[Equest-users] VRF performance curve

Jones, Christopher cjones at halsall.com
Wed May 27 07:09:56 PDT 2015

As Cory noted, WSHP works well for water source VRF systems.  Up here in the north, these systems typically have a boiler and fluid cooler for maintaining the refrigerant loop temperature along with a circulating pump.  The WSHP system captures the effects of “moving” energy from one side of the building to the other without post processing.  Two of the three Daikin curves can be implemented in the HP units and show additional savings.

Christopher Jones, P.Eng.
Tel: 416.644.4226 • Toll Free: 1.888.425.7255 x 527

From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nathan Miller
Sent: Wednesday, May 27, 2015 9:05 AM
To: Rathna Shree; BldgSim Mailing List; equest-users at onebuilding.org
Subject: Re: [Bldg-sim] [Equest-users] VRF performance curve

When I have modeled VRF systems I have always used the PVVT system type in eQUEST as recommended in this presentation: http://energytrust.org/library/bsug-files/modeling_real_performance_of_vrf_systems_kc-05.15.13.pdf

Using the efficiencies and the curves for the VRF system will get you pretty close, but if you want to account for heat-recovery within the system (one terminal unit in cooling while another is in heating), you will have to do some post-processing calculations.

Nathan Miller, PE, LEED AP BD+C – Mechanical Engineer/Senior Energy Analyst
RUSHING | D 206-788-4577 | O 206-285-7100

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Rathna Shree
Sent: Wednesday, May 27, 2015 3:18 AM
To: BldgSim Mailing List; equest-users at onebuilding.org<mailto:equest-users at onebuilding.org>
Subject: [Equest-users] VRF performance curve

Dear All,

I worked on a couple of projects in equest  using the VRF performance curves from Daikin and LG. The methodology i followed is as below:

1) Modelled packaged VAV with minimum flow ratio 1.
2) Created systems based on number of ODU's and assigned multiple zones to the respective ODU. (Just like modelling a AHU)
3) Inputted the ODU Cooling capacity and supply flow
4) Fans will be constant volume.
5) Since it is a cooling only system, i assigned only the "Cool EIR - fEWB-OAT", "Cool-EIR-fPLR" and "Cool cap-fEWB&OAT" curves. Rest were all default DX unit curves.

 PVAV system is used as PSZ system cannot handle multiple zones well thus causing unmet hours.

I did 2 trials, one with default DX curves and the other with performance curves from LG and Daikin. The results showed a decrease in cooling energy consumption by more than 30% thus impacting the overall energy consumption by more than 10%.

Is the simulation methodology and results appropriate? I feel the savings is on a higher side.

Please advise.


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