radiator heating half way

Ben_13

I removed the vent and it does vent air in the beginning as the first few sections begin to heat up. After a while it stops venting air. I can leave the vent off completely and nothing comes out. At that point the first 3 or 4 sections are very hot but the rest are ice cold.

Ben_13

Radiator only heating halfway

I have a one pipe steam system in a 3 story building. The boiler is located in the basement in the rear of the building and there is a one story extension above the boiler room. In this extension there are two rooms, each with large radiators. In this part of the building there is nothing above so the pipes that feed these radiators do not feed others above.

When the heat goes on both radiators begin to come to life and the vents start hissing and allow air out and steam in. The first sections of each radiator begin to heat up. However, on one of the radiators only the first 3 or 4 sections heat up. The remaining sections stay cold even while the sections on the other radiator heat and the boiler continues to fire.

I have gone so far as to remove the vent completely to be sure that this is not the issue. The sections beyond the first few stay cold and it doesn't appear that air is being forced out any longer.

Any ideas on what could be stopping the progression of the steam? The rest of the radiators in the building appear to be working fine.

Thanks

martin

Part cold rad

Check by removing vent when system first starts up does it vent air and then just stop? If so no steam is getting in at that point ,nothing in nothing out

Phil_17

What happens if you close the valve to the radiator that gets hot all the way across? Does the cold radiator heat all the way then? Are both radiators fed from the same main? Assuming they are, does the hot radiator come first on that main? How big are these radiators (how much EDR), what size are the pipes? It is possible that the main/runout is undersized for the EDR and the first rad hogs all the steam.

Do you have a copy of Dan's book?

Ben_13

Thanks for these tips/questions, I will try turning the one radiator off next time I'm over there to see how it impacts things.

To give a little more info on how they are laid out, there is a pipe that comes off the boiler that then has two equal sized pipes that come off of it, one right after the other. Each one feeds one radiator only and the run is no more than 5 ft.

After giving the radiator a bit more time I see that it does eventually heat up at least most of the way across but it does so at such a slow pace that the boiler needs to cycle for a very long time, around 30+ minutes for it to fully heat. These are pretty large radiators, about 3-4 feet high, 2-3 feet wide and about 8 inches deep.