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Joined on September 15, 2010

Last Post on April 16, 2014

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main vents and boiler size

@ January 9, 2011 9:07 AM in Pressurtrol needs help

If the burner is cycling on and off it is operating normally, the pressuretrol will do that until the thermostat is satisfied. Also it's to your advantage to get the pressure as low as you can, high pressure is bad for everything - especially the fuel bill.

What kind of main vents do you have? How long and what diameter are your steam mains? If the main vents are too small the pressure will build faster than it should, especially on the initial burn.

What is the make and model of your boiler, and what is it rated for in sq ft of steam? how many radiators does it drive and what size are they? List the radiators height, width, depth, # of sections and the # of columns per section. This worksheet will let you figure out the load you are driving and then we can tell if the boiler is properly sized.


We need more information

@ January 9, 2011 8:54 AM in Need Help!!

Does the boiler shut off on pressure before the thermostat is satisfied?

What pressure is the pressuretrol set to? The front tab should be set to 0.5 (you can adjust it with the screw on top of the pressuretrol) and the internal dial should be on 1. That will let the boiler run between 0.5 and 1.5 PSI. Pressure higher than that just wastes fuel and magnifies whatever other problems you might have.

What does the pressure gauge read just before the boiler stops firing? If that is a 0-30 PSI gauge, they are not very good at low pressure.

Give us the make and model of that boiler. Also tell how many radiators it drives and what size each one is (height, width, depth, # of sections, # of columns per section). that information will let us determine if the boiler is matched to your load.

With that information we can start to figure out what is wrong.


Too long

@ January 8, 2011 10:06 PM in main vents

What model boiler do you have and what is the nameplate rating in sq ft of steam? Next how many radiators do you have and what size is each one? Add them all up and see how close your load is to the boilers rating.

Use this to calculate what you have -   - and ask if you have any questions.

If the system is very well balanced it takes a long time to build pressure, as long as the house heats ok and there aren't any unresolved issues you could be fine.

My system is much smaller that yours and way overfired (boiler has more capacity than the load warrants) , it takes 15-18 minutes to reach the 12 oz cutout limit from a cold start.


Too low

@ January 8, 2011 9:49 PM in Inadequate Venting

My guess is that your main steam line venting is much too low. Is that  2" an outside or inside diameter?

Also the presuuretrol should be set to 0.5PSI on the front tab and 1 on the wheel inside the front of the pressuretrol. That would let the boiler run between 0.5 and 1.5 PSI until the thermostat is satisfied. Your pressuretrol is the new type but see if you can get it lower, take a close up ,picture so we can see the settings.

Steamhead gave you good advise - follow it.

One other thing, all the pipes in the basement should have a minimum of 1" of pipe insulation on them.


firing rate

@ January 8, 2011 9:40 PM in Is my boiler just undersized???

The oil burner tech usually leaves you with a tag or printout that tells you what size nozzle they installed. The other fly in the ointment would be if the pump oil pressure was too low (140 seems to be the average number for modern oil guns), but that would usually screw up the combustion test. But then, anything is possible.

i am not qualified to say what settings might lower the heat output of the oil burner beyond that.

I suspect the problem lies in the venting balancing.


Still fine

@ January 8, 2011 8:52 PM in Is my boiler just undersized???

I thought the numbers referred to which floor and that's what I get for assuming.

If your boiler is rated at 453 sq ft of steam AND you are firing at the rated GPH  (for oil) or gas pressure than your revised 388 sq ft of load should be no problem - especially since you have insulated your piping. Just make sure the firing rate is what it should be.


Gorton #2

@ January 8, 2011 7:58 PM in Increasing main venting

if each main is 45 ft of 2-12" pipe you need more venting than one or two Gorton D's; you would want a Gorton #2 on each one. More would not help because of the 1/4" tapping your coming through.


0-30's are not very good at low pressure

@ January 8, 2011 7:52 PM in main vents

Actually if it takes that long it may indicate the boiler is sized correctly to the radiator load, assuming everything else is ok. The 0-30 PSI gauge on most boilers isn't very useful at low pressure. A lot of people have added an auxiliary 0-3PSI gauge so they can see exactly whats going on.

