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Gas Heating Control

asked 2017-03-08 12:32:49 -0500

updated 2017-03-08 13:32:25 -0500

EnergyPlus v8.5 I cannot figure out direct control of a gas heating coil; which should be really simple. This would be for an AirLoopHVACLUnitarySystem, with Dx and Gas. It serves multiple zones, with no reheat; but its my control zone with unmet hours. I thought this would be with a SetPointManager...but am coming up empty handed & confused...? I have many unmet heating hours in the control zone, and it appears as though my heating coil is either not turning on or not putting out warm enough air (all capacities are autosized). Note: Not concerned with unmet hours in the slave zones, just the unmet in the control zone....

I have gone back to the HVACTemplate example file for guidance. It creates a bunch of other objects (as expected). It produces a SetpointManager:SingleZone:Cooling, but not the accompanying 'heating' one. There are ZoneControl:Thermostat (s) and these are DualSetpoint types. There aren't many unmet heating hours here....so I am further contused....

So, what am I missing here? I have a feeling this should be really easy, but I cannot get the gas heating coil to put out hot air...

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answered 2017-03-08 12:55:19 -0500

For the UnitarySystem, there is load and set point based control types. For load control you would use only a thermostat in the control zone. For set point control you would use a set point manager to place a set point at the coil outlets, and depending on what type of set point manager is used, you might also need the thermostat.

AirLoopHVAC:UnitarySystem,
  GasHeat DXAC Furnace 1,  !- Name
  Load,                    !- Control Type
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Ok, changing back to Load Control with one of the 'worse' exposure zones really cuts down the unmet hours....that's good. For AirLoopHVAC:UnitarySystem then, that system responds only to the ZoneControl:Thermostat and associociate sch'ds?

Tried Deleting the Setpoint Manager associated with the Heating Coil, and Severe Error/crash....So, even with Load control a Setpoint Manager is needed for this coil? (cont)

dradair gravatar image dradair  ( 2017-03-08 13:32:18 -0500 )edit

Previously had 'Set Point', and set up a Setpoint:Scheduled, with a 105F DAT....but still was not seeing 105F off of that coil; and the unmet hour persisted. If a setpoint manager control is used...does the zone thermostat set the mode and call for heating/cooling or...how is that relayed? OR - how do the heating/cooling coils not end up fighting?

dradair gravatar image dradair  ( 2017-03-08 13:32:33 -0500 )edit

Maybe this is the better question. If the AirLoopHVAC:Unitary System is set with Load control, and set to a specific zone. In this case, what does the SetpointManger on the outlet node of the AirLoopHVAC:Unitary mean/control/do?

dradair gravatar image dradair  ( 2017-03-08 14:38:15 -0500 )edit

When Load control is used, the set point at the outlet of the system is not used and not needed. The Tstat calculates a zone load, then that load (W) is used to control the unitary system. For Setpoint control, the outlet node (or better yet the coil outlet nodes) will have a set point to control to. In this case, the Tstat will still calculate a load and that load is converted to a temperature at the current air flow rate. Then the unitary system controls to that temperature. If the Setpoint manager doesn't use a Tstat (e.g., SetpointManager:Scheduled) the you would not even need the Tstat.

rraustad gravatar image rraustad  ( 2017-03-15 15:38:43 -0500 )edit

The Severe Error/crash you described may be due to something else in the input that required the set point manager, not the UnitarySystem.

rraustad gravatar image rraustad  ( 2017-03-15 15:40:36 -0500 )edit

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Asked: 2017-03-08 12:32:49 -0500

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Last updated: Mar 08 '17