Water hammer in radiator

Nelson_4

Hi,

I have one-pipe steam. Newer Burnham MegaSteam.

I am getting water hammer in one radiator when the boiler is running. It happens about every 5 seconds, sounds like someone tapping the radiator with a wooden spoon. Then there are a few sporadic clangs after the boiler shuts off.

I have already pitched the radiator back toward the supply.

If this is what level looks like (trying to draw a bubble here!):

|  |()|  |

Mine is currently straddling the line:

| (|) |  |

Should I try to raise it even more, to:

()|  |  |

I thought I heard that raising it too much can cause even more problems...

Thanks for any thoughts.

Can provide pictures if necessary later tonight, if you don't understand my artwork!

BobC

Piping

As long as the radiator slopes towards the input valve you should be ok. Check the pipes that feed that radiator and make sure they all slope back towards the boiler. do the same with the steam main.



When the boiler was changed did they replace the main air vents? Also what steam pressure are you running at and is the sight glass bouncing up and down a lot?



Bob

Nelson_4

More info...

Thanks, Bob,

The pressure gauge says "0" when it is running. The pressuretrol is set to 2 on the "main" and 1.5 on the "diff".

The water moves in the sight glass, but it more of a gentle up and down movement, nothing vigorous or violent.

In the picture, the problem radiator is on the second floor attached to the takeoff that is second from the end on the left.

You can see a vent on the return, but there are no vents on the main 2" pipe. The vents on the radiators are all new.

Since this picture was taken, I have insulated the main 3" risers and the 2" pipes with 1" fiberglass, but haven't finished the takeoff pipes.

Does this help?

jpf321

noting the obvious ..

is the supply valve for that rad fully open?

did you try a slower venting rate on the rad?

are your pipes of sufficient size to support both steam and condensate for this size rad?

when did this start happening? what has changed to cause it to happen?

does it quiet once the rad is fully hot and the air vent on it has closed?

if you close the supply valve for this rad do you still hear the noise?

if you flip your airvent upside down (supply fully open) (assuming not a heat timer varivent) .. does the noise stop?



your pressure is too high, should be 0.5 outside scale , 1 inside dial .. it's a nice clean by the book install it looks like .. what does your installer think about your banging? i am disappointed that your installer set the pressure so high .. good at pipes and directions, bad at steam perhaps?



you may want to give this current thread a read ..

http://www.heatinghelp.com/forum-thread/134644/2-Plumbers-Stumped-The-Gurgling-Radiator

Mike Kusiak_2

Pressuretrol setting

Looks from the photo that he might have a L404B pressuretrol with subtractive differential. Nelson says present settings are 2 PSI main, with 1.5 differential ( 2 PSI cutout, .5 PSI cutin ). So his settings are not all that bad, although they probably could be reduced a bit.

BobC

Try pressure and lift the whole radiator

It sounds like everything has been done right but getting that boiler pressure down would help. Is that pressuretol the new type with the dual scales on the front? I don't know how far you can turn those down but it would be worth a try. Post a closeup of the pressuretrol's front and give us the model number.



The only other thing that comes to mind is there may be a short piece of horizontal pipe under that radiator on the second floor. If that doesn't have any slope it can be a problem, they shimming both sets of legs up by 1/2 or 3/4" and then add quarters under the vent side to get the slope right. Use a lever and a fulcrum to lift the radiator GENTLY, you don't want to crack anything.



Bob

Nelson_4

More info

Yes, supply is fully open. I have not played with the venting rate or turning off the supply valve, I'll have to try it and get back to you...All pipes are original (maybe 1940?), so I assume they are adequately sized. House has never changed since built. Maybe the banging has always happened, but now this is our daughter's room and I have a baby monitor in there, so now I hear the knocking! Haven't consulted the installer yet (Norm Harvey) because he is not local, but he has a great reputation with steam.

Nelson_4

Model

Hi, thanks, sorry I couldn't get a picture, but I Googled the image of the L404B and that is exactly what I have.

Nelson_4

Thanks

My guess is that the pipe goes straight up from the basement...Any clue why the main gauge is "0" when the boiler is running? Shouldn't I see least .5? It goes to 30, but it never moves!

I will have to get back to you...I can try raising the radiator. What do you recommend for the pressutrol's settings?

Nelson_4

Just found another pic...

Maybe not helpful because the pressuretrol is partially cropped out of the photo...

Mike Kusiak_2

Pressure

If the size of the boiler is well matched to the amount of radiation you have, then the pressure will rise very little and you may never notice the gauge move. Unless the system is recovering from a setback, you may not see any measureable rise of pressure. If this is the case, the pressuretrol settings become less critical, since you may never reach the pressuretrol limit setting under normal use. The calibration markings are undefined below the settings you have, so the only accurate way to set them would be to add an additional low pressure gauge and set the limits accordingly. I would leave the settings as is for now as they are not unreasonable.



Norm Harvey is a long time Wall contributor and very well regarded with respect to steam. His install looks first rate and I would contact him and get his input before making any changes to the settings.