Jon:

If I understand your email/system description correctly, isn't your underfloor system just a series fan powered box, with a zone fan to mix to 65F?

I do agree with you that your idea to setup a different AHU for the underfloor system by making reasonable assumptions for fan energy (and make sure you change the other AHU as well) is a good one.

However, you might want to consider how the UFAD system is heated. This could be an issue especially if your system gets 55F constantly, or if the supply air to be mixed is varied based on a reset schedule. I know that we don't really think about it much, but heating energy can be tricky, especially in UFAD systems.

??Andy Phelps, PE?

Message: 6
Date: Mon, 7 Jun 2010 15:06:00 -0700
From: Jon Pfantz To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Underfloor Air Distribution Supply Air
Temperature
Message-ID:
Content-Type: text/plain; charset="windows-1252"

Hello all,

Is anybody aware of a method of modeling an underfloor air distribution system with different supply air temperatures? My air handling unit partially serves an overhead system with 55 degree SAT and partially serves an underfloor system which mixes the 55 degree air with some return air to achieve 65 degree SAT. I?m assuming the best way to model this would be to create two separate systems, one for the overhead and one for the underfloor, however I?m concerned that I won?t be able to achieve realistic system performance.

Thanks,

Jonathon