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

[Michael Wilson]

Last summer I did a VRF model for an office building. I used a 4 pipe fan coil served by a loop-to-loop heat pump. For the condenser loop I used a Lake loop, which in turn was connected to a ground heat exchanger. Then I specified the ground temps as equivalent to the outdoor air temps (8760 hour schedule). Although this sounds complicated, it worked fairly well and has some benefits. The loop-to-loop HP allows heat to be transferred between zones. While the condenser loop with outdoor air temps allows the heat pump to act like an air cooled heat pump when in that mode. The trickiest part was developing equipment curves, but that would be the case no matter which way you model it.

 

 

Michael Wilson, P.Eng.

PO Box 1911 - 458 Abbs Rd.

Gibsons, BC  V0N 1V0

604-886-9864

www.enerficiency.ca

 

 

 

From: Paul Diglio [mailto:paul.diglio at sbcglobal.net] 
Sent: January-12-12 1:35 PM
To: Neil Bulger; Loi Ng; equest-users at onebuilding.org
Subject: Re: [Equest-users] Help - Modeling VRV-VRF System with eQuest

 

Neil:

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
203-415-0082

 

www.pdigliollc.com

 

 

  _____  

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 (typically).

 

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

________________________________

I N T E G R A L

                          GROUP

 

427 13th Street, Oakland CA 94612
510 663 2070 x 235
 <mailto:nbulger at integralgroup.com> nbulger at integralgroup.com
 <http://www.integralgroup.com/> www.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

 

Hi,

 

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?

 

Thanks!   

 

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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