Heat pump water heater ducting question?

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begreen

Mooderator
Staff member
Nov 18, 2005
96,219
South Puget Sound, WA
Do you think that below you on a different floor is the same thing as a closet in the same room or on the other side of an interior wall? Hopefully the newest models are quieter, quieter is better.
Put some micore or roxul in the closet wall as a sound barrier if you are light sleepers. At 49db we are talking pretty low noise.
 
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brenndatomu

Minister of Fire
Aug 21, 2013
7,505
NE Ohio
Put some micore or roxul in the closet wall as a sound barrier if you are light sleepers. At 49db we are talking pretty low noise.
Yeah I think I have heard ceiling fans that make more noise than that!
We run a small desk fan in the bedroom to drown out various minor noises...I used to need it dead quiet, but have gotten used to the fan, and its hard to sleep without it now.
 
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EbS-P

Minister of Fire
Jan 19, 2019
3,511
SE North Carolina
Looks like mine is 55db. A bit louder. It will be noticeable but probably no more than the exhaust fan down there now.
 

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brenndatomu

Minister of Fire
Aug 21, 2013
7,505
NE Ohio
Mine says it is running on low all the time...guess I haven't heard high yet? Might be a big difference in noise?
Not sure how you would make it run on high since the dishwasher was run, and 3 baths/showers were taken all in about 2-3 hours...I would think that would do it if anything would...upper/lower tank temps were both way down. I am set to "heat pump only" mode though...not hybrid. Wanted to try it out that way first...so far so good.
 

MacinJosh

Feeling the Heat
Mar 4, 2015
310
Crestwood, KY
Mine says it is running on low all the time...guess I haven't heard high yet? Might be a big difference in noise?
Not sure how you would make it run on high since the dishwasher was run, and 3 baths/showers were taken all in about 2-3 hours...I would think that would do it if anything would...upper/lower tank temps were both way down. I am set to "heat pump only" mode though...not hybrid. Wanted to try it out that way first...so far so good.

I started that way too but in the winter months the heat pump just couldn’t keep up alone. There are four of us in the house and even with 80 gallons, one element would kick on to bring it up quicker. If you are okay waiting for long recovery periods after a quick high demand, you should be ok. I want “hot” water at all times, not luke warm after a big demand.

In the summer time, it never uses anything but the HP.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,505
NE Ohio
I started that way too but in the winter months the heat pump just couldn’t keep up alone. There are four of us in the house and even with 80 gallons, one element would kick on to bring it up quicker. If you are okay waiting for long recovery periods after a quick high demand, you should be ok. I want “hot” water at all times, not luke warm after a big demand.

In the summer time, it never uses anything but the HP.
Summer/winter won't matter much here...my wood furnace is about 15' away, so truth be told, it will probably have warmer ambient air temps to work with in the winter than in the summer.
So far the water temp been very adequate even in just HP mode. My wife is the only one in the house that likes "hot" showers, so as long as she doesn't go last of the 4 of us (and that never happens) probably never be an issue at all.
 
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jetsam

Minister of Fire
Dec 12, 2015
5,337
Long Island, NY
youtu.be
Put some micore or roxul in the closet wall as a sound barrier if you are light sleepers. At 49db we are talking pretty low noise.

Homasote is an easy answer for a closet too. You can put it under drywall, or use it as drywall if you don't mind a slightly funky wall texture in the closet.

(side story: I laughed at one of their sales reps one time when he told me that stuff was waterproof. He looked at me, broke off a chunk of the stuff, threw it in a cup of water, and said, "Come back and look at it in a week."

He was right! )
 

EbS-P

Minister of Fire
Jan 19, 2019
3,511
SE North Carolina
Well following up on this two years later…. Maybe only one since I installed the ducting. The room is no longer a bedroom it’s a library with an open door way connected to the rest of the basement. Mechanical room is now closed off by louvered bifold doors.

The reason is it it completely vented indoors. With the ducting kit and 2 adjustable elbows an some flex duct, the intake draws air from above the the bifold doors from the library through an extra filter (and a bit from the suspended ceiling space). The exhaust elbow points down to the floor. This arrangement keeps the air very stratified. Hot moist air up too cold dry air down low.

The HPWH can cook the basement significantly when we use lots of hot water. Last winter it was not uncommon to have basement temps in the high 59s low 60s. We didn’t spend much time down there and I was still trying to heat 100 % with wood from upstairs. This winter has been warm and we are using the heat pump more and now we have the wood insert installed.

I am a bit concerned about condensation on the outside rear of the unit. It’s enough at times to run down the side but I never see a puddle at the bottom. This usually happens during the summer but it was warm and humid enough for it to occur yesterday. I don’t see any way to avoid it. Eventually if it runs enough it dries out.

Thinking of the absolute best way to vent would be to exhaust to the the air return we only have one). But running cold 40-50 degree air through the crawl space is asking for moisture issues I think. Any colder climate than ours it’s going to increase heating load if venting/ installed in a finished space.

It’s been a great investment and has cut the amount of time we run a Dehumidifier in half.

Evan
 
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begreen

Mooderator
Staff member
Nov 18, 2005
96,219
South Puget Sound, WA
I'm confused. I thought the HWHP would cool the space as it pulls warmth from the air to heat the water.
 

EbS-P

Minister of Fire
Jan 19, 2019
3,511
SE North Carolina
I'm confused. I thought the HWHP would cool the space as it pulls warmth from the air to heat the water.
It does. And if you are heating 80 gallons it takes a lot of heat out of the living space. So during the winter it can make it quite a bit colder down there.
 

maple1

Minister of Fire
Sep 15, 2011
10,963
Nova Scotia
It does. And if you are heating 80 gallons it takes a lot of heat out of the living space. So during the winter it can make it quite a bit colder down there.
Maybe when you said cook the basement, you meant cool?
 