The one thing to watch out for is that your pigtail doesn't become clogged. The pigtail isolates the pressuretrol from the live steam and if that pigtail gets clogged the pressuretrol can't see the boiler pressure. i would worry about that if things start to hiss a lot loader and the boiler runs for very long periods of time. If your 0-30 read 0 when cold and increases to 1-2PSI under steam your probably fine.

All of this will become clear after you've read the book, in fact once you understand that you might want to read "The Lost Art of Steam Heat" for a thorough understanding on the subject.

good luck,


mains heating equally

@ January 8, 2011 7:41 PM in Is my boiler just undersized???

Do your mains heat to the ends at about the same time? How long does it take them to heat? Steam will take the path of least resistance so delaying the arrival of steam to the early radiators on the mains may force it into the radiators that don't heat up. I've enclosed the rough calculations I did for your reference.

Again, the slope on all radiators and piping has to be proper.

system pressure

@ January 8, 2011 6:55 PM in main vents

The air has to leave the radiators and piping so steam can enter them. On a lot of systems the steam mains total volume are very large and they have to be emptied of air before steam will be available to feed the radiator pipes that feed from the steam mains.You want to vent those mains fast.

Do you know what pressure the boiler is running at just before the boiler shuts down? There is a pressuretrol on the boiler and it's purpose is to set the limit for pressure. Systems work best, and cheapest, when the maximum pressure is 1-1/2 to 2 PSI - any higher and your wasting fuel.


Boiler should be adequate

@ January 8, 2011 6:37 PM in Is my boiler just undersized???

A quick calculation shows less than 300 sq ft of load, not counting that baseboard.

The boiler seems more than adequate so your problem is probably getting that radiator venting balanced out.

The heat timer will vent between 0.158 and 0.85 CFM while a Hoffman 1A goes between 0.026 and 0.225CFM. Try closing the heat timers as far as you can and see if that makes a difference. If not you need to go with smaller vents.

Also make sure the pipe and radiator slopes are all correct.


How many columns

@ January 8, 2011 5:32 PM in Is my boiler just undersized???

You have listed the size and the number of rungs. The other piece of info we need is how many columns in each rung - 2 or 3??

Are all the radiators and their piping sloped correctly?

If those are heat timer vents they have very high venting rates even when they are closed down. You may have to use Hoffman 1A adjustable vents to get the venting rates down so all the radiators can get steam.


Pay me now or pay me later.

@ January 8, 2011 3:24 PM in Improper near boiler piping and other issues

How well does the building heat now? This is single pipe steam?

To me the venting and that one main with a dip in it should be fixed asap for fuel efficiency. Those two items are probably burning a lot of gas just to push the air out of the pipes.

The makeup air and boiler room door issues have to be dealt with just from an insurance point not to mention general safety.

I would try to get some other quotes but remember you are probably burning a lot of gas that you don't have to. The excess gas usage over 10 years is going to be be a big number.



@ January 8, 2011 1:01 PM in Banging radiators - Again I know it's been beat to death...

Have you tried swapping air vents with another radiator?

Make sure the pipes that feed this radiator are sloped properly so water can drain back to the steam main and make sure the slope on the steam main is ok.

If none of that works try removing the vent on the radiator and see if any air is coming out of the vent tapping. Do this when the boiler firs comes on and the system is not steam hot.
Put that air vent back on when the test is done.

If you get no air coming out as the system begins to produce steam your input radiator valve might be stuck closed, not letting any steam in. I don't see why that would cause hammering without any trapped water in the main or at the start of the radiator feed pipe where it comes off the main.


1/4" CFM

@ January 8, 2011 8:42 AM in Increasing main venting

That main contains about 1.5 cu ft of air. I'm guessing a 1/4 tapping will be good for 2CFM at 2oz of pressure so it should work.

The table I'm using lists a 1/8" pipe as good for 2cfm and a 1/2' pipe as good for 3.4cfm at 2 oz (Greening Steam pg131). There is nothing for 1/4' pipe and I assume the 1/8" figure is actually for the 1/4' pipe. Does anybody know if my assumption is right??


We don't know

@ January 7, 2011 9:22 PM in Best radiator vents?


i think you've nailed it. i assumed they were tube radiators but I really don't know. Let's hope the homeowner looks at that link and tells us which type of radiators he has.

have a great weekend,


Piping and pressure

@ January 7, 2011 7:11 PM in Small steam leak at shut off

It looks like the installer used a reducer on the boilers steam output port, that is not good. The piping should be at least full size from the steam output through the header and up to the steam main. If it's not you may well be getting wet steam that reduces the systems efficiency. take a look at the install manuals piping diagram and you'll see they are VERY specific on the size of pipe that should be used.

