[Equest-users] Energy Recovery Wheel on VAV System

Mon Feb 1 10:50:46 PST 2016

I’m actually wrestling with re-understanding these issues in parallel with
you, Miles.

The DOE-2 entry for EXHAUST-FLOW specifies zonal exhaust doesn’t get back
to the air handler for exposure to heat recovery equipment at the system
level (*I wish it were an option*):

This diagram illustrates my current understanding/impression of what plays
into the exhaust airflow seen for recovery:

This is however the first I’ve heard that zonal exhaust doesn’t actually
work into the balance to determine exhaust/relief exposed to energy
recovery.  Some parametric tinkering is certainly in order!

My immediate thought is to wonder if the zonal EXHAUST-SOURCE (i.e. air
handler vs. infiltration) could be playing into that observation?  Seems to
fit logic…

~Nick

*NICK CATON, P.E.*
*Owner*

*Caton Energy Consulting*
  306 N Ferrel

  Olathe, KS  66061

  office:  785.410.3317

www.catonenergy.com

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On
Behalf Of bfountain at greensim.com
Sent: Monday, February 01, 2016 11:22 AM
To: Daniel Knapp
Cc: Miles H. Martschink; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Energy Recovery Wheel on VAV System

Sadly Daniel, I do not think this is quite correct.  In the current version
of eQUEST/DOE2.2, if you add zonal exhaust the total amount of heat
recovery does not change.  I agree that it should -- heat recovery should
go down as zonal exhaust is increased, but eQUEST does not currently do
this.  I was quite surprised when it was pointed out to me.

  A quick parametric test run where zonal exhaust is added will show that
the total heat input will not go up when it should and on the ERV report
(in the .sim) the amount of recovered heat will not change.

If however, you set the return fan volume lower than the supply fan volume
(on the fan -> flow parameters tab), then the heat recovery capacity will
be reduced appropriately.

*From:* Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] *On
Behalf Of *Daniel Knapp
*Sent:* Monday, February 01, 2016 10:42 AM
*To:* Miles H. Martschink
*Cc:* equest-users at lists.onebuilding.org
*Subject:* Re: [Equest-users] Energy Recovery Wheel on VAV System

Zone exhaust is presumed to exhaust directly to the outside without going
back to the system, i.e. it is assumed that you are specifying a separate
zonal exhaust fan that is not connected to the main VAV system. If you
remove the zone exhaust, the system level exhaust will be determined by the
outdoor air fraction of the supply air. This outdoor air fraction will
depend on the demand for outdoor air from the zones. i.e. the outdoor air
is specified at the zone level, and determines the outdoor air supply at
the system level.

Hope that helps,

Dan

—
Daniel Knapp PhD, P Phys, LEED AP O+M
danielk at arborus.ca

Energy Efficiency Expert
Arborus Consulting
76 Chamberlain Ave
Ottawa ON K1S 1V9
(613) 234-7178

—
Daniel Knapp PhD, P Phys, LEED AP O+M
danielk at arborus.ca

Energy Efficiency Expert
Arborus Consulting
76 Chamberlain Ave
Ottawa ON K1S 1V9
(613) 234-7178

On Feb 1, 2016, at 11:28 AM, Miles H. Martschink <miles.martschink at rmf.com>
wrote:

Hello All,

I am trying to model an enthalpy energy recovery wheel on a VAV air handler
serving multiple zones, and I cannot seem to get any exhaust air to pass
through the wheel. I have specified the design exhaust loads at the Zonal
Level and I have also setup the wheel control sequence using values that
others on this forum have posted:

·        Operation = OA Exhaust DT

o   DT = 5 degree F

·        Operating Mode = OA Heat/Cool

·        Make up Air Temp Cntrl = Mixed Air Reset

·        Capacity Control = Bypass OA

Whenever I run the model I get an error stating, “Energy Recovery
ventilator: S1 Sys (VAVS) has an exhaust flow 50% of the supply flow.
Performance may be compromised. OA & Exhaust: 7313. 0.” The total sum of
all the Zonal Exhaust Loads in 5505 CFM, and none of this is making it to
the wheel. Does anyone have any insight as to what I might be doing wrong
here? My end goal is to have the wheel modulate the return airflow in order
to match the Outside Air CFM demand by the VAV system. Any input is greatly
appreciated.

Thanks,

*Miles Martschink, Jr*

Mechanical Design Engineer

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