"Oversized" pressuretol, dead gauge

MrDvorak

Hello all, first time poster here. I am a homeowner from Boston area, trying to prepare for the first winter in my "new" (*1936) house. I have a one-pipe system with a Weil-McLain GoldOil boiler that seems to be in a quite good condition. There are several paper tags in the basement showing that it (or its predecessor) was serviced annually for at least the last ten years. I want to check a few things before I invite that company or some other contractor to inspect and adjust my boiler. I learned a bit more about steam heating systems from the marvelous book "We got steam heat" by this site's owner. Tremendous book especially for someone who came from Europe and did not even know steam heating existed ten years ago. 





I try to do my homework before I call the pros. I am covering pipes in the basement with 1" thick insulation. I replaced  vents in my recessed cast iron convectors, except for two where the is not enough clearance between the radiator body and the vent tip to unscrew it (I wonder how they installed them there, even my wife gave up - I hope I will not have to pull the whole radiator out do it). I am going to replace the main vents ASAP, too; they are almost certainly shot. Empowered by the knowledge from the book, I also gave the boiler a hard look; and I found a few things that are not entirely kosher IMHO.





1. the pressuretrol is Honeywell PA 404A 1025 with a main cut-out scale of 3-15 PSI. That seems a little high to me if the optimal pressure is to be kept below 1.5PSI. How quickly should it trip the burner? It lets the boiler runs for 20-30 minutes without interrupting it once\, but I cannot really tell what the actual pressure is because...





2. ... the pressure gauge (0-15 PSI) is dead. Not moving at all. Nothing. Nada. 





My logic tells me that the pigtail is likely clogged, and/or the gauge is dead, and that the pressuretrol is not really a good fit, probably dead too, and that it deserves to be replaced with something more accurate and fit for the job anyway (perhaps a Vaporstat as discussed in another thread?).





Am I confused or is my analysis sound?

Thank you for help.

-MrD

Dave in QCA

that is a possibility

It is possible that your pigtail is plugged.  Cleaning it out will tell you the answer to that question.

The other possibility is that your boiler is closely sized to your load, and therefore is not building up any pressure.  Therefore, it does not need to cutout, and the pressure gauge that you have shows no movement.  Check the pigtail and you will know more.

Most folks on here will recommend getting a low pressure gauge and using a vaporstat for control. 

BobC

How comfortable are you . .

About all you can do with a pressuretrol is to set the main scale on the front down as low as it will go and the differential wheel to inside to 1. These things are not at all accurate but the boiler manufactures use them because they are the only game in town unless they want to pay the extra for a vaporstat. I installed a low pressure gauge and a vaporstat just so i could operate the system at 12 OX. If your system is correctly sized you may just be running at too low a pressure for the 30PSI gauge to register.



It would not be hard to remove that pigtail if your comfortable with doing so, they do sometimes clog up. To test it you can unscrew the gauge with a wrench and see if you can blow into the pigtail, if you can't it's blocked and has to be cleaned or replaced. Just make sure the boiler is cool and power is off before attempting this.



If it's not blocked I would put the gauge and power back on and fire up the boiler and watch it carefully to see how long it takes for the boiler output pipes to get steam hot and then how much longer it takes for your main air vent to get hot. My Burnham v75 takes a little over 6 minutes to start making steam and 3 more minutes for the vent to see steam, the radiators start to warm up a few minutes later. My boiler is oversized so yours may well take longer. While it's making steam listen to see if the main steam vent is hissing very loudly (also the radiator vents), they do hiss but they should not be terribly loud. Also see how long it takes for the radiators to start heating up after the main air vent gets hot.



If you examine the inside of the pressuretrol with the cover off (careful there is 120v on those switch terminals) you will see a small piston that comes up and moves the silver lever that actuates the microswitch. You can use a small screwdriver to move that lever up and that should actuate the switch and tell you if the microswitch is good - it does not tell you if the diaphram and piston is good.



If you need any advice just ask and someone will get you the information you need, the folks on this site are happy to help and a lot of them know a hell of a lot more about steam systems than i do.



I live just south of Boston and it's going to get cold tonight with perhaps a touch of snow so it's time to get that heat on.



Bob

MrDvorak

Thank you!

