Heat Pump Water Heater Yes or No?

sixstars

Hello everyone. I’ve got an opportunity to receive a Heat Pump water heater for no money through a current state sponsored program. I’m trying to determine if this is a good idea for my home/current set up/needs.

A bit more information:

-I’m located in the Northeast.
-I currently have an oil fired boiler that heats our home with baseboards.
-The same boiler supplies our hot water.
-The boiler does not have any type of a holding tank.
-The boiler is located in a combination basement/garage and is on the “garage” side of the basement about a car length from the garage doors.
-Temperatures can drop to the high 30’s or low 40’s in the winter.
-I’m unaware of the brand or capacity of the heat pump water heater being offered.
-My boiler is about 3 years old.
-Currently two occupants in our home
-Water is supplied by a well which has higher than preferred levels of iron, manganese, hydrogen sulfide, and is slightly acidic.
-Currently have a neutralizer filter to increase PH, iron filter to address iron, manganese, and hydrogen sulfide, and softener to reduce hardness from neutralizer filter.
-As long as I’m current on all water filtration maintenance, water quality is good.

I’ve tried to determine if having this heat pump water heater installed will be a benefit and I’m having a hard time doing so.

My concerns are:

-Will this save us money?
-Will the lifespan of the unit be a concern considering my water quality?
-Will the colder temperatures in its installed location reduce the heat pump’s efficiency to the point where it doesn’t make sense to have it installed?

I haven’t determined how many gallons of oil we average per year or looked at what our current electric rates are.

At this point I’m trying to figure out if in general this is a good idea or not.

Thank you.

EBEBRATT-Ed

During the heating season (7 months) your running the boiler anyhow. Depending on how much hot water you use i wouldn't think you would save much.

The verdict is still out on the HPWH as far as I am concerned. Expensive, a lot of parts to fail. They will save money however, how much is up in the air.

I suppose if you can get it for free what have you got to loose? You can always go back to the boiler

psb75

Get the free HP water heater. Use it for 5-6 months of the year (the warmest ones) and then switch back to the boiler HW in the other cold months of the year. You will save money on operating costs for making domestic hot water.

JakeCK

Yes. Being free makes it even better.

I have one my self. Installed it in October. 

I agree with using it during the warmer months and using the boiler in the heating season for dhw. The heat from the hpwh is coming from that anyways.

yesimon

Yes this will unequivocally save you money year-round in the northeast if HPWH is free and you can get it installed cheaply. The efficiency will be higher than oil because your garage/basement is unlikely to ever fall below 40F.
You can replace anode rods yourself if you're worried about water quality. It's a more complex device that has more components that can fail. They are also typically quite large (50 gallons+).

hot_rod

If you’d you run it in heat pump mode, recovery is very slow. My 80 gallon takes 12 hours to go from 55- 120F with no load

JakeCK

hot_rod said:

If you’d you run it in heat pump mode, recovery is very slow. My 80 gallon takes 12 hours to go from 55- 120F with no load

I still don't understand why there is such a difference between your HP and mine. I've ran mine cool on more than one occasion during a shower and it has always been able to recover in a few hours on hp mode. Sure it's only 50 gallons but it doesn't seem like a doubling of water volume would cause a 6x increase in recovery time? And I heat mine to 140f.

The schedule I have set is 8am heat pump 140f, 4:30pm heat pump 110f, 9pm off. Today was a total run time of 5 hours, 3.5 for the morning recovery, and afternoon recovery after a couple showers that was 1.5 hours. 2.3kwh total energy used for the day.

sixstars

Thank you everyone for your replies.

A few more questions based off of your feedback.

-If I were to use the hpwh only in the non-heating months I’m assuming I’d have to have it plumbed so I can switch back and forth between the two. Would the plumbing simply be a bypass? Water inlet and outlet on both the boiler and the hpwh would need a shut off valve?
-Is there a concern with recovery time with a hpwh? As in could you potentially run out of hot water during a shower? I have to admit that at times I may take a bit too long of a hot shower.
-Could someone please explain a schedule? Right now my assumption is that my boiler fires whenever the water temperature in the small internal “tank” reaches the low set point? With a hpwh it sounds like you can determine different temperatures for it to maintain throughout the day based on your homes typical usage or demand for hot water?


The only issue we’re currently experiencing with our current set-up is what I would call response time or a delay. Depending on the conditions, the water temperatures start to drop and it seems like the boiler is not responding quickly enough to the water temperatures dropping before it fires up again. After a few minutes of lower temperatures the boiler finally kicks on and it’s ok again. It never did this with our previous boiler so my assumption is that it needs to be adjusted. Maybe a low set point? The water temperatures when the boiler is running is not the issue.

I think I’d like to find out the brand, model, and capacity of hpwh and share that information as well.

Thank you again everyone!

