radiator heats slowly

dobro23

im probably overlooking something so simple! I went to a house today where i installed a megasteam 396 in mid august of this year. the day it was installed i did a quick skim and told them i would be back at the beginning of the heating season to dial in the radiator vents and skim more thoroughly after the system had run for a few weeks. that was today.... customer is very happy with everything and says its better in every way compared to the system that we had taken out. but one thing stayed the same.. the master bedroom takes forever to heat! I wasn't aware of this before but he told me it was the same with the old boiler. Im going back on Friday to have a closer look. this is what i know as of now. the house has 2 2" mains. they are around 40 and 50 feet. (I dont have the exact length handy) all of the steam piping is uninsulated at this time. both mains each have a Gorton #2 on them correctly placed. the radiator that isn't heating is the last one on the longer of the 2 mains. it is a 1-1/2" horizontal run out for about 3 feet then 1" vertical up to the second floor bedroom. the radiator it serves is a 2 column 8 section with a brand new hoffman 1a set at 6. the radiator is pitched correctly and is only connected across the bottom. it is the only radiator of this type in the house and is painted silver. the radiator valve *seems* to operate correctly. feels smooth and stops when fully open and closed. when I close it during a call I can hear air being sucked back in the 1a. after about 30 minutes of a heat call the valve began to get hot. 10 minutes after that the first section and so on. after an hour the 4th section was barely warm. this was with the vent completely removed from the radiator! all the other radiators in the house work fine ~ just this one takes forever. the room is cold because the call satisfies long before it ever gets warm. my gut tells me there is an obstruction in the valve only because i dont know what else to look for. any suggestions would be appreciated.

Jamie Hall

Can you compare when steam starts to move into that runout with when it arrives at the next one back? And then get a feel for how fast it moves up the riser? You don't mention a main vent near the end of that main -- is there one? I'm trying to get a feel for where the steam is being slowed down.

dobro23

it is the last take off on that main and a gorton #2 is about 18 inches past it. then 2 feet after that is the drop to the wet return. the previous run out is about 6 feet before it but serves a 1st floor radiator. i didnt think to compare times but i can say every radiator in the house is warm in about 10 minutes except this one.

Dave T_2

You may be able to solve this by slowing down all the other radiators by adjusting their vents. You will get the system to run longer to satisfy the thermostat and more steam will be available to move to further areas.

Jamie Hall

Next time you're over there, check and see when steam hits that main vent. It should be no more than a minute or two after it hits the runout to the 1st floor radiator. Then follow it up the problem child's runout and riser. I wonder... I suppose that Gorton is working? They're pretty reliable -- but anything can fail!

dobro23

i will on friday. BUT even with the radiator vent completely removed from the radiator it still didnt get hot. seems like the valve is blocked. im trying so hard to NOT diagnose it ahead of time...

Jamie Hall

Valves have been known to become blocked... fortunately, unless it's a real antique, that's not the hardest thing to fix. Usually... That will show up by the main getting nice and hot nice and quickly to the main vent -- but proceeding very very slowly on the runout and up the riser.

EBEBRATT-Ed

The disk could be broken inside the valve. Also check the EDR of that radiator against the pipe size. 1" doesn't carry a lot on one pipe steam. Remember you have steam killing condensate coming back down the pipe.

It's all about pressure drop. If that radiator and pipe has more pressure drop it will be slow to heat

BobC

If there is a horizontal run of pipe under that radiator it could be pitched wrong and you could have a pool of water in that pipe. That pool will condense any steam passing over it until that short hoirizontal pipe is really hot.

See if you can lift the whole radiator up and put it on blocks to repitch that pipe.

Bob

Fred

I'm thinking a 1" riser, at the end of a Main, if the other risers are larger, may be problematic, especially on a normal heat cycle.

ethicalpaul

I’m with @BobC. It sounds exactly what I went through with my bedroom radiator where I had to repipe it. 

The key is that steam won’t go to it even without a vent. Rule out the valve then try to raise it to correct a hidden pitch issue. 

dopey27177

In my opinion the 1" PIPE GOING TO THE
SECOND FLOOR IS THE CULPRIT.
This pipe should be increased to at least 1 1/4". If you want the system to be more efficient insulate all your steam Piping in the basement.
In one pipe steam systems the use of a 1" supply is a no no.

Jake

STEAM DOCTOR

@dopey27177 There are probably hundreds of thousands one pipe radiators that are piped with 1". And they work just fine. 1" will and does work.  Up until a point. Larger radiators will need larger pipe. I don't have the lost art in front of me, but the numbers are there. 

ethicalpaul

All my upstairs radiators were 1” in poorly insulated wall spaces, but they worked fine I must say. About 20 EDR each. Just the one with the bad pitch gave me trouble.

