Slow heating radiator

emk2badknees

I have a 1-pipe steam system and am having problems with one of my radiators. It takes far longer to heat than any other radiator in the system. When it finally gets hot, it seems to gurgle (it sounds like a pot does when water just starts to boil) and the surface temperature runs only 185 vs 210 for the other radiators in the system.

What could cause this behavior?

I could think of a few possibilities:

1. The air vent is going bad: I removed the air vent and ran the system to see if the radiator heated faster and found that this radiator was still the slowest radiator in the system to heat up.
   
2. There is something wrong with the steam valve: It was replaced 3 years ago along with all of the valves in the system, but the one on this radiator looks different (different style, looks tarnished, doesn't have a size cast into the housing). I also noticed that I was only able to turn this valve 1 revolution, whereas the steam valves on the other radiators can be turned 5 revolutions or so.
   
3. There is something obstructing the steam line from the main to the radiator - we had our radiators taken out for sand blasting and powder coating, so I suppose anything is possible. I looked at the total expected pressure drop in that run and it isn't any higher than the pressure drop expected for the other runs in the system.
   

Are there any other possibilities? Everything I can think of suggests I have to take off the steam valve (and maybe replace it), which I don't have any experience with.

MilanD

Possible they used water valve in that one if it won't turn, or it was defective out of the box. On the other hand, rad could be bigger for the riser capacity. There may originally have been a smaller rad there. One thing you can do is slow down with slower vents a few other radiators on the system to nudge more steam to this rad. Try by closing one of the other radiators off. Depending on the vent, you may be able to just turn the vent upside down, or if not sure, use the valve.

Which vents are you using? A few strategically placed maid-o-mists or Hoffman 1A may help dial it in by slowing down venting rate on other rads by which making more steam available to this radiator.

Post the pic of the valve vs. other valves, and what vents you are using on the rads.

emk2badknees

Here is the steam valve for the slow heating radiator. The knob is a hexagon with "Hoffman Specialty, ITT McDonnell & Miller" printed in it. There is no indication of valve size on the valve.


Here's the type of steam valve that is on all of the other radiators. The knob and body say "Legend" and the valve size is cast into the body.


The radiator that is slow to heat is not particularly larger. The EDR is about 19 sqft (4 x 38" 4-tube sections). The inlet pipe looks like 1", which should be enough, so I suspect the riser size is not the issue.

The vent on the slow heating radiator is a maid-o-mist #6. Most of the other valves are varivalve, many of which have been set to nearly closed to try to balance the system. However, this radiator heated up slowly even when the vent was removed and all that was there was a gaping hole, so I have a hard time believing that this is a balancing issue.

BobC

Those varivents are probably pretty aggressive even when dialed down. If their are no pipe slope issues (check radiator slope also) and the main venting is adequate I might suggest replacing the varivents with something less aggressive.

Bob

MilanD

That valve does look strange - not like a steam valve. May have been some old valve they had and thought valve is a valve. Would explain it being slow. Good thing the fix was recent - you can easily replace with a new valve and it's not expensive either. Looks like 1" pipe - valves are 12 bucks or so. All bushings look new(er) too, should all come out with no problem. A couple of 24" pipe wrenches and you'll be back in business in 30 minutes.

And as Bob says, try a few different and even slower vents on other working rads so it would nudge a bit more steam to this slow to heat radiator.

Fred

If that radiator is gurggling, it has water in it, or possibly in a horizontal pipe under the floor. Make sure that radiator is pitched back slightly towards the valve.
If that doesn't fix it, try to raise the entire radiator slightly and then repitch it. That will raise the end of any horizontal pipe, under the floor and give it some pitch too.
Before I raised the entire radiator though, I would take the radiator loose at that coupling and take a look inside the valve. If that valve only turns one turn, it is very possible it is not opening all the way and not letting the water drain out of the radiator and the steam is condensing as soon as it hits that pool of water.
As has been said, that doesn't look like a typical steam valve.

emk2badknees

The riser goes straight up from the basement (I got to see it during a renovation), so I suspect the gurgling is coming from the radiator itself or its inlet.

I checked the pitch and it seems okay. A contractor pitched it and the other radiators several years ago after the radiators were refurbished and installed (although not at first, contributing to some big problems when we first started the system up after the renovation - water shooting out of this particular radiator's air vent). It seems like the pitch is correct now though.

I guess the first thing to do is check the steam valve.

Regarding air vents, what is a good alternative to varivalves? Should one always maintain all air vents from the same manufacturer? I read that in "The Lost Art of Steam Heating", but I didn't fully understand the logic.

Fred

The Hoffman 1A's Vent-Rite 1"s and Maid-o-Mist are all adjustable radiator vents that are very reliable. All the vents don't have to be the same but it does simplify adjusting them as a setting "3" on one brand may be a "2 or a "4" on another. I would say buy a good one and a spare for when you need it and work towards eventually replacing them all, as they fail.

Big Ed_4

You have saggy riser to that radiator ..I assume added on after original install ... Can you raise radiator enough to pitch pipes back to main...That's an must ..or add an drip with trap