Pressure is Rising

TomH42

Just ordered "We Got Steam Heat", but this issue cannot wait.

We have a Dunkirk PVSB 5 for a 1.5 story in St. Louis City.  It is a one pipe system.  There are 5 registers on the 1st floor and 1 on the second floor.  Last night the pop safety valve opened up in the basement sending steam everywhere and my wife into panic mode (deservedly so).  We turned the system off and slept with extra covers.

This morning I fired up the system and after about 30 minutes the safety value again came into use.  I cleaned the area and started the system again and saw the pressure guage climb over 6 psi.  I turned the system off at that point. 

The cut in is set for .5 psi.  However, on the Honeywell indicator there is no where to adjust the cutoff setpoint. Cut-in, yes.  Cut-off, not to my knowledge. 

So, a couple questions:

1.  Are there systems that do not have a cut-off set point?  If not, where should I be looking for cut-off adjustment? 

2.  Would the first logical reason for rising pressure perhaps be a clogged relief valve in the basement next to the boiler? 

Thanks for any help!

Jamie Hall

Oh boy!

This a major safety issue.  The pressure relief valve used to be called a safety valve, for a very good reason.  It should never be called upon to open -- it is the very last line of defence!



The Honeywell thing you mention is the pressuretrol, and it looks as though it is set correctly -- that is, with the cutin at 0.5 psi.  If you were to take the cover off, there is a wheel inside called the differential, which is most likely set at 1 -- which is fine.  That added to the cutin gives you the cutout -- which should be around 1.5 psi.



That isn't happening!  Unless you are very handy, you need to get a pro.  The most likely problem is either a defective pressuretrol (contacts welded shut, or just not operating) or a plugged pigtail (the pipe leading to the pressuretrol).  You could try disconnecting the pressuretrol (with the power off, please -- that's full house power across the contacts) and taking the pigtail off (gently gently -- you don't want to break it or the pipe into the boiler!) and cleaning it out or at least seeing if it's clogged.  Then reinstalling it; if it was clogged, give the system another try.  If it wasn't, that wasn't it!



You should also have the pro. replace the safety valve.  Although they are usually OK after tripping, sometimes they aren't -- and as I say, that's your last resort.

BobC

Plugged pigtail?

If you take the front cover off you will see a white wheel, that should be set to 1. The releif valve was just doing it's job by releasing the steam when it got too high.



It sounds like the pigtail your pressuretrol mounts on might be plugged, or the pressuretrol might have failed. . The pressuretrol has to be unwired (power off at the ckt breaker) and removed (see if you can just twist it off). Then the pigtail has to be cleaned out, sometimes a heavy piece of wire will do it but you usually have to remove it and fight to get the gunk out. And sometimes you have to replace the pigtail because you can't ream it out.



It's about 27 here now, Hopefully it's a lot warmer there. The better part of valor might be to call a serviceman and pony up the cash. If you decide to attempt a repair yourself, send us some pictures of the boiler and the pressuretroll / pigtail.



good luck,



Bob

TomH42

Good Info

Thanks for the responses.  Low of 24 tonight.  I'm not that handy but can do small repairs.  I took off the cover and saw the differential which was set to 1.5.  I set it back to 1.

I also see the pigtail and understand the concept but unfortunately I have to go to work. Will call a technician.  At least I will know how to explain the problem.

I really appreciate your prompt and accurate replies! 

Tom

TomH42

Update

Had a professional come out this afternoon.  He took off the pressuretrol and blew out the pigtail from the end the pressuretrol was connected to.  When he did this air came out the vent.  He did not take the pig tail off the pipe that leads to the glass tube. 



Everything was cleaned and quite a bit of sediment came out of the system.  After hooking everything backup, the pressure continued to rise without shutting off.  The cutoff did not work.  So, does this mean either the pigtail was not cleaned completely or the pressuretrol is shot?  Isn't there a portion of the pressuretrol that also may have build up? 



