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Modelling a GSHP (for space heating and DHW) in H2k!?

  • 8 Dec 2022 2:48 PM
    Message # 13018704
    Anonymous

    Hello,

    I have a customer with a GSHP (GeoStar) connected to both radiant floor and (thru a heat exchange) the home's DHW - I'm trying to determine the best way to model in H2k.

    A few specifics about the solutions:

    - the system has a 60 gallon buffer tank (with no backup electric element) for the radiant floor loop 

    - system has an "Advanced Metal Pres" 80 gallon storage tank (with a back-up electric element for when the GSHP is in cooling mode) that heats the DHW thru a heat exchange (i.e. the hot water from the GSHP heats the domestic hot water but without mixing the two sets of fluids)

    I'm planning on modelling it as follows in H2k - any thoughts or feedback?

    - Model Type 2 system as GSHP (the spec is known)

    - Model a Primary DHW to account for the heat loss from the DHW tank

    - Model a Secondary DHW to account for the heat loss from the buffer tank. 

    General question - any guidelines or best practices that I should adopt in this modelling (I cannot find guidance from NRCan). Specifically, should the primary / secondary DHW be modelled as Conventional electric tanks or as Heat Pump? (In the former scenario, the energy usage for water heating is 33% of total which seems high).

    See attached images of system.


    Many thanks for your thoughts - any input welcomed!


    Rick Martin

    250 207 3674


    3 files
  • 9 Dec 2022 9:02 AM
    Reply # 13019603 on 13018704

    Hi Rick, this is a great question. There are many other details we need to consider when modeling a GSHP in H2K. The efficiencies generated from the FHR are way off. If the DHW systems are electric with integrated heat pump, model per ERS procedure. If they are just storage reservoirs, with a loop to the heat pump without back up, model them with an EF of 1, as there are no heating elements. The typical indirect tank procedure is also meant for nat gas heating system. EF of 0.79 is much too low.

  • 9 Dec 2022 9:32 AM
    Reply # 13019643 on 13018704
    Anonymous

    Angela also noted (couldn't log into the chat)


    This sounds like he could use rhe GSHP desuperheater procedure from Hot2000 manual steps.

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