One pipe system: 2 questions/concerns related to main vents

Marc_J

I live in a 1922 four-square in Westchester County, NY. It's heated with a one-pipe steam system. Boiler was replaced 3 years ago when we converted the house from oil to gas. First off, thanks to everyone who makes this forum possible. I find it both incredibly resourceful and entirely fascinating. Second, I have some questions that I'd love to get answers to. I'll start with two of them, both related to venting the mains.

1) The main was vented in two locations. Each with Hoffman #4's. First one was at about the halfway point of the full main loop - approximately 20' into a total 40' loop. The second one is in the proper location just past the last radiator at the end of the main and located about 8" up on an extension. Why would someone (living or likely dead in this case) vent in two locations, practically diametrically opposed locations in the system?

2) I've recently built a 3 way "tree" of vents and put them ALL at the end of the line and plugged the one that was halfway through. Even after the radiators in the house have all begun to heat, the main vents on the tree are still letting out air. Is that normal and, if not, what's my next move to fix that? I should mention that even in the previous configuration, with the two different main vent locations, I was still getting air and sometimes steam through the main vents even after the radiators were well on their way to hot.

Jamie Hall

Question 1 -- who knows? Strange things happen...

Question 2 -- you may well be getting some air out for some time after the radiators begin to heat. You shouldn't get any steam, though -- the vent should close.

Fred

The main vents should be at the end of the main or on the return. The one that was halfway down the main would close well before all the air was out of the system, leaving only the single main vent to handle all the air in that last half of the main. Depending on the diameter of the Main, those Hoffman vents probably are too small. A 40 ft. main, 2 to 2.5" diameter would be better served with one Barns and Jones Big Mouth vent.

To your second question:
- Either the main vents are not closing like they should
- the system pressure is high enough to blow those vents open, or
- and most likely, the vents on the radiators are large enough that they become the path of least resistance for the steam. Get the main venting correct, then adjust the radiator vents to balance the system.

Marc_J

Thanks Fred. Pressure is set from .5-1.5. Got 2 big mouths on order and will get those in then see what's next!

Fred

Marc_J said:

Thanks Fred. Pressure is set from .5-1.5. Got 2 big mouths on order and will get those in then see what's next!

Make sure that the pigtail the Pressuretrol is mounted on isn't clogged, otherwise the Pressuretrol won't see the system pressure, rendering that control useless.

JUGHNE

Just a story concerning vents in the middle of the run.
My first steam job of any consequence was a church, (+550,000 btu boiler). It had no main vents at all.
I found a plug on each 3" main about 1/2 down each side of the church. Put vents there. Helped the front of the church a lot.
Eventually had to redo dry returns and antlered up with 5 G-2's per side/main at the end of returns.
Only the front of the church was used on weekdays and was always warmer as needed. Eventually put faster rad vents on the front 2 per side, removed the half way main vents.
Still the front is warmer by design....incentive to sit near the front. Set back occurs during the service on weekdays.
They coast on radiant mass. (no pun intended).

That was the logic for my "method to the madness".

Marc_J

Fred said:

Marc_J said:

Thanks Fred. Pressure is set from .5-1.5. Got 2 big mouths on order and will get those in then see what's next!

Make sure that the pigtail the Pressuretrol is mounted on isn't clogged, otherwise the Pressuretrol won't see the system pressure, rendering that control useless.

Good tip.. so when you refer to a clogged pigtail, I assume that if i pushed a wire down through it it shouldn't come back out black and soupy, like an oil dipstick from a car engine? [head in hand]. To make matters even more interesting, the pigtail and pressuretrol were clearly installed before the gas-line & skim pipe were attached. No easy way to get them off now...

nicholas bonham-carter

Post a picture of the pigtail, and maybe we can suggest a removal/cleaning procedure.—NBC

Marc_J

Between a rock and a hard place. I can cut it off and install a new one with longer stems so the pressuretrol sits above the boiler. Or...
I had taken the gauge off to probe a wire into the loop since I can't get the Pressuretrol to spin off, thus the funky angle. New low pressure gauge 0-3 also on the way with Big Mouths.

nicholas bonham-carter said:

Post a picture of the pigtail, and maybe we can suggest a removal/cleaning procedure.—NBC

nicholas bonham-carter

A hacksaw may be required for that removal.
Put it back on with a brass union, on the pigtail, so the pressuretrol can be removed.—NBC

Fred

That pigtail should be cleaned out yearly. You will have to probably cut the pigtail off and add a nipple/coupling to raise the Pressuretrol up enough to clear the top of the boiler. (Will that give you enough clearance (from your Skim port) to turn the pigtail? if so, put a new pigtail on and add a coupling/nipple to raise the Pressuretrol above the boiler

Marc_J

Thanks guys. To be continued tomorrow. Looks like I can just about spin a new pigtail in past the skim port if there are no fittings on the end and the new one is no larger than the existing one. I'll plan to move the entire assembly including the gauge and the T up above the boiler. No issue adding 4 inches or so in height on that correct?

Anything else I need to know about installing a pigtail? Something about filling it with water?

Last question (s): best way to clean out the base of the pressuretrol before reinstalling?
Does polarity matter on the pressuretrol switch wires?

