[Equest-users] 90.1 Supply Fan Energy

[Paul Diglio]

Michael:

Just out of curiosity, what did you calculate for the kW/CFM?

I have modeled buildings where the ventilation fans use much more energy than 
the heating and cooling energy combined.

Paul Diglio





________________________________
From: Carol Gardner <cmg750 at gmail.com>
To: M. Shields <mshields at fstrategies.com>
Cc: equest-users at lists.onebuilding.org
Sent: Wed, April 6, 2011 5:46:30 PM
Subject: Re: [Equest-users] 90.1 Supply Fan Energy

Yes, that is correct and obviously there isn't a large number in there. The 
default is 0.5 cfm/sf. I really think it's your outdoor air. Try changing it to 
cfm/person.


On Wed, Apr 6, 2011 at 1:47 PM, M. Shields <mshields at fstrategies.com> wrote:

Do you mean under the Systems->Fans->Flow Parameters Min Flow cfm/ft2?  I left 
this blank thinking that equest would then size the flow rate based on my design 
parameters for supply air temp and zone temp as Appendix G requires, is that 
incorrect?
> 
>From:Carol Gardner [mailto:cmg750 at gmail.com] 
>Sent: Wednesday, April 06, 2011 4:04 PM
>
>To: M. Shields
>Cc: equest-users at lists.onebuilding.org
>Subject: Re: [Equest-users] 90.1 Supply Fan Energy
> 
>Under the HVAC systems tab, go to the Air Flow screen and look for the field 
>labeled cfm/sf. It usually defaults to 0.5 cfm/sf, something I've been going on 
>about a bit lately on this listserv. A better number is 1 or so, usually but it 
>depends on building type, exposure, etc. For you, make sure it is not too large. 
>I suspect, however, that this is not where your problem is. I suspect you have 
>accidentally entered too much OA. I suggest you go back and simply put in the 
>Standard 62 cfm/person rate and call it good. I have never specified it as a cfm 
>rate but that sounds like not such a good idea for energy modeling. See if that 
>helps.
>On Wed, Apr 6, 2011 at 12:57 PM, M. Shields <mshields at fstrategies.com> wrote:
>I looked at the ACH based on the SV-A system CFM and the volume of the zone and 
>it does seem high (2-5 ACH), but I let equest calculate the system CFM for me.
> 
>I have one system per zone so I specified OA in the zone tab as a overall CFM 
>rate based on the 62.1 calculations I did.
> 
>From:Carol Gardner [mailto:cmg750 at gmail.com] 
>Sent: Wednesday, April 06, 2011 3:37 PM
>To: M. Shields
>Cc: equest-users at lists.onebuilding.org
>Subject: Re: [Equest-users] 90.1 Supply Fan Energy
> 
>Check your cfm/sf number in your systems, that would definitely cause this if 
>it's set too high. Also what field are you using for your OA ventilaton? 
>
>
>Carol
>On Wed, Apr 6, 2011 at 12:22 PM, M. Shields <mshields at fstrategies.com> wrote:
>Hi all,
> 
>I am in the process of breaking out the fan energy from my HVAC system per 
>ASHRAE 2004 G3.1.2.1, following G3.1.2.9.  The amount of energy coming from my 
>fans seems massive and I’m not sure if that is typical, or if I’ve messed 
>something up.  I started by setting the temperature difference of 20 degrees 
>between supply and desired temp (55/75 cooling and 90/70 for heating) and 
>specified 62.1-2004 ventilation for outside air.  I then ran equest and used the 
>SV-A reports to get supply CFM for each system.  From that number I then used 
>Table G3.1.2.9 to get BHP for each system, which I then converted to kW using 
>the formula in ASHRAE.  I then took that number and divided by CFM to get kw/CFM 
>and entered this number on the system->fan tab.  When I go to the SV-A report 
>the system kW is exactly what I calculated it to be, but the energy required for 
>my ventilation fans is about the same as my heating and cooling load combined, 
>which seems outrageous.  
>
> 
>Is this typical?  Have I entered it In the wrong way? I would think fan 
>consumption would typically be a fraction of the actually heating and cooling 
>energy.  Thanks for any thoughts.
> 
>____________________________
>Michael Shields
>Facility Strategies Group, LLC
>1012 Market Street, Suite 307
>Fort Mill, SC 29708
>Phone: 803-493-4507
>Fax: 803-548-2511
>Email: mshields at fstrategies.com
> 
>
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>
>-- 
>Carol Gardner PE
>
>
>
>-- 
>Carol Gardner PE
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-- 
Carol Gardner PE
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