Cooling coil leaving temp error

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I'm running a simulation where I get the following error:

In EL1 Sys1 (VAVS) (G) , cooling coil leaving temperature must

be at least 6F higher than entering water temp.

I checked my temps - the entering water temp is 44 degrees, and the coil leaving temp is 55. I have a 5 degree delta T on the fan - could that be causing this?

Vikram Sami

vsami's picture
Joined: 2013-05-31
Reputation: 1

I would say that is the likely culprit. The commonly used keyword is zone entering temperature (MIN-SUPPLY-T), not the coil leaving temperature. The coil temperature will be variable depending on how much heat gain the fan provides and the throttling range of the coil controller. In this case, the coil leaving temperature would likely be around 50 degrees if you have that much fan gain and I could see that generating that error. 5 degrees is on the high side for a fan, so check what number you are using to determine what the power input is. I always use the bhp not the nameplate to determine the kw/cfm of the fans.

Brendan Hall, PE, LEED AP BD+C

Hall, Brendan's picture
Joined: 2011-09-30
Reputation: 1

If you want to bypass the error completely you can set your chilled water supply temperature lower (say 41) to satisfy the 6 Deg delta T eQuest is looking for and then use a temperature reset schedule to have the chilled water loop operate where you want it too. Good trick for low air temp systems where this error gets in the way.

Chris Lowen, P.E.

Chris Lowen's picture
Joined: 2011-12-16
Reputation: 0