Turn Off Your AC and Save the Earth!

[dogmush]

I'm not exactly certain that 118 air temp and 98% relative humidity is possible.... The hotter the air gets the less capable it is of carrying moisture...

If it were possible, it would give a relative heat index, or "feels like" temp in excess of 300 deg F if I'm calculating it correctly.

That's what the weather translator on the boat spit out.  We've got a weather station on the mast that feeds us the local conditions.  It is possible that outside conditions were giving bad readings, but that's what the instruments said.

The "feels like" temperature is close though.

[K Frame]

Are you sure you weren't sinking at the time?

[Ben]

That's what the weather translator on the boat spit out.  We've got a weather station on the mast that feeds us the local conditions.  It is possible that outside conditions were giving bad readings, but that's what the instruments said.

The "feels like" temperature is close though.

At that ambient temp, I'm sure the met station was giving a pretty close reading to the micro-climate, especially if you guys were on the water. There's going to be a decent amount of surface offgassing and water micro-droplets that the sensors will pick up, even up at the mast. It would likely be a different humidity reading if taken even 100 yards past the beach.

I feel for you though. I'd be dying there (and would also want to keep things cool at home!).

[230RN]

^^ "I'm not exactly certain that 118 air temp and 98% relative humidity is possible.... The hotter the air gets the less capable it is of carrying moisture..."

The operative word is "relative," which is a ratio.

If air at a given temp can only hold 1 gram of water vapor per cubic meter, but it's really only holding 0.98 grams of water per cubic meter at that temp, that's 98% relative humidity: (0.98 grams ÷ 1.00 grams) X 100  = 98% Relative Humidity, R.H. or RH.

(That would be around minus 4°F, by the way,)

See:
http://www.engineeringtoolbox.com/maximum-moisture-content-air-d_1403.html

Air at 104°F (40° C) can carry 51.1 grams of water (per m³) as a vapor.  If that cubic meter is only actually carrying 50.078 grams of water, that's 98% relative humidity.

If the air at that temperature is actually carrying the full 51.1 grams of water, it is "saturated," and is at the dew point for that temperature and is at 100% R.H. No further net evaporation can take place in "saturated" conditions.  So your sweat won't evaporate and cool you off.

You will also note in that chart that the water-carrying capacity of air goes up with temperature.

You might be thinking in terms of "live steam" or something, I don't know.

Incidentally, all the values cited are at a given standard pressure, usually 760mm of mercury, i.e., sea level air pressure.

Terry, 230RN

" 10^-3 kg/m³ " in the table heading.

Note the table is headed 10^-3 kilograms per cubic meter.  That's grams per cubic meter to the man in the street.

Edited for housekeeping, especially WRT the superscripting.

[Perd Hapley]

I'm not exactly certain that 118 air temp and 98% relative humidity is possible.... The hotter the air gets the less capable it is of carrying moisture...

If it were possible, it would give a relative heat index, or "feels like" temp in excess of 300 deg F if I'm calculating it correctly.

I believe that combination is known as "Fort Polk."

[230RN]

I think I figured out what Mike Irwin was thinking.

Looking at the 1 gram of water at -4°F (100% RH) that a volume of air can possibly hold, if we raise the temperature to, say, 32°F, that volume of air can now hold more water vapor, indeed a little over 4 grams.

This makes the new relative humidity less than 25%.... (1 gram ÷ 4 grams) X 100 = 25% RH.

The absolute amount of water vapor in that self-same volume of air hasn't changed, but the arithmetic does when you raise the temperature.

That may be the root of why Mike thought that air can hold less water vapor at higher temperatures...  Mike?

Terry

[K Frame]

I've got to think about this for awhile, because I'm digging WAY back into science classes that happened decades ago...

[230RN]

It ain't easy.  It took a while to figure it out, what with juggling multiple variables.

[K Frame]

I figured it out...



IT'S *expletive deleted*ing HOT!

Sent from my SCH-I545 using Tapatalk

[230RN]

Yes, the rate of warm water molecules jumping out of your sweat is reduced as the humidity goes up, limiting its cooling effect.

[K Frame]

Yes, the rate of warm water molecules jumping out of your sweat is reduced as the humidity goes up, limiting its cooling effect.

Which is the entire core of the relative heat index, I believe... the decrease in evaparative cooling capability...

I know what I'm trying to say regarding my statement below, but I just can't explain it. When I try to think about it, it gets roiled up in things I'm half remembering from high school science class, college, etc.

[Ben]

Aaaaaand... I apparently jinxed myself starting this thread. The AC just started blowing room temp air. The weather forecast is for a potentially record breaking heatwave:

SAT: 104
SUN: 109
MON: 110
TUE: 110
WED: 109
THU: 104
FRI: 99

Which means my AC guy is going to be swamped all week, and tomorrow is Sat. I likely won't see him till midweek next week. 

Not all may be lost. I did try a trick he told me about when he couldn't make it to one of my rentals in the past fast enough for a whining tenant, which is to kill the breaker to the AC, wait 10 minutes and reset and restart. Doing that got cold air to blow out again at 61deg by my IR thermometer. Of course it's 2100 right now and only 83 outside. Not sure what I'll be getting when it's 110. I forgot what part(s) that usually indicates is failing, but when that trick worked at the rental unit, it was like a $1400 repair.

