Radiator banging noise

MacBosnia

Anyone know what could cause banging in the pipes leading to the radiators?  We've heard louder banging in the pipes lately.  Our furnace is gas powered and has a water boiler.  It's a big house with many radiators.

Gordan

Is this your first winter in that house?

Banging in hot water systems is typically caused by either water hammer from zone valves closing too fast, or it's caused by thermal expansion - as pipes heat up, they expand and, if something is causing them to bind or get stuck (like rubbing on wood framing or at wall/floor penetrations), they let go - loudly.



When does the banging happen - when the heat comes on or when it turns off? How many thermostats do you have in the house?

MacBosnia

Radiator banging

No, I've been in the house 8 years.  This is the only winter I've heard this amount of banging (and it hasn't been the coldest winter in the last 8 years).  There is 1 thermostat in the house, on the 1st floor.  The banging seems to be noisiest on the 2nd and 3rd floors.  One of the radiators on the 2nd floor is getting extremely hot (although the thermostat is only set at 63).  All 3 radiators on the 3rd floor are cold.  Friends have told me that there could be air pockets, perhaps on the 3rd floor.  We are planning to bleed the three 3rd floor radiators tomorrow and see what happens... 

MacBosnia

Radiator banging-2

To answer your question, the furnace kicks on all day (depending on the heat of the house), but we seem to hear the most banging in the middle of the night (like 3am).

Gordan

Is the thermostat a programmable one?

If so, do you have it set for night setback (lower temperature) and when is it programmed to come out of setback?



Expansion noises will be the loudest when the temperature of the water changes most rapidly. This would typically be after the boiler has not fired for awhile, such as during night setback.



Has anything been changed since last heating season?



The cold radiators on 3rd could be air, or it could be something else. Were those rads heating up last season? Let us know what happens after you bleed it. If it is air, you should hear (and feel with your hand) air escaping, then gurgling water, then water should come out. If there's no air but water comes out immediately, you've got a flow problem of some sort and we'll need to troubleshoot further. If air is actually being sucked IN, and not expelled, then your system pressure is too low and we'll need to troubleshoot further. Air in pipes shouldn't cause banging noises directly, but if it's stopping water from going to all the radiators, then it might make the water in the pipes where there IS flow, heat up more rapidly.

faster340

Banging radiators - Again I know it's been beat to death...

I have one radiator fiercely bangs. It's a one pipe system. The radiators that don't bang I hear the valves hissing when it's making heat. The radiator that does bang I don't hear the valve hissing. Could this be a bad valve causing the banging because it can't release pressure?



Thanks.

STEVE PAUL_3

The banging radiators

sound to me like the cause is low water pressure in the system. The giveaway clues are: 

No heat in the 3rd floor radiators (no pressure, no water, radiators are cold) The "Banging" is only in the second floor, very hot radiators (Low pressure). I think that the water temperature is extremely high (over 212*) and is flashing to steam in the 2nd floor radiators.

I would check the high limit control to be certain that it is properