[Equest-users] eQuest Dedicated Ventilation System

Joshua D. Wolfe jwolfe at geo-marine.com
Wed Jun 25 10:40:02 PDT 2008

Here is what I am having problems with in eQuest. The perimeter system which
I am trying to model is fan coils served by an outside ventilation unit. The
outside ventilation unit is constant volume but has an outside air
economizer (i.e. minimum outside air is 25% and max is 100%, but a constant
33,000 cfm through the fan). It supplies the fan coils with a constant
volume of air but this primary air can be any mixture of OA from 25% to 100%
based on the ventilation unit economizer. The fan coils have constant volume
fans but re-circulate about 85% of the room (secondary) air.


I have made each fan coil its own system serving the corresponding thermal
zone. Then I have used the outside air from other system command to bring in
primary air from the ventilation unit on which I have placed the dual
enthalpy economizer. I have had to add a fake zone b/c the model will not
run if the main ventilation unit is not serving at least one conditioned


After running hourly reports on the ventilation unit I have noticed it never
economizes, therefore it brings in the minimum 8250 cfm year around which is
25% of 33000. With hourly reports of the space I noticed there were cooling
loads during the winter when this unit should be economizing but was not. I
have changed every setpoint for the main ventilation unit's economizer and
have even changed it to dual-temp with a low limit of 0F to a high of 100F
and it still will not economize throughout the year. So I am stumped, thanks
for your help.



Joshua D. Wolfe, EIT

Project Engineer

Geo-Marine, Inc. Energy Services

146 Market Place Boulevard

Phone:  865.692.0084 ext. 216

Fax: 865.692.0560

jwolfe at geo-marine.com


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