Knowledgebase: HVAC
Dual layer controls for radiant systems removed in v5.0
Posted by Michael J. Witte, Last modified by Michael J. Witte on 28 November 2017 07:16 PM
Question: In the 5.0 release notes, I read "Dual layer controls for radiant systems removed." In the 5.0 I/O Reference I also saw there are three sentences added to the first paragraph of the ZoneHVAC:LowTemperatureRadiant:VariableFlow. These sentences essentially describe how the object has its own set of "radiant system controls." These three sentences sound like they're describing the controls that were in place for the radiant system in 4.0 and they are describing what is essentially a second (dual) layer of controls (which the release notes suggest were removed). Could you please help me understand what is different between 4.0 and 5.0? Thanks!

Answer: In v4.0 and before, the main zone thermostat (ZoneControl:Thermostat, or HVACTemplate:Thermostat) impacted the operation of the radiant system controls. For example, the zone thermostat (responding to air or operative temperature) had to request heating in order for the radiant heating function to activate. If the radiant heat was active, then it would control based on the inputs in the radiant object.

In v5.0 this interaction with the zone thermostat has been removed. So, the controls in the radiant object will be honored no matter what the zone thermostat may be requesting. This allows the zone thermostat to be used to control other HVAC equipment based on air temperature without impacting the operation of the radiant system controls.

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