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Posted by Cam Greener on September 15, 2008 at 10:48:41:
In Reply to: Re: Heatmaker M2 HW 130 posted by HeatPro on September 15, 2008 at 00:20:57:
: : This boiler seems to operate correctly until it reaches its high control setting and the burner shuts down.
: +++ When a boiler shuts down only on the high limit control, it is malfunctioning from incorrect wiring and design. There should be enough radiator to get rid of all the heat the boiler can make before it gets near a high limit.
: The burner doesn't come back on unless the low limit tells it to, or the operating control tells it to via the house thermostat.
: +++ That is a proper function.
: the low limit not shutting the burner down even near the high limit.
: +++ It is not the job of a low limit control to shut the burner down; it turns the burner on to satisfy a minimum water temperature. and shuts the burner off when the water is warm enough to make hot water. The burner should turn off due to the rooms not needing heat any longer or the hot water demand is ended. If it doesn't allow the burner to shut down, it is miswired.
Perhaps it is miswired, or needs a new computer control module. The issue isn't necessarily temperature regulation, (and the high control correctly shuts down the system, not the high limit), rather the post-burn purge cycle does not end or restarts itself continuously. When it needs more heat the burner works correctly, its just that after the post-burn purge cycle the system seems to reset and either: repeat the post-burn purge; or it could be that it is starting a new burn cycle pre purge, but once the pre burn purge is complete is figures out that it doesn't need to burn since the water is already at temperature.
Basically, the unit never goes into stand-by mode, it stays in purge cycle (which cycles on and off continuously until a new call for heat).
I assume one of two things is happening:
1-the purge system has a malfunction (I assume this is the fault of the computer control module)
2-for some reason there is a call for additional heat which is shortly negated by some other operating control in the unit
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