Steam boiler replacement invovling a 2 pipe vapor system

Steamhead (in transit)

First get a copy of Dan's book "The Lost Art of Steam Heating". The Dunham systems are in chapter 15.

One way or another you'll have to get at those traps at the ends of the mains to fix them. Put some access hatches in.

That's not a "bucket" trap, it's a "return trap" or "alternating receiver". It is essentially a pressure-powered pump that makes sure water can return to the boiler. First thing to check is whether the check valves are clean and working.

With the traps repaired and the check valves clean, the system should work much better. Post some pics here if you can.

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Steam boiler replacement invovling a 2 pipe vapor system

I have recently replaced an old gas fired steam boiler that was converted from coal fired, with a Burnham Independence 11 natural gas fired steam boiler. The boiler was sized on the existing radiation at 849 square feet. The piping appears to be a 2 pipe vapor system. There are two mains that are dripped several places on each run and return wet under the concrete floor. I can,t see the end of the mains,they are above a finished ceiling but I believe they are vented with thermostatic traps like those found on a radiatior. The radiators are all dry returns that come together at the boiler where there is an air eliminating trap (vent), a return (bucket) trap, and a bunch of swing checks. All the parts were made by Dunham.
The problem I am having is that once the boiler gets up and steaming 2 of 16 radiatiors fail to heat. Many are slow to heat. ( The radiators are 20" coventors recessed in to the wall.) I believe radiator traps are the problem there. I have ordered repair parts for all of the traps. That should take care of the radiators lacking heat. The real problem is from a cold start after about 45 minutes the boiler beings to cycle off on the low water cut out. It will also start to cycle off on pressure. (pressuretrol main is set at 2 psi and the differential is set at .5 psi) The air vent gets loud when this happens. I am sure getting the radiator traps repaired will help with this situation. However I don't understand why the boiler is building pressure. I also don't knwo how to trouble shoot the air vent and bucket trap. Any advise would be appreciated. I am a small mechanical contractor, and I don't claim to know all there is to know about anything.

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Thanks Steamhead

I did read Dans Book. In fact I use it for reference all the time. The system I am working on is pictured on page 239 of the Dans books. (not exactly pipe the same but very close) I will try to post pictures on Saturday.

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Thanks Steamhead

I did read Dans Book. In fact I use it for reference all the time. The system I am working on is pictured on page 239 of the Dans books. (not exactly piped the same but very close) I will try to post pictures on Saturday.