[Equest-users] VRF Heat Recovery Calculations

[Daniel Knapp]

If you are seeing negative heating energy there is a probably a problem with the performance curves. 

If you are trying to model the Daikin system I recommend checking out this discussion on UnmetHours. The gist is that there is an line length error in the Daikin VRV curves for eQUEST that causes a negative heating energy. Fortunately it is easy to fix. See the answer from Julien Marrec:

https://unmethours.com/question/4459/modeling-daikin-vrf-in-equest-too-high-heating-consumption/

“I've been trying to model a Daikin VRV system and trying to figure out why I was getting 100 times more space heating in the proposed (VRV) model compared to the baseline model (PTHP). After isolating the problem to the VRV, I found a conversation from March 2014 between a few folks (Byron Burns and Bill Bishop mostly - thank you both!), that basically explained why I was getting the issue: the .inp data from Daikin isn't importing correctly.

I just wanted to say that we're in July now, and this still hasn't been fixed (I downloaded the curve from Daikin a few days ago), so if you're having the problem, the fix proposed by Byron and Bill still works. It consists in to replacing the VRV Heating Curve with … 

"VRV Heating EIR-F-EWB/ODB AC" = CURVE-FIT      
    TYPE             = BI-QUADRATIC-T
    INPUT-TYPE       = COEFFICIENTS
    COEFFICIENTS     = ( -1.85025, 0.0620141, -0.000312822, 0.07145853,
        -0.0003626328, -0.0007776424 )
    ..

—
Daniel Knapp, PhD, PPhys, 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 Jul 29, 2015, at 6:21 PM, Travis Miller <tmiller at dcengineering.net> wrote:
> 
> I have created some heat recovery calculations for a VRF system following the Energy Trust of Oregon guidelines and I am getting some underwhelming savings.
>  
> The project is a 4-story office building, one of the floors is a basement, and there is approximately 9000 SF per floor. 1 VRF air cooled unit per floor except for the third, where there are two. There might not be enough load diversity between zones to generate much heat recovery. One strange thing is that I am getting negative elec input to heat/cool numbers exported from the CSV hourly reports. Has anybody encountered this before?
>  
> I have attached my excel file for reference (sorry for the size – not sure how to compress an excel file). Any feedback would be much appreciated. Thanks in advance for your help.
>  
> Travis Miller, PE
> DC Engineering
> O: 406-829-8828; x. 209
> 123 W. Spruce ST.
> Missoula, MT 59802
> www.dcengineering.net
>  
> <First Federal Proposed - 2015.07.29.xlsx>_______________________________________________
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