Solving Plant temperatures are getting far too hot
Hello,
Good day to all.
I am modeling an HVAC system for an offices building with 8 floors which has several AHUs and FCUs installed. The simulation stops with the following error (Copied as is):
** Severe ** Plant temperatures are getting far too hot, check controls and relative loads and capacities
** ~~~ ** PlantLoop Name (DemandSide)= HOT WATER LOOP
** ~~~ ** PlantLoop Setpoint Temperature=67.0 {C}
** ~~~ ** PlantLoop Inlet Node (SupplySide) does not have a Setpoint.
** ~~~ ** PlantLoop Inlet Node (DemandSide) does not have a Setpoint.
** ~~~ ** PlantLoop Outlet Node (SupplySide) has a Setpoint.
** ~~~ ** PlantLoop Outlet Node (DemandSide) does not have a Setpoint.
** ~~~ ** PlantLoop Outlet Node (DemandSide) "NODE 134" has temperature=300.1 {C}
** ~~~ ** PlantLoop Inlet Node (DemandSide) "NODE 133" has temperature=300.2 {C}
** ~~~ ** PlantLoop Minimum Temperature=0.0 {C}
** ~~~ ** PlantLoop Maximum Temperature=100.0 {C}
** ~~~ ** PlantLoop Flow Request (SupplySide)=6.9 {kg/s}
** ~~~ ** PlantLoop Flow Request (DemandSide)=0.6 {kg/s}
** ~~~ ** PlantLoop Node (DemandSide) "NODE 134" has mass flow rate =0.6 {kg/s}
** ~~~ ** PlantLoop PumpHeat (SupplySide)=1982.2 {W}
** ~~~ ** PlantLoop PumpHeat (DemandSide)=185.5 {W}
** ~~~ ** PlantLoop Cooling Demand=6855817.6 {W}
** ~~~ ** PlantLoop Heating Demand=0.0 {W}
** ~~~ ** PlantLoop Demand not Dispatched=0.0 {W}
** ~~~ ** PlantLoop Unmet Demand=-6855817.6 {W}
** ~~~ ** PlantLoop Capacity=411062.5 {W}
** ~~~ ** PlantLoop Capacity (SupplySide)=411062.5 {W}
** ~~~ ** PlantLoop Capacity (DemandSide)=0.0 {W}
** ~~~ ** PlantLoop Operation Scheme=HOT WATER LOOP OPERATION SCHEMES
** ~~~ ** PlantLoop Operation Dispatched Load = 0.0 {W}
** ~~~ ** PlantLoop Operation Dispatched Load (SupplySide)= 0.0 {W}
** ~~~ ** PlantLoop Operation Dispatched Load (DemandSide)= 0.0 {W}
I read the other posts asking questions related to what I am asking too but I wasn't able to locate the problem.
The following are photos for the supply/demand of the loop (There are a lot of heating coils so I took two screenshots showing the essentials):
The outlet node supply side set point is set to 80 C. The pumps are intermittent. Both AHUs and FCUs coils inlet water temperatures are set to 80 C and outlet water temperatures to 69 C. The AHUs coils capacities range between 5 kw to 10 kw (I have about 11 coils for the AHUs). The boiler design flow rate is auto-sized. The plant design loop exit temperature is 80 C and loop design temperature difference is 11 C.
I can't seem to solve my problem. Can you assist ?
Many thanks in advance.
Why do you have a pump on the demand inlet branch?
There are two hot water pumps in the building, one primary and the second secondary. I added a pump in the demand side and used the common pipe option for the loop
I just removed it and left only the supply branch one and I still have the same problem
I would recommend to stay away from Common Pipe option, and instead use two PlantLoops connected by a HeatExchanger:FluidToFluid. You can find more info In the example 3 of Plant Application Guide: https://bigladdersoftware.com/epx/doc...
Your eplusout.err message seems to indicate there is a need for a (lot of) cooling on your demand side, not sure what's causing this for the limited amount of info I have.
The basic loops I have are the: air loops for the AHUs, two air loops for two split units on the roof, a chilled water loop, a condenser loop, a hot water loop and two service hot water loops (These take hot water from electric heaters). What can you recommend for me to check on ? I honestly don't know too why this is happening but it is stopping me from continuing my project. Any advice would be highly appreciated. Thanks Julien.
No clue without seeing the model itself. If you want to share it, I can spare a few minutes