In my house I have a low pressure steam boiler with McD & Miller

Paul Willimas

In my house I have a low pressure steam boiler with McD & Miller Series 67 Low Water Cut-off and also Series 101-A electric water feeder - out of the top of the cut-off (2nd opening) they have siphon loop (parrallel to cut-off) which goes up to Y configuration with Honeywell Pressuretrols, both are PA404A 1033 additive I think, (actual # shows PA404A 1009)at each end of Y -
the pressuretrol on the left is set at 4th mark up on psi main scale indicator (out of six marks) with adjustment differential dial at 4 on inside - it is wired to the electrial box
the pressuretrol on the right is set at the 2nd mark up on psi main scale indicator (looks like a 2) with adjustment differential dial at 3 on inside - this is wired into low water cut-off
my boiler is gas fired, Peerless (#G-8105-SP)with heating capacity gross output BTU/hr. 161,000 - max W.P. steam @ 15 psi -
I am trying to learn my heating system - can you explain the purpose, operation, setings, etc. of the 2 pressuretrols in the Y configuration that are connected at top of low water cut-off
thanks for your help

JJ_4

Pressure Controls

My system has two controls also. My home was originally a commercial building and I was told that two were required as failsafe in commercial buildings. Others may know better.

EBEBRATT-Ed

Most likley both pressure controls do the same job and are wired in series. One set at a higher pressure as a high limit the other could be an operating control which is set lower. In some locations two controls could be a code requirement.

On larger burners with two stage operation one may be used as a high limit to cut off all fuel on high pressure and the other control could operate the second stage of the burner so only part of the burner runs as needed.

Hard to say exactly without seeing the controls and how they are wired.

Ed

Long Beach Ed

Commercial Systems

... in some areas require two controls. Often one of them has to lock out on high pressure and require manual resetting.

They should both be on separate pigtails. Otherwise a clog will render them both inoperatve.

LB Ed