Heat pump water heating

[mlparham]

I had a heat pump assisted cold water heating system today and I am so confused. There are two heat pumps, one for each level of the home. The water lines for the cold water heating system runs to one heat pump but the wiring from the cold water heating control panel runs to the heat pump that does not have any water piping.

My gut feel is that this is not right?

[Marc]

Are you saying that domestic hot water is supplied by a heat pump?

Marc

[mlparham]

Are you saying that domestic hot water is supplied by a heat pump?

Marc

There is a 50 gallon electric cold water heater that is supplemented by a heat pump.

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[Marc]

Strange configuration. Might be some HVAC tech's wild attempt at backyard engineering or maybe I just haven't seen it yet. As far as I can discern from the photos, the refrigeration circuits of the two outdoor units are linked together, then a single set of refrigeration lines links the duo to the indoor heat exchanger which supplies supplemental heat to the domestic hot water supply.

If you have the brand and model numbers, I'd like to check it out but it's possible it's connected the way it's supposed to.

Marc

[David Meiland]

The water lines for the cold water heating system runs to one heat pump

Are you saying that water lines ran to an outdoor unit? Or that they ran to a heat exchanger (presumably that box on the wall in your indoor photo) fed by one outdoor unit?

In your photo of the dead grass between the two outdoor units, there appears to be some sort of tubing connecting the two.

The stuff looks old enough that I suspect a home-made design, but could be completely wrong.

[Marc]

The outdoor units are 2005 or earlier. Label in photo indicates 10 SEER and the feds started requiring 13 SEER in Jan, 2006 - as per Wikipedia.

Marc

[mlparham]

The water lines for the cold water heating system runs to one heat pump

Are you saying that water lines ran to an outdoor unit? Or that they ran to a heat exchanger (presumably that box on the wall in your indoor photo) fed by one outdoor unit?

In your photo of the dead grass between the two outdoor units, there appears to be some sort of tubing connecting the two.

The stuff looks old enough that I suspect a home-made design, but could be completely wrong.

In the first picture you can see the water lines on the wall running to the left unit. On the ground between the unit are the refrigerant lines. The heat pumps are not interconnected. At the right unit you can see conduit runs. One is the power the other comes from the indoor control panel.

[Marc]

Tell me about the refrigerant line sets exiting the two outdoor units in photo 016. Where do they go, as evinced in the photo?

Marc

[Mark P]

I don't know if this will be helpful information or not since I have never seen or heard of an air source heat pump augmenting a domestic water heater, but here it is none the less.

In a geothermal system there is usually something called a desuperheater. It takes the heat that is being removed from the house (in the summer) and transfers it into your hot water tank. If there are two water heaters connected in series then only the first water heater is piped to the coLd-water inlet. The 2nd water heater receives preheated water from the 1st.

[David Meiland]

I really can't tell what's going on there, but my questions are, if one heat pump is somehow providing heat for water AND heat/cooling for air, how are the two coils piped from the outdoor unit? Are there controls and valves that operate one of the two zones at a time, do they both operate together, or what? Or, is it simply that water is piped through the outdoor unit in a way that allows it to harvest some heat from the unit when in cooling mode? Seems like that too would require valves/controls so that you're not sending your incoming water outside to get colder during the winter.

Hell, I don't know, but someone else will.

[Marc]

During the summer season, the compressor discharge is routed to a loop that's immersed in the hot water heater. Whatever excess heat is left after that is then dissipated by the condenser coil. It's a good idea that I first observed over 30 years ago but for some reason it never really caught on with the public. Back then, these were termed by the manufacturer - Rheem - as 'Heat Recovery' units.

I'm not sure what's going on in Morgan's case.

Marc

[mlparham]

Tell me about the refrigerant line sets exiting the two outdoor units in photo 016. Where do they go, as evinced in the photo?

Marc

A refrigerant line set from each compressor enters the house under the drain lines between the compressors. Each line set serves its own air handler.

The compressors are not interconnected.

[mlparham]

During the summer season, the compressor discharge is routed to a loop that's immersed in the hot water heater. Whatever excess heat is left after that is then dissipated by the condenser coil. It's a good idea that I first observed over 30 years ago but for some reason it never really caught on with the public.

I'm not sure what's going on in Morgan's case.

Marc

That is the way that this system works except it uses a heat exchanger. What has me puzzled is the wiring. I would expect the wiring from the control panel to be connected to the unit that is being used to heat the water. That way when the heat pump comes on it triggers the pump to circulate the water (or whatever liquid is being used).

Look at this way. Ignore the refrigerant line sets, they are fine. The left unit is being used to heat the water but the wiring from the control panel is connected to the right unit. It seems to me that water is being circulated only when the right unit is running. It should be circulating only when the left unit is running. I think that the control panel wiring should be connected to the left unit.

[Marc]

I see what you're getting at and with just the photos, it makes sense but I wouldn't be writing up something like that unless I could confirm it by turning a condenser on and feeling the 'recovery' lines for heat. Then I'd be all too happy to add this finding to my report with mention that it may have been this way since installed over 8 years ago.

Marc