[Equest-users] Help - Modeling VRV-VRF System with eQuest

Paul Diglio paul.diglio at sbcglobal.net
Thu Jan 12 13:34:54 PST 2012


I have modeled VRF systems as PTHP systems for high rise residential buildings 
where the required baseline system is a PTHP.

The compressor on the PTHP can be specified as variable speed. so it seems to 
work well.  I just finished a 7 story building using a Daikin system.  I built 4 
custom curves per condensing unit and used the exceptional calculation method 
outlined in the BSUG slide presentation to calculate the recovered energy.  The 
curves I created are the Cooling Capacity f(EWB,ODB), Cooling EIR f(EWB,ODB), 
Heating Capacity f(EDB, ODB) and Heating EIR f(EDB, ODB). 

I ended up with a 28% cost savings for the proposed HVAC system compared to the 
baseline 90.1-2004 system which is in the range claimed by the manufacturer.

 Paul Diglio, CEM, CBCP

87 Fairmont Avenue
New Haven, CT  06513


From: Neil Bulger <nbulger at integralgroup.com>
To: Loi Ng <Lng at DIVENG.COM>; "equest-users at onebuilding.org" 
<equest-users at onebuilding.org>
Sent: Thu, January 12, 2012 4:21:19 PM
Subject: Re: [Equest-users] Help - Modeling VRV-VRF System with eQuest

Hi Loi,
I have run across this as well with trying to model VRV in eQuest. PVVT is a 
difficult system to work with because it requires specifying 1 zone as the 
thermostat that drives the whole system. Therefore, 1 zone will drive what 
supply air temperature the central AHU delivers to each zone. This can make 
hours out of range on cooling difficult but, if heating is the issue you may 
have more flexibility with zone-level heating options (reheat or baseboards). 
However, that can start to look strange when in reality, these features do not 
exist. But, the hours out of range typically stem from this 
single-zone-thermostat issue with PVVT.
Another approach I have not perfected yet that I thought of was to try using the 
eQuest Water Heat Pump system. The Water Heat Pump ties to a WLHP water-loop (it 
appears yellow in the Water-Side tab). If you were to place a dry-cooling tower 
on this loop, effectively, the dry cooling tower would be (in my mind) the same 
as an air-source condenser, like we would see in reality with a VRV system 
This may be good or bad on the airside in eQuest (I am hoping good) in that it 
provides another set of options and heat flow control at each system. Again, I 
have not dug into how this would go together best and I would imagine some post 
processing would be needed to understand the results.
Would love to hear any other creative ideas out there for VRV work-arounds.
Neil Bulger
Project Engineer
427 13th Street, Oakland CA 94612
510 663 2070 x 235
nbulger at integralgroup.com
DEEP GREEN Engineering.
From:equest-users-bounces at lists.onebuilding.org 
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Loi Ng
Sent: Thursday, January 12, 2012 9:38 AM
To: equest-users at onebuilding.org
Subject: [Equest-users] Help - Modeling VRV-VRF System with eQuest
I am modeling VRV system based on a “Energy Trust of Oregon, Inc.” guidance 
document (attached) posted by Mathew Larson of Colorado dated 12/12/2011.  The 
document recommends using a PVVT system to simulate a VRV system.  I used an air 
cooled PVVT system to model a VRV system.  However, the unmet hours on the 
heating is very high.  The cooling part is okay.  Does anyone has experience on 
bringing down the unmet hours?
Loi Ng
Mechanical Engineer, LEED® AP
Diversified Engineering, Inc.
914 Silver Spring Avenue, Suite 208
Silver Spring, MD 20190
Tel: 301-565-2000 x 234
Fax 301-495-1563 
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