[Hap-users] Boiler Hot Water Reset

Reba Schaber Rschaber at PHMECH.com
Tue Aug 16 10:46:05 PDT 2011

I just had this issue.  GBCI has not reviewed it yet, but my strategy was to average the two conditions.  180 with 130 degree return is a 50 degree delta-T.  150 with 130 degree is a 20 degree delta-T.  I ran the simulation once with the boiler and plant at a 50 degree delta-T and ran it a second time with a 20 degree delta-T.  Then I used the average values of the two runs.  I left the system delta-T at 50 for both runs.  The system delta-T did not seen to effect the simulation results.

A better approximation might be a weighted average using the ambient dry bulb in the TMY data to figure how many hours would be spent at each delta-T.  Of course you'd want to exclude the hours when the system is not scheduled to operate.

When I emailed Carrier HAP support they said, "We cannot currently model Hot Water reset of boiler temperature in HAP 4.51. For purposes of LEED, you must write a narrative explaining that the program you are using for LEED does not have this capability.

We do have Supply Air Temp reset on a hot water coil in an air system.

Hot Water Boiler reset is on our list for a future version of HAP."

Good luck.

         Reba Schaber      Mechanical Engineer, P.E.
                                     LEED Accredited Professional

From: hap-users-bounces at lists.onebuilding.org [mailto:hap-users-bounces at lists.onebuilding.org] On Behalf Of Jason D. Plumpton
Sent: Monday, July 25, 2011 12:54 PM
To: hap-users at onebuilding.org
Subject: [Hap-users] Boiler Hot Water Reset


Has anyone had any luck modeling HW reset in HAP 4.51?

90.1-2007 Appendix G calls for this type of control in G3.1.3.4, and I am assuming that there must be some way of modeling this reset control in HAP.

Any advice/help would be greatly appreciated.

Thank You,

Jason D Plumpton, P.E. LEED-AP
M/E Engineering, P.C.

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