Radiator not getting hot!

scott_block

Hi Guys,

I have a steam boiler system and recently had an entirely new system installed. I also have a tankless coil thats heating 2 radiant zones a baseboard zone and an indirect hot water tank with individual circulator pumps.

On the second floor there are 3 radiators which are all new from castrads.com. Two of the radiators are off of one 1.5 inch riser which T's off to each of the two radiators. There is also that old style blow in insulation in the floor between the first and second floor. One of those radiators off the T is relatively small and gets hot pretty quick. The other radiator off of the T takes forever to heat up and never gets fully hot. Out of the 12 sections maybe 3 or 4 get hot. I have a D size air vent off of it with a trv and it had a new valve as well. I made sure the radiator is pitched right and cant for the life of me understand why 3 to 4 feet to the right of the T is a small radiator that gets hot all the way through and pretty quick and a radiator about 6 feet to the left of the T takes so long to even start getting hot and doesn't ever get fully hot. Also the radiator off of a separate riser towards the back of the house on the second floor gets hot similarly to the small radiator.

Any thoughts what this could be? Is it possible the pipe from the radiator to the T could be clogged? I don't know for sure because its in the floor but I don't think the pipe could be so badly pitched given the distance. The valve itself by the floor also seems to eventually get pretty hot but not the radiator.

This was also happening with the previous radiator similarly sized before I replaced it.

EdTheHeaterMan

Try removing the TRV from the problem radiator vent. If the smaller rad next to it (in the same riser) is getting heat quickly... that vent is letting air out so the steam can get in. The slow heating radiator is not releasing the air as quickly. the TRV may be restricting the airflow out of the vent or the vent may be a slow-acting vent or it may be partially blocked.

Air and steam don't mix so, if there is air in that radiator then there is no place for the steam to go. By removing the restriction at the vent you will see if the vent is the problem. If the steam is still slow in filling the radiator... then there may be a blockage in the steam pipe feeding that radiator. Could be something solid in the pipe or could be water blocking the pipe... but that would cause some banging noise in my experience. I would remove the vent first to see if the steam gets in there any faster.

Once I know the answer to that problem then I can select the proper vent and decide if the TRV is needed or not.

Jamie Hall

How do the Ts run? Or is it just one T, with the riser coming in the bull and the runouts going straight off either side? If it's the latter, one of the two runouts is pitched incorrectly -- and it sounds like it's the longer one. If the riser comes into one arm of the T, and the runout goes straight out the bull, and then a nipple and another T or an elbow, then both aren't pitched properly, but it won't make much difference on a small radiator and a short runout.

So that's one possibility.

Another is that you mention a TRV. Are you sure that it's opening completely? And staying that way? If it closes early in a cycle the radiator can't heat across no matter what you do until the boiler turns off and gives it a chance to reopen.

scott_block

@Jamie Hall I cant see much of the piping. I have one of those inspection cameras thats a flexible wire and I stuck it down in the side of the cut wood floor around the valve on both radiators and got the jist that the rise I see from the first floor comes up very close to where the small radiator is and from the first floor below looking in the wall to the best I can there is no other pipe so it has to T off up there. The radiator that is not getting hot seems to have an elbow facing straight up and then theres a nipple that comes off of that and comes up out of the floor.

scott_block

As for the TRV, how would I know for sure? The small radiator and radiator in the far room off a different riser are both using the same TRV's with maid o mist air vents with the interchangeable buttons. I have a D on this one now just to see what would happen and I do here air come out but its sporadic and it will be silent for a while then theres a couple of good hisses and then silent for a bit.

The thing that makes me think its not the vent is that prior to putting this new raditor/trv/airvent/valve the old raditor/airvent/valve had the same issue. Also the plumber had taken the air vent off completely on the old radiator and put a bbq lighter near it and could see the flame moving and sometimes going out like air was coming out.

PS I do hear a light light gurgling sometimes.

ethicalpaul

You could turn the vent upside down on the radiator that gets hot to see if the difficult radiator gets hot. The gurgling probably indicates there is a water trap in the supply pipe to the cold radiator. 

It might eventually get steam during a long call for heat after all the other radiators are full of steam

BobC

If the longer pipe feeding the problem radiator has a little bad pitch it will trap some water and that will collapse steam trying to get past it. The gurgle you hear could be water sloshing in that pipe. Try lifting the whole problem radiator up (use a 2x4 and be gentle) and shim the feet to hold it there.

Grallert

Is it at all possible that the "problem" radiator stops heating because the thermostat where ever that is, is satisfied? I would think that if water(condensate) were the issue you'd be hearing hammering at some point after a number of cycles.

ethicalpaul

I think that is exactly the problem. But it is still a problem because he wants the problem radiator to get hot during a normal call for heat, which it isn't.

