Is it possible to have 2 seperate systems serving one space, except of course for the "baseboard" option that is allowed on any system? Eg. A large exhaust load, with a make up air unit with chilled and hot water coils to heat air to 72 but then a seperate packed rooftop satisfying the heat loss and gain of the space?
Thank you,
Jason Robinet
Ameresco
Hi Jason,
Fundamental issue with eQuest: You are limited to one system per zone.
This requires some creative thinking to model such cases with large
conditioning makeup units as you're describing. Same issue pops up with
dedicated outside air systems (DOAS).
While I haven't modeled your explicit situation, I am pretty sure the
route I would take in your shoes would involve creating a "dummy zone"
(no internal/external loads) with OA requirements in quantity to match
the real zone, condition it's OA to 72 with a dedicated system - to
match your conditioning makeup air system, and then specify the separate
RTU over the "real" zone to take 100% of its OA from the dummy zone's
system. You may be able to get by without specifying the quantities of
ventilation air (letting eQuest auto-size the dummy system), but I have
had the desire to use DCV controls throw a wrench into such plans before
- it might be a good idea before getting started to be sure you have a
clear understanding of exactly how the OA required is expected to be
controlled.
You can find much more detail and discussion regarding such "dummy
zones" by searching for that term (perhaps also "DOAS") in the mailing
list archives. Feel free to post any new questions you're having
troubles with of course ;).
Best of luck!
NICK CATON, E.I.T.