One steam radiator not getting hot

songsparrow

I have a one-pipe boiler + cast iron steam radiator heating system - radiators on two floors, 5 radiators on the first floor and 3 radiators on the second floor. One radiator on the first floor is not getting hot and the room is cold. It is the furthest from the boiler on the first floor. The radiator did get hot years ago, but it has not been working well the past couple years. It was particularly noticeable this year, so I took the radiator cover off and checked it out. The pipe that feeds the boiler runs through the basement, where the pipe is uninsulated, and then through a crawl space where the pipe is enclosed above the rigid ceiling insulation.

The boiler is over 10 years old (the label on it was hard to read - may have said 1998). The only recent changes that have been made to the system have been: (1) A couple years ago we had the crawl space under the back room floored with concrete and the walls and ceiling of the crawl space were covered with rigid insulation panels; the pipe that runs through the crawl space to the one malfunctioning radiator is now above (enclosed in) that rigid insulation. (2) A small radiator in the first floor powder room hadn't been working; last year, we had the inlet valve replaced and now it is heating up (it's quite large for the tiny room so the powder room gets very warm now).

I checked:
* The inlet valve is all the way open and there is no indication of leaks.
* I removed the air vent. I was going to try to clean it, but I was able to blow air through it. It is a Varivalve and the slide was almost closed, so I opened it all the way and put it back on the boiler. Then the boiler went through a brief cycle (on and off in ~4 minutes) and the radiator and inlet pipe did not get hot at all.
* I removed the air vent completely and turned the thermostat up 2 degrees so the boiler would run longer. On that cycle, the inlet pipe heated up and the right half of the radiator (closest to the inlet pipe) got hot but the left half of the radiator by the air vent stayed cold. No steam escaped from the air vent. We did get a couple bangs from the pipe this time; we used to get a bang or two in that room every time the boiler would run, but I hadn't heard any bangs back there in at least the last year or two.
* I checked the water level in the boiler, and I let a quart or two of water out of the drain at the bottom of the pipes and then refilled. The water was clear in both the glass tube and that came out of the drain. There was a second valve coming out the side of the boiler that also had a knob and spigot on it so I thought it was also a drain, but when I opened that nothing came out.
* Ordered the book We Got Steam Heat! by Dan Holohan

Possible things still to try:
* I saw three main valves on the piping in the basement. Two look like Gorton valves and are installed right by the boiler. The third looks like a Matco-Norca style valve and is installed near where the pipe for the malfunctioning radiator exits the basement and goes through the wall into the crawl space. I am not aware of any of these being replaced since the boiler was installed, if then. Is there a way to test these to see if any need to be replaced?
* I saw recommendations to try cleaning the system. Does that mean anything more than removing dirty water from the boiler drains? The boiler hasn't been serviced in a couple years, so I plan to have the plumber come out to do that.
* Insulating the pipes that run through the unfinished basement. I've read conflicting info as to whether this is a good idea. I like having them warm the basement to keep water pipes down there from freezing. I also think that the floors on the first floor are warmer since there is some warmth in the basement. Should I insulate the pipes? Is there a way to keep the basement from getting too cold if I do so? Should I also insulate the pipes that run through the first floor living spaces on the way to the second floor?

Any other suggestions? Thanks!

Abracadabra

Sounds like that Matco-Norca vents the main to the radiator that doesn't work. Confirm and if that's the case, install a faster main vent there.

songsparrow

Thank you for the reply! How do I confirm it? Is that something that I can do myself, or do I need to ask the plumber to do it?

Big Ed_4

System is out of wack and needs to be balanced ... First insulate all the steam supply pipes ... Pull all those varivalves on all the radiators for now ... Start by replacing the plugged or undersized main vents at the end of the of each steam main .. Install an float type slow adjustable radiator vent like an Hoffman #1 . The float is an added safety incase of a overfilled boiler , The float will raise if flooded and shut of the opening of the vent. Ok setting the rad vents..Start with the smallest setting on the smallest radiator , the second setting for the medium radiator and the third setting for the big boy ..

The system is not designed to work properly with out supply pipe insulation , reinstall it ... Yes you can heat the basement with an condensation loop . .. back to balancing ..

Keep the thought everything in nature travels and wants to go to the least resistant .. Main vent are large with almost no resistance, the steam will head to them first .. Resistance at the radiators helps insure the main fills with steam first .. Once the main vents shut the main is full of steam across the entire floor of the house ... Now all that dry steam ( Thanks to the insulation on the mains) wants out and is now heading up the risers to the radiator vents ... We adjusted the radiator vents to the size of the radiators but kept resistance hoping to heat them all up at the same time .. Give it a whirl and fine tune if needed ..

Steam vents let the air escape ahead of the rushing steam . They shut off once steam enters the vent .. If not replace

System now will be quiet and comfortable and you should not be adding any water .. The system will run less and that saves you on fuel ...

Big Ed_4

To Add , Varivents by Heat Timer are way to fast for your system , They are designed to be used with an Heat Timer control used in an apartment building ..

songsparrow

Thank you for the many replies! Based on your advice, my plan is to:
1. Have the plumber service the boiler and replace at least the one main vent.
2. Insulate the steam pipes in the basement.
3. Replace the Vari-Vent air valve on the cold radiator with the Gorton.
4. Check/replace the valves on the other radiators and balance the system.

Does that sound like a good plan? Any other or different advice?

Fred

Have him check the pitch on each radiator as well. They should all pitch back towards the supply valve side so water can drain.