[Equest-users] VRF performance curve

[Nathan Miller]

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
www.rushingco.com<http://www.rushingco.com/>

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
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.

Regards,
Rathnashree
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