[Bldg-sim] sizing for baseline case acc to App. G
James V Dirkes II, PE
jvd2pe at tds.net
Wed Jun 23 16:15:58 PDT 2010
Dear Vinay,
I'm not sure of the rationale for the ASHRAE 90.1 oversizing requirements,
however here are my thoughts:
. I think the principal engineering rationale for oversizing is to
allow a building to reach its setpoint temperature quickly after a period of
inactivity. As an example, if a building is inactive during a holiday and
the temperature is allowed to float several degrees lower (in winter), the
additional 25% heating capacity will enable faster return to the normal
setpoint temperature. Steam heating systems can need even more capacity for
proper warmup capacity.
. Oversizing is also a common practice as a "safety factor". Most
load calculation software even has a separate input for adding this "safety
factor".
The Building Performance Team
James V. Dirkes II, P.E., LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Vinay
Devanathan
Sent: Wednesday, June 23, 2010 10:00 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] sizing for baseline case acc to App. G
Hello All,
Just to clarify a point -
What does the oversizing of capacities by 15% for cooling and 25% for
heating exactly mean? Do we only size the cooling and heating capacity or
also increase the airflow rate corresponding to the oversizing?
Thank you.
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