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Thread: Hot water makeup air unit
02-04-2010, 07:40 PM #1Professional Member
- Join Date
- Feb 2006
Hot water makeup air unit
The scenario: 100% outdoor air unit, 2 position OA damper, 2 way modulating HW valve, glycol content minimal. Unit will be located indoors with OA ducted to it. It will be shut off when exhausts are shutdown. I'm speculating that the supply air temp can be a constant 60-70 deg. Not a Face & Bypass unit, it's a basic Fan Coil arrangement. I was approached to provide an operating sequence for this platform, but I'm not sure of a foolproof way to do it that will provide reliable operation. I'm aware of freeze protection concerns, and I am confident I could devise a control scheme to operate it, but reliably ? No nuisance freeze trips? I'm not real confident that this is the best equipment scheme for the application. Once I commit to this, I own it. I welcome any opinions or advice on this situation. Thanks --- gman
02-04-2010, 07:55 PM #2
Is the MUA the properly size to the fixed exhuast?
Is the HW actuator 135ohm control?
If all Yes then I would just control the discharge air with a proportional stat. Add a freeze stat to the discharge air. Install a end switch to the inlet damper to control the fan. And make sure the MUA is interlocked to the exhuast fans.
02-04-2010, 10:55 PM #3Steamfitters Local 602
02-05-2010, 02:25 AM #4Professional Member
- Join Date
- Jan 2003
- Kansas City
Plate heat exchanger and separate pump. Glycol mix as needed and standard control package.
02-10-2010, 10:22 PM #5
Would you like a full sequence of operation or just as it applies to the hw coil and freezestat? There's no such thing as no nuisance trips with a freezestat unless you jump it out.It might get loud!