Hello,
??????????? I am trying to determine how equest/doe2 sizes loop design flow. I
would assume that that the program looks at the max coil load and divide it by
the loop deltaT to obtain the loop design flow and the capacity. However in my
case the program is over?sizing the loop by more than two times. I have attached
the PS-H report and it is evident that the peak load is only 2.7 MBTU. The SS-D
report also confirms that the peak load is 2.7 MBTU. However the cooling
capacity of the loop is 6.9 MBTU! The loop gets loaded to a max of 50%. I did
not enter any values for loop/pump flow and let the program auto-size. The
deltaT on the loop is set to 12 F with a supply temperature of 44 F.
?
I see a similar problem if I have primary only or a primary-secondary looping
configuration. Also, I set the system sizing option to coincident. If the loop
size ratio is set?to 0.3 run again, I do not get any significant increase in the
unmet hours, proving that the loop can meet the system demand at 1/3rd the
flow!.
?
The only place that hints us about how the loop is being sized is in the
definition of LOOP-SIZE ?RATIO
?
?LOOP-SIZE-RATIO
The safety factor for loop sizing. (Note that safety factors could have already
been specified within the secondary HVAC systems attached to this loop). This
keyword is used only when SIZING-OPTION = SECONDARY-EQUIP; it is ignored for the
PRIMARY-EQUIP sizing method. When primary equipment is to be auto-sized by the
program, this keyword modifies the default capacity assigned. Note that this
keyword affects only the auto-sizing of the primary equipment based on secondary
loop loads. It has no effect on the design loop flow;? the loop flow is based on
the sum of the coil flows or other loads attached to the loop. However, the
design pump flow can be modified via keywords in the PUMP command.?
?
I am puzzled why it is not using the sum of coil loads to size the loop.
?
Thanks for your inputs.
?
Raj.