HPWH, learning curve

hot_rod · January 19

I’ve noticed manufacturers showing outside venting options and kits now. Possibly heaters are being installed in rooms with inadequate volume? Installers not reading the installation manuals? Also townhomes and small buildings that just are unable to provide adequate exchange air.

Years ago I remember a hp system out of Poland that had both exhaust and intake ducted outside. The unit installed in a corner with ducting out the opposite walls.

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ethicalpaul · January 19

My rheem from 2020 is set up for ducting, I'm not sure when it would be a good idea…maybe if it was in an air-conditioned space in a hot climate??

hot_rod · January 19

mainly when they are installed in closets or small mechanical spaces.

Also inadequate filters are allowing the finned HXers to plug

Both HPWH and mod cons should have generously sized intake filter options.
Another example of a bug in the system.

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Kaos · January 19

Ducting helps with sound. A length of flex even if not run anywhere will really cut down on fan and airflow noise.

As for ducting outside, that only works in above freezing climate. Anything near freezing, you need defrost and reversing valve, that sounds too complicated for a water heater.

DCContrarian · January 19

Outside venting, or just venting? In almost all climates venting a HPWH to the outside is a terrible idea. But venting to another part of the house is often a good idea.

The thing about outdoor venting is that the air you send out has to be replaced with outdoor air. So in heating season, if the outside air is colder than the exhaust air, there's an energy penalty. In cooling season there's always an energy penalty. The only time there isn't an energy penalty is when it's heating season but the outside temperature is warmer than the exhaust air, 50F or so. Which is pretty rare weather in most places.

Larry Weingarten · January 19

Gary Klein has been studying this, and the normal 700 or so cubic foot space manufacturers say is adequate really isn't most of the time. You cannot get enough heat transfer through even uninsulated walls to "feed" the heat needs of the unit. Balanced ducting or bigger spaces that aren't part of the living space are needed.

Yours, Larry

ethicalpaul · January 19

https://forum.heatinghelp.com/discussion/comment/1836089#Comment_1836089

I'm confused. Why is there an energy penalty during cooling season? Do you mean if you have it vented outside?

hot_rod · January 19

I found that dumping 43 degree air into my 800 square foot shop didn’t work so well either. Getting the cold air out where it is not detrimental,along with some noise has some value? Obviously that air needs to be replaced, so winter vs summer makes a difference.

Taking a gas or electric WH out of a small utility closet and sticking a HPWH, is doomed to fail also.

DCContrarian · January 19

https://forum.heatinghelp.com/discussion/comment/1836098#Comment_1836098

Yes, dumping it outside. If it's 85F outside and you're pumping 50F air out of the building and replacing it with outdoor air you're making the AC work harder when you could be taking some of the load off.

ethicalpaul · January 19

OK yes I get that. I think what you'd have to do is have a switchable venting that you'd change seasonally. But I'm happy with always using basement air. People definitely worry too much about this. Try one sometime and you'll see, it's quiet and don't affect the space in a noticeable way.

Kaos · January 19

Typical average DHW load for a family is 2500BTU, not something that I would worry about. When the unit is running, that 45F does feel cool but the place quickly equalizes as soon as the unit shuts off.

@ethicalpaul The ducting kit works very well for retrofit utility room installs. You can vent the cold air outside the room (NOT outside the building) and use a louvered door for intake.

If you want to get creative with venting, behind the fridge is a good spot (fridge puts about 1000BTU of heat into the house), so is into a conditioned crawlspace.

hot_rod · January 19

https://forum.heatinghelp.com/discussion/comment/1836113#Comment_1836113

But isn't yours sitting next to a steam boiler radiating energy to be grabbed?

ethicalpaul · January 19

https://forum.heatinghelp.com/discussion/comment/1836115#Comment_1836115

Yes, that's why I'm happy using the basement air. In the summer there is heat to grab and in the winter there is heat to grab, much of which was going to be lost to the basement walls anyway.

DCContrarian · January 19

"I think what you'd have to do is have a switchable venting that you'd change seasonally."