Max W

Member
Feb 4, 2021
137
Maine
Must mean cool. Looks like the install worked out well overall. We also appreciate the dehumidifying we get from our HWHP In the basement. I’m far from a pro but I managed to install ours. I’m guessing your HP must have has condensate drain and the backside condensate is separate from that?
 

EbS-P

Minister of Fire
Jan 19, 2019
3,511
SE North Carolina
Must mean cool. Looks like the install worked out well overall. We also appreciate the dehumidifying we get from our HWHP In the basement. I’m far from a pro but I managed to install ours. I’m guessing your HP must have has condensate drain and the backside condensate is separate from that?
Yet you are correct I meant cool. And yes separate from the drain.

7FFB5286-8F45-45A3-A26F-06E415A33601.jpeg
 

Max W

Member
Feb 4, 2021
137
Maine
It looks like the plastic nipple is the condensate drain and if it is it should have a drain tube. I was lucky to have a cellar gravity drain to run the clear plastic line pictured to.

48D6CD8B-0CD4-4B8C-AFBA-AD329DBCD9E5.jpeg
 

EbS-P

Minister of Fire
Jan 19, 2019
3,511
SE North Carolina
It looks like the plastic nipple is the condensate drain and if it is it should have a drain tube. I was lucky to have a cellar gravity drain to run the clear plastic line pictured to.

View attachment 289083
My understanding is both are draining the condensation. The small one is there if the the big one gets plugged the water has somewhere intentional to go.
 
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Max W

Member
Feb 4, 2021
137
Maine
My understanding is both are draining the condensation. The small one is there if the the big one gets plugged the water has somewhere intentional to go.
Clearly then that’s not the cause of the moisture. I wonder that there is a cold area where the moisture condenses on the metal jacket and if a thin layer of foam insulation, like what’s used in a toilet tank, over that would prevent the condensation. It does sound like it’s evaporating. I thought about ducting the air intake on ours from outside and leaving the exhaust as is in the summer for some gain but that didn’t seem worth the initial effort and the twice a year changing over. I guess that would add additional moisture for the system to drain off as well. My unheated cellar drops as low as 45 or 50 at the coldest times. I pretty much keep it electric mode at 50 or below.
 
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EbS-P

Minister of Fire
Jan 19, 2019
3,511
SE North Carolina
Clearly then that’s not the cause of the moisture. I wonder that there is a cold area where the moisture condenses on the metal jacket and if a thin layer of foam insulation, like what’s used in a toilet tank, over that would prevent the condensation. It does sound like it’s evaporating. I thought about ducting the air intake on ours from outside and leaving the exhaust as is in the summer for some gain but that didn’t seem worth the initial effort and the twice a year changing over. I guess that would add additional moisture for the system to drain off as well. My unheated cellar drops as low as 45 or 50 at the coldest times. I pretty much keep it electric mode at 50 or below.
Intake from the outside negates any dehumidification during the summer for us. I agree it’s not worth the hassle of swapping. I would like to the how the efficiency changes with temp on these units.
 

jetsam

Minister of Fire
Dec 12, 2015
5,337
Long Island, NY
youtu.be
The biggest part of efficiency is how ya use it. Mine has a resistive-only mode, a heat pump only mode, and a mode where it can choose between the two based on demand.

(Fun fact: If you put it in heat pump only mode, the app constantly displays a large banner warning you that you need to put it in automatic mode for best efficiency.... )
 

EbS-P

Minister of Fire
Jan 19, 2019
3,511
SE North Carolina
The biggest part of efficiency is how ya use it. Mine has a resistive-only mode, a heat pump only mode, and a mode where it can choose between the two based on demand.

(Fun fact: If you put it in heat pump only mode, the app constantly displays a large banner warning you that you need to put it in automatic mode for best efficiency.... )
I run mine in heatpump only. Is there an explanation why automatic mode would be more efficient? I can’t think of one. I can see users complaining that they ran out of hot water sooner because they are no longer using the top element. We ran with an old 40 gallon unit for so long that a cold shower was common and it was a rule that mom always got the first bath and the dishwasher always was set with the delay function.
 

mellow

Resident Stove Connoisseur
Jan 19, 2008
5,433
Salisbury, MD
I run mine in hybrid mode and still saw enough of an electrical usage drop vs our old WH that I have just left it that way. Mine is in an unheated insulated attached garage so I like to make sure it its warm with 4 people using it.

My WH used $1.15 in electric yesterday and it was 17 degrees out, usually runs about half that. I am even OK with $1/day for as much as we use hot water including the dish waster.
 
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jetsam

Minister of Fire
Dec 12, 2015
5,337
Long Island, NY
youtu.be
I run mine in heatpump only. Is there an explanation why automatic mode would be more efficient? I can’t think of one.
I puzzled over that for a while. I only came up with a couple ideas...

1) As intake air temperature decreases, there is a point where resistive is more efficient. On the other hand, presumably that point is around freezing, and hopefully that doesn't happen much in your house? Maybe it pertains to bad installs where the unit is shut in a closet with insufficient airflow?

2) Every other part of the app is riddled with bugs; why would it be a surprise that this warning is attached to the wrong mode?
 
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begreen

Mooderator
Staff member
Nov 18, 2005
96,219
South Puget Sound, WA
The HPWH can cook the basement significantly when we use lots of hot water. Last winter it was not uncommon to have basement temps in the high 59s low 60s
Sounds like there is a typo here. Did you mean cools, not cooks?
 

stoveliker

Minister of Fire
Nov 17, 2019
6,165
Long Island NY
Yes was noted before.