Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
I don't think you're wrong anywhere in this case. First, I'd watch closely what the loop setpoint temperature is. It appears to be 56C. You probably want to do something like Indirect Heat setpoint is 56 C, and set the tank heater's setpoint temp (cut-off) to something like 55 or 54 C, so that you have a deadband in between the two.
But this is likely not going to suffice: most importantly you want to check carefully the sizing parameters and resulting component sizes. Indeed, I see that this example file is largely autosized, and I would expect you'll get problems from that. You do want to make sure that technically the source loop can provide most of the required heat and that you have an adequate amount of storage capacity (m3).
That being said, I do find that in most cases it's a lot easier to have two WaterHeater:Mixed or one HeatExchanger:FluidToFluid + one WaterHeater:Mixed. You put the tank (with no heating element) or HX served by the boiler loop first in the Plant equipment list, and the other one - the backup with electric heater - second, and you make sure the PlantLoop has a Load Distribution Scheme set to SequentialLoad so that the load falls on the source loop first, Then only if not sufficient the backup heater will turn on.
| | 2 | No.2 Revision |
I don't think you're wrong anywhere in this case.
case, but here are a couple potential things to check:
First, I'd watch closely what the loop setpoint temperature is. It appears to be 56C. You probably want to do something like Indirect Heat setpoint is 56 C, and set the tank heater's setpoint temp (cut-off) to something like 55 or 54 C, so that you have a deadband in between the two.
But this is likely not going to suffice: most importantly you want to check carefully the sizing parameters and resulting component sizes. Indeed, I see that this example file is largely autosized, and I would expect you'll get problems from that. You do want to make sure that technically the source loop can provide most of the required heat and that you have an adequate amount of storage capacity (m3).
That being said, I do find that in most cases it's a lot easier to have two WaterHeater:Mixed or one HeatExchanger:FluidToFluid + one WaterHeater:Mixed. You put the tank (with no heating element) or HX served by the boiler loop first in the Plant equipment list, and the other one - the backup with electric heater - second, and you make sure the PlantLoop has a Load Distribution Scheme set to SequentialLoad so that the load falls on the source loop first, Then only if not sufficient the backup heater will turn on.
