Dear Forum,
I have been trying to determine why the attached file produces a “RootController” error, since I think that is the cause of terrible boiler loop operation.
I am presuming that the cause is somewhere in my definition of the hot water plant loop. A brief description of that loop is:
· 2 hot water boilers on the Supply side with a single constant speed pump
· An assortment of air handler coils, reheat coils and baseboard on the demand side, served by a variable speed pump
· There are two PlantEquipmentOperationSchemes which “mirror” each other
o In one, Boiler #1 operates alone, then both boilers operate together, based on the load
o In the second one, it reverses – first Boiler #2, then both
· Although I am using a SetPointManager:OutdoorAirReset, it (for the moment) is set for a constant value of 82C
When I run this file for a Summer and Winter DesignDay, the following occurs:
· Everything appears proper during the SummerDesignDay
· Nothing is proper for WinterDesignDay
o Neither boiler is operating (no water flow, no energy)
o Reheat coils in zones Bakery and Deli are using a minute amount of energy (even though the boilers are off)
o Zone temps are uniformly dismal - not even close to the SP
o Unmet Heating load hours are zero everywhere (despite the dismal zone temp)
o The error message indicates that the setpoint is a value different than specified and the water temp is approaching 0 (not very good for a heating loop!)
My checking has included:
· the schedule functions for the PlantEquipmentOperationSchemes; one of them is always ON
· Water and zone setpoints are unchanging for Summer or Winter DesignDay and are correctly reflected in the output
· The same two boilers are used in both Summer or Winter DesignDays ..but only Summer DesignDay works (not Winter)
· the hot water loop setpoint is 82C and is correctly reflected in the output
· the air node setpoints at system coils and zone reheat coils are all much higher than actual node temps, so it seems that there is a demand for heat
It is my understanding that 90% of the time, these errors occur when the hot water loop is colder than the leaving air setpoint. That makes sense, but it does not make sense that the hot water loop should ever be colder than the zone air.
What else would prevent the boiler from operating? What else should I check or report?
I am hoping that one of you can see something obvious which has escaped my attention! Thank in advance.
p.s., I doubt it matters much, but I am using TMY data for Grand Rapids, MI USA
p.p.s., This is a great example of a file which runs, demonstrates dramatic “savings” (no boiler operation) … and is completely false. As a commissioning colleague was fond of saying, “You get what you inspect, not what you expect”.
Making me think….
"He who is kind is free, even if he is a slave. He who is evil is a slave, even if he is king."