Thank you very much for your help gentlemen. I played with the system a little bit last night, removed the gauge and the pressuretrol (dirty water spilled out of of the fitting when I removed the gauge - another indication of a clog in the pigtail?), I will try the pigtail blow test later today. I plan to install a low pressure gauge next to the 30PSI one and to replace the 3-15 PSI pressuretrol with a 16oz Vaporstat.







I am now quite sure that the main vents need to be replaced (with Gorton #2s), they look like they are pretty old, they are noisy, one of them does not seem to release any air at all. I have tried to unscrew them but it is impossible to loosen them. It looks like a piece of black tape of some sort was used to seal them, this will be fun (not). They are screwed directly into 1" (IIRC) pipes that take them about 12" above the return lines and I feel like I am twisting the return lines with them. I saw some tips how to remove stubborn vents in this forum, wish me luck.

Thank you,

MrD

MrDvorak

Clogged indeed

FWIW, I did the blow-in-the-hole test and the pigtail was clogged indeed. I managed to unclog it in situ (I am not very proud of the method though - a few gentle strokes from a bike tire pump dislodged the plug, but I guess it went straight to the boiler, oh well). Now after ~20 minutes, the 30PSI gauge finally shows some movement as it hovers around 1PSI.







This is a hack and I will replace the pigtail with a new vertical one later, but the next major milestone is the replacement of the bad main vents. Thank you again gents!

BobC

Great news

I'm glad it all worked out for you. Using that bike pump was a good move to get everything working again.



When you replace that pigtail you can probably boil the old one clean and keep it for a spare.



Bob

MrDvorak

A few pictures

A few pictures. First new vents. Those things are massive! I have to figure out how to get them away from those other pipes under the ceiling.







And a detailed view





The 3PSI precision gauge installed, behind a ball valve:





And a detail of the gauges in action. The 3PSI gauge bounces around 0.1 PSI for ~ 15 minutes, then it goes quickly up. The 30PSI gauge fails to register pressure under 2 PSI and then it shows about 1PSI less. That thing may be required by code/insurance, but it is not to be depended on!

nicholas bonham-carter

New vents and new gauge for new steam system owner

Good job with the vents and gauges. I think you could also reduce the pressure cut out on the pressuretrol, as 2.5 is more than your system needs. But beware! When I tried to reduce the pressure on my new pressuretrol, the linkage must have become disengaged, and my pressure shot up out of control. Luckily, I was watching, and I went straight away to the supply house for a vaporstat! Subsequently, I found the gaugestore site and got a good low-pressure gauge with which to verify what was happening.--nbc

MrDvorak

Thank you

Thank you Nicholas. My pressuretrol's lowest cut out setting is gigantic 3PSI so I bought a 16oz Vaporstat as a replacement but I will keep the PT as a backup. The gauge arrived and was installed today, I will have the 'stat there later this week. The main vents made a huge difference btw., no more 1" bouncing of water in the glass tube and the radiator vents are now almost entirely quiet with the exception of a few clicks now and then (all new Hoffman 1As plus one 1B upstairs). It feels good to be in charge of at least small improvements!

Dave in QCA

Excellent!

Excellent intallation! 

Rod

Very Nice Work!

Very Nice work!  If you need replacement pigtail the best source I have found is McMaster Carr   http://www.mcmaster.com/#   Just type the word pigtail in the "Find" window. They have a huge assortment of sizes and materials, Get one in red brass ("bronze")

- Rod

MrDvorak

Brief "vacuum" in the system

Thank you gentlemen, you are very kind.



Now that I can observe the pressure with far greater accuracy, I am spending some quality time sitting in front of the boiler and observe what happens during a complete heat cycle.



The 3PSI gauge can go negative and it does so during the final stage. I.e. when I let the pressure go to .5 PSI and switch off the burner, the pressure drops to 0 in about 45 seconds but it does not stop there as the pressure goes negative up to approx. -.5 PSI at which moment the main vents open and quickly equalize the pressure to zero again. You can hear those things suck air but I am surprised that it takes so long time for them to open.

MrDvorak

A closure

The old pigtail is finally replaced with a new one, it was full of goo and quite nasty. A new Vaporstat replaced the old big pressuretrol, too. The tee with gauges and vaporstat is sitting on a union which made the reassembly a breeze. The system runs at less than two ounces per inch most of the time, then it begins cycling between two and eight ounces.



Thank you again for your help.