Boiler Off With Pipes Still Banging?

Deadman

I need some help with this one. 

I installed a new gas fired steam boiler and put in all new vents in the system.  I insulated all the straight runs of pipes in the basement (they were never insulated before), but didn't insulate the elbows.  (See attached pic just after boiler installation) 

The boiler fires nicely, good supply of steam within 5 to 10 minutes (1,200sf house with two floors), house heats, thermostat shuts boiler down... and then about 20 minutes later.....BANG... two minutes after that... BANG... very loud... coming from main steam line in basement.  There also some minor banging coming from largest radiator in the house, but nothing like the basement noise.

I don't remember them banging like this with the old boiler when there was no insulation on the straight runs of pipes.  I used to get a ton of water hammer with the old boiler, but I re-pitched the main return, and no water hammer at any point during the running of the new boiler.

So, with the system running, no noise.  Shut the system off... loud bangs 15 to 20 minutes after.

What's up with this?

Are the pipes contracting?

Is this normal?

Thanks,

Mike

Jamie Hall

Nice looking job

My bet, though, is that what you are hearing is a pipe contracting as it cools, and sticking on something, and then finally releasing.  It really isn't the same sound as a water hammer (if you've really heard them both, they are quite distinct), but it can be quite a bang.  Look around and see if you can find somewhere where a pipe -- quite possibly a main -- is hanging up on something so it can't move easily when it expands and contracts.



For starters, anyway...

Unknown

Water Hammer

Very nice piping job!   If it is water hammer you are hearing, it is probably caused by collapsing steam.  For people reading this new to steam, this happens when a steam bubble gets trapped in the condensate and collapses. The thumb rule is: A cubic foot of steam collapses into a cubic inch of water. A steam bubble collapses almost instantaneously causing a vacuum void to be created. The surrounding condensate rushes it to fill the void and the impact of the water coming together is what we call water hammer.



This is kind of a long shot. In situations like this if the problem isn't obvious I look for things that are "unusual" and in looking over your boiler piping the only thing I see "unusual" is you have a very short and high Wet Return. The large elbow just where it connects the Equalizer is also "unusual". Now whether either of these are causing the water hammer I have no idea. What you might want to do is immediately after the pressuretrol cuts off the burner, shut the power off (so the burner doesn't come on again) and close the valve on the pipe below the elbow going into the equalizer and observe what happens as things cool down. 

You might want to go through a couple of regular hammer cycles first and time when the the hammering begins after shut down and the interval in between the first few "hammers" as then you will know what to expect when you shut the valve for the "test".

Just my 2 cents!

- Rod

Brian_74

Just out of curiosity…

What did you paint the pipes with? I looks cool. Is it insulation, too?



Brian, who also likes shinny things. :-)

jpf321

just curious...

how did you color the pipes? paint them after the fact .. that sounds messy, but it doesn't look like there's any mess. 

Charlie from wmass

Nice paint.

Is the drop enough on the return? looks very close on the Hartford loop for elevation but it may be the angle of the camera. I like to drop the returns closer to the floor for a bit more seal. Are there any low spots on the dry return? or reductions that are not eccentric.

Deadman

Thanks for the help...

First of all, the banging is happening when the boiler is not running.  On warmer days, it bangs the most.  On colder days (boiler running more frequently) it never seems to bang.  This has led me to believe that Jamie is on the right track.  Pipe hangers "too tight" or something restricting the piping from contracting naturally.  I have to move around some insulation to fix this problem and will do so soon and then come back to this thread.

Ron had good info and mentioned the "unusual" high wet return with large elbow.  Charlie also mentioned this.  The large elbow was all I had at the time.  Also, the high wet return was done that way so I could easily fit the drain into the bucket.  In retrospect, it might have been kind of stupid of me on both counts, but I am just a homeowner who reads a lot and if this becomes a problem, then I can fix it.  Thanks for the heads up.

Lastly, I painted the pipes because I needed something to do when I was testing out the new boiler.  So I sat there painting.  Also, some fittings were used and rusted and it looked bad, so I painted.  I used an ICI DuLux brand oil based safety orange (which I was told is OSHA code for steam pipes).  As far as not being messy goes, I only put the paint where I wanted it to be.

Thanks to all,

Mike  

Unknown

Pipe Noise

OK ...I was under the impression that the banging occurred when the boiler was hot and after it had just shut off and was still full of steam.  If the "banging" is from pipe expansion /contraction - cut some strips off a plastic milk bottle and place them around the pipe at the hangers or where ever the pipe touches something. This should help the pipe slip a bit rather than "jump" - Rod

Deadman

Solutions

Rod,

Hey... thanks so much... That sounds like a great tip.  I will do that and get back.

Thanks,

Mike

Dezso3

Radiator making banging noise

We just had our old boiler replaced, and afterward the steam pipes (mains) starting

making an extremely loud banging noise (water hammer), so we called the

contractor who had installed it, and they managed to fix it. However,

one of the radiators was also modified. It had been shut off for quite

some time, probably about one year. The living room was getting really

cold though, so we decided to re-open it. We also installed a Gorton

No. 5 vapor equalizing valve on it. What is very bizarre is when I turn

the thermostat on during the day and set it to 70 degrees, I can't hear

that particular radiator making any noise. However, for two nights in a

row I woke up for seemingly no reason, and when I put my hand on top of

the radiator cover, it was hot, so it had to have made a noise in order

to wake me. Overnight, the thermostat is set to 65 degrees, so I don't

know if the colder radiators warming up to the same temperature vs.

from 70 degrees while heating up has anything to do with the noise. =\

jpf321

please see your other thread for response

please see your other thread for response

http://www.heatinghelp.com/forum-thread/129186/Radiator-making-banging-noise

Deadman

Think I Found The Problem

From reading all the tips here and doing some investigating, I found the problem with the banging pipes.

First off, the banging noises are coming from contracting pipes, not water hammer.

Second of all, I found that the living room radiator (fairly long run from the main) was the culprit.  It was guilty for two reasons: 

1.  Some flooring repair had been done over the summer and the flooring guy replaced some rotted hardwood in the valve area.  He cut in new pieces oak tighter than a bulls **** at fly time.  The pipe is being strangled and can't move.

2.  The house was insulated with blown insulation and then sided... all except for the front, which is brick.  Since the radiator is along the front side of the house, it cools and contracts really fast from the coldness of the wall.

So, with the tightness of the piping, and the cold wall....BANG...BANG... you got the big noises coming from that radiator and traveling down to the main.

I was tricked for a while because it did it at night more than during the day.  But during the day, the sun heats the brick front and the wall doesn't get that cold.  But at night, it gets really cold.  So, that's why we noticed it more at night and not so much during the day.  Also, the banging was traveling down the feed back to the main and that was faking me out too.

So, it was an easy fix for now.  I shut it off!  The house is hotter than the hinges of hell anyway.  I will fix it all up toward the end of the winter.

Thanks everyone for all your help.

Mike

jpf321

glad to hear

glad to hear you have a handle on the problem .. i really like your similes .. it is often recommended here that you try to slip a piece of plastic milk jug btwn the pipe and the surface that it's rubbing against .. seems to allow smoother expand/contract surface.