[Equest-users] 90.1 Supply Fan Energy

[Carol Gardner]

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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