Author Topic: Tankless water heaters? (Read 7921 times)

JAlexander · « **on:** January 10, 2007, 10:51:04 AM »

Does anyone know anything about them, pro or con? It'd be going into a sixties-vintage home in south Texas, where the winters don't usually get that cold, and the heat source would probably be electric.

James

mtnbkr · « **Reply #1 on:** January 10, 2007, 11:02:53 AM »

I hear nothing but good from the folks that have them in their homes, but I've never used one myself.

That said, I think it would be nice to have one on the top floor of my house. It can take 1-2min for hot water to reach the upstairs showers. The sink faucets take even longer.

Chris

K Frame · « **Reply #2 on:** January 10, 2007, 11:13:06 AM »

A 1960s vintage home simply may not have the electrical horsepower needed to power one of these critters without a service upgrade.

The electric ones SUCK the juice.

You'd need an electrician to look over the home, the current electrical demands, and the new water heater.

K Frame · « **Reply #3 on:** January 10, 2007, 11:13:52 AM »

Chris,

You should consider a bypass circulator pump.

Easy to install.

Brad Johnson · « **Reply #4 on:** January 10, 2007, 11:15:03 AM »

My sister and brother-in-law have them. It's nice having instant hot water! One of theirs is propane. The electricity in their rural area can be a bit spotty - if the power fails at least they can still take a hot shower.

Brad

Mabs2 · « **Reply #5 on:** January 10, 2007, 11:20:04 AM »

My understanding is they're way more ineffecient than normal gas hot water heaters (which are around 80%) or so, so look to pay a lot more for your hot water.
Were it my house, I'd got with a large solar hot water heater with a smaller electric backup...but that's me.

Brad Johnson · « **Reply #6 on:** January 10, 2007, 11:24:35 AM »

Quote from: mbs357 on January 10, 2007, 10:20:04 AM

My understanding is they're way more ineffecient than normal gas hot water heaters (which are around 80%) or so, so look to pay a lot more for your hot water.
Were it my house, I'd got with a large solar hot water heater with a smaller electric backup...but that's me.

More ineffient at spot heating, yes. However, you're not trying to keep 40 gallons of water hot all the time, either. For most households there is a net decrease in energy use with instant heaters. If you have a household that uses a lot of water on a constant basis then a tank-style heater and a circulation system might be more efficient (presuming that the heater and all the supply pipes are well insulated against heat loss).

Brad

mtnbkr · « **Reply #7 on:** January 10, 2007, 11:26:16 AM »

Quote from: Mike Irwin on January 10, 2007, 10:13:52 AM

Chris,
You should consider a bypass circulator pump.
Easy to install.

Next time you're over, remind me.

BTW, the tankless heaters I've known people to use have all been gas. Never known anyone to use an electric one, if that matters...

Chris

wingnutx · « **Reply #8 on:** January 10, 2007, 11:32:02 AM »

Heating water is a tankless job.

wingnutx · « **Reply #9 on:** January 10, 2007, 11:35:35 AM »

http://www.askthebuilder.com/451_Tankless_Water_Heaters_-_Some_Surprising_Facts.shtml

ilbob · « **Reply #10 on:** January 10, 2007, 11:39:12 AM »

I don't have any personal experience with them, but from talking to people who have them, mostly they are pretty happy. There are some issues. The gas ones need to be sized correctly or they will not work very well when heating relatively small volumes of water. You won't save any energy in most cases.

An electric one would have the issue of needing a lot of juice while the heater is running. Most showers are 3-5 gpm. You would need about a 40kW heater for such an application. Thats about 180 amps for a typical 220V residential system. Most homes just are not going to have that much current available from their service.

If you want instant hot water, maybe a better answer is a small electric hot water heater near the point of use. Feed the existing hot water line to the POU heater so there is always hot water at the POU. It does not need to be real big.

K Frame · « **Reply #11 on:** January 10, 2007, 11:48:19 AM »

"Next time you're over, remind me."

[Professor Farnesworth voice]Wha... huh? Good news, everybody, I don't know what the hell you're talking about![/Professor Farnesworth voice]

Sylvilagus Aquaticus · « **Reply #12 on:** January 10, 2007, 06:39:41 PM »

I've got a recirculating pump in my house's hot water line. Goes from tepid to hot within a second of turning on the tap and I don't consider it to use any excessive energy. I turned off the pump once just to see how long it took to get hot water to the longest run (the house is really spread out) and it took almost 2 minutes for it to come up to temp.

Given my druthers, I'd prefer to have a solar hot water heater and a full compliment of solar panels, bateries, and a windmill. With 3 full baths and a half, I can't justify retrofitting to the tankless models.

Regards,
Rabbit.

cassandra and sara's daddy · « **Reply #13 on:** January 10, 2007, 07:24:53 PM »

if your gonna remodel and can upgrade to 400 amp electric service you can go electric otherwise its as and i plan on replacing my heater with one of the instant ones.. i've installed em and they apparently save money. at least thats what my clients tell me.

K Frame · « **Reply #14 on:** January 11, 2007, 05:30:15 AM »

Jesus, 400 amps? shocked

Why not just drop a nuke plant in the back yard?

ilbob · « **Reply #15 on:** January 11, 2007, 05:34:00 AM »

Quote from: cassandrasdaddy on January 10, 2007, 06:24:53 PM

if your gonna remodel and can upgrade to 400 amp electric service you can go electric otherwise its as and i plan on replacing my heater with one of the instant ones.. i've installed em and they apparently save money. at least thats what my clients tell me.

