PA404A - does this Pressuretrol look/sound broken to you?

HenrikW

Hi!

I live a neighborhood in Queens with mostly steam heat. Read Dan's book to fix some nuisance problems with my own and later others' systems in the neighborhood. Now I bought an old pre-war and have to do a lot of work on that steam system as well.

The PA404A additive pressuretrol doesn't seem to follow the setting anymore. I have cut-in at 0.5 and differential set at 1. However, the ptrol doesn't actually open the circuit with the "click" until about 7 PSI or so. When I checked out the inside of the box I found a long lateral crack in the plastic enclosed switch right above the Differential set wheel. I think it widens as I increase the diff setting. The result is that the boiler runs at around 6 PSI constant as it doesn't really get to Cut-Out point with all radiators spewing steam from their old, soon to be replaced, air vents until the house is at set temp.



I tried using my smallest hex key and then later my smallest cell phone repair drivers to change the set screw of the push rod but either I just don't have the right size or the screw is rusted/stripped. Or I am doing something wrong. Also, there was a discussion about a similarly old pressuretrol and someone mentioned a tiny hole that one would have to unclog but I just don't seem to be able to find it.

Please see the picture of the ptrol guts with the crack. The pressuretrol cuts out at around 6.5-7 PSI no matter what the differential is set to. Is this fixable? I'd like to run the system at 2 PSI max.

Cheers,


Henrik

Gsmith

Make sure the pigtail below the ptrol is clean, remove and flush out

Gordo

I'd say that switch is broken and the whole pressurerol needs to be replaced. I've seen that failure before. It's not very common, but it does happen.

gerry gill

And when you get a replacement, don't assume it operates correctly. Those devices are more times than not, not operating correctly right out of the box. We are trying to operate at the very bottom of the scale. I'm sure that is not where they are calibrated at. Gordo has a video of how to field test one. Perhaps you can search for it in a thread, or maybe Gordo can find and repost it.

Fred

You do need to replace that Pressuretrol. When you turn the Differential wheel and it widens that crack, it is not applying more/less tension on the switch mechanism like it should. It is just widening/narrowing the cracked switch housing.
It needs to be replaced before you put new vents on the radiators. Running at the pressures you currently run will damage the new vents. They don't like pressures above about 3 PSI and even that is too high.

EBEBRATT-Ed

It's a safety control and should be replaced asap. Crack is not normal.

HenrikW

thank you all - ordering a replacement and installing / testing before replacing radiator vents