\"panting\" radiators

billygoat22

We went back today and drained/refilled boiler. HO said 2 problem ones working now. I had leveled the one before we left and HO put a brick under the other.
Made some adjustments to the air vents since was late in day when got over there, since it took nearlt 1/2 hour for the last two to heat this time

billygoat22

panting rads

Been awhile since I got a steam boiler install. Put in a small Dunkirk this week, new main vents sized for the piping volume. Also checked slope on mains, not a lot of slope but they're parallel flow. 24" above boiler water line to header. Getting 1 lb psi after running awhile. 50' longest main.
Homeowner has had problems with several rads heating. Replaced several rad vents and 2 problem rads heat.

But.. two at the end of one line are heating only to the valve. Pull off vent and air puffs intermittantly. opened up valve on one and same result. I looked in the Lost Art since I recall reading about panting rads in one chapter.
The case I read didn't seem to match up perfectly with this situation.
My theorey now is water backing up in pipe just before dry return drops out end and blocking the last two runouts (being at the lowest end of main).

Anyone had a similar problem?

Burnerman

Could be poor condensate return. try a higher fireing rate if possible. You may be simmering instead of steaming. Are all of the lines insulated? If the panting rads are longes runs insulation may be key.

billygoat22

One of the radiators had the runout sloped wrong, a trap in line, so I repiped with 1/4"/ft back to main. This line is only 30" or so and the other is under 5'.
They're 2' from end of main, 2' apart. Both pipes get good and hot to valve (not insulated) and main is insulated in basement. The shorter run is under 30', uninsulated and all the rads there work.
Ther are some newer fittings in that area, so there may have been attempts made to fix problem before. I was thinking condensate was backing up in line (no water hammer though) due to restriction in dry return?

Steamhead (in transit)

Flush out the runouts

betcha there is some debris in them... especially the one that was off-pitch.

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