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Posted by HeatPro on December 08, 2010 at 10:28:19:
In Reply to: Re: M&M LWCO #67 posted by Jim Hankinson on December 08, 2010 at 09:05:59:
It's a simple float-operated switch that cuts off the burner power when the float falls low, and reestablished the power to the burner when the water rises enough in the body of the 67 control.
If a feed water solenoid is wired to open when the water falls, it usually overfills the system, as steam cycles often leave steam in the system to return as condensate water at a later time than when the control allows water in.
Other auto-fill devices that would be attached to the 67 contacts involve a metered amount of water and a delay to prevent overfilling.
Novices often believe an auto-fill device is a good idea; however, stuck valves or changed timings have the occasional fault of making a one-pipe system into an upstairs sprinkler system when the valve hangs open or keeps adding water on each cycle due to dirt in the radiators, piping, or failing vents.
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