but I agree I’d rather they were all 1-1/4 

dobro23

At the house now.  I removed the radiator and valve.  No problems there.  Turned off all radiators and built up a little head of steam.  Opened valve and problem radiator and had PLENTY!  reinstalled radiator with vent removed.  Opened valve and radiator heats fully in only a minute or so.  Replaced vent and set to highest capacity.  Verified radiator pitch etc. New theory is that I'm using all the steam in the other radiators and there is almost none left for this last one although the boiler is  sized for the connected load.  Maybe the lack of insulation etc is just pushing it past it's breaking point.  Customer was supposed to insulate over the summer but hasn't gotten to it yet.   The main was slightly back pitched near this radiator but it is corrected now.  Also the runout servicing this radiator in improperly pitched but need to come back with threading machines to fix it if it is necessary. It's about 1/8 out. Not sure if that's enough to make a difference on 1-1/4 pipe.  There is no water hammer anywhere in the system.   The main is 2" and the horizontal run out is 1-1/4 not 1-1/2. The 90 on the end is where it reduces to 1" and it appears to be a straight shot up to the second floor.  All first floor radiators are 1-1/4 valves and all 2nd floor are 1".  Pressuretrol is subtractive and set at 2 with 1.5 differential.  Normal running pressure is about 1 oz.  Choked down all other radiator vents and max fired boiler in an effort to push more steam further down the line before the heating cycle ends.  Cust will call Monday to update. 

EBEBRATT-Ed

@dobro23

Just like I said previously steam will take the path of least resistance. 1" pipe will not do a second floor radiator unless it is fairly small you have condensate coming back down that pipe which will kill the steam.

Removing the radiator and letting the steam come out an open pipe proves nothing.....there is no condensate flowing back down.

Picture steam and condensate trying to get around that 1 1/4 x 1 90 at the bottom of the riser.

Choking down the other vents and max firing may work at the risk of burning more fuel

Dave T_2

Fire the boiler to try to match the connected load and slow the vents that are heating easily until you get heat in the problem radiator. Keep in mind the heat from radiator(s) near the thermostat will determine how long the system will run, if they heat too easily the system may shut off before the problem radiator has a chance to heat up.

Jamie Hall

Actually, @dobro23 , running the thing as you described does prove something. In fact, quite a bit that's helpful. Steam can freely get through that pipe and riser and so on -- which eliminates a whole host of headaches. It would be nice to get the pitches better, but if it's working, that's going to be just nice to do, not necessary.

Now it looks really like a real balance problem -- compounded by the lack of insulation. Probably not helped any by the relatively small riser -- but that may be hard to fix, depending on how the thing is run.

motoguy128

1” vertical is OK if it’s a small radiator. That’s not a small radiator.

I suspect the disc however is in fact broken. I also wonder if the 1” pipe is partially blocked.

Also, be aware that in many cases, a long vertical riser may appear to feed a radiator directly on the 2nd floor, but in fact has 2 horizontal pipe nipples to fine tune the location, create a swing joint and to make sure the pipe is pitched but the radiator valve is level and square in both directions.

Steam will flow slower if a horizontal nipple pipe isn’t pitched. Might need to raise the whole radiator a little.


Also, In my endeavors of tuning my own system, I’ve found that with steam vapor, lateral size will balance a system like an orifice almost as much as the radiator vents. I have a larger radiators (48-64 EDR) with a ventrite set at 5-7 that heat up about as fast as a smaller 25-30 EDR radiators with a Gorton 4 or ventrite set at 3-4.

When I vented everything with larger vents and had less main venting, I’d have erratic heating and some radiators would not heat at all.

ethicalpaul

Jamie Hall said:

Actually, @dobro23 , running the thing as you described does prove something. In fact, quite a bit that's helpful. Steam can freely get through that pipe and riser and so on -- which eliminates a whole host of headaches. It would be nice to get the pitches better, but if it's working, that's going to be just nice to do, not necessary. Now it looks really like a real balance problem -- compounded by the lack of insulation. Probably not helped any by the relatively small riser -- but that may be hard to fix, depending on how the thing is run.

Respectfully, I don’t think it proves much. He turned off all the radiators and built steam pressure then opened the problem radiator. Of course steam got through. I wouldn’t assume freely, however, based on this experiment.

Steam got through before, it just took a long time, he said. Probably it just took time to heat up that alleged standing water to near 212

He can try throttling down every other radiator to force this one to get some steam but I imagine that will make balancing very difficult or impossible.

I hope I’m wrong but I think the angles have to be addressed. Good luck!

ADEY_NorthAmerica

@dobro23 have you checked the system for iron oxide?
Iron oxide can build up in the bottom of radiators, causing a reduction in heat transfer and therefore radiator cold spots.
Iron oxide is a result of oxidation in an untreated system.
It might be worth checking just in case. If there is iron oxide present, we suggest a clean, flush, magnetic filter installed and a hose of inhibitor. Hope this helps.

ethicalpaul

ADEY_NorthAmerica said:

@dobro23 have you checked the system for iron oxide?
Iron oxide can build up in the bottom of radiators, causing a reduction in heat transfer and therefore radiator cold spots.
Iron oxide is a result of oxidation in an untreated system.
It might be worth checking just in case. If there is iron oxide present, we suggest a clean, flush, magnetic filter installed and a hose of inhibitor. Hope this helps.

We are talking about a steam radiator here. There is most definitely iron oxide present, but I think you might be talking about a hot water system. There is no magnetic filter for a steam radiator, and no concern about cold spots on the bottom.