I'm keeping my fingers crossed that this workaround will work over the weekend. Otherwise I'm thinking of throwing a bag in the truck and heading up to the Oregon coast for the week, where the high is going to be in the high 60s. 

[Scout26]

Or you could head over to Fistful's.  Or his friend the Catlady....

[Ben]

Or his friend the Catlady....

https://www.youtube.com/watch?v=h8MyoYZvgjk

[KD5NRH]

Which means my AC guy is going to be swamped all week, and tomorrow is Sat. I likely won't see him till midweek next week.

Cheapest window unit you can find in the smallest room you can manage to sleep and use a laptop in.  Divide a room with blankets if necessary to make a smaller space.  You'd be amazed how cold a small unit can keep a reasonably well insulated ~80sf bug-in room.

A project I've considered for trimming the power bills even more is to build one of the coroplast shelters from http://www.elkinsdiy.com/stationary-shelters/homeless-emergency-shelter/
Indoors, with an inlet vent to heat and cool it from a window unit and a small space heater, it essentially reduces sleeping space to the minimum you can get away with keeping comfy.  Since that's more than half the time a typical full-time worker spends at home, it could make a big dent in the bills, especially for an older home where insulating properly is a huge expense. 
Could also be an effective and cheap way to segregate sleeping space for several people in a relatively small room, so there's a way to make bunkhouses a bit less distasteful.

[Jim147]

Calling for a heat index of 110 today should be a nice movie day

[230RN]

Aaaaaand... I apparently jinxed myself starting this thread. The AC just started blowing room temp air. The weather forecast is for a potentially record breaking heatwave:

SAT: 104
SUN: 109
MON: 110
TUE: 110
WED: 109
THU: 104
FRI: 99

Which means my AC guy is going to be swamped all week, and tomorrow is Sat. I likely won't see him till midweek next week.  

Not all may be lost. I did try a trick he told me about when he couldn't make it to one of my rentals in the past fast enough for a whining tenant, which is to kill the breaker to the AC, wait 10 minutes and reset and restart. Doing that got cold air to blow out again at 61deg by my IR thermometer. Of course it's 2100 right now and only 83 outside. Not sure what I'll be getting when it's 110. I forgot what part(s) that usually indicates is failing, but when that trick worked at the rental unit, it was like a $1400 repair.

I'm keeping my fingers crossed that this workaround will work over the weekend. Otherwise I'm thinking of throwing a bag in the truck and heading up to the Oregon coast for the week, where the high is going to be in the high 60s.  

The way I understand it, that happens sometimes in brownouts and other low voltage situations... like another motor starting up simultaneously.

The compressor may be trying to start up with a pressure load on the output (condenser) side, and can't.  So it keeps trying until its thermal protection cuts out.

Unplugging it or yanking the breaker for ten minutes (or more) allows both the pressure to equalize (or the compressed refrigerant to condense) , thereby making startup easier, as well as letting the thermal cutout cool off and re-establish power to the compressor.

In the meantime, since the blower fan is not usually interconnected to the compressor power circuits, it keeps turning anyhow, blowing the warm air in the room around.

I'm no HVAC guru, but that's how the building A/C guy told me it works when I had that problem with the A/C in my rather old apartment building.

The same kind of thing can happen with refrigerators.

A year later, I had them install a brand new A/C anyhow.

Terry

[Ben]

The way I understand it, that happens sometimes in brownouts and other low voltage situations... like another motor starting up simultaneously.

You know, until you mentioned it I had forgotten the issue at my rental happened right after a blackout (where I am) and when my tenant called she described a brownout. Then today, I either experienced a brownout or surge, not sure which, just heard my UPS units all go wacky, and the AC made a strange noise and was back to room temp air. Off and on again brought cold air back. It could very well be that with this ridiculous heatwave the grid is being taxed. I'm still gonna have the AC guy come check things out just to make sure all is okay.

[230RN]

Quote from: 230RN on Today at 07:25:27 PM

The way I understand it, that happens sometimes in brownouts and other low voltage situations... like another motor starting up simultaneously

You know, until you mentioned it I had forgotten the issue at my rental happened right after a blackout (where I am) and when my tenant called she described a brownout. Then today, I either experienced a brownout or surge, not sure which, just heard my UPS units all go wacky, and the AC made a strange noise and was back to room temp air. Off and on again brought cold air back. It could very well be that with this ridiculous heatwave the grid is being taxed. I'm still gonna have the AC guy come check things out just to make sure all is okay.

My work here is done.

I hasten to point out that the guy who 'splained all that to me worked directly for the apartment management service, on an hourly wage, for all kinds of building maintenance stuff.

We sat around my place yakking for an hour "making sure it was working" and my impression was he was glad to show off his specialized knowledge to someone who could understand it.  And of course, he could report to management that he had fixed it, and saved them the cost of a new replacement unit.

Good deal all around.

Terry, 230RN