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# Control current heating load of a boiler for every timestep

I'm trying to build a simulation where i can adjust the heating load of a boiler for every time step. The boiler is connected to four different baseboards. I used the HVACTemplate-5ZoneBaseBoardHeat.idf example file from the energyplus documentation as a basis. In the .edd file I found an actuator called Plant Component Boiler:HotWater,On/Off Supervisory, [W]. I tried to use that actuator to specify a custom heating load for the boiler, but it seems to have no effect on the simulation.

Right now, I'm using a work around in which i modify a heating schedule linked to a ThermostatSetpoint:DualSetpoint. Through that, i can control the current heating load of the boiler by setting a higher demanded temperature when I want the boiler to heat up the Baseboards. But I'm still looking for a way to set the current heating load of the boiler in Watts for every timestep. Is the Plant Component Boiler:HotWater,On/Off Supervisory, [W] actuator the right way to go or am I missing something?

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## 1 Answer

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The EMS Application Guide description for actuator Plant Component, On/Off Supervisory is incorrect. It should read:

Setting the value of this actuator to 0.0 directs the component’s water flow rate to shut down regardless of what other controls indicate. Any other component on the same branch will also be shut down. Setting the value of this actuator to any value <=1.0 sets the current load for this component to the actuator value times the component maximum operating capacity which is the nominal capacity multiplied by the maximum part load ratio.

So the units for this actuator should be [fraction], not [W]. A new issue has been posted to fix this and the docs.

If I am following correctly, the baseboards will need a high zone thermostat setpoint so that they will accept all of the heat delivered by the boiler.

Finally, ThermostatSetpoint:DualSetpoint only works for dual-purpose loops such as a water loop heat pump. The upper setpoint is used as a cooling setpoint and the lower setpoint is used as a heating setpoint. It will not set an on/off range for a boiler loop.

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Asked: 2018-10-25 09:31:03 -0600

Seen: 85 times

Last updated: Oct 30 '18