[Equest-users] Modeling VRV System

[Paul Diglio]

Michael:

For the past year every model I have worked on is a VRV system with ERV(s) 
included to supply ventilation air.  I originally was modeling the VRV system as 
a PVVT as recommended in the Energy Trust slide presentation.  I am not sure why 
a PVVT system was suggested since all of the VRV fan coils I have modeled are 
equipped with constant volume fan motors.

I have since switched to using an air-cooled PTAC with heat-pump heating as the 
system type for the VRV system, especially in projects where the baseline system 
is a PTAC.  You can specify that the PTAC has a variable speed compressor and 
can plug in the custom curves that you create.  The results are what I expect, 
with an 8%-10% HVAC savings over a 90.1 baseline compliant HVAC system.  The 
overall building improvements range from 28.5% to 35%, depending on the other 
improvements to the building, such as a better envelope and glazing. 


The heat recovery savings depend on the building design.  Most of the projects I 
have worked on do not have a core that requires cooling when the perimeter 
spaces require heating, or vice versa, so the heat recovery savings calculated 
by the exceptional method outlined in the slides, is minimal.

 Paul Diglio, CEM, CBCP


87 Fairmont Avenue
New Haven, CT  06513
203-415-0082


www.pdigliollc.com




________________________________
From: Daniel Knapp <danielk at arborus.ca>
To: equest-users <equest-users at lists.onebuilding.org>
Sent: Mon, March 12, 2012 9:52:24 AM
Subject: Re: [Equest-users] Modeling VRV System

On the subject of modelling VRF systems, I recently did some tests on a 
box-model in Ontario (climate zone 6) and compared the results of using PVVT and 
the WSHP systems.  I found that the ability to use variable speed compressors in 
the PVVT systems – which are not available to the WSHP systems – made a huge 
difference to the energy savings and that the PVVT performed much better than 
the WSHP.  In this case I was modelling the Mitsubishi system with no heat 
recovery and was using the performance curves from the “Application for Adoption 
of Variable Refrigerant Flow Systems Under the Tile 24-2008 Nonresidential ACM 
Procedures”.  

Your mileage may vary, and I would strongly recommend building a test building 
using the wizard that allows you to test your performance curves and VRF 
modelling approach to make sure you are getting the results you are looking for. 
 

Cheers,
Dan
—
Daniel Knapp, PhD, LEED® AP O+M
danielk at arborus.ca

Arborus Consulting
Energy Strategies for the Built Environment
www.arborus.ca
76 Chamberlain Avenue 
Ottawa, ON, K1S 1V9 
Phone: (613) 234-7178 ext. 113
Fax: (613) 234-0740



On 2012-03-12, at 9:37 AM, Michael Marvin wrote:

Hi Everyone,
> 
>I know that there’s been some chatter about this in the past, but has anyone 
>determined a good way to simulate a VRV system accurately in eQuest? I’ve seen 
>posts where some people have recommended using PVVT or the Water Heat Pump 
>System, but I’m curious to hear if anyone has found a workaround that they feel 
>works better than the others.
> 
>Thanks,
>Michael Marvin, LEED AP
>Buro Happold
>100 Broadway 
>New York, NY 10005
>USA
>
>Tel: (+1) 212 334 2025
>Email: michael.marvin at burohappold.com
>www.burohappold.com
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