[Equest-users] Active Chilled Beam/Fan Coil System

[Greg Collins]

Thanks to everybody for the interest and feedback so far..

 

Chilled water supply to the beams is 56F.  

 

I've attached my inp and pd2 files in case anybody wants a closer look.


 

Greg

 

From: Bruce Easterbrook [mailto:bruce5 at bellnet.ca] 
Sent: Friday, April 09, 2010 2:24 PM
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Active Chilled Beam/Fan Coil System

 

Maybe you are now running into what eQuest uses to prevent condensation
on the chilled beam coil.  Condensation would be allowed in the FCU as
it could/would have a drain tray.  Where the mixing takes place is
important on the chilled beam.  eQuest should consider the mixing takes
place after the coil and the warm humid air is entering the coil.  I
would think eQuest would be set up to prevent condensation on the coil,
you don't want water dripping out of the unit.  What is the temperature
of your chilled water supply?
Bruce

On 09/04/2010 04:32 PM, Greg Collins wrote: 

I have tried it, but I end up getting an error saying the leaving air
temp off the coil needs to be at least 6F higher than the entering water
temp to the coil, and for some reason I don't get the same error for the
FCU.  In an active chilled beam, the coil is actually just cooling the
room induction air, then mixing it with the primary air from the DOAS.
I think that equest assumes the air mixes before entering the coil,
which fundamentally is the same thing, but the numbers trip this error
message.  I'll look into more why the FC system doesn't make that
happen, but the two seem to be essentially the same system except for
the fan (which I make 0.000001 kW/cfm anyway).

 

From: Grando, John [mailto:JGrando at cosentini.com] 
Sent: Friday, April 09, 2010 1:00 PM
To: Greg Collins; Bruce Easterbrook
Cc: equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Active Chilled Beam/Fan Coil System

 

Have you looked into SYSTEM TYPE = IU (Induction Unit).  This may be a
better path to try.

 


John Grando LEED AP| Mechanical Engineer


  

 

 

________________________________

From: Greg Collins [mailto:GCollins at glumac.com] 
Sent: Friday, April 09, 2010 2:00 PM
To: Bruce Easterbrook
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Active Chilled Beam/Fan Coil System

Bruce,

 

I agree with your theory and the justification, but the question is
ultimately "how to model it?"  I don't think you can put in negative
heat for a baseboard system, hook it up to a chilled water loop and get
results you can count on. 

 

Greg

 

From: Bruce Easterbrook [mailto:bruce5 at bellnet.ca] 
Sent: Friday, April 09, 2010 8:59 AM
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Active Chilled Beam/Fan Coil System

 

    I'm not totally up on using DOAS with eQuest or with chilled beams
being in Canada but it would seem to me the OA will have to be used to
control humidity in the space.  The chilled beam should not be used for
latent cooling, sensible only, to prevent condensation issues.  The DOAS
will need to control the dewpoint of the room air and maintain it below
the operating temperature of the coil in the chilled beam.  The chilled
beam would only be dealing with the sensible load from the space.  The
DOAS would do everything else.  The question would be will eQuest allow
a single zone AHU c/w economizer and a baseboard system with negative
heat?  I have never tried that with eQuest.
Bruce Easterbrook
Abode Engineering

On 08/04/2010 04:46 PM, James Hansen wrote: 

I'm interested in this as well - I know that in DOAS systems like active
chilled beams, the primary air often takes on a fairly large chunk of
space latent cooling, and if this can't be passed on from the DOAS
system to the space, then I don't see how we can believe the results.

 

GHT Limited
James Hansen, PE, LEED AP

Senior Associate

1010 N. Glebe Rd, Suite 200

Arlington, VA  22201-4749

703-338-5754 (Cell)

703-243-1200 (Office)

703-276-1376 (Fax)

www.ghtltd.com <http://www.ghtltd.com/> 

 

 

From: equest-users-bounces at lists.onebuilding.org [
mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Greg
Collins
Sent: Thursday, April 08, 2010 4:39 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Active Chilled Beam/Fan Coil System

 

Hi all,

 

I'm working on modeling an active chilled beam system.  It consists of
the chilled beams and a dedicated unit to provide primary air (mainly
ventilation air) to the beams at 55 degrees.  I've modeled the chilled
beam system as a fan coil system, but am wondering about my options for
modeling the primary air.  

 

My question is this:  If I attach the primary/ventilation air unit to
the fan coil system in the FC's Outdoor Air tab under "Outside Air from
System" will the temperature of the air coming from that unit have an
impact on the load in the space?  I have a ton of hours at very low load
during the winter months, and I want eQuest to use the 55 degree primary
air as the first stage of cooling for the space and not "double up" the
cooling energy by cooling the 55 degree air and then not use that for
cooling in the zones.

 

If anybody has some input, it would be appreciated. 

 

Greg Collins
Design Engineer / Energy Analyst

Mechanical Department
LEED(r) Accredited Professional

  <http://www.glumac.com/> 

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