2 Pipe Steam Radiator Questions

tamerf

I have a 2 pipe steam heating system in a multi-story house. The supply attaches at the top of the radiators and the returns are at the bottom opposite end. The radiators are the antique cast iron column type with inlets on the top and bottom on both sides and there are no angle values attached to release trapped air but they all have Hoffman check valves on the return outlets. There is also a very large Hoffman main vacuum valve by the boiler.  The problem I'm having is that some radiators work, others get warm but not hot, and some stay cold and I am sure that the supply valves are fully open on each unit.

Any idea what the problem could be? Should I replace the units and if so, are cast ray's better than the newer cast tubes? My understanding is that the check valves serve as air vents so these radiators don't need angle vents installed, is that accurate?

Any advice would be greatly appreciated.

JUGHNE

Those Hoffman "check valves" are most certainly steam traps.

They will pass air until steam gets to them and then close.
They will then open momentarily to pass condensate water back to the boiler.

On the top of the traps There should be a model number.
On the large vent in the basement there will be a model number.

Please post pictures of these items and your boiler showing all the piping around it from floor to ceiling. Also the nameplates on the boiler.

Pictures will get you a lot of help here.

STEAM DOCTOR

Absolutely positively, do not replace the radiators. The radiators are just Big empty pieces of metal. 

STEAM DOCTOR

You can never be sure that the shut off valves are really open. Parts may have broken off internally, leaving the valve shut, regardless of the handle position.

Steamhead

@tamerf , I'd bet in the basement you will find a Hoffman Differential Loop or a Hoffman Boiler Return Trap, in the piping near the boiler. These were the two main variations of Hoffman's Vapor system, which is what you have. Post pics of these as well.

Also, where are you located?

Jamie Hall

There is only one reason a steam radiator doesn't warm up, or warm up enough. Not enough steam, if any, can get in. Nothing to do with the radiator.

Most likely the problem lies with the "check valves" which are, as @JUGHNE says, not chicke valves. They will let air and condensate escape, but not steam. They have been known to fail -- particularly if the system pressure is too high -- but they are easy to check: When the system is running, the outlet pipe -- going down into the floor -- may be warm, even very warm, but should not be as hot as the radiator. If it is hot, the trap is failed open. If it is cool, the trap is failed closed. The are very easy (and cheap) to replace. The next possibility is that one of the traps is failed and letting steam through -- which will prevent steam from getting into the nearby radiators. That happens too. The third possibility is that a valve has failed, which may or may not be likely -- a picture of a valve would help.

Now -- as @Steamhead said, it's very likely this is a Hoffman Equipped vapour system -- in which case the pressure at which the system is running is really very critical -- it must be less than half a pound per square inch. Can you provide a picture of the boiler with the controls and any odd devices nearby?

Steamhead

@Jamie Hall , I've seen cases where the "vacuum vent" is not the #11 we associate with these systems, but a much smaller one. This can also cause uneven heating. Cure is to replace it with a Gorton #2.

Jamie Hall

Steamhead said:

@Jamie Hall , I've seen cases where the "vacuum vent" is not the #11 we associate with these systems, but a much smaller one. This can also cause uneven heating. Cure is to replace it with a Gorton #2.

Indeed.