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Re: Aquastat wiring and setting

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Posted by heatpro.us on January 31, 2012 at 20:59:21:

In Reply to: Aquastat wiring and setting posted by Stan on January 31, 2012 at 07:55:22:

You're looking for an antique where the paper probably fell apart decades ago.

If the #541 control has independent controls within the box, and not like the combined White Rodgers 11A61-103 control, then the right side high limit control would run power from the burner relay to the burner through the high limit control side R to B contacts on most old controls, to disconnect power when the water got too hot at 200F.

The left side single pole double switch would run power from the relay through the circulator switch to the circulator when the water got hot enough at 150F or so through R and W on most old controls.

As the control is used for more functions in different boilers the other contact on the double pole single throw control switch could do other things but isn't needed.

Both sides wouldn't be in series R to B to R to B, unless using the combination control for double high limit safety. You wouldn't want to do that as the lower setting would be the maximum temperature.

Some old boilers tended to leak between sections unless kept warm by using the two sides in parallel, so the RBW control side kept the boiler warm at about 140F or so through R to B and the circulator would run through R to W when warmed.

The separate two contact high limit control would be wired in parallel with the other 3 contact side, so either could disconnect the burner when calling for heat through both sides until warm enough or too warm.


: Hello;
: I'm running an early sixties Homart cast iron boiler w/ tankless coil.
: The "Triple Hot Water Control", model # 541.9166 is wired; the left hand switch controlling the circulator, only, the right hand switch controlling the burner.
: I understand that the right hand switch is a High Limit switch and is supposed to be a safety, to prevent a burner runaway.
: The LH switch is a double throw switch. Should I wire it in series with the high limit switch? If
: I do that, how should the Adjustable Differential be set?
: Reason I'm asking is that the burner short cycles because the RH switch's trip points are so close with no adjustable hysteresis.
: The wiring / adjustment card is missing from the cover, have only the single sheet with specifications.
: Question, does the Differential adjustment offset the low point, or the high?

: Thanks for any help, especially a pointer to a correct wiring diagram and setup info.

: Stan

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