There's no season where venting outside is a good idea.

If anything, it would be a switchable vent for when the outside temperature is between 55F and 75F. But the benefit to doing that is so miniscule that it's not worth doing.

I harp on this because I run into a lot of people who think that HPWH need to be vented to the exterior. I don't know why they think this. Maybe because it has a vent, they think it's like a gas water heater. Or maybe there's an "expert" on YouTube spreading this idea. I don't know where it comes from but it's out there.

ethicalpaul · January 19

Just to be clear, as a HPWH owner, I agree with you completely that venting is unnecessary and not worthwhile.

But how would it not be beneficial to vent and intake outside during the hot months? at least theoretically? Especially if you didn't have a basement. Like if you lived in the south, where water heaters are in garages and sheds?

Kaos · January 19

https://forum.heatinghelp.com/discussion/comment/1836125#Comment_1836125

Because you are now loosing the free cooling to the outdoors. The COP of the unit will be slightly higher but it doesn't offset the overall energy loss.

hot_rod · January 19

https://forum.heatinghelp.com/discussion/comment/1836127#Comment_1836127

”free” cooling, where do I sign up?

DCContrarian · January 19

”free” cooling, where do I sign up?

It's included when you join the HPWH cult.

ethicalpaul · January 19

I don’t really understand the mocking or vitriol against this tech and us “cult members”. It does cool as a free side effect, just like refrigerators warm as a free side effect.

I traded an inefficient gas appliance that constantly lost heat out the flue (while also causing more outside air infiltration), for a quiet, very efficient unit that costs dramatically less to operate.

45 kWh per month

LRCCBJ · January 19

@ethicalpaul
I don’t really understand the mocking or vitriol against this tech and us “cult members”.

I do.

The general population now has an aversion to the facts. Their emotions rule the day and they have "alternate facts". Just look at the response by the general population to Dr., Anthony Fauci, a worldwide respected immunologist. The "general population" did everything they possibly could to discredit him………..facts irrelevant.

Hot_water_fan · January 19

Here I am blissfully using an electric resistance tank 😊

ethicalpaul · January 19

nothing wrong with that! Way better than using a boiler

PC7060 · January 19

The folks I know that are unhappy with heat pump water heaters have the ones that failed. All were replaced under warranty, but was a nuisance.

One happy HPWH owner discharges the dehumidified exhaust air into his gun safe.

DCContrarian · January 19

I don’t really understand the mocking or vitriol against this tech and us “cult members”.

I hope you appreciate that I was being glib with my "cult" comment. I am a full-fledged member of the cult and always on the lookout to lure in unsuspecting new members.

pecmsg · January 19

Like all Tecnologies there is a learning curve. There were high COP CO2 systems unfortunately less than 1% can work on them.

R-290 and 600 are promising but explosive.

Like air-to-air heat pumps the technology will advance it still needs more real-world use.

TAG · January 19

My water heaters in SC are in an attic … too hot for a heat pump in the summer.

I have one of those Rheems there now … it was basically free. I'm trying to figure out the best way to set it up. In the winter the attic is would be fine.

Mine are in tandem and that's another problem because the HP units don't want hot water flowing into them

ethicalpaul · January 19

https://forum.heatinghelp.com/discussion/comment/1836187#Comment_1836187

Thanks for the clarification haha I can't keep track of who owns what equipment in order to determine jokes 😅

ethicalpaul · January 19

My water heaters in SC are in an attic … too hot for a heat pump in the summer.

Do they advise against it? It's too hot for a heat pump that is trying to cool perhaps, but this one is trying to heat.

TAG · January 19

https://forum.heatinghelp.com/discussion/comment/1836296#Comment_1836296

Yes — There was a max heat environment for the units .. correct.

I forget were I read about the incoming water temp

ethicalpaul · January 19

Thanks. I see the Rheem wants a max ambient temp of 145. Your attic gets pretty hot I guess!

DCContrarian · January 19

If your attic is over 145F you could just put a tank up there, no need for heating it.

HPWH, learning curve

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