Determine if heating and cooling control is overlapping

Applicable Systems

• Primary: AHU, RTU, MUA, ERV, UV

Objective/Method/Outcome

• Objective: Determine if a heating and cooling control sequence overlap exists.

• Method: Check if the HCV and the CCV are both open while the unit is on.

• Outcome: An insight is generated if the amount of time the HCV and CCV are open simultaneously in a week exceeds the allowable hours’ threshold.

Logic

• Input both (normalized to 5-minute inputs) cooling and heating coil valve readings against the valve open threshold allowed.
• The coil valve is ‘open’ if the open threshold is exceeded.
• If the unit is on and both coil valves are open for at least one hour, calculate the hours of irregularity.
• Aggregate hours on a weekly basis.
• If weekly hours exceed the allowable hours per week, generate an insight.

if( CCV > Open Threshold && HCV > Open Threshold && Unit is On )
   {
   Count hours
   if (Hours > Weekly Acceptable hours)
      {
      Trigger insight - HCV and CCV are simultaneously open
      }
   }

Description / Method

Determine if a heating and cooling control sequence overlap exists by checking if the heating coil valve and the cooling coil valve are both open while the unit is on. {AHU|RTU|MUA|ERV|UV}

Diagnosis / Recommended Action

1. Error in the control sequence. Review and modify the programmed sequence of operations.
2. Automatic control has been overridden. Revert equipment back to automatic control.

Message

The heating coil valve and cooling coil valve are simultaneously open for over 4 hours in the week. Review and modify the programmed sequence of operations.

Notes

Not valid for systems using the cooling coil for de-humidification as well as cooling.Default logic flow is designed for % open, where the CCV/HCV is considered open beyond 2%Default Constants:

• Const. – Valve Open Threshold [%]: 2
• Const. – Acceptable Hours per Week [hrs]: 4

CTL Generated:

• Weekly Hours CCV/HCV Overlap

Rule Template Type

• Insight Type: Fault Detection
• Trigger Type: Active High

Default Priority

High

Inputs

Inputs	Units	Default Value	Tags	Description
Cooling Coil Valve	%		cmd, cool, water, valve	Cooling coil valve position (command or feedback)
Heating Coil Valve	%		cmd, heat, water, valve	Heating coil valve position (command or feedback)
Equipment Status			fan, status|cmd	Unit on status. Alternatively, building occupancy can be used
Const. – Valve Open Threshold	%	2		Value above which the coil valve is considered open
Const. – Allowable Hours per Week	hrs	4		The acceptable hours of overlap per week

Output Calculated Trend Logs

Output CTL	Units	Description
Weekly Hours CCV/HCV Overlap	hrs	Trended number of hours per week that CCV and HCV are open simultaneously