Two Pressuretrol's One Boiler

heidleml

Model 80 steam that has two pressuretrols. There is a Cut-Out pressuretrol which is being quite troublesome as well as a Cut-In pressuretrol. We seem to think that the second pressuretrol is supposed to be a redundant cut-in version and somewhere along the line someone replaced it with a cut-out. Weil McLain tech support has been zero help. We are having some trouble wrapping our head around the settings here. The cut out will only make if we dial the setting down to 1/2 or lower and even at that point it is being very touchy. Can someone confirm that this system should be operating with two of the same controls?

KC_Jones

Weil can't really help too much as the situation you are in (redundant safeties) typically relates to local codes. Normally they are different, with one set higher than the other and having a manual reset button. That is the back up that is basically saying "fix me" if it activates.

Pictures of what you have would help a whole lot on this one.

EdTheHeaterMan

More information needed. The WM 80 boiler can come equipped with several burners and control setups. Is this in a commercial building? Is the building open to the public (like a school or church) or a factory? This will determine the type of control system that is supposed to be installed. The WM tech support likes to talk to professionals... building owners (non professional) not so much.

Pictures of the control system from far enough back to see the burner and front of the boiler. Also further back to see the near boiler piping

Jamie Hall

Two (or more) pressurtrols is not uncommon. In fact, I recommend it. However, they both (or all) need to be wired so that they cutout on pressure rise, and wired in series.

I'm not surprised that Weil-McClain isn't being helpful -- it's not their problem in any way.

So -- the question is, exactly which models of pressuretrols (full model number, please) do you have, how, exactly, are they wired (which terminals are used and how are they interconnected, and what are they set for?

Just as a start, if they are standard PA404A type, one should be being used as a safety -- cutin set for perhaps 3 psi -- and the other, if this is a standard low pressure steam system, set for a cutin of 0.7 psi. Both should have a 1 psi (additive differential). They are wired in series. There are, however, a number of other pressuretrol types. Some are additive, some are subtractive. Some are SPST break on rise, some are SPST make on rise. Some are DPST, and can be wired to either break or make on rise.

What do you have?

heidleml

It is a large single family home. One pipe system. Carlin oil burner.
Two pressuretrols are wired in series. One is the PA404A with additive differential and the other is PA404B with additive differential. I am confused as to why we would have the 404B that makes on pressure rise...

KC_Jones

heidleml said:

It is a large single family home. One pipe system. Carlin oil burner.
Two pressuretrols are wired in series. One is the PA404A with additive differential and the other is PA404B with additive differential. I am confused as to why we would have the 404B that makes on pressure rise...

Someone put the wrong device on possibly. Pictures may help, but if that 404B is actually required then the wiring would need traced to see what it's controlling.

The PA404A will function by itself, pressure rise, trip, pressure fall, reset.

We need pictures of both of them so we can see the settings, also with the cover off so we can see the setting on the white wheel that is inside.

heidleml

@KC_Jones Not on site right now but both are set for 1/2 psi and both differentials are set to 1. The wiring is simple series through both. The only way we can get it to operate is if we back off the main setting on the 404B to 1/2 psi or less and then the set screw pops out of the spring. Doesn't seem right- I would imagine this set up would just have two 404A 's and the second being set a bit higher as a safety.

Jamie Hall

The 404B make on rise is, plain and simple, the wrong device. Lose it. If the owner wants two -- and I wouldn't blame him -- or you do -- you can have two 404As, with the second set higher as a backup safety.

Tinman

Most of the commercial Weils I’ve seen in Chicago, 80’s and 88’s, had two pressuretrols and a transducer on the manifolds. The transducer is what did the heavy lifting, cycling the IC burner. 

EBEBRATT-Ed

I see no reason for a PA404B at least not to run the burner and if it is wired in series with the other control then the "B" is the wrong control.

If it had separate wiring it might be for lo-hi lo burner control or used to power an alarm if the boiler lost steam

heidleml

All- I really appreciate the quick feedback. I have always said the toughest part of a serviceman's job is realizing when someone before may have made a mistake or shortcoming. Sometimes it is blatantly obvious and other times it is a minor nuance. This seems to be one of those times. We are installing a second 404A today and setting it up as a backup/safety. This site is such an amazing resource for the nitty gritty of things most plumbers have never considered and I truly thank you all. Have a great Thanksgiving!! @KC_Jones @Jamie Hall