[Hap-users] what is the required fresh air supply temp?

[Reba Schaber]

I take no exceptions to Michael's answer.  But I wonder if you noticed there is a "CAV - Tempering Ventilation" air system type?  Then the HAP defaults are 75 F for cooling and 70 F for heating.

Similarly, if you choose equipment type "Terminal Units" and "Common Ventilation System" you will have the options of pre-cooling and pre-heating coils.  Again the defaults are 75 F for cooling and 70 F for heating.

From: hap-users-bounces at lists.onebuilding.org [mailto:hap-users-bounces at lists.onebuilding.org] On Behalf Of Michael Hardy
Sent: Tuesday, February 05, 2013 10:56 AM
To: 'dele omotayo'; Hap-users at lists.onebuilding.org
Subject: Re: [Hap-users] what is the required fresh air supply temp?

If you're talking about a Dedicated Outdoor Air Supply (DOAS) of system, where there is additional equipment that is able to heat and cool and controls the individual zone temperatures, then I usually try to select a supply air temperature setpoint that will minimize the amount of reheat or recooling required.  A precise answer would have to take into account the specific building (how many zones are in heating verses cooling at the same time), the climate (whether predominately heating or cooling) and the efficiency of the DOAS and zone equipment.  The goal would be to select a temperature that will be the most efficient given all the different variables that go into each project.

For me, where most of my projects are in a heating-dominated climate (northwest US) and there aren't very many annual hours where pre-cooling is necessary, I usually keep my temperature close to my cooling setpoint (58 F in your example).  This way, I'm preheating up to 58 F, then the zone equipment can continue heating, but there is very little cooling necessary.  If my projects are in a predominately cooling dominated climate (CA and HI), where there is very little need for heating, then the same 58 F supply air setpoint works without much reheating.

If you are talking about make-up air systems WITHUOT additional equipment to provide zone temperature controls, then my make-up air temperature setpoints are all over the map depending on things like what is the acceptable room temperature range (45 - 95 F??), how much internal load is generated (ovens, equipment, etc??) and again, whether the project is located I a predominately heating or cooling climate.

If HAP could add a supply air temperature reset schedule similar to the Hot/Cold water reset schedules for Plants, then we could get more realistic results from our air systems.

Good luck!

Michael L. Hardy, PE, F.NSPE
Black Oak Engineering, Inc.
Cell 503.314.5244

From: hap-users-bounces at lists.onebuilding.org<mailto:hap-users-bounces at lists.onebuilding.org> [mailto:hap-users-bounces at lists.onebuilding.org] On Behalf Of dele omotayo
Sent: Tuesday, February 05, 2013 7:13 AM
To: Hap-users at lists.onebuilding.org<mailto:Hap-users at lists.onebuilding.org>
Subject: [Hap-users] what is the required fresh air supply temp?

By default, the central cooling(from air system properties--system component tab) supply temp is 58 F which is the desired supply temp for just cooling. My question is, what should the temp be if the system is to be designed to temper outdoor air i.e what is the fresh air supply temp?
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