All,
I am currently having a problem where the compressors on my DX units are still kicking on during the Winter months even though I have an OA economizer. This change in results happened after I added Demand Control Ventilation as a parametric run. The overall savings were greater, but I was surprised how much cooling increased in the winter. My design is using Bridgeport, CT weather.
I have attached the .pd2, .inp, and .prd files. My concern is only for units labled RTU-1, AHU-2, and AHU-3. Please ignore all the little PSZ's.
I have done a thorough search through the archives and have found this link
Here are two of the screen shots of how I set up RTU-1, which is essentially the same as the 2 other units:
[cid:image005.jpg at 01CCBFE8.0B2DF1A0]
[cid:image006.jpg at 01CCBFE8.0B2DF1A0]
Other notes: I only have a few unmet hours. SS-A report will show that winter cooling is more of a problem with RTU-1 and AHU-3. AHU-2 happens to be a 100% OA unit for Kitchen makeup and it has much less winter cooling load (not surprising since it is 100% OA so it is 'economizing' all the time. I also have modeled this project in Trace and the results in Trace have no winter cooling as expected (this project is a training exercise for me in eQuest.)
Any help is appreciated.
Jeremy Rapoza, P.E., LEED AP
Not sure if this is the reason, but the three units you mentioned all have "no" as the value for lockout compressor in the economizer tab. Try turning these to yes and see if it solves the problem.
Vikram Sami, LEED AP BD+C
Jeremy,
Another thing I noticed in your model is that the schedule you have built for outside air doesn't allow for the economizer to come online. If you use the value 0.001 in the fraction schedule it makes the economizer available.
Vikram Sami, LEED AP BD+C
Vikram,
Changing the value to 0.001 was the solution. Thanks.
Jeremy Rapoza, P.E., LEED AP