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RE: [EnergyPlus_Support] Learn from my mistakes - EMS to avoid DX coil freeze - bad implementation
Thank you!
Elegant and more robust.
p.s., When using outdoor air, a single node (outdoor air) is monitored. When using the coil inlet temperature, we?ll have to monitor each coil?s inlet node.
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Jean marais
Sent: Friday, July 06, 2012 1:20 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Learn from my mistakes - EMS to avoid DX coil freeze - bad implementation
Dear Group,
It's always better to learn from the mistakes of other. So I'm sharing my mistake with you all.
I implemented a simple EMS to avoid DX coil freeze. The situation occurs when you have a room with high loads that needs cooling when the ODA temp is in the minus region and the same space needs loads of ODA.
So the current bit of EMS floating around here on the forum monitors the ODA temp and turns off the coil below a certain ODA temp.
A better place to monitor would be the DX coil inlet node as it may take into account the mixed air stream temp if the DX is after the mixing box...why? Because cold climates should a) have a freeze protection heating coil to avoid air at minus deg C temperatures from entering any system, regardless. This is imperitive for start up and start up from setback.
It's difficalt to startup a system when everything is frozen up.
b) The coil may need to operate at very cold outdoor temps. Examples include
1) coming back from a very high setback temperature after the building is nice and warm after the weekend, and the change over from setback happens to be on a cold early morning before occupation.
2) a server room still needs cooling...ODA has been preheated from -14 deg C ODA to +2. The DX coil is still seeing a massive load in the server room and tries to operate at max with an inflow air temp of +2. This is a DOAS because someone decided that the exhaust air does not go back to this AHU but is exhausted elsewhere.
I hope this helps.
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