I speak from deep personal experience that you can have a partial water trap in a supply pipe that prevents steam from making it to that radiator, and yet not have hammering.

ChicagoCooperator

Not sure if it's been asked yet, it doesn't look like it, but are the rooms comfortable? The radiators won't heat fully if temps are satisfied at the thermostat even if they aren't "fully heated."

mattmia2

Was the vlavle replaced with the radiator? Has anyone checked that the valve is opening fully, that it is a steam valve, ans that it doesn't have debris or a loose washer sitting in it?

scott_block

As for turning the air-vent upside down on one of the working radiators, On the small radiator off of the same T I closed the steam valve just to see if that would do anything and thought maybe it was stealing to much steam and it didn't do anything, the radiator was still cold when the others were hot.

As for the thermostat being satisfied, I jack up the thermostat so the heat doesn't go off to see if the radiator eventually heats up and after an extremely long time the other rooms are close to 77-78 degrees and the problem the radiators first 3 or 4 fins will start to be hot.

I ideally do want the radiator to get fully hot but understand that if they do in some cases if the radiator is oversized the room would get too hot or the living room downstairs where the thermostat is could be satisfied already and shut off. The issue is, its almost like the radiator doesn't exist because by the time the other rooms are a comfortable lets say 72 degrees this radiator is still cold so its as if it doesn't even exist.

The valve was replaced and is definitely open, before it was installed opening and closing it, it fully opens and nice and smooth. These are some heavy duty, decorative valves from castrads.com and the other two new radiators and valves don't have any issues with the valves.

Also I have a nest thermostat and have one of the remote sensors which is in the problem radiator bedroom and at night the heat kicks on based on that sensor and not the thermostat in the living room. Since that room is colder because of the non heating radiator that room doesn't get satisfied for a long time and the other rooms are 77-78 degrees then.

Jamie Hall

Oops. Is that Nest properly programmed for steam heat? All the learning and smart features disabled? No setback? Set for true radiant?

scott_block

@Jamie Hall yes that’s essentially how it’s set. I don’t think it’s a thermostat issue because if I crank up the heat and it’s running for a good period of time all the radiators except the problem one will be hot.

how long would you say the boiler should run for to heat up the radiators? How often should the boiler be kicking on?

ethicalpaul

My money is on that cold radiator having a water trap in its supply pipe. Nest might suck, but it can't keep a single radiator cold when the rest of the radiators are hot.

scott_block

@ethicalpaul thats sort of what i am leaning towards, its just not what I want to hear because how do you fix this? I have to cut the floor open over in that area and then have the floor repaired?

ethicalpaul

You can try to raise the overall height of the cold radiator. Raise it slowly, like 1/4" per day, to see if it starts to heat. If it does, you can be pretty sure that by raising the radiator, you altered the angle of the pipe to eliminate the trap.

I tried raising my problem radiator. It got better (stopped banging) but still wouldn't get warm. I ended up re-running my supply pipe, see discussion here: https://forum.heatinghelp.com/discussion/177777/autumn-saturday-radiator-repipe

bburd

If you have to get at the piping, it might be easier to cut and patch the ceiling below rather than the floor above. 

SteamCrazy

Hi, it looks.like from pic of radiator that it's pitched in wrong direction. 

scott_block

The ceiling is plaster below so, im not sure how much better going from underneath is, but I guess I will have to see.

For the pitch I have about 7 quarters on the side opposite the valve, i am pretty sure its pitched towards the valve but I cant really check because the radiator is not flat so I cant really put a level on it.

I am going to see what I can dig up to try and raise the whole radiator and see if it changes the pitch of the pipe and let you guys know how that works.

mattmia2

Plaster is easy to repair if you know what you are doing. splicing in subfloor then strip flooring and trying to get it to match is a whole lot of work.

HarryL

@scott_block "the radiator is not flat so I cant really put a level on it"

I've had the same issue with putting a level on the top of some of mine. You can use two small blocks of wood of the same thickness, one on each end and put the level across those. You might need a longer 2x4 to span the distance if you don't have a long level. I've also tried putting the level vertically on the ends this seems to work too.

I have wondered if when columns don't line up across the top if more careful measurements are needed to be sure there aren't low spots in these sections, or if these are just manufacturing differences in the sections but the connections at the bottom are in fact a straight "pipe" pitched correctly as long as the two ends are pitched correctly relative to each other.

ethicalpaul

mattmia2 said:

Plaster is easy to repair if you know what you are doing. splicing in subfloor then strip flooring and trying to get it to match is a whole lot of work.

"Luckily" in my house just about every radiator valve has leaked at some point in the last 100 years, so the plaster and lathe below each of them is long gone, having been replaced by staple-up pressed tiles