Stuck Danfoss Straight Valve

jweob

TL;DR - why would a new straight air vent fail closed after only a few day's use, and what is the best plan for replacing it?


I am experiencing my first winter with one pipe steam system in a four story townhouse built 1910.

My first problem was that the system was controlled by a thermostat in a warm corridor on the 3rd floor, which left all the rooms in the house either way too cold or way too hot. I installed thermostatic Danfoss valves in the hottest rooms and bought a Nest thermostat with remote sensor. I put the remote sensor in the coldest room.

Since I was reading the "Lost Art of Steam Heating" and had read about the importance of balancing the system I got used varivent straight air vents with the Danfoss thermostatic valves. These replaced the original Gorton angle valves. However I found that a lot of condensate spewed out of the vents. I replaced them with Danfoss straight air vents and found that although they were much noisier they closed with a satisfying click and did not let any water out.

That worked for a couple of days and I had even heat in all the rooms, but then I woke up to find my child's room was cold because the Danfoss vent had failed closed. The first time this happened I noted that the radiator was not pitched at all, so I pitched it slightly towards the supply valve and heard a satisfying gurgle. That didn't fix the problem, but giving the vent a slight tap did (vent started to hiss). However a day later it failed again, and this time no amount of tapping restored the vent to life. I removed the whole thermostatic valve assembly and replaced it with the original Gorton No. 6 angled vent, which works fine but because it is angled couldn't go onto the thermostatic assembly.

The stuck Danfoss vent I removed rattles when I shake it and also sounds like there might be water stuck in it that I can't shake out. I can't blow air through it.

I want to put the thermostatic valve back on the radiator but don't want to waste money on another vent that will fail, so I'm hoping on getting some guidance on whether I should...
a) Chalk the failure up to bad luck and put on a new Danfoss vent (reluctant to do this without understanding why it failed, and also it is very noisy)
b) Angle the thermostatic valve assembly at 90 degrees and use the original gorton No.6, which performs well with no condensate leaking and not much noise
c) Use an entirely different vent

Any advice would be greatly appreciated. Below are pictures of the radiator from both sides and wireless tag readings showing the temperature in the room when it failed (blue line) versus the temperature in another room

nicholas bonham-carter

Noisy vents signify a couple of things: pressure too high, and main venting inadequacy.
First, forget about the thermostatic vents, and replace them with decent Hoffman 40’s. Then look downstairs at your piping, and locate the main vents, and post some pictures. Post a picture of your pressuretrol, and boiler piping for more advice.
TRV’s are useful for some fine tuning, but cannot compensate for an unbalanced system.—NBC

jweob

Thanks for the quick response! Here are the photos

Boiler


Boiler piping (boiler at bottom right of photo). There are two mains. The boiler is at the back of the house, one long main goes to front one goes a short distance to the back wall


Pressuretrol settings



Main vent on the main running to the front of the house. I had this replaced recently because the old one was badly corroded and the heating contractor I used for boiler service said it needed replacement. Note that this area is under the front stoop and has so much ventilation from a big duct installed in this area it is basically open to the outside (i.e. it is cold).



I couldn't find the main vent on the main running to the back. There are two risers that go into some drywall in the basement ceiling and seem to terminate under the floor. I will rip out the drywall tomorrow and check.

I've seen radiators hiss and spit at both the front and back of the house. The one with the stuck valve is at the top floor back of the house.

For the hoffman valves, I saw that there is also a hoffman 41 which is a straight valve and so could be conceivably used with my TRV. It's labelled as a "convector" valve though. Would it be a terrible idea to use this rather than the hoffman 40 you recommend so that I could still use the TRV once I get the system tuned?

Fred

The Pressuretrol is set too high. (The gray box) set that front dial to .5 PSI by turning the screw on the top. Take the cover off (screw on the front bottom, center) and make sure the white dial inside is set to "1" (the "1" faces out towards the front of the box). The other Pressuretrol is a manual reset should your primary Pressuretrol fail. It is set fine.

Both the Hoffman 40 and 41 are the same vent. One is angle the other is straight. It says for convectors because most convectors mount the vent on the top, requiring a straight vent. It is fine to use on your Danfoss.

That Gorton #1 vent on your main is small. If it is on your long main, it is way too small. Your should put a Barnes and Jones Big Mouth vent on the long main. They are available from Amazon. If your short main is 10 ft. or less, you can use that Gorton #1 on it. Both mains need to be vented otherwise your radiator vents have to do all the work to get the air out of the mains.