No pressure at boiler gauge

Jamie Hall

is that until the radiators are pretty well heated up, the only pressure you're going to see is simply what it takes to get steam from the boiler through the lines to the radiators -- the pressure in the radiators, so long as they are still condensing steam, will be zero gauge, or awfully close to it (or should be... of course, if your vents aren't working...). That isn't much pressure (we're talking ounces here). The pressure doesn't really build until the vents or traps shut (depending the type of steam system) -- at which point, the boiler should shut down for a while; the steam already in the system will condense (providing heat still) and the pressure will drop and so on.

Peter_5

Looking for help with zero pressure at new boiler. Steam systems converted from oil to gas. Two family, seperate systems, second floor works fine and set for 5psi high limit, this boiler will cycle on/off every 15min until stat is satisfied. By reading this web site I'm thinking it should be set aroud 2psi.?.
First floor is the problem, steam takes a very long time to return to boiler. Zero psi on boiler. No leaks! Everything seems normal but very slow to heat and no pressure in system. I cant seem to find anyone to help. All say, never heard of zero pressure before...
Any help would be appreciated.
Thank You!

Steamhead

Have these things checked

Input (firing) rate to gas burners

Cleanliness of boiler water

If a 2-pipe system, look for a short-circiut betwen steam and return lines- posibly a bad trap.

BTW, the second floor boiler is set too high. Residential steam systems were designed for no more than 2 pounds. Crank it down!

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John@Reliable_9

Was the new.............

system designed by guessing or by load connected to it? If the fuel input isn't enough to "fill" the system it can run all day and never build psi. Also "leaks" on steam are not always water on the floor,but a leak that will go into the air as in a vent leak This too can and will cause zero psi. Last could be as simple as tape or dope blocking inlet on gauge, don't ask how I know this can happen lol! Hope this helps John@Reliable

Peter_5

Thanks for the quick response. Your correct, this is a 2-pipe system.
Boilers are new and alike, systems are 50+ years old with all new vents. Not sure what you mean by firing rate/short-circiut/bad trap?

Thanks for the 2 psi info.

Steamhead

Does this system

have shutoff valves at the inlet and outlet of each radiator, and a vent on each radiator?

Or is there a valve at the inlet and a round thing (the trap) at the outlet? If this is the case, there should not be a vent on the radiator.

If you're not sure what you're looking at, take some pics and post them here. We should be able to identify your system.

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Peter_5

There is one manual old valve (some not working but all open) and new adjustable (0-10 round white dial) vent on each radiator. Single pipe going to each radiator that branches off the main line that returns to boiler. Main does seem to be pitched correctly. I do not think there is what you describe as a trap.

Steamhead

Only one pipe

going to each radiator? If so, it's a one-pipe system.

Post some pics if you're not sure what you're looking at.

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