Welcome to the new Home Performance Forum.

It looks like you're new here. If you want to get involved, click one of these buttons!

Modeling Water Loop Heat Pump in REM 15

Hey guys -

Recent mechanical engineering graduate working in building science for the past year or so.

I understand REM Rate isn't really meant to model central systems such as water loop heat pumps, yet here I am.
RESNET's MultiFamily Guidelines (page 20) aren't the most detailed either.

I am modelling 5 units in a high rise which have one or more air-source heat pumps serving each unit's conditioned space.
Attached is a riser diagram, as well as mechanical schedules.
Here's what I have:

First step is to find the SEEReq (from MF guidelines) which is what my spreadsheet does - also attached.
I am not 100% sure about this step -
Capacity is chiller system output (EVAPCO 217, so 217 *2 because there are two chillers = 434) in BTU/hour so times 3412.142 (kW to BTU/hr)
Input is chiller system power in Watts (is this 2 * 8 * 1000 Watts = 16,000)
AUX is the total of the pumping and fan power in Watts - this is the basically all the pumps that are responsible for "normal service operation" - I guessed 60 hp, CPWP-1&2, but I am really unsure, plus 2*20 (motor from fan in chiller) so 100 HP converted to Watts - I assumed motor efficiency of 0.8

Assuming my SEEReq is correct - 13.30 how should I proceed inputting this into REM, meaning what should I input into library type in the mechanical equipment screen?

Should I select Space Heating/Cooling, or select Air Source Heat Pump (new for version 15)?

I am modelling heating as per page 19 in same RESNET document.

Thank you,
Joseph

Comments

  • David ButlerDavid Butler Posts: 3,838
    edited April 25
    I don't have v15 REM/Rate so I can't help with inputs, but your SEEReq calculation looks suspect. The Evapco 217 is only a cooling tower, not a chiller. What tipped me off is that when B9 is set to 0 to remove Aux power from the B10 formula, you end up with an equivalent SEER of 92 for just the "chiller"! The fact that the formula produced a reasonable SEEReq is just a coincidence resulting from adding the Aux load to the cooling tower EER.

    Also, keep in mind the capacity of the cooling towers is irrelevant. But the cooling toward input power (16kW) must be added to the chiller / heat pump unit(s) as part of the Aux load.

  • David ButlerDavid Butler Posts: 3,838
    edited April 25
    Also, those cooling towers are 600 tons nominal (each), so they obviously support A/C chillers or heat pumps for a lot more than the units you're modeling. So you must allocate only the portion of their input power that supports the modeled units. I recommend making this allocation based on nominal tonnage.

    Hopefully someone else will chime in with advice on REM 15 inputs.
  • joekhubjoekhub Posts: 2
    David,

    Thank you for your guidance - after some more careful discussion with my coworkers, I seem to agree with you that the SEER of 13.3 was just a coincidental, "nice number." Will attach new spreadsheet at some point later, and I am also inclined to ask my provider, the BER, their thought on the matter.

    Unfortunately, REM is notoriously inefficient at modelling central systems of any sort - which is understandable.

    Regards,
    Joseph

    PS don't close this yet
Sign In or Register to comment.