Steam base radiator, sometimes hot and warm, other times totally cold, why?

georgearoush

My apartment is heated with steam based radiators. All eight radiators are single-pipe systems with air vents. Most of the time, all the radiators heat up just fine. However, occasionally, one or two radiators fail to heat up at all—and this can go on for 2–3 days, and then, out of the blues they start to heat up again!

What’s puzzling is that it’s not always the same radiators that stop working. If it were, I’d have a clear place to start troubleshooting. I’ve already replaced all the air vents and checked the valves, so those shouldn’t be the issue.

When a radiator doesn’t heat up for over a day or two, while the others are heated, the "fix" I’ve found is this:

1. Remove the air vent.
2. Place a vacuum hose over the vent opening.
3. Run the vacuum for 1–2 minutes until hot air starts flowing into the radiator.
4. Place the air vent back on.

After doing this, the radiator heats up normally when the boiler is running, at least until it cools off again.

Does anyone have an idea what might be causing this intermittent issue?

Big Ed_4

Seems like there is water trapping in your steam supply . Check the supply valve first..

ethicalpaul

I too would be looking for places where water could be collecting, but if the issue moves around to multiple radiators, that makes that possibility less likely (unless several radiators all have supply pipes with water trapped in them).

Another cause could be radical overventing of many radiators. In this case, the steam will just go "wherever" in unpredictable ways.