Removing a Pressuretrol

04090

My one pipe steam system has a PA404A pressuretrol. The system shuts off after about 20 minutes of use and I've traced the cause to the pressuretrol. The system runs well if I set it to 6PSI. Original setting was 0.5 on the outside and 1.3 on the dial.



After scouring this site for causes, I'd like to clean the pigtail, but am not sure how to remove the pressuretrol. I assume the four screws on the underside come out, the box can "hang" free and that the base of the unit then unscrews. Not wanting to break anything.... is that the right way to do it?



The device is next to the boiler and there's not enough room to take it off as one piece.

Dave in QCA

Do not remove the screws!

To remove the pressuretrol, you unthread from the pipe that it is screwed on to.  Do not remove the screws, you will dissassembling the pressuretrol itself, and you will likely damage it.



Can you post some pics?



6 psi is way too much pressure.  When your boiler shut off because of pressuretrol, were the radiators hot, was there still a little steam pressure.  If your pressuretrol shut your boiler off because of pressure, that is what it is supposed to do.  Its job is to limit the pressure in the boiler.  It does that by shutting off the fire until the pressure drops, at which point the boiler should start to fire again, unless the thermostat is statisfied.

04090

response

The back of the pressuretrol box is almost at the face of the boiler, there's no way to unscrew it from the pigtail. The pigtail connection at the boiler is heavily corroded and looks like it'll self destruct if removed.



I will post photos tomorrow.



The boiler ran long enough to allow the radiators to get a tad warm before the pressuretrol shut the system down. The pressure gauge on the boiler had no noticeable reading. When I changed the setting, the boiler ran and the radiators clunked and hissed as they always do (sounds we are comforted with knowing the system works). The pressure gauge didn't get over 2.

Dave in QCA

Time to call a Pro

You will have to unscrew it from the boiler.  The corroded area may very will be where it is clogged up, if in fact it is.  Better call a qualified boiler man to get this thing corrected.

hungrytech

tech ?

if pigtail was clogged boiler would not shut down at 2lbs of pressure .  how long has it been since boiler was serviced?

04090

update

Sorry if I wasn't clear earlier.... this infrequently used steam system (uses about 25 gallons annually and tank was last filled and service was last done three years ago) ran about 20 minutes and shut down. The radiators were barely warm. I checked with a VOM to see where the break in the power to the burner was and found it to be at the pressuretrol. It was set to 0.5 and when I set it to 6 the burner resumed operation. The pressure gauge on the boiler did not exceed 2 during the heating cycle.



Would like to remove the pressuretrol and clean out the pigtail, but the pressuretrol is to close to the boiler to unscrew it, and to remove the pigtail with the pressuretrol means I'd also have to remove the pressure gauge because it's in the way.



Is there an easier way of doing this?

Dave in QCA

Nope

Sorry, wish there was an easier way, but the way this was designed, that is the only choice you have.

Jamie Hall

Your problem

may not necessarily be the pressuretrol.  If it shut the boiler down when it was set at 2, and then restarted the burner when it was cranked up to 6 it seems to me that it is seeing pressure.  Not that it would hurt to clean the pigtail, but...



What is that pressure gauge?  If it's a 0 to 30, do you really believe it at the low range?  If so, why?  What does it read when the system is cold?

ryanr256

Ptrol disassembly

Having unscrewed the fours screws on the bottom of the Pressuretrol, I can tell you what is involved.

The four screws hold the switch trip mechanism in place. The body of the Pressuretrol is sandwiched between the trip mechanism and the "base", which is actually the pressure diaphragm (the part that screws to the pigtail).

If you remove the four screws the spring that loads the trip mechanism will more than likely unload and become unhooked. You will also expose the pressure diaphragm and the button that rests on it. This button has an indent at the top into which a pin on the trip mechanism fits. The trip mechanism is a rocker assembly that is loaded by the spring/cut-in screw on one side and the button/pressure diaphragm on the other. When the pressure rises the diaphragm pushes up on the button which then pushes up on the rocker assembly which pulls down on the spring. The screw adjusts the tension on the spring which changes the behaviour of the rocker assembly.

When you remove those screws, all of the working internals of the Pressuretrol are no longer held in place. They will be free to move around and possible fall out and get damaged. The microswitch is attached to the body and will not come out though.

Once they are removed, they must be reinstalled. It is difficult to balance everything inside that little Pressuretrol body while making sure everything is lined up and assembled correctly. The button, pin, spring, screw, etc. all have to be aligned properly and there isn't much room for error. And, the Pressuretrol is considered to be a safety device and it's generally not a good idea to be disassembling it unless you are absolutely sure of what you are doing. And, even then, it's not a good idea.

Lastly, it's always a good idea to turn off the power whenever you remove the cover to the Pressuretrol. There's current/voltage involved and the risk of a short is present because of the exposed terminals on the switch.

Oh, and my explanation is for the microswitch type Pressuretrol and not the mercury switch type.

-Bob

BobC

Just do it.

Why not just unwire the pressuretrol (circuit breaker or fuse OFF), unscrew the pressure gauge, and twist off the pigtail / pressuretrol. Clean out the pigtail and add a 2" brass nipple with a coupler at the boiler and then a brass 1/4" union on top of the pigtail so you will never have to go through this again. Then screw the 0-30 gauge back in.



If you want to know whats really going on add a T so you can mount both the pressuretrol and a low pressure auxiliary gauge. I'll bet that 0-30 on the boiler is not working right at the low end of it's range. I've got a union that I'll add onto my setup when I get around to it, luckily my boiler is old enough that they used longer pigtails so I didn't have to build in an extendo.



Bob

Dave in QCA

equipment on top?

Bob, what are the devices on the top of the boiler?  I don't think I have ever seen those options in the Burnham catalog.  

BobC

The detritus of a lifetime.

Dave,



I worked as an engineer in the power supply field for 35 years, those are just some of the treasures I've collected over the years. When I croak, it's going to take a LOT of work to unload that cellar.



Finally finished shoveling out, time for some bourbon (for medicinal purposes of course)



have a great night,



Bob

04090

followup

One more question, not related to the pressuretrol nor worth starting a new thread on.



Is this the same model Burnham that I now see posted repeatedly on this site as leaking and/or cracking? And if so, should we just replace it while it's convenient this spring rather than waiting for what may be an inevitable break?

Charlie from wmass

Not all Burnhams are leakers

Having the system looked over by a reputable pro should be able to see if you have indications of a problem coming.