This question has been asked before but I could not find that a response
was posted to the forum. Baseline case hot water pump power is 19
W/gpm, where is this value input?
First you have to pull out the loop/pump flow from the PV-A report, then
multiply by 19 W, and enter that as the pump KW. I think you also have
to set the pump/motor efficiencies to 1.0 since the ASHRAE 90.1 value of
19 W / gpm should automatically include losses. Someone feel free to
correct me on that if it's not right.
First you have to pull out the loop/pump flow from the PV-A report, then
multiply by 19 W, and enter that as the pump KW. I think you also have
to set the pump/motor efficiencies to 1.0 since the ASHRAE 90.1 value of
19 W / gpm should automatically include losses. Someone feel free to
correct me on that if it's not right.
James Hansen, PE, LEED AP
James is right.
The way that we were taught to do it was:
"There are several approaches to model 19W/GPM pump power. In one approach,
a simulation can be
performed without entering inputs for pump flow and pump power. The eQuest
report "PV-A Plant
Design Parameters" provides software generated values for pump power and
pump flow. This report
should always be used to verify the W/GPM of the baseline pumps. If the
ratio of pump power to pump
flow is equal to 0.019 kW/GPM, the pump power is ASHRAE compliant. If not,
the mechanical
efficiency should be modified to increase or decrease pump power.
Alternatively, the pump power input
can be modified. However, the flow rate should not be modified in the
baseline model since this may
result in unintended eQuest errors. Please note that as screenshot below
shows, 19 W/GPM
consumption is about equal to a pump having 60% combined motor and
mechanical efficiency operating
at 60ft head. Please refer to note 6 of ASHRAE 90.1 -2004 Table 11.3.2 A for
additional clarification."
Cheers,
Kevin Kelly, LEED AP