Cold radiator, likely causes?

movin2gas

First heating season in a new-to-us house. The boiler piping is clearly crazy, but the system is nonetheless pretty quiet and fairly well behaved. Except for a large radiator in the 1st-floor kitchen which is stone cold. Has a new air vent, so that's not the issue. The radiator was removed and reconnected when the floor was redone in that room and hasn't worked since. The closest main leading to that radiator gets hot, but runs another 15 feet or so out of sight. The 2nd floor radiator that I believe (but not 100% sure) is fed by the same main gets hot. So, before I bring someone in, is there anything easy I can try at the radiator itself which may help out?



Thanks!

steamedchicago

valve get hot?

Real obvious first check:  The valve is open, right?  Does the pipe leading to the valve get hot, or at least warm?  If it does, then the valve is no good, the vent is no good.  Take the vent off, and test whether air comes out when the boiler runs.  A piece of tissue paper arranged so it flutters works fine, and you can't burn yourself with steam that way.  If no air comes out, then the valve is no good, or the radiator is plugged up.  Bet on the valve. 



If the pipe to the valve doesn't get hot, the problem is something down stream of the radiator.  Maybe it got disconnected during the remodel. 

ChrisJ

Vents

Have you removed the vent and tried to blow through it (the vent) with your mouth?  I wouldn't assume just because it's new that it is good.



Were any other vents changed and what brand / size vents were used?

Jamie Hall

When the floor was redone

was the radiator put back at exactly the same elevation as it was before?  Particularly if it was lowered there might be a dip or sag in that 15 foot lateral.  You would think it would hammer, but if the sag is enough so that the pipe is full of water somewhere, or nearly so, it might not and just show up as a cold radiator.

movin2gas

RE: Cold Radiator, likely causes

Thanks for the suggestions, everyone. The supply valve is definitely open and the air vent is a Vent Rite #1, as are all the other valves in the house (some were already VR#1s, but I replaced all of them). I did do the blow test before putting it on (and again since), so that's not the issue. I have not been able to detect any heat in the supply valve or the radiator so far. Next step, I will try propping the end up to create more of a slope, since perhaps the new floor changed it. The new floor is a kitchen laminate that was put omn top of the old tile, so it's slightly higher than before. For what it's worth, when we did our home inspection back in April, this radiator was quite slow to get any heat (to the point where I was afraid it wasn't working at all), but it did eventually get there. If increasing the slope doesn't help, I'll disconnect it and see if I can detect any air.

movin2gas

More info

The 4 inches or so of pipe leading to the radiator supply valve from the wall definitely is not getting hot (or even warm) so the problem must be somewhere in the 15 feet between the exposed basement pipe (which is hot) and there? If the supply valve was blocked, would that prevent steam from reaching anywhere near it, or would it get hot up to the valve itself?

ChrisJ

Yep

If you don't vent air out steam will not go into the pipe.



Do you have a torpedo level or any kind of level you can put on the pipe? I'm not sure how common it is for a valve to get blocked on a radiator but I know I had a radiator that didn't want to heat after some work was done.



The person who reconnected the radiator made the vertical piece that connects the radiator to the runout too long causing water to lay in the run out. Are you 100% sure no one changed any piping? A lot of my runouts are tight against the joist near the end and have been that way since the 1920s when the system was installed. That being the case, there is no way you could raise a radiator 4 inches without changing the vertical connection to a longer piece. You can't really raise any of mine at all for that matter without changing things.

j a_2

I agree

With the last post….If you have done all you said it definitely seems like a liquid block..If you feel comfortable doing it,disconnect the rad. at the valve and using a small compressor

blow it down…Then run boiler and see if steam appears, if so, problem found….Maybe shut off a couple of rads in that vicinity and see what happens….to the one in question….Hope this helps

movin2gas

No repiping

Quite sure there was no repiping, this was a 3.5mm linoleum sheet laid on top of an existing floor, so the change in height was minimal.

movin2gas

This is going to be a stupid question

So, I disconnected the radiator from the supply valve. The shutoff knob only turns slightly more than 1/4 turn, and looking into the valve, there is no orifice that appears when all the way "on". Is it possible that the floor installers messed with the nut which connects the shutoff stem to the handle, and that it was left in a state where it is not openable? Or that the valve is just broken, and I need to get a new one? This is a newer-looking valve than many in the house, with a plastic knob. I once successfully repacked a valve like this, so I think I'll just take it apart tomorrow and have a look, when the stores are open and I can get a new one if necessary.

ChrisJ

Packing nut

You should be able to loosen the packing nut (counter-clockwise looking down) and see if you can get the knob to turn. If you are successful at getting it to work then snug the nut down while rocking the knob back and forth until you feel the nut cause a slight resistance. From there only tighten if you see it leaking.



I wouldn't loosen the nut more than one full turn if even that as it shouldn't be necessary.



On my valves I have the packing nuts fairly tight as none of the valves work anyway and I didn't want to mess with them again so I put them pretty tight.



Please make sure the boiler is off before doing this.