eQuest Users,
I am modeling a large WSHP job with a separate CHW system for a large
computer room. Everything was going good after several simulations when
a series of warning messages appeared stating something about CURINV:
Result out of limits for CURVE: ... (see attached). I am still in the DD
Wizard.
Can anyone assist on how to identify the culprit.
Thanks
Bob Vogt
Along with the warning will be a series of numbers which are the curve
coefficients. If (in detailed mode) you go to "spreadsheet view" and look
at the performance curves you can see the list of coefficients and can
quickly identify which curve is going out of range.
If I had to guess, I would guess it is a pump curve from a pump which is
being allowed to autosize -- probably a hot water pump.
Yep -- by sizing the loop on primary (which I suggest) you are setting the
loop size equal to the boiler (or chiller) sizing (the primary equipment
sizing). Under secondary sizing the loop is sized as the sum of all the
heating coils on the loop. For a VAV system, the reheat coils would be
full capacity at full airflow -- much larger than would really be needed
by the building.
So I recommend sizing your loops on primary, setting your primary
equipment sizes a little larger than the SS-D report values and then
verifying on your PS-D report that you are not getting overloaded hours.
I had CURINV warnings due to my hot water loop control set to "OA Reset" setpoint control, along with a default outdoor air reset schedule. No idea why or how, but when I put setpoint control back to "fixed" and got rid of the reset schedule, warnings disappeared.
Note that my CURINV coefficients corresponded with my pump head curve. I can speculate that outdoor air reset changed pump flows and created these warnings for some hours of the year, but I am looking into it more.