VRV System Modeling

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In reference to your e-mail below, I also have created custom heating and
cooling EIR curves for eQuest.

I downloaded the performance tables from the Daikin site, but could not find RPM
or the minimum cycling part load ratio performance. I heard second hand from
the local Daikin
distributor that the minimum load on the condenser is 50% of rated capacity. Is
this your experience?

Could you tell me where to find the RPM and part load ratio performance? I am
modeling the REYQ-PTJU
Heat Recovery system.

Thank you,

Paul Diglio


I have heard the rumors about a VRV system being added to DOE 2.2 in the
future as well. The last time I heard the rumor, the package was
supposed to be out this spring. As is true of the entire software
industry, that likely means it will appear sometime in the year 2012.
(Predicted release date + 3 years = Actual release date)

I hope there is someone on here who can better clarify the date and
progress of the package...

To your second point, our office has been modeling Daikin VRV systems in
eQuest for a few months now. Don't get too excited... we haven't
actually installed one yet so we have no real data with which to prove
that we are modeling the systems correctly. That said, we also have only
modeled their "Heat-Pump" line and not their "Energy Recovery" line,
which allows simultaneous heating and cooling between zones.

We created custom curves with which to model the compressor by taking
Daikin Engineering data out of Daikin tables and plugging it into
eQuest. Then we model the system using the "Packaged Single Zone" system
type. We set the Indoor fan to two-speed and gave it a very light static
pressure, due to the fact that the system has multiple indoor fans with
low static vs. one fan with lots of static. We hard-keyed the CFMs, the
rated capacities, the compressor RPMs, low and high, the minimum cycling
part load ratio, the cooling (and heating) EIR, and set the compressor
to variable speed type and gave it a minimum unload ratio, again, all
from Daikin literature. We used eQuest's default low-speed EIR curve.
The capacity curve and the EIR curves we custom-created using eQuest and
Daikin data.

The results seem logical. Again, it's hard to prove that things are
dead-on because we have no real building to compare our results to.
Hopefully, though, that will give you a place to start.

I am not confident that I am modeling defrost correctly, and winter
results in general seem more sketchy. I am using eQuest's default
defrost running time fraction, which I assume is more pertinent to
standard unitary equipment. Daikin's defrost seems more efficient. It
also doesn't help that Daikin doesn't use either resistive or reverse
cycle for their defrost strategy... it's actually hot-gas bypass.

One last thing, all of the engineering data that we obtained from Daikin
was published on their website, www.daikinac.com.

I hope this helps. Good luck!

Gary Schrader

Paul Diglio's picture
Joined: 2011-09-30
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