One pipe steam help

Debaser517

One pipe steam heating system in 5 story building. Trying to list everything pertinent as I’ve been poring over posts here trying to get to the bottom of this before I have to try to fix it tomorrow. (fingers crossed)

anyway... Top (5th) floor rads seem to take a while to warm up (risers get hot to the touch fairly quickly), some rads seem to come on quicker than others, but they only all uniformly get hot when it is very cold outside and the boiler has been on for a long time.

One very large rad has a loud hammer in it when the heat is on. None of the air Vents appear to be blocked. A small amount of air escapes the vents when the boiler turns on before the risers heat up. You can feel cool air on your finger tip. The control valves are open all the way, and the 1.5” pipe feeding the valve and going into the rad gets pretty hot (and also past the valve) but the rad itself does not seem to warm up.

I closed the control valve and removed the air vent... the tongue is still present and you can blow into it.

Is this a sloping issue? Temperature too hot by the thermostat (on 2nd floor)? I also purchased Maid o Mist #C vents I was going to try and install on the top floor rads.

Not sure where the main vent is... there’s an air vent way up near the ceiling on the riser pipes on the top floor... but I didn’t see one in the basement. I haven’t checked the air vent on the riser pipe for being clogged yet, as that pipe gets hot.

Any help would be appreciated... total Noob to steam, and only know a bit about hot water systems, steam is a mystery.

Jamie Hall

What kind of vents are on the risers on the top floor? Picture? That's a good place to vent a five story riser -- there's a lot of air in there to get out and until it does, those top floor radiators are going to be kind of chilly. Probably could use bigger vents.

And if there are vents on all the risers, you don't need them on the mains in the basement.

The hammer is almost surely a pitch issue -- make sure that radiator and it's runout have a decent pitch to drain, and that the valve really is all the way open.

Debaser517

Thanks for your reply! The vents on the risers look to be the same as the ones on the rads. 1/8 angled chrome hoffman’s. I dont know the nozzle size as I didnt climb up there yet (not at the location now so can’t take pics).

You think I might try putting the #c maid o mist vents on there? I have a #d too I was going to put on the very large rad.

Jamie Hall

I'd go whole hog and put Gorton #1s or even 2s on the risers! Or, for that matter, Big Mouths since you'll never get water that high. You have a lot of air in those risers, and you want to get steam up there as fast as you can -- then you can control what gets into the radiators with smaller vents.

Fred

You need much larger vents on the risers than a small radiator vent. If the steam can't push all the air out, during a heating cycle, the top floor or two will never get steam. The issues sound like some water laying in the radiator or pipe to the rad that hammers (needs to be properly pitched), need for larger vents, like a Big Mouth on the top of those risers and then the radiators need to be balance to even out the heat/steam flow.

Debaser517

Swapped all the vents out, and things were working great when I was there (much thanks to the fine info here!), but the top floor folks are now complaining the system isn’t working (10pm). Will try reducing the vent sizes on the rads by the thermostat, tomorrow but I also noticed when I was at the boiler that the secondary lwco (probe type) has a steady red and steady green light.

I think this is kicking off the boiler. Is it hard to clean the probe? or is it as simple as unscrewing the housing and removing the probe with the boiler off, cleaning and replacing. Do I need to wait for the pressure/temp to drop?

nicholas bonham-carter

How many risers are there, and do they feed multiple floors?
Where is the thermostat location?
The main vents in the basement could be enlarged to Big Mouths, to obtain the ideal sub 2 ounce venting backpressure.
The top radiators could have Gorton D’s, and the intermediate floor radiators could have Hoffman 40’s. This would fill all the basement mains first, for good horizontal balance. Next, all the risers would fill to the top floor, and when the Gortons have closed, the lower floors will fill.
I would find a spot in the most exposed corner of the top floor foe a remote wired sensor connected to a Honeywell VisionPro thermostat. This will ensure the boiler starts as soon as dropping temperatures are felt, and the improved venting will enable steam to hit all the risers simultaneously.
Don’t use setbacks, but instead select a lower constant temperature.—NBC

Fred

@Debaser517 to clean the probe, you will have to drain the boiler. How old is the probe? I'd be inclined to replace it if it is a few years old.