Do you have any idea what an "upgrade" from a typical service to a 400A service is going to cost you?

We are talking in the neighbourhood of $5000.

All that so you can barely do better than break even on your energy costs.

danny · « **Reply #16 on:** January 11, 2007, 05:41:55 AM »

We've had a Thermar natural gas tankless water heater for well over 20 years. Our gas bill dropped substantially when we put it in. I don't think they make that brand any more.
It heats the water as we use it and so, as mentioned, we're not paying to keep a tank hot around the clock. It's also impossible to run out of hot water. It takes some getting used to. The water gets hot enough that one must add cold water in the shower but it never gets scalding hot like a tank-type heater can. As a result we must use a dishwasher which has the capability to heat the water a bit more.
While showering, you must have the dishwasher and/or clothes washer off or it'll exceed the flow-rate for full temperature.
The only maintenance in all these years has been to replace a $3 rubber diaphragm every few years.

mgdavis · « **Reply #17 on:** January 11, 2007, 11:16:51 AM »

My Dad, who has been in the propane industry for something like 25 years, installed a Rinai water heater on an outside wall of their house a few years back. I liked it when I was living there, no need to worry about a shower getting cut short. By installing on the exterior you can even recover the space that was being used by your tank. I'm not sure about how much more effecient it is, they went from an electric tank to the LPG tankless. My Dad says Rinai has great customer support, you can call and talk to a real person who knows what they're talking about.

ilbob · « **Reply #18 on:** January 11, 2007, 11:20:35 AM »

Quote from: danny on January 11, 2007, 04:41:55 AM

We've had a Thermar natural gas tankless water heater for well over 20 years. Our gas bill dropped substantially when we put it in. I don't think they make that brand any more.

I don't see how a tankless heater would change your gas bill a whole lot over a modern standard gas water heater. The tankless units are less efficient at heating water than a standard tank type unit. The main difference is that you do not lose as much heat while it is not in use. But, for modern water heaters, that kind of heat loss is relatively low anyway.

I would not be surprised to see a substantial drop in gas usage if the old water heater was worn out, poorly insulated, and used a standing pilot.

You will get the advantage of an endless shower if you so desire. But that will NOT reduce your gas usage.

danny · « **Reply #19 on:** January 11, 2007, 01:19:54 PM »

ilbob,
Indeed our tankless is less efficient. How many minutes a day do you actually draw water? For these, relatively few, minutes it's running at not much more than 50% efficiency. A tank-type heater, while more efficient, is experiencing a steady heat loss 24 hours a day. Even well-insulated, this loss adds up.
Our winter gas bill didn't change much as the furnace draws so much more than the water heating that savings weren't very obvious but it became VERY significant in the summer.
They've been using these for a long time in Europe where energy costs are much higher than here.
More recently we replaced our furnace with a 95% model. that's when the savings REALLY started.

Mabs2 · « **Reply #20 on:** January 11, 2007, 03:48:38 PM »

Yea, but with tank'd electric hot water heaters that are well insulated they hardly come on when not in use anyways.
...whereas a gas heater with its heat exchange running through the tank in contact with the hot water, the water will heat the air in the heat exchange causing it to rise and be replaced with cold air...which'll heat up and rise. So it kicks on occasionally for nothing.

Which is why solar is so great.
Get a solar hot water heater with a pump to circulate the water on a photovotaic(sp?) panel and you've got almost free hot water.

cassandra and sara's daddy · « **Reply #21 on:** January 14, 2007, 01:38:15 PM »

5 k? you can do em for less than 1/2 that . if you are already running service the power company here charges 75 bucks more and you need a bigger panel box. most of the new homes here are getting 400 amp standard now

box will cost you 250 bucks on ebay buried service can be more but check wih power company last conversion i did the house already had right cable all i had to do waas pull panel box and swap in new one was 2300 bucks done deal and with 400 amps you can run all the power toys your heart desires

K Frame · « **Reply #22 on:** January 14, 2007, 05:06:51 PM »

"the water will heat the air in the heat exchange causing it to rise and be replaced with cold air...which'll heat up and rise. So it kicks on occasionally for nothing."

Not if the thermostat is properly located, it shouldn't. The thermostat reads the temperature of the water in tank, not the air in the heat exchange tubes

Mabs2 · « **Reply #23 on:** January 14, 2007, 05:46:28 PM »

The air rising will constantly cool the water...I didn't say it ready the tempurature of the air.

Desertdog · « **Reply #24 on:** January 14, 2007, 07:37:58 PM »

Savings will depend more on your lifestyle than just what equipment you install.
Tankless WH have certain flow rates per minute with temperature rise. Too much flow and the temp drops.

Research tankless and tank waterheaters on the internet. Do not pay much attention to the tank ads, but pay attention to the specifacations and cost of equipment.

Tankless are more expensive to buy and to install than tank type. The biggest selling point I have seen in researching them is there is no standby heat loss. My summer gas bill, two people in 3 BR house, is under $20 for the water heating, cooking and gas clothes dryer.

Everything else I have read on tankless WH has not convinced me that they are that good of a deal.
Natural gas is the cheapest type of fuel if available. Propane is the next cheapest, and normally it can be put into any home at a reasonable price.
Electric is the most expensive to use.

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Author Topic: Tankless water heaters? (Read 7921 times)

cassandra and sara's daddy

cassandra and sara's daddy