Equest, heat recovery and separate outside air systems

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First up, thanks to Bill and David for answering my last question.
My follow up is this:

I'm trying to model a separate outside air system with heat recovery. So I
set it up so all systems take outside air from my OA system (defined first).
But if I then try to add heat recovery to the OA system total energy (due to
cooling and fans) goes up.

I'm guessing that a factor in this is that the air goes to all the other
systems but then doesn't come back to the original OA system. (How to you
specify that?) Although, cooling loads should still go down since exhaust
air, whose quantify I specified, is still cooler than outside air.

So, how do I show any saving with OA heat (or coolth) recovery, which I know
will be huge?

thanks in advance.

Nicholas Lander's picture
Joined: 2011-09-30
Reputation: 0

Dear Nicholas,

If you mean that the consumption of the fans will increase when you add the
Heat recovery wheel ; this because of leaving the DP on the default value (1
in.wg). the default number is very high .

You should either use the actual value or you can set this value as zero if
you included the heat wheel effect on the fan KW/cfm .

The eQUEST users archive have a good information about this issue , also the
eQUEST help can provide a good support.



Mohammad Almasri's picture
Joined: 2011-09-30
Reputation: 400

To give you a more detailed answer you'd have to let us know what system
type you are using and a bit more info. It'd be best if you attached your
.pd2 and .inp files for us to see.


cmg750's picture
Joined: 2010-10-05
Reputation: 0


I know this has been discussed in the forums but I can't find a good
post for you. My understanding is that eQUEST does not model heat
recovery from the zones supplied by an OA-FROM-SYSTEM. The workaround
that I use is to specify heat recovery for each system that receives
ventilation from a DOAS. I calculate the kW/cfm of the DOAS fan(s),
select "Self Contained" for the ERV fans and copy the kW/cfm into the
makeup and exhaust fan fields. (You have to enter it in the "kW" field
first to allow you to enter values in the kW/cfm field, or else use the
"User-Defined Default" option.) If the DOAS has a heating coil, I add
preheat coils to all the systems. One of the problems with this
work-around is that the system fans have to be operating for any hour
that you wish to provide ventilation.


William Bishop, PE, BEMP, LEED(r) AP

Bishop, Bill2's picture
Joined: 2011-09-30
Reputation: 0


I am struggling to get more information from anywhere else in the forum on DOAS modelling itself. The training video in this website does not discuss the following & it will be great if you can help with some ideas:

1. DOAS airflow capacity (outdoor air cfm) to be input at the DOAS system tab or at dummy zone or at each system or zone served by this DOAS?

2. Which is the more appropriate system to use for DOAS, my other systems are PIUs and FCUs?

3. I tried using different systems & input outdoor air CFM, thermostat schedule & cooling capacities for the DOAS. But I am getting too much unmet hours and my energy consumption seems to be very high.  

4. For LEED, is it required to model DOAS in basecase as well? Or can we just input zonewise OA CFM for basecase & model DOAS in Proposed case with all the Heat recovery units & VFDs to show energy savings? But modeling DOAS with HRW seems only to increase the energy consumption.

Someone please help. 

errol's picture
Joined: 2017-04-30
Reputation: 0