Heat Pump Water Heater used with indirect tank

The Tank Heat Pump Water Heater used with indirect tank

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  • #19748
    bawilson
    Participant

    Thanks for all the great reading in the forum. What an eye opener!

    I just purchased a GE GeoSpring HPWH and want to connect it inline with my existing system. I currently have an indirect system using an Amtrol Boilermate. Based on the estimated hot water usage and timing, I think the 50-Gallon GE will not keep up without bumping up the mode (less efficient).

    I am wondering if there is a preferred arrangement to place the GE and use my existing Boilermate as a storage tank? I would like to shut my boiler off for the summer months if possible. I have considered simply putting the GE in line prior to the Boilermate with the hot supply from the GE going to the cold inlet of the Boilermate. This would appear to work as long as we are using hot water on a fairly frequent basis.

    Is there a better option with a mixing valve or other connections/valving? Any help, descriptions, or experiences are greatly appreciated.

    #19749
    Larry Weingarten
    Participant

    Hello: This sketch shows how I like to valve tanks in series. Shown is the way to get the most gallons, but either tank can be bypassed also. Ball valves are good. 😉

    Yours, Larry

    Attached files

    #19750
    bawilson
    Participant

    Thanks, Larry. That was the configuration I had in mind.

    I plan to start out with the GE unit set at 130F as a test and see how long the Boilermate will hold that temperature without any use. My wife takes a bath around 8 p.m. and the next heavy water use is usually my shower around 5 a.m. I’m curious what the temp in the Boilermate will be after 9 hours and if I would be starting out with a lukewarm shower? If that is the case, I think the options would be to up the temperature to allow for a longer period of cooling or to somehow mix the two. Does this make sense or am I off base here?

    #19752
    Larry Weingarten
    Participant

    Hello; I don’t know the fuel source for the Boilermate, or its’ cost, but thinking of winter/summer modes, how about in winter, simply keeping the heat pump low, like 100 degrees to preheat the Boilermate? This setting depends on how fast the Boilermate can recover, but keeps the heat pump in its most efficient operating mode. In summer, bypass the Boilermate and turn up the heat pump setpoint.

    Yours, Larry

    #19754
    bawilson
    Participant

    Thanks, Larry. Oil is the fuel source. I’m going to hook up per your suggestion and see what happens!

    #19755
    Larry Weingarten
    Participant

    Hello: One more thought. If you posed the same question on “The Wall” at http://www.heatinghelp.com you would be bound to get some more intelligent answers… I’m just a hot water guy, not a heating guy. 😉

    Yours, Larry

    #19806
    danielc0307
    Participant

    Why would you have the geospring only preheat? Since it uses so much less energy, why not let it heat all the way to 130 and the oil heater set to 110 or so just in case of very heavy usage? Last weekend I installed almost the exact same configuration! I’ll have to post a pic.

    #19809
    Larry Weingarten
    Participant

    Hello: Heat pumps work better in higher ambient temperatures (within reason), so depending on climate may have a lower coefficient of performance (COP) in winter. In unhappy situations, COP can fall under one. That’s why I answered as I did. You don’t want the heat pump to go into electric resistance heating mode. 😎

    Yours, Larry

    #26582
    rjobrien
    Participant

    This is a great string; thanks for posting.

    One technical question: in the dead of winter, when the boiler is working regularly to heat the house and thus providing cheap indirect hot water, how will the indirect storage tank reduce heating demand from the heat-pump water heater? I guess each winter you would need to manually turn off the HPWH or bypass it by manually closing/opening valves?

    There’s no signal from the indirect storage tank to the HPWH to reduce demand, I’m guessing. As someone said in this string, maybe set the HPWH to 100 degrees in the winter to pre-warm the indirect storage tank water?

    My question is: there’s no *automatic* way in which these two systems will toggle between whichever one is working most efficiently, right? If the HPWH is working full time in the summer and dumping fully heated water in the storage tank, that signals to the boiler not to run the indirect (great!). But it doesn’t work the other direction, correct? A fully heated storage tank by the indirect in the winter doesn’t signal to the HPWH not to run (because the cold source is always entering the HPWH when hot water is drawn from the storage tank)?

    Just checking assumptions. Thank you!

    #26584
    Larry Weingarten
    Participant

    Hi and yes, you read it right. You need to follow the water flow. Putting the heat pump first in line allows it to work with cold water, which it does most efficiently. Also, it can be kept in heat pump only mode so resistance heating is not used. No doubt controls could be worked to reverse flow at times, but the complexity vs the potential benefit likely doesn’t pencil out unless there is a LOT of water being heated. A side benefit of this two tank system is more available hot water to play with 😉

    Yours,  Larry

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