Water to water HP for SHW use

asked Mar 7

jferamo89
75 ●2 ●5

updated Mar 9

Aaron Boranian

14315 ●89 ●25 http://bigladdersoftware.com/

Hi everyone,

I’m modeling a domestic hot water (DHW) system for a production plant in Spain where the source is waste heat from chillers at 45 °C. The real system uses a water‐source heat pump (WSHP) and a storage tank with no internal heating element—all heating is done by the WSHP. However, my simulation tool (DesignBuilder) only provides an air‐source heat pump for DHW, and I can’t directly model a water‐to‐water system.

Has anyone dealt with this? What’s the best workaround to configure a “fake” air‐to‐water heat pump that behaves like a WSHP at 45 °C inlet? Any suggestion is appreciated.

ASHP settings in Design Builder (E+): C:\fakepath\Air source Heat pump settings.jpg

Actual heat pump specifications: C:\fakepath\SHW heat pump efficiency.png

Thanks, Julio

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answered Mar 8

Greg Estep
889 ●28 ●6

updated Mar 13

Hi Julio, DesignBuilder can do this. Add a DHW loop (not a HP water heater in a zone), edit the water heater, check the external heating plant connection, and uncheck the internal heating element. Set the source water flow rate to the design flow of the W2WHP.

add a heat pump heating loop and connect the demand side of the loop to the water heater.

You can connect the chiller condenser loop to the DHW loop using fluid heat exchangers.

update: 3/13/2025 Attached are two configurations. one is a single condenser loop connected to the chiller and the HP heating loop. This would just be mixing. The other is dedicated condenser loops and an intermediate condenser loop. This option would provided better temperature and flow control. C:\fakepath\chiller and HP heater to same condenser loop.PNG C:\fakepath\chiller and HP heater dedicated condenser loops and intermediate cond loop.PNG

link

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Hi Greg,

I tried that, I think it is not possible. At least I was not able to do it.

Thanks anyways

jferamo89 ( Mar 9 )

which part did you try? I know you can indirectly heat a water heater by a W2WHP.

Can you further describe the chiller condenser loop? Surely, you have a fluid cooler or cooling tower to reject heat that the W2WHP can not fully source.

Greg Estep ( Mar 9 )

Hi Greg, I have no fluid cooler or cooling tower. The W2WHP uses the waste heat from the chillers. However, for some reason, this cannot be connected to the W2WHP Design Builder component. Another limitation is that air-cooled chillers do not have an option for heat recovery. I don't fully understand why this is not possible.

jferamo89 ( Mar 9 )

I posted a response that said you could make this connection, but maybe not. My designbuilder is locked up in a parametric analysis. I have some ideas and will get back to you. I was thinking about an intermediate condenser loop with no components, just recirculation. Or, if that gives an error, use a tower or fluid cooler, set availability to off, and connect the demand side to both the HXs in the chiller condenser loop and the heat pump condenser loop.

Greg Estep ( Mar 9 )

The only alternative that worked so far was to set a DHW ASHP with a constant mains temperature of 45C imitating the real case of waste heat from chillers at that temperature (because of the high intensity use of the spaces cooling occurs all year around and waste heat will always be available). The DHW ASHP condenser side is set at 45C. Although not ideal, it worked.

jferamo89 ( Mar 10 )

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