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

[Bruce Easterbrook]

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.
>
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> *From:* equest-users-bounces at lists.onebuilding.org 
> <mailto: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 
> <mailto: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® Accredited Professional
>
> http://www.glumac.com/glumacsig.gif <http://www.glumac.com/>
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