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Heat Timer Model EPU Program Clock is in "Off" Period

Good Afternoon,

This morning, our 18 unit building steam boiler stopped working (outside temperature 40 degrees). The cycle time indicator was stuck on 10 and neither the red or amber lights were lit.

I manually rotated it until it hit zero and the boiler started up and the red light lit up. The boiler ran for quite a bit, as it hadn't run for hours and the building warmed up. The amber light came on and then the boiler continued running, during which the cycle time indicator was turning.

After 6 minutes (B setting @ 40 degrees is about right according to the Heat Timer charts) the boiler shut down and the amber light turned off. The cycle time indicator stopped turning. A minute later, the red light also turned off.

The boiler did not fire again, neither the red or amber lights turned on and the cycle time indicator remained stuck between 5 and 10. Three hours later, I again manually moved the cycle time indicator to zero. Just as before, the boiler turned on, heated up the building and then turned off and has remained dormant since: both lights are off and the cycle time indicator is stuck between 5 and 10.

So is the stuck cycle time indicator the cause of this, or is it because the the red light is not turning on, or because the amber light is not staying on?

Thank you for any help anyone can give on this.


  • 109A_5
    109A_5 Member Posts: 1,339
    Hello @Bendico,

    If your unit is of the technology I suspect, there is a basically an old style synchronous clock motor in it. Those motors after spinning for many years their bearings wear out enough that often when the extra load is applied to change the state of the controlled device at a set-point time the motor stalls.

    I have no idea if a replacement motor is available. They are probably easy to change if you can get the correct replacement motor.
    National - U.S. Gas Boiler 45+ Years Old
    Steam 300 SQ. FT. - EDR 347
    One Pipe System