[Bldg-sim] RTUs with HW coils

W. Peter Anderson panderson at jpengineer.com
Wed Jan 30 13:13:41 PST 2008

Thanks Dave-
I modeled a single zone (the floor) and a single RTU.  I did not notice any independant method for controlling the base board.  I assumed it worked off the setpoint on the HVAC system screen.

I checked SS-K and I was getting temperature drop with out the HW coil and overshoot with the hot water coil.  

Peter Anderson
  ----- Original Message ----- 
  From: David S Eldridge 
  To: Building Model 
  Sent: Wednesday, January 30, 2008 3:06 PM
  Subject: Re: [Bldg-sim] RTUs with HW coils

  How many zones are there, and are there the same number of single-zone AHUs in your base case?  How are the baseboards controlled?


  5,229 btu/sf/yr is pretty low for heating, depending on your climate.  The other figure may be high for an office (again depending on climate) but looks to be the right order of magnitude if there is significant cold weather.


  I would start with the SS-O reports, and also compare the total number of unmet hours for both cases, to verify that you are providing the same conditions for each alternative.


  That level of difference between the alternatives sounds more like the first case has cooler than expected zones rather than the result of a system type change (even to a multizone).






  From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of W. Peter Anderson
  Sent: Wednesday, January 30, 2008 12:09 PM
  To: Building Model
  Subject: [Bldg-sim] RTUs with HW coils



  I am preplxed by a dramtic increase in heating load for my building- 35000 sq ft two story office.


  Base case equipment is Packaged Single Zone DX, fixed outside air (15%).  Base board perimeter radiators to heat.


  The Propsed Case is Packaged Multizone with HW heat.  I added economizers, and kept the same baseboard.

  The base case condtion used 183 MMBTU/year.

  The revised model consumes 3338 MMBTU/year.


  Space temperatures looked slightly different, but with in 2F-5F


  Any thoughts?  All things are identical expect the RTUs.  I have checked everything I could think off.



  W. Peter Anderson, P.E
  JP Engineering
  41 Mechanic Street
  Windsor, CT 06095
  Ph: 860/688-5223
  Fax: 860/688-5269


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