That pressure is too high. Turn the screw on top of the pressuretrol to set that tab down to 0.5PSI and ten take off the front cover and adjust the wheel to 1. That should let the boiler cycle between 0.5 and 1.5PSI whil;e it's steaming. the 0-30 gauge isn't much good at that low a pressure. A lot of people add an auxiliary 0-3PSI gauge so they can see exactly whats going on.

I see a lot of rust in the lower part of your sight glass, is that just on the inside of the glass? Is the water in the glass bouncing around a lot when the boiler is steaming?

Also all the steam piping should have a minimum of 1" pipe insulation on it.


Pressure and piping

@ January 7, 2011 6:58 PM in piping help with pictures

It looks like the pressure is higher than it should be. that tab on the front of the pressuretrol should be set to 0.5 9turn the screw on to till it goes down to 0.5); thake the cover off the pressuretrol and make sure the wheel is set to 1, no higher. That should allow the boiler to cycle between 0.5 and 1.5PSI when it is making steam.

The water in the sight glass looks like the boiler needs to be flushed and skimmed. If you decide to repipe do this after repiping.
Your boiler is an eight section boiler and it has two steam takeoffs, the reason the water level jumps up when it's off might be because only one of them is being used. The other reason is there really is no header, the output of the boiler just goes up to the main. If you decide to have the near boiler piping redone you might want to ask them to use both steam outputs and pipe them up to a drtop header and then feed the main from a header after the two steam feeds. Do not let them pipe the main from between the two steam feeds from the boiler. Your installation manual shows how this should be done.

I'm sure other here will have ideas on how this should be done as well.

Let us know what current problems you are having with the system now.



@ January 7, 2011 5:44 PM in Small steam leak at shut off

You state that you have been finding leaks all over the place. If the system didn't leak before this might indicate the pressure is too high.

What pressure is the pressuretrol set to. The pressuretrol is a small grey box that senses the pressure inside the boiler. The common type should have the tab on front set to 0.5 and the white wheel inside should be set to 1.

Take some pictures of the front of the boiler that shows the pressuretrol and the sight glass and take one that shows the whole boiler and the piping around it 9stand back so we see how it's all set up).

Are you sure the water isn't coming out of the valve stem and then dripping down to that seam? When you try and tighten that valve don't go overboard with the wrench.



@ January 7, 2011 5:35 PM in piping help with pictures

If the boiler is not piped per the installation manuals piping diagram it is not going to work right. Those pictures show the installer was not famililiar with steam boilers.

You state the system has been repaired 7 times in the 2 yours since it was installed. What were the problems and what did they do to correct them.

What problems are you having now?

What pressure is the system operating at?

Are the main vents and the radiator air vents all working?

Is the water in the sight glass bouncing up and down a lot?

Is anything banging or hammering?

Take some pictures of the front of the boiler showing the sight glass and pressuretrol. Then take some shots that sow the boiler and it's piping from a ways back so we can get a good idea of how it's all tied in.

good luck,



@ January 7, 2011 2:08 PM in Leaky Joints On New Steam Piping Install

Make sure the white dial on the inside of the pressuretrol is set to 1, that would have the boiler cycling between 0.5 and 1.5PSI. The 0-30 gauge on the boiler really is not very useful at low pressure, you would have to add an auxiliary 0-3PSI to really see whats going on.

To get lower pressure you would have to replace the pressuretrol with a vaporstat; that would let you get down to much lower pressure but they don't give them away.

If you see a lot of bouncing in the sight glass after the piping is fixed, the boiler may have to be flushed or skimmed again.



@ January 7, 2011 2:01 PM in Proper Main Vent size

If that 85 ft of pipe is 2" Id then you have about 1.85 cu ft of air in it plus whatever is in the header and boiler. That existing vent looks like a Hoffman #75 which is rated at 0.75 cu ft at 2oz of pressure. You need at least twice that so you might want to think about a Gorton #2 that is rated at 1.75 cu ft at 2oz. Two Hoffman 75's would work but that would cost more $$.

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