Results 1 to 13 of 24
01-18-2013, 09:06 AM #1Regular Guest
- Join Date
- Jan 2013
Freeze Stat trips, when OA temp drops to 30F, but zone is need of cooling.
Hi, I looked all over this forum and didnt find my answer, so here is my question.
My equipment (AHU) trips on freeze stat and shuts down the unit, I do have a few AHU's that back each other up, but here's what going on. I have a zone that is always hot and needs cooling, OA temp is in the low 30's, and OA damper is modulated and is open 100% to try to satisfy the zone after a few minutes or so, the freeze stat trips and unit is shutdown. Freeze stat is located after the HW coil, but before the CHW Coil. Freeze stat is set to trip at 33F
What can be done to prevent the trips in the future? I have full admin rights to the BMS, and can change the coding as I please, would it be logical to override the OA dampers to go to its minimum position, if the OA temp dropps below 35F?
But then thinking about this, wouldnt it start to open the CHW valve, and in doing so, it sends a start signal to the Chiller plant and start up the chillers when OA temp is 30F? BMS has chillers to be locked out if the OA temp drops below 45F. So chillers wouldnt start anyway. I guess what im asking is, what is the right thing to do, I know the Freeze stat is to protect the coil, but if the space is in need of cooling, then what do i do?
Thanks in advance.