Marc_J

nicholas bonham-carter said:

A hacksaw may be required for that removal.
Put it back on with a brass union, on the pigtail, so the pressuretrol can be removed.—NBC

Perhaps the brass union before the T is the better option here rather than moving the entire assembly up. Means I can remove the assembly annually without having to even spin the pressuretrol right? Thanks for sharing the wisdom!

Fred

@Marc_J , You can fill the new pigtail with water but it will fill with condensate pretty quickly. The wires can go back on either terminal. The Pressuretrol is just a "make/Break" switch and the wire is just two ends of the same wire. The port on the Pressuretrol is very small. If it looks like it too is clogged, you can take a pin to clean it out. The diaphragm in it is metal so you don't have top worry about poking a hole in it.

Christian Garibaldi

If you have a clearance issue with trying to remove the pigtail with the pressuretrol attached up top, and you cant spin off the pressuretrol unit due to the housing hitting the boiler jacketing, you perhaps can but yourself some wiggle room by disassembling the pressuretrol base from its upper housing. There are 4 small screws underneath (Torx head on mine) that face upwards and attache the diaphram housing to the main box. If you remove those four screws, you can lift off the upper portion (There is a small spacer concave spacer that acts as a pushrod for the microswitch that you will see that just sits in the middle and has to go back in when you put it back together, its pretty self explanatory when you see it) and that should give you the additional space you would need to just unscrew the diaphram portion of the bottom of the pressuretrol. I ran into the same issue on my boiler where I went to remove my pigtail for the first time and there just wasnt a way to unscrew it from the tapping with the pressuretrol attached. I removed those four screws, took off the top of the pressuretrol, which left just the sealed diaphram portion threaded on and unscrewed that from the pigtail and then that gave me the room to get just the pigtail off by itself. after that I added a short nipple and a union with an elbow and nipples up to raise the assembly. I also wound up adding a tee and branched off to add a low pressure gauge and a vaporstat along with two more unions so that now in the future, getting any of it off for cleaning, inspection, maintenance etc is easy and simple.

Fred

@Christian Garibaldi said: If you have a clearance issue with trying to remove the pigtail with the pressuretrol attached up top, and you cant spin off the pressuretrol unit due to the housing hitting the boiler jacketing, you perhaps can but yourself some wiggle room by disassembling the pressuretrol base from its upper housing

Don't take those four screws out! There is a free floating pellet in there that has to be centered on the metal diaphragm and those Pressuretrols usually already need to be calibrated. Getting that tiny pellet perfectly centered is next to impossible, especially during reassembly. Cut the pigtail and install a new one!

amp3d

> @Christian Garibaldi said:

What’s the valve at the bottom for?

Fred

amp3d said:

> @Christian Garibaldi said:



What’s the valve at the bottom for?

About the only purpose is to isolate the pigtails, gauges and controls. I have to assume the boiler tapping is somewhere below the boiler water line (like on the top of a McDonnell Miller Low water cut off. You can close that valve and then remove any of the pigtails, controls/gauges without boiler water running out.

Chris_L

@Fred wrote:
Don't take those four screws out! There is a free floating pellet in there that has to be centered on the metal diaphragm and those Pressuretrols usually already need to be calibrated. Getting that tiny pellet perfectly centered is next to impossible, especially during reassembly. Cut the pigtail and install a new one!

No need to cut the pigtails. Before installing unions on my Pressuretrols, I took the screws out many times. The trick is to turn down the pressure on the Pressuretrol as much as possible--even until the spring comes--off before putting it back together.

Then, as you reassemble it, the pointed screw on the lever arm will stay in the depression in the top of the pellet, and the pellet will stay in center of the diaphragm.

With all the tension off, you'll be able to start the screws while keeping everything aligned. Tighten the four screws evenly a bit at a time, and you should be all set.

BobC

@Fred That's good to know, thanks for the tip.

Bob

Christian Garibaldi

I understand the warning you mention about that pellet as you call it, I referred to it as a spacer. its basically a small turned metal peice which has a flat on the bottom and a concave depression on the top. the center point of the pressuretrol calibration adjuster sits down in the middle on the switch side, and the flat bottom of the pellet rests against the diaphragm on the pressuretrol base. In my instance, I didnt have any issue with getting it back together. I had mine adjusted all the way down which may have had something to do with it, but when I went to put the screws back in, I was able to easily line up the point in the center concave section and wiggle it to make sure and then slowly and evenly draw the four screws home until seated. the unit still operated fine. I mean for sure, dont force it, and yes, it could be messed up if you arent careful, but Ive done it a couple of times without issue. I was only offering an alternative idea to cutting the pigtail if needed, certainly not declaring that as the best way or correct way, it was jsut what I had done when faced with the similar dilemma.

As for the valve at the bottom of the assembly, I just added it because I had it. May be overkill, but I just figured it could allow me to quickly crack it and see if a bunch of crud aver came out or maybe help to drop any sludge easily if need be. For instance I could pull the vaporstat and pressuretrol unions off, and either flush or blow out the pigtails without sending anything back into the boiler, just open the port and let it fly out the bottom. But then again in that case I would jsut pull the unions and clean and inspect it anyway. So in short, the valve certainly wasnt necessary, but then again, I am a sucker for valves and knobs so who wouldnt want more stuff to turn, flip and play with when youre hanging out with your boiler? hahahahahaha (Just kidding)