Banging after radiator refurbishment

homesteadbuilder

I had a small steam radiator sandblasted and powder coated in a rental apartment this past summer. When the system was turned on last week there was banging in the radiator. I have made sure there is good pitch back toward the valve and have installed a new air vent. The radiator seems fine when I check it out during the day but the tenant says the radiator bangs at night and she winds up just turning the heat off. Do you think it's possible that some rust or other debris came loose inside the radiator during the trip over and back from the powder coating place and this is causing the condensate to drain slowly enough to cause the banging? If so how to fix. It's a one pipe steam system. The radiator seems to match the oldest radiators in the house which I'm guessing were installed in the early 1900's. The radiator in question is located the farthest from the boiler. There doesn't seem to be any issues with any of the other radiators and the radiator seemed to be working fine last season prior to the refurbishment. Thanks

Jamie Hall

When it was put back, was it at least as high off the floor as it is now? And is it pitched at least as much?

The other thing to check is if the valve to the supply is really fully open. They do fail partly closed...

homesteadbuilder

Thanks for the reply. Yes radiator put back in same position. Valve completely open. Banging at night. I then added some shims to increase the pitch more and still banging at night. I double checked the valve and it is all the way open but the valve is pretty old could there be something inside that has come loose? How would I check that? Thanks

Jamie Hall

There could indeed be something inside that came loose, particularly if you operated the valve while working on the radiator. Most valves you can see what's going on either by unscrewing the bonnet; you might also be able to see in from the side with the radiator disconnected.

It wouldn't be the first time that the washer assembly came adrift...

homesteadbuilder

Thanks again, I was thinking I might try and take the radiator outside and see if I could flush it out with a hose. Any thoughts on that idea? I would try and look inside the valve first to see if I can see if anything is loose.

EBEBRATT-Ed

Taking it outside and flushing is fine. I would suspect the old valve as well. About the only other thing to try is check the pitch on all the branch pipes feeding the radiator and possible try a smaller radiator vent to vent it a little slower. Sometimes that helps

homesteadbuilder

Thanks for the reply. The banging was worse last night. The temperature dropped so there was more cycling of the system. I removed the radiator brought it outside and flushed it hoping that it would be filled with gunk. The water was absolutely clean. No rust, no crud just clean water came pouring back out. Turned the radiator upside down filled it with water turned it back down and clean water came pouring out the bottom and the vent hole so nothing clogging the radiator. I looked inside the valve while the rad was disconnected. Everything I could see looked fine. I opened and closed the valve and all looked good.

Is there any chance it could be a boiler issue? The boiler was installed about 5 years ago and I skimmed the boiler after it was installed. I would think that if it was the boiler then there would be banging in some of the other radiators closer to the boiler and it seems the only banging is the radiator farthest from the boiler. I drained a little water from the bottom of the boiler and a small amount of typical very dirty boiler water came out and then it also ran clean.

I think I might try the smaller vent. The tenant said the radiator was slow to heat up so I put in a no. 6 maid-o-mist valve. There had been an old adjustable valve when the banging was first reported. So I just put in a fairly large valve because the radiator was far from the boiler. Do you really think it's possible that the valve could be the problem or just make an existing problem a little worse?

The radiator is on the second floor so I don't know if I can check the pitch on the branch pipes. The pipe coming out of the floor is pulled up as much as it would go in order to hook up the radiator. I assume the pipe turns 90 when it runs under the floor. Since the part that comes up thru the floor is pulled up tight (there may have been a layer of flooring added during a past remodel) I would think that it has probably the most pitch it could have?

I might add that the radiator does not bang on it's initial heat up. That is to say that if the boiler has been off for awhile like in the middle of the day and I turn up the thermostat the radiator gets hot with only slight noise. It gets much worse on a cold night when the boiler needed to cycle to keep up.

Thanks for any more input.

EBEBRATT-Ed

Venting slower may help. Make sure the radiator is pitched. What pressure do you get on the boilers gauge (if any) too high of a pressure can cause some issues as well. Is the boiler water line steady while it is steaming?

homesteadbuilder

Thanks again. Boiler water seems steady. I'll go later and check on the boiler gauge pressure reading. I'd be happy to drain refill and then skim boiler if I thought that would help. I would think if that was part of the problem I would hear some banging on the initial firing after the boiler has been off for awhile. Would also have issues on radiators closer to the boiler. I'm wondering if there could be some kind of blockage at the top of the riser where it would enter the floor and then run horizontally under the floor to the radiator. It seems as if boiler has to cycle several times as the banging occurs somewhere around 3 or 4 in the morning when I guess the temperature is the coldest. If there was some kind of blockage that might slow down the condensate from returning and then it may build up enough after several cycles that it could cause the banging then? Years ago in another part of the same house there would be loud banging on one particular section. It was an exposed riser in the living room. It drove me crazy. Then one day it just stopped. I always wondered if there was some kind of blockage at the top of the riser that just somehow loosened up. Oh and there is a lot of pitch. Probably half a bubble. In order to get the radiator hooked up to the valve the rad is tilted so far that the back legs are probably 3/8 inch off the ground. Thanks again.

homesteadbuilder

Looked at the boiler gauge and was reading zero. After a full cycle and I guess all the radiators were full the gauge went up to around 4 psi then the pressuretrol cut everything out. 4 psi seems pretty high. I adjusted it down. It was colder today so easier to run a bunch of cycles. I turned the heat up enough that the thermostat would be calling for heat for awhile. The adjusted pressuretrol cut out at about 2-1/2 psi which seems much better. Watched the boiler go thru about 3 cycles and always cut out at 2-1/2. This is on a 0 to 30 gauge so I don't know how accurate but way better that 4 psi. Left heat on and came back an hour later. Boiler was still on and seemed to be cycling nicely with no banging. It is supposed to get cold tonight so will see if that solved the problem. I also followed Ed's suggestion and put a smaller vent on the offending radiator. I had put a number 6 Maid-o-mist since it was the furthest from the boiler so I swapped in a no 5. So we will see tonight. Thanks

bburd

See if you can get the pressure down a bit further, two psi or less is ideal. Be careful you don't adjust the pressuretrol so low that the mechanism becomes disconnected though.

homesteadbuilder

Thanks I'll try. I'd like to get a 0 to 5 or 0 to 3 gauge. Any recommendations on a brand? Maybe something I can just order from Amazon? I think I'd be a little more comfortable trying to adjust the pressuertrol with a low pressure gauge.

ethicalpaul

This is a no-name but is probably the simplest/cheapest solution. By far better is a Magnahelic by Dwyer which can be found either used or NOS on ebay for not much more than this, but is a little more effort to mount.

https://www.amazon.com/Capsule-Pressure-Connection-Adjustment-blackSteel/dp/B086942GKG/