No pressure in single-pipe steam system

Steamhead (in transit)

are your steam mains insulated?

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Charles_6

Is it plumbed correctly?

Recently I moved into a 100 year old house (a small 3 bedroom Cape Cod in Maine) that has very old but functional radiators and a newer oil-fired steam boiler installed about 1980.

I am puzzled because there is never any pressure on the gauge (the gauge works, and I also substituted another to verify). The Pressuretrol, (currently set to cut off at 3 psi and resume at 1.5 psi) does not cycle the burner, either.

There is SOME pressure, of course, since the house does heat promptly and steam does go to the radiators! The radiators get very hot on their input ends but not the farthest sections, and the vent valves don't close either (constant hissing noise while heating).

After spending some time online learning about steam heat (and also Hartford loops), I looked and my system definitely doesn't have one, nor is there an equalizer line. There is a very old and rusty looking "Float Vent" valve at the end of the loop just before it drops straight down to the boiler return, and it hisses and makes gurgling noises the whole time the burner is on, too.

I thought the boiler might be undersized for the house, but it has a healthy appetite of 1.6 gph (can get more numbers off the data plate if helpful). I've also got the radiators shut off in the dining room, hallway, and two bedrooms! So the main loop is only feeding the upstairs bedroom and bathroom radiators, and the living room.

Another interesting finding is severe overshoot when changing thermostat setting. The (beehive) thermostat is in the living room and it is about 7-8 feet from the radiator hot end. If the actual temp was at 60, matching the thermostat setting, when I turn the thermostat up only 3 degrees the living room heats to almost 70 after the thermostat satisfies at 63. There's a lot of thermal mass in all that cast iron, I guess. I tried changing the heat anticipator setting from the recommended 0.3 but it didn't help.

Edit: this is a really great site. I've been browsing the "Problems that plague steam systems" section. Much of the loop in the basement is not insulated, and the long vertical runs to the upstairs aren't insulated either. Looks like I definitely need to fix that too.

So what other things are wrong and what should I do to fix them? Thanks for any helpful hints.
-Charles