[Equest-users] Overcooling

[Jonathan Chew]

Hi Ben,

Bill's solution is correct. Maintaining a temperature of 72F is not achieved efficiently by having a single set point. In that scenario, the temperature drifts constantly around the set point, requiring rapid switching between the heating and cooling coils.

Hope this helps.



Jonathan Chew
Mechanical Engineering Services
[cid:image50187a.JPG at 44df8078.41b5f615]The Walter Fedy Partnership
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________________________________
From: Bishop, Bill [mailto:wbishop at pathfinder-ea.com]
Sent: Tuesday, April 12, 2011 3:50 PM
To: Dombrowski, Ben; equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Overcooling

Ben,
Yes, first thing you should do is establish a deadband between heating and cooling (such as using 70F heating thermostat and 75F cooling). Even 70F heating, 72F cooling would perform better in the model than say, 71F heating and cooling. If the museum really does have only one temperature setpoint, there are probably controls that lock out cooling during certain months of the year (or based on OA temperature), or maybe you have a combination of heating-only and cooling-only systems with well-established zones. One way to model the controls is to modify your heating and cooling thermostat schedules so that cooling months/weeks/days have a lower heating setpoint and heating periods have a higher cooling setpoint. Another way is to use a system COOLING-SCHEDULE.
Regards,
Bill

William Bishop, PE, BEMP, LEED® AP | Pathfinder Engineers & Architects LLP
Mechanical Engineer

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________________________________
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Dombrowski, Ben
Sent: Tuesday, April 12, 2011 2:43 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Overcooling

I am working on an existing museum with both constant volume and variable volume system. I have modeled in the cooling coil capacity for the ahus and on about half of the units it says the cooling coil capacity is not large enough. I know that the coils are large enough since the building is properly cooled. Also overall the system is cooling a lot more than the bills are saying. Could a problem be that my heating and cooling temperature set point is the same? Any ideas would be great.

Ben Dombrowski, EI
Mechanical Engineer Intern
[cid:image002.jpg at 01CBF928.E8712B90] l Global Buildings North America
111 Corning Road Suite 200 l Cary, NC l 27518
Office 919.859.5751 l Fax 919.783.5882
Ben.Dombrowski at jacobs.com<blocked::mailto:Ben.Dombrowski at jacobs.com>



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