8 EPU‐D Installation and Operation Manual
059840‐00 Rev. A
Heat‐Timer Corp.
Typical Configurations
The EPU‐D works with virtually any non‐vacuum one or two‐pipe steam‐heated system. The EPU‐D can control
the boiler directly to create steam or, for systems where a central plant provides steam, the EPU‐D controls a
motorized valve to allow or prevent steam from entering the heating system.
Based upon the specific layout of the steam heating system, there are several differences in locating the heating
system sensor and in the output wiring to the boiler or motorized valve that must be considered. It is important
to carefully check the piping diagram to determine which of the following layouts matches your heating system:
• One Pipe Steam ‐ Direct Burner Operation (see Figure 7 on page 38)
• Two‐Pipe Steam ‐ Direct Burner Operation (see Figure 8 on page 39)
• Two‐Pipe Steam ‐ Motorized Valve Operation (see Figure 9 on page 40)
EPU‐D Inputs
Heating System Sensor
The EPU‐D is designed to connect to the provided Heat‐Timer heating system sensor (p/n 904220‐00).
The heating system sensor is located where it will show that heat has reached the furthest location in the
building. The EPU‐D uses the temperature information from the heating system sensor combined with the
outdoor temperature sensor to control the heat level in the building.
Pressuretrol Sensor
The EPU‐D can optionally connect to a pressuretrol sensor instead of the system temperature sensor.
The pressuretrol sensor must be a reverse‐acting pressuretrol that indicates when to start the heating cycle
based on a specified pressure setting.
Outdoor Temperature Sensor
The EPU‐D is designed to connect to the provided Heat‐Timer temperature sensor (p/n 904220‐00).
The outdoor temperature sensor is a solid‐state sensor located on the exterior of the building. The EPU‐D uses
the temperature information from the outdoor temperature sensor combined with the system temperature
sensor to control the heat level in the building.
