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two-stage DX cooling coil not running?

asked 2017-11-08 18:54:05 -0500

Matt Koch gravatar image

updated 2017-11-09 10:35:47 -0500

OK, so, I have several air loops, each with a two-stage DX Cooling Coil. I have auto-sized ALL parameters for this coil, EXCEPT for the low and high-Speed COP. They all seem to be sizing appropriately, but during a simulation, they all seem to remain off as the zone temperatures go up much beyond setpoint. Also, the electric power [W] and energy [J] reported for "Cooling" is tiny.

The only major difference to another model of this kind which ran successfully is that the "Rated Low Speed Air Flow Rate" for the two-stage DX Cooling Coil was NOT Autosized there, but selected for Hard Sized, but the field was then simply empty, i.e. did not even have a number in it.

So I am rerunning the model with that adjustment and cross my fingers it will perform. However, it would be nice if anyone had observed this behavior as well, or whether this is a known issue?

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What does the thermostat look like for the sizing period? If you hard size the capacity do you see any changes? What have you chosen for type of load to size on in OS:Sizing:System for the air loops? Also just to clarify, are you using Coil:CoolingDXTwoSpeed, or Coil:Cooling:DX:TwoStageWithHumidityControlMode

David Goldwasser gravatar image David Goldwasser  ( 2017-11-09 00:37:23 -0500 )edit

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answered 2017-11-10 13:01:09 -0500

Matt Koch gravatar image

It seems that something got muddled up in the process of creating the model. I ended up deleting all HVAC systems and saving just the building, then recreating the HVAC systems by adding the proper air loops, instead of adding empty air loops and then back-populating them. The numbers make more sense now. I suspect that I changed too many of the defaults, so in this latest effort, I kept as many defaults as I felt comfortable with.

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Asked: 2017-11-08 18:54:05 -0500

Seen: 183 times

Last updated: Nov 10 '17