[bldg-sim] heat recovery in eQuest

[Graham & Megan]

I found similar results when i first started using total heat recovery
wheels.  You need to be careful of several things:
- If outdoor air and exhaust are pass through the heat exchanger all
operational hours, with the wheel speed used for capacity control (Modulate
HX), then you are paying a fan energy penalty.  The added fan energy will
heat in winter and increase your system cooling loads in the cooling season.
Dedicated fans can overcome this problem where the added static pressure is
only an issue when the heat recovery wheel is in use.

- With total heat recovery (enthalpy) you need to be very careful how you
control it.  Controlling to a mixed air temperature setpoint (dry bulb) will
likely introduce an elevated mixed air humidity level and thus place a
latent load on the coil that can easily fully offset andy reduction in
sensible load.  You can set DT and DH thresholds (depending on control
variable) for heat recovery wheel operation that will assist in overcoming
these issues.  I've checked hourly reports and have satisfied myself that
the enthalpy wheels in DOE-2.2 / Equest are doing what they should.

The 2.2 Dictionary PDF explains the leywords and options thoroughly.

Regards,
Graham
----- Original Message ----- 
From: "Dang, Arvinder" <adang at syska.com>
To: <bldg-sim at gard.com>
Sent: Tuesday, May 03, 2005 3:33 AM
Subject: [bldg-sim] heat recovery in eQuest


A follow up on a discussion which happened a few weeks back on heat
recovery in eQUEST. I am facing a similar problem where on using an
Enthalpy wheel for heat recovery my heating energy reduces significantly
but my cooling energy also increases ( this seems incorrect). Brian you
had mentioned that the Make up Air temperature control should be set to
Mixed Air Reset instead of float to avoid recovering all year round.
However when you set this it asks for an option for capacity control.
The different options include
Trim Economizer,Bypass OA, Bypass Exhaust, Modulate HX.
Could you or anyone else explain what these different options mean and
how would they effect the results.

Thanks

Arvinder  Dang
Sustainable Design Specialist
LEED(r) Accredited
Syska Hennessy Group, Inc.

  11500 W. Olympic Boulevard,
Suite 680
Los Angeles, CA 90064
Tel: 310.312.0200, x3730
Direct: 310.254.3730
Email: mailto:adang at syska.com
http://www.syska.com


-----Original Message-----
From: postman at gard.com [mailto:postman at gard.com] On Behalf Of JRR
Sent: Wednesday, April 13, 2005 2:59 PM
To: BLDG-SIM at GARD.COM
Cc: BLDG-SIM at GARD.COM
Subject: [BLDG-SIM] heat recovery in eQuest

Do the  exhaust conditions cause condensation?
john ross

Renee J. Azerbegi wrote:

>I am having trouble modeling heat recovery in eQuest. For this project,

>it is a 100% outside air constant volume system (a base case) for a
>multi-zone laboratory air handling unit with heat recovery added to it
>(50% effectiveness, cross-flow). My cooling load increases
>significantly and my heating load decreases significantly for a total
>change in energy cost of 1% INCREASE. Has anyone run into this issue
>with eQuest? I've used heat recovery before in eQuest and it never
>seems to change the energy results by more than 1 or 2%, however basic
>hand calculations show much higher savings typically.
>
>Thanks much!
>
>Renee Azerbegi
>
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>



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