cycle my loop circulators for a few minute every hour (or some other duty cycle). It's just just a quick software mod, but I can't figure out how that could really help. Is it really that easy? Wouldn't I need to do something else as well? Like mix in fresh water, purge the old water, or something?
Point me to a good reference.
Phil.
www.OurCoolHouse.com
Post by: K Frame on September 14, 2005, 01:42:50 PM
The important difference is, did you see slab systems heated with a domestic water heater that were ALSO heating the same water for household use and MIXING that water?
I would bet a resounding NO.
The problem with stagnation is that chlorine AND oxygen levels in the water, your first and best defenses against many very nasty critters, very quickly deplete after sitting.
Any bacteria that haven't been killed by the system then have a wonderful avenue in which to breed to toxic levels.
Moving the water replentishes the chlorine and oxygen levels in the loop, which helps keep any bacteria that are present, at bay.
The cheapest way around this is to do what 280 says.
The SAFEST way to deal with this is to completely isolate your heating and potable water systems.
If you want more information on this, contact you local water supplier, the ag extension office at a local university, etc.
Post by: Guest on September 14, 2005, 01:44:03 PM
Quote from: cfabe
To revisist Barbara's original question: "Anyone have any experience with these heat pumps? They sound great..about twice as expensive to start with, but if the savings are up to 40% per year, that should be recovered quickly enough. One of my biggest questions is how effective they'd be in a cold Mid-western winter."
I don't know exactly what a "Mid western winter" is (mild, cold or really cold), but I live in the mountains of Western Maryland, and it gets plenty cold here. In just the last two winters we've had one weekend where we got 52" of snow, and I've several 0 F degree days. Brrrr.In my book that's pretty cold... but I don't know about you guys.
My GSHP (Ground Source Heat Pump) has faired very well in this climate. I use a combination of Radiant heat and ducted air. Both are geothermal. I also get all my DHW from the GSHP.
GSHP's are most effective in extreme climates where the energy you save is significant. My potable water unit only gets 300% efficiency, but units designed exclusivley for space heating can get up to 400+% (yes a HEATING system with a COP of 4.1)
Makes a high efficiency gas heater look pretty sad with a COP of less than 1)
The other benefit of a GSHP is that it's kind on the environment. Over a summer/winter cycle you may actually put back all the heat you extracted from the earth... The net environmental heating is much smaller. That's a good thing. And since they are electric, there's the option to use a green energy supplier.
Just say NO to fossil fuels (it will keep the price of gas down over the winter:).
Phil Malone
www.OurCoolHouse.com
Post by: 280plus on September 14, 2005, 04:27:59 PM
Moving the water regularly flushes it out of the system before it has time to foster bacteria growth.
When slab heat first redeveloped many people were using the DHW heater to share both duties of heat and make DHW. It was later determined that this wasn't such a good idea. That may be a cause of some of the confusion.
Post by: DustinD on September 18, 2005, 12:59:13 AM
www.otherpower.com has lots of info about DIY solar panels, windmills, solar heating, and other DIY stuff.
www.backwoodshome.com Libertarian bent self sufficiency magazine.
www.motherearthnews.com You may not like their politics but they have a huge archive with occasionally some useful information.
www.homepower.com their past issue archive is great if you are into alternate power.
www.earthshelter.com earth bermed homes, they seem a bit pricey.
www.multiaqua.com uses cold water to cool homes without ductwork. It can also be used to heat homes. I personally like that duct free homes have less problem with dust in them.
I have lots more links if you are interested.
Personally I would go with solar hot water panels. www.otherpower.com and www.homepower.com have some great advice and examples of DIY systems that are very cheap.
Windmills are much more cost effective than solar panels for electricity production (especially if you build them yourself). I plan on building some and selling all of the excess power that the law allows once I get some land of my own.
If you earth berm your house you may not need air conditioning in Michigan. The earth will always be cooler than you want your home. Properly positioned and angled awnings can let sun light inside in the winter, but keep it out in the summer. You will also need a bit more insulation in earth bermed homes between the walls and the ground to ward off mold and to keep them from feeling like a basement or cave, but it is easily doable.
Post by: Guest on September 18, 2005, 03:29:42 AM
This makes me feel stupid, though. I think I'm in over my head.
Post by: 280plus on September 18, 2005, 12:46:13 PM
oops, I mean go back and read the thread, especially the synopsis, that was a pretty good run down. Don't feel overwhelmed by looking at it as a whole. Look at it it terms of systems and research each separately.
Post by: Guest on September 18, 2005, 01:29:46 PM
I found this..depending on what my oldest is doing next week (he leaves for the Navy in two weeks and I'm trying to spend all the time I can with him) I'd like to attend. If I can't catch this one, I'll definitely try to hit the next one they have.
Maybe they can explain this all to me with sock puppets and stick figures.
http://www.glrea.org/education/RenewableEnergySeminar_092405.html
Post by: 280plus on September 19, 2005, 12:42:48 AM
Give your son my best wishes, the 18th was the 30th anniversary of MY joining the USN. Of course my more favorite day is the 17th, which was my 25th anniversary of GETTING OUT of the USN.