[Bldg-sim] FW: FW:

[Chien Si Harriman]

Hi Andrew, that is really helpful.  I missed that section of the code.
 
Now, a few points that maybe someone could elucidate, maybe even you:
 
1.)  Does 50% of the peak design flow rate imply that, if, for example, the min vol setpoint is 30%, then the recirc coming in parallel is 20%?
2.)  That makes sense, except I am guessing this CFM value is the 50% peak design flow rate?  That would only be logical.
3.)  This min setpoint is for the primary air.
4.)  The design condition they are referring to is the summer design condition, or the winter design condition or both?  I am guessing it is both.
 
 
That is a great help, thanks for everything so far.
 
Sincerely,
Chien
 
 
 

________________________________

From: Andrew Craig [mailto:andrew_c at ieice.com]
Sent: Thu 21/02/2008 22:12
To: Chien Si Harriman; bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] FW:



Chien---

 

Section G3.1.3.14 of Appendix G hit on requirements for fan powered boxes.  They are:

 

1.)     FTUs shall be sized for 50% of the peak design flow rate 

2.)     FTUs shall be modeled with 0.35 W/cfm fan power.

3.)     Minimum volume setpoints for FTUs shall be equal to 30% of the peak design flow rate or the rate required to meet minimum OSA ventilation, whichever is larger.

4.)     The supply air temperature setpoint shall be constant at the design condition.

 

Hope that helps.  Good luck.


Regards,

 

Andrew Craig, EIT,LEED AP/ Mechanical Designer 
INTERFACE ENGINEERING 
direct 503.382.2696 

________________________________

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Chien Si Harriman
Sent: Thursday, February 21, 2008 2:07 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] FW:

 

 

 

________________________________

From: Chien Si Harriman
Sent: Thu 21/02/2008 21:46
To: bldg-sim at lists.onebuilding.org
Subject: 

Hi there-

 

I've been tasked with modeling a parallel fan powered box as my baseline system for ASHRAE 90.1 Appendix G, and basically I am wondering if there is anyone who knows of modeling guidelines for that FPB?  I have the capability of modeling any sort of conditions I would like, so I can vary the flow rate of the recirc air, the control sequencing of the fan-assist, and even whether that fan is variable volume or constant volume.

 

I can't find any guidelines that exist anywhere on this topic in ASHRAE 90.1, and this is the first time I've had to model it (I've never designed an electrically-heated building before).  Does anyone know whether:

 

1.)  There is a specific ratio for the amount of recirc air to minimum primary air?

2.)  Whether the amount of recirc air should vary (ie-a variable speed fan)?

3.)  You can just use a real FPB with data from a company like Carrier, and just call it a day on the simultion effort?

 

 

 

Any guidance would be really helpful.

 

 

Thanks in advance,

Chien Harriman

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