Fun With The Heat Pump Water Heater

In July I installed a hybrid heatpump/electric water heater and shut down the coal boiler for the Summer. The results have been very good and electric use and cost have been minimal compared to my old electric water heater and using coal. After installation I accidently left the valves open to the indirect water heater and to my surprise, it thermosyphoned the indirect up to operating temp. Being that the indirect is just a big heat exchanger between boiler water and domestic water I wondered if it would work backwards???

The first attempt I just let the natural thermosyphon heat the boiler by opening the zone valve in the indirect water heater and ruining the circulator pump. That didn't work to good.

Last night I connected the drain of the indirect to the drain of the heat pump water heater and helped it with a Taco 007 pump. That worked great!
Soon we were sending 130 degree water from the indirect to the boiler. The boiler temp with one radiator in the Livingroom running stayed between 125 and 130. We did cheat a little for this test. I set the water heater to "High Demand" mode instead of "Heat Pump" mode. I also raised the set point to 135 from 115. Now that we know this works, we can try it in different modes and lower set points to make it use a little less electricity.

Roll The Video!


-Don

Hook up your Dr-Kill-O-Watt and get measured kwh vs. guessing. Post results in 1-3 mo.

New toys .. all like new toys...until they break, then we blame the wifey

It’s good to have options. Another great video to. Thanks, Scott

Glad you enjoyed it!

It's shut down now. Upper 70's and even 80's forecast for this week so no heat needed. Now that I know it works I'll do a more permanent installation of the pump and insulate the pipes. That way when I need it I can just turn a few valves and turn the pump on. -Don

Next thing ? A home made sauna !

StokerDon wrote: ↑

Fri. Sep. 29, 2023 1:04 pm

Soon we were sending 130 degree water from the indirect to the boiler.

The BTU's in your house are gonna be so dizzy and confused ...

BunkerdCaddis wrote: ↑

Sun. Oct. 01, 2023 1:23 pm

The BTU's in your house are gonna be so dizzy and confused ...

It's nice to have yet one more place to extract home heating BTUs!

-Don

Well, I never did fire up the Van Wert. I decided to push on with the heat pump water heater. We're going to try to make it through October. So far it's been keeping up with no problem. That's kind of surprising.
I lied, I said I was going to make a permanent install and insulate the pipes. The only thing I managed to do was replace the leaking seal inside the 007 pump. I didn't even buy a new seal. I stole it out of another pump I had laying on the shelf, I'm so ashamed.

Anyway, here are the monthly electric bill results. We fired this Baby up on July 4th. Figured out that we could heat the house with it at the end of September. If the October bill comes in super high, then we know this ain't a good idea.

September - 561kWh used, $110.97
August - 793kWh used, $151.32
July - 1,311kWh used, $250.33
June (coal HW) - 1,026kWh used, $198.64

-Don

How cold has your downstairs dropped to?

hotblast1357 wrote: ↑

Sat. Oct. 21, 2023 8:04 pm

How cold has your downstairs dropped to?

The boiler, piping and the indirect give off a little heat so the basement temp has been 68 to 72 degrees.

-Don

But the heat pump is extracting that heat out of the basement correct? So you haven’t seen a steady drop in temp down there?

hotblast1357 wrote: ↑

Sun. Oct. 22, 2023 4:50 pm

But the heat pump is extracting that heat out of the basement correct? So you haven’t seen a steady drop in temp down there?

No, I haven't. If anything it has kept the basement a little warmer than it would be with no heat at all. I'm pretty sure that means I should insulate everything better.

-Don

StokerDon wrote: ↑

Sat. Oct. 28, 2023 9:27 am

No, I haven't. If anything it has kept the basement a little warmer than it would be with no heat at all. I'm pretty sure that means I should insulate everything better.
-Don

Perpetual heat?? You better patent whatever goes on in that basement... and don't let big energy find out...

Unless I’m missing something.. this makes no sense at all. Your heat pump water heater is removing heat from the basement to heat the hot water, that’s just what it does, are you saying that by sending that heated water in through the boiler and back out to the heating system in the basement it is actually warming it up?

You are using the electric heating elements though right? So are you not running in full heat pump mode?

hotblast1357 wrote: ↑

Sat. Oct. 28, 2023 11:48 am

Unless I’m missing something.. this makes no sense at all.

Well I don't think it's magic and I don't know a whole lot about heat pumps but I'm pretty sure they operate using temperature and pressure differences of Freon. I take that to mean that the colder the basement gets the less efficient it is. But it will still work even if the basement get cold.

I have been running it in Heat Pump mode about half the time. This week since it is colder, I ran it in High Demand mode which I'm sure runs the electric elements. This works better probably because of the low BTU output of the water heater and the BTU loss by using a heat exchanger.

October bill is in!

October - 1376kWh used, $253.83
September - 561kWh used, $110.97
August - 793kWh used, $151.32
July - 1,311kWh used, $250.33
June (coal HW) - 1,026kWh used, $198.64

This is about $160 more than a normal October so I probably saved a little coal, but not much. I'll be firing up the Van Wert in the coming week.

-Don