[Hap-users] Central Heating Question

Michael Hardy mhardy at blackoakengineering.com
Fri Oct 31 09:26:04 PDT 2014

>From your question, I assume you are setting your System Type as one of the
"Constant Volume." system types.


If you've selected "Constant Volume - Single Zone" as your system type, then
in the System Inputs, "System Components/Supply Fan" input, there is a "Fan
Control" option that specifies 1-speed or multiple speed fans.  You need to
have the "1-speed fan cooling and heating" selected.  Otherwise, HAP looks
at a lot of other settings and calculates the supply air flow from there.


If you have any of the other "Constant Volume" systems types, then the "Fan
Control" options are not available and you are back to having HAP calculate
the supply air flows differently for heating and cooling based on things
like space temperature, supply air temperature setpoint, heating and cooling
loads, etc.


If you have one of the other Constant Volume system types, you may be able
to force a constant supply air flow by adjusting the minimum airflows under
the "Zone Component/Supply Terminal/Minimum Airflow" settings.  I haven't
played with that setting for this application though.


Good luck.


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


From: Hap-users [mailto:hap-users-bounces at lists.onebuilding.org] On Behalf
Of Ahmed Kamel
Sent: Thursday, October 30, 2014 3:14 PM
To: hap-users at lists.onebuilding.org
Subject: [Hap-users] Central Heating Question



I have a question regarding designing a central heating system and I would
like your help.

Why does my central heating system has less cfm than my central cooling?
Shouldn't they be the same since it's the same fan?

Also, I want to condition my rooms at 70 f during the winter season. Is it
okay to set the "design temperature" of the central heating system to 72 f
and let the heating loads bring it down to 70 f?

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