I watched the technician take off the pressuretrol and feel confident I could do this if necessary.  At this point do I spend the $140 on a new pressuretrol or attempt to remove the pigtail completely and clean it and the pressuretrol a bit more?

BobC

Testing pressuretrol

If he was able to blow through that pigtail it should be all set. Did he check to see if the pressuretrol switch was shorted (had welded contacts)?



The attached picture shows a pressuretrol, if you look just above the hex head screw that holds the front cover on you will see a silver colored "beam" that sits between the adjustable spring (that sets the pressure cut in) and the piston that comes up from the diaphragm that reacts to the boiler pressure.



Turn the power to the burner off for this test. If you put your fingernail, or a small screwdriver under that beam (just above the hex head screw) and pull it up, you can easily operate that switch. You can hear it click on and off.



Next turn the power back on and set the thermostat so the boiler runs. With the boiler running, actuate that switch (keep your fingers away from the screws on top of that switch - 120v) and the boiler should turn off - THE BOILER HAS TO TURN OFF.



If the boiler does not turn off, the switch may be welded closed or the boilers wiring is wrong. If the boiler does turn off, the diaphragm inside the pressuretrol may have failed. If you unwire and remove the pressuretrol and look up into the brass coupling you will see a small hole (1/16") that has to be clear so the diaphragm can see the boilers pressure.



Turn the power to the boiler back off until you get that pressuretrol working properly.



Bob

TomH42

Making Progress

Thanks Bob.  The boiler did turn off when I actuated the switch.  I will now unwire pressuretrol and clean out the hole as instructed.

TomH42

Cleaning pressuretrol

Bob, here is a picture of the pressuretrol end.  I'm not sure what a clean end looks like so I'm providing the photo.  I have cleaned out some junk with a screwdriver but was wondering if there is a more effective way to clean it (if necessary).  Thanks for your help. 

AlexT

Looks really corroded to me

I just removed my Pressurtrol to install a gauge, and the base looked much much cleaner than that one. Looks like yours may be junk at this point.

TomH42

Cleaned (I think)

Thanks Alex.  I was able to clean it up a bit so that at least the hole Bob refers to is open.  I'm testing it as I write this.

TomH42

Unit is 18 years old

I failed to mention the unit is 18 years old and has worked well up to 48 hours ago.

TomH42

It's working!!

Pressuretrol just shut off unit at appropriate psi.  Thanks for the suggestion of cleaning in the pressuretrol itself Bob.  Wish the tech would have done that yesterday.

Next up, a better gauge. 

BobC

great news

Tom,



Glad to hear your up and running again, it's always nice to win one! Just keep an eye on that to make sure it stays clean



Bob

04090

Adjusting the adjustment

Is it possible for the inner dial to be turned more than one revolution?   I hestate to try at this time.



A system at my place is running at 7PSI and I couldn't get the 404 pressuretrol to shut it down.  I turned the adjusting screw on the top of the case down from 3 to 0.5 but that didn't help.  So I was thinking maybe the white dial adjustment may be off....



Or maybe I'm looking at a clogged pigtail again?  What's the right procedure for checking the device out?

BobC

Pressure

Steam systems should run at low pressure, you should be able to get down to about 1.5PSI with that pressuretrol. There is a chance your pressure gauge is not working right, does it read zero when the boiler is cool?



That white wheel only turns about 270 degrees, it should be set down to 1 or less. The left scale should be set as low as it will go.



Bob

04090

Success?

Well, thanks to the help on this board I knew to look for a suspect pressuretrol and was able to fix it.



The intimitating pressuretrol was readily removed, and the pigtail was found full of water.  With a little gentle persuasion the pigtail came off and was cleaned of black muck.  I pushed a mass through it just to be sure all the crud was out, and clean water readily flowed though it.  The sensor part was clean - not at all like Tom's picture posted above.



It's set for 2PSI and will turn it down as much as possible in use.  I see on the board that 1.5 is a common setting, but since this supplies radiators on the second floor thought it best to start a bit higher.  Actually looking forward to the next heating cycle. 



Thank you.

04090

double posted

double posted, how can I get this removed?