EBEBRATT-Ed

The other problem not mentioned is the electric utility and there rebates and a free water heater.

I can assure everyone that under those conditions they would not allow this to be installed in conjunction with hot water produced by the boiler. When I mentioned in my first post "back to the boiler" I wasn't intending for them to be hooked up at the same time

sixstars

EBEBRATT-Ed said:

The other problem not mentioned is the electric utility and there rebates and a free water heater.

I can assure everyone that under those conditions they would not allow this to be installed in conjunction with hot water produced by the boiler. When I mentioned in my first post "back to the boiler" I wasn't intending for them to be hooked up at the same time

I thought about that as well. If I had them hooked up at the same time I’d most likely have to do it “after” the initial installation.

hot_rod

JakeCK said:

hot_rod said:

If you’d you run it in heat pump mode, recovery is very slow. My 80 gallon takes 12 hours to go from 55- 120F with no load

I still don't understand why there is such a difference between your HP and mine. I've ran mine cool on more than one occasion during a shower and it has always been able to recover in a few hours on hp mode. Sure it's only 50 gallons but it doesn't seem like a doubling of water volume would cause a 6x increase in recovery time? And I heat mine to 140f.

The schedule I have set is 8am heat pump 140f, 4:30pm heat pump 110f, 9pm off. Today was a total run time of 5 hours, 3.5 for the morning recovery, and afternoon recovery after a couple showers that was 1.5 hours. 2.3kwh total energy used for the day.

What is the temperature surrounding your tank? Mine was in the shop, door open 48F ambient. The tank was filled with 55F water. Is yours in a cold space, does the entire tank drop to 55F?  I was right next to it for 8 hours any it was around 90F when I left it after 8 hours.
Could be different compressors, how many amps does your pull when running?
Ive heard some models do kick in resistence if the recovery is taking too long, that’s why I kept the Amprobe clamped on mine to make sure it was HP only.

JakeCK

@hot_rod The ambient is whatever my basement is so maybe low 60's? It is noticeably cooler with the HP now. I have a 240v 30 amp version. I've read that my rheem tank will over ride settings in certain circumstances. I have not yet experienced that. My enphase setup for solar monitors my electric usage and I can see if the elements kick in. There isn't much in the house besides the stove that can draw more. It has only used the elements the few times I turned them on myself by setting it to high demand and they ran for maybe 15-20 minutes before switching back off. But I did that in anticipation of demand not the few times I ran it cool on accident. And I'll admit I did not run it down to 55f. Maybe the low 80s upper 70s.

JakeCK

sixstars said:

Thank you everyone for your replies. A few more questions based off of your feedback. -If I were to use the hpwh only in the non-heating months I’m assuming I’d have to have it plumbed so I can switch back and forth between the two. Would the plumbing simply be a bypass? Water inlet and outlet on both the boiler and the hpwh would need a shut off valve? -Is there a concern with recovery time with a hpwh? As in could you potentially run out of hot water during a shower? I have to admit that at times I may take a bit too long of a hot shower. -Could someone please explain a schedule? Right now my assumption is that my boiler fires whenever the water temperature in the small internal “tank” reaches the low set point? With a hpwh it sounds like you can determine different temperatures for it to maintain throughout the day based on your homes typical usage or demand for hot water? The only issue we’re currently experiencing with our current set-up is what I would call response time or a delay. Depending on the conditions, the water temperatures start to drop and it seems like the boiler is not responding quickly enough to the water temperatures dropping before it fires up again. After a few minutes of lower temperatures the boiler finally kicks on and it’s ok again. It never did this with our previous boiler so my assumption is that it needs to be adjusted. Maybe a low set point? The water temperatures when the boiler is running is not the issue. I think I’d like to find out the brand, model, and capacity of hpwh and share that information as well. Thank you again everyone!

There are several ways you could plumb this to work with the boiler. And yea the rebate would probably make this difficult too. Discounting the rebate issue, there is one way this could be plumbed to solve your current problem of getting that lag in response. Have it in series where the HP feeds the boiler preheated water or the boiler feeds the HP. And in the summer just shut down the boiler. This would have the advantage of recovering waste heat from the boiler as well during the winter. You would want a summer bypass so you are not heating or cooling the boiler during the summer.

There can be concerns for recovery. Normally the few times I've ran my cool(both during a shower) it was shortly after the wife ran laundry and had showered herself. And I've been the only one to experience that so far. I only have a 50 gallon, wish I had the 80 but there really wasn't space. Bigger is better. 

All of the HPWH's I've seen have been wifi connected models. This allows you to control and program schedules on your phone. I have a PV system on my roof so I have the tank programmed to tank advantage of solar production. Under normal circumstances the advantage is limited unless you have time of use based electric rates. 

I can't speak to your boiler settings.

Full disclosure I'm not an expert, just a homeowner. This is my personal experience with it.

ethicalpaul

Yes