reheat in eQuest

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Hi All,

I'm modeling a building that uses a single air handler to serve multiple
zones. One set of zones ("A zones") require 55F supply air temperature for
cooling, the other set of zones ("B zones") require 67F supply air
temperature. This can be accomplished either by cooling all the air to 55,
then reheating the air sent to "B zones" to 67. The other way to accomplish
this is to heat some air to 55, supply 55 to "A zones" and mix some return
air with the 55F air to create 67F air for "B zones."

The question is: can eQuest do such a thing? I have loosely approximated
the second option by modeling two different air handlers for the "A" and "B"
zones, one having a MIN-SUPPLY-T of 55 and the other of 67. Is there a
better way to model this?

How can I model the first option? If I use a reheat coil, it only comes on
if the spaces need heat, and thus doesn't accurately model the constant
reheat required to heat the supply air from 55 to 67.

Any input/ideas are really appreciated.


Karen Walkerman

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Joined: 2011-09-30
Reputation: 200

Hi All,

Thanks for your comments and responses. The system is VAV. I've tried all
kinds of controls to model mandatory cooling of supply air to 55 and then
reheat to 67. Bottom line is that I can't make eQuest do it. If 55 F air
is required to cool a space, it won't reheat to 67, and if 67 is all that's
needed, it won't first cool to 55. Mandatory cooling and reheat simply
doesn't make any sense to the program. It doesn't make much sense in
reality either, except that it is the least expensive way to provide 55 F
air to some zones and 67 to others. 67 is required for some zones as the
air will be blown directly on people, and 55 is extremely uncomfortable for
humans, thus the required reheat.

The system is VAV, which complicates things as the volume of air, and thus
the energy needed to condition it, is constantly changing. I have finally
decided to go with the spreadsheet method to develop a rough estimate, as
this is all that is needed in this case. However, this foray has led me to
desire some additonal controls capabilitys for airside systems in eQuest.

Actually, I've thought that it might make sense for some cases to run eQuest
to output hourly zone loads, Then you could input these loads into another
program that could handle more complex heating and cooling delivery systems,
not necessarily do this for all projects, just the extra-special ones. Does
anyone know if trnsys can handle this type of thing? Are there any other
programs that can handle this type of thing?

Thanks again,


No Username provide's picture
Joined: 2011-09-30
Reputation: 200