[Bldg-sim] M&V metering of VRF systems

Aaron Smith asmith at mreng.ca
Fri May 23 06:49:51 PDT 2014


Thanks for all the information Chris.  I agree.  I seem to remember reading
in an article that the VRF system used more energy than "expected" which is
a much better comparison but even at that, the loads on the system may have
been higher or occupancy may have been different than expected, etc. so a
post occupancy evaluation is required.

And validated modeling software would be great to provide us with more
confidence when we perform modeling to compare systems.  Now, I just need to
take the time to learn a new software program!

Aaron

 
Aaron Smith, P.Eng 
M&R Engineering 

-----Original Message-----
From: Chris Balbach [mailto:cbalbach at psdconsulting.com] 
Sent: Friday, May 23, 2014 10:11 AM
To: Aaron Smith; Jones, Christopher; bldg
Subject: RE: [Bldg-sim] M&V metering of VRF systems

Aaron, et al.:

Along the lines of a specific GSHP system outperforming a specific VRF
system @ ASHRAE HQ - my understanding is that this is not such an easy claim
to make. The two different technologies serve different space-types within
the HQ building - making a comparison of actual energy use/EER between the
two technologies not that useful, IMHO. Never mind that a GSHP system with a
grossly oversized ground exchanger and good pump controls can outperform
nearly any system that I am aware of.

A more interesting comparison of the ASHRAE HQ experience, from my point of
view, would be to compare the predicted vs actual energy use of each
technology - to learn how well current modeling tools/methods/procedures can
be applied to better predict the performance of either of these complex HVAC
technologies.

This leads us to the issue of what can sometimes be described as the 'black
art' of the current state of VRF modeling used by practitioners modeling VRF
in most simulation tools - But things are changing on that front as well.
EnergyPlus has included a fully documented and tested method of VRF modeling
for several releases. Some of you may have caught the importnant DOE /LG
press release 10 days ago -
http://www.energymanagertoday.com/lg-puts-air-conditioning-attributes-techno
logy-exchange-0101043/ . In this release, DOE announced the uploading of the
first set of expanded performance tables from a major VRF manufacturer into
the TPEx (Technology Performance Exchange) portal. TPEx is a simulation
agnostic web portal for supporting technology evaluation, which has been
designed to seamlessly exchange data with the BCL (Building Component
Library). BCL is another (simulation agnostic) warehouse of downloadable
modeling components, currently populated with mostly OpenStudio modeling
components.

Which brings us full circle. Expect, within several weeks, to see a method
made available for direct extraction of manufacturer's VRF equipment
expanded performance charts/tables from the TPEx to create BCL objects (VRF
Performance Curves) for direct import into a user's OpenStudio model. True
end-to-end data exchange direct from manufacturers most up-to-date published
performance data, and sub-hourly. No more manual curve fits. This can
radically change the way we currently predict the performance of VRF
systems. Once data exchange systems like these are in place, we can start to
use our tools to tune models for comparing actual vs predicted energy of
specific VRF systems (indoor/outdoor combinations).

PSD will briefly demonstrate this method during our next free OpenStudio
webinar, which will covering features available in OpenStudio v1.4.0 - watch
for an announcement sometime in June.

All the Best,

_Chris

Chris Balbach, PE, CEM, CMVP, BESA
Vice President of Research and Development
Performance Systems Development of NY, LLC
124 Brindley Street, Suite 4, Ithaca, NY 14850
http://www.psdconsulting.com
ph: (607)-327-1647


-----Original Message-----
From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of
Aaron Smith
Sent: Friday, May 23, 2014 8:08 AM
To: Jones, Christopher; bldg
Subject: Re: [Bldg-sim] M&V metering of VRF systems

Chris,

I've talked to my local Mitsubishi rep in the past about installing VRF
‎systems in a condo building. Apparently they offer a package that monitors
the expansion valve positions of the indoor units along with the branch box
modes and energy use of the outdoor unit so that it can assign an energy use
to each condo for billing purposes.   It probably isn't up to measurement
canada specifications but may be fine for M&V.

I'd be interested in how your system performance plays out. You may be aware
of the reports of the GSHP out-performing VRF (VRF uses much more than
expected)  at ASHRAE headquarters. I haven't done M&V on a VRF system but
the building energy use for a couple of our (air and water cooled) projects
is much higher than expected.

Something that we've noticed ‎on a recent air-cooled project that we're
modeling with HAP is that it shows a significant penalty for systems that
have a vertical height difference - it says the 1st floor would use 33% more
heating energy than the 10th floor with roof mounted outdoor units. I
realize there is a capacity reduction (which varies by manufacturer) but
there must also be a corresponding increase in compressor electricity use.
Or at least that's what I gather from the results.  I'll need to request
their algorithms.

Hope that helps,
Aaron

Aaron Smith, P.Eng
M&R Engineering Ltd.

Sent from my BlackBerry 10 smartphone on the TELUS network.
  Original Message
From: Jones, Christopher
Sent: Thursday, May 22, 2014 14:02
To: bldg
Subject: [Bldg-sim] M&V metering of VRF systems

I am developing an M&V plan for a building with a VRF system. I am wondering
if it is possible to meter the heating, cooling and fan energy of the VRF
units given that the unit power is provided by a single feed.

It seems like a complex task to accurately measure the heating and cooling
energy given that the system includes the VRF cassettes, water cooled
condenser, the fluid cooler, the branch controllers, and the boiler.

Thanks for any insights!

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


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