[bldg-sim] equest recovery

Brian Fountain bfountain at greensim.com
Thu Feb 2 08:42:58 PST 2006


Note that the default "Make-up air temperature control" for energy
recovery ventilators in eQUEST is to "Float" the supply air
temperature -- meaning they will continue to recover heat regardless
of discharge air temperature, increasing the cooling load unless the
default is changed.   Changing it to "Mixed Air Reset" has a
considerable effect -- eliminating most of the excess cooling.  

I guess it depends on your economizer operation -- whether it is on a
fixed drybulb or on differential drybulb or enthalpy.

-----Original Message-----
From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Brian
Thornton
Sent: February 2, 2006 11:23 AM
To: bldg-sim at gard.com
Subject: [bldg-sim] equest recovery



One thing I wondered about this was the amount of cooling increase
showing
with eQuest modeling of an ERV.  I have not done a real study, but
tried
modeling one case without any added fan energy, and running it with
the
economizer active with the ERV run control set to WHEN-MIN-OA, which
turns
off the heat recovery when the economizer is active (stops the wheel
for a
wheel type).  Even with these two strategies, which should eliminate
the
bulk of increased cooling, there is still significant increased
cooling.  

Have others tried this, and are there other explanations for the
cooling
results?

Brian 

Thornton Energy Consulting
p. 503-231-6600 f. 503-231-3555
thorntonenergy at comcast.net


-----Original Message-----
From: bldg-sim at gard.com [mailto:bldg-sim at gard.com] On Behalf Of Andy
Lau
Sent: Wednesday, February 01, 2006 12:17 PM
To: bldg-sim at gard.com
Cc: bldg-sim at gard.com
Subject: [bldg-sim] equest recovery

Of course one cannot say conclusively what is happening here, but my
work with heat recovery systems has shown that they often increase
cooling energy for two reasons:

1.  They can eliminate the possibility of operating an air-side
economizer and getting "free-cooling."
2.  The fan power associated with heat recovery can be significant,
which will also increase cooling load.

I attach a paper that was presented at Simbuild 2004 on this subject 
(not attached to bldg-sim because it exceeds allowable size)

Andy Lau, P.E.
7group, www.sevengroup.com

fernando varela wrote:
> Hello:
>
> I'm trying a Packaged VAV system with exhaust recovery, and 
> surprisingly, when I add a recuperator, cooling consumption
increases, 
> instead of reducing!! Can anybody explain this to me?????
>
> Thank you.
>
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