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Re: [EnergyPlus_Support] Re: water heater issue
1) Maybe It is not able to divide the flow, if components are water
heaters, parallel arranged.
Since water heaters do not "set" the flow rates on the WH's use or
source nodes, the splitter will not know how to split the flow. This is
probably what you are seeing. I am not the expert on this type of system
or it's connections. I guess you could try putting the tanks "use" side
nodes in series (on 1 branch in the hot water supply side) or you could
try putting the HP and solar collector in series, use 1 hot water tank
and see what happens.
2) I want it to charge the tank as much as possible, even if the
building doesn't need heating
As far as having a HP connected to a hot water tank, this is not a
typical system. When the HP provides heating to the building, the source
side of the HP will COOL the source water (the tank will get colder).
When the HP provides cooling to the building, the source side of the HP
will HEAT the source water (the tank will get hotter). But if the source
water is already hot (the water in the tank is hot), the HP will not be
able to cool very well (if at all).
Now for your system: It sounds like you are trying to provide the demand
side of the hot water loop with the first water heater. But I am still
unsure what you are doing with the "load" side of the water-to-water HP.
If the load side of the HP is connected to the demand side of the
chilled water loop, this will not work very well since the source side
of the water-to-water HP connected to the hot water tank is already hot.
It should be cool water on the HP's source inlet when the HP is in
cooling mode. And I don't think you can connect the load side of the HP
to the demand side of the hot water loop if the first hot water tank is
already doing that. It sounds like you would need 2 hot water loops and
I have never done that (or even know if it's possible).
If all you want the HP to do is heat water (and not provide cooling to
the demand side of the chilled water loop), try using the Heat
Pump:Water Heater and connect the solar collector to that type of tank.
When the solar collector can not heat the water, the heat pump water
heater will turn on. There can also be a backup electric heating element
if neither system can heat the water sufficiently.
Maybe someone else will have other suggestions.
davide.loba wrote:
>
> I try to be as clear as I can.
>
> On the supply side of the main hot water loop there are two
> water:heater objects. The first one receives heat from solar
> collectors, stores it and supplies it to the demand side of the main
> loop, when necessary.
>
> The second one, receives heat from a heat pump, instead from solar
> collectors. I connected the HP to the water heater because I want it
> to charge the tank as much as possibile, even if the building doesn't
> need heating. When HP is unable to maintain the tank's temperature
> above the minimum, there are two gas boilers.
>
> The problem is there is not flow through the use side of water heater
> (which stores the heat coming from HP). I suppose is a problem about
> the splitter. Maybe It is not able to divide the flow, if components
> are water heaters, parallel arranged. Indeed, the whole flow goes
> through the first component of the supply side.
> This is what I have figured out from outputs.
>
> Thank you very much for your usefull help
> Loba
>
>
--
Richard A. Raustad
Senior Research Engineer
Florida Solar Energy Center
University of Central Florida
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