Heat-Timer® Corporation


Light Commercial Steam Cycling Control


The EPU-D is a steam cycling control designed specifically for light commercial building applications with a single steam boiler or steam valve. The EPU-D effectively regulates the boiler runtime based on the outdoor temperature. As the outdoor temperature falls, the EPU-D will run the boiler for a longer period allowing more heat into the building. This cycling concept maintains the ambient building temperature constant and comfortable. The EPU-D is equipped with an outdoor sensor and a heating system sensor. The heating system sensor signals to the panel that Steam has circulated throughout the building and begins the heating cycle. The heating system sensor will also determine if there is residual heat within the building and prevent a new heating cycle from starting, thus preventing overheating of the building and maximum energy savings.

  • Automatically cycles boiler operation based on outdoor temperature.
  • A reliable, easily installed, “Weatherhead”. This sensor monitors outdoor temperature and can be run up to 500′ from the panel.
  • Heating System Sensor to indicate heat has circulated to all parts of the building. This sensor is strapped onto a system return pipe and can be run up to 500′ from the Control.
    • Day and Night Scheduling for adjustable heat levels:
    • Day or Normal heat levels for when the building is occupied or tenants are active
    • Night or setback heat levels for when the building is empty or for when tenants are sleeping
  • Morning Warm up to quickly return the building to comfortable heat levels after Night or setback period
  • Separate Day and Night outdoor temperature cutoff set points
  • Separate Day and Night heat adjustments
EPU-D 926840-00

Even on very cold days, my Heat-Timer steam heating control sometimes has the boiler turned off and is not making steam. Is my MPC defective?
The MPC is working properly. The MPC or MPCQ Platinum are steam cycling controls for single boiler or multiple boiler steam heated buildings. They run steam cycles which are normally 60 minutes long (the length of the cycle depends on the type of radiation in the system). During this 60 minute period, the boilers will be on and making steam for part of the 60 minutes, and will be turned off for the remaining period. As the outdoor temperature drops, the length of the on periods will increase, and the length of the off periods will decrease. For example, on a 50°F day, the boiler may be on for a mere 5 minutes, and will be off for 55 minutes. However, on a 15°F day, the boiler may be on for 35 minutes, and off for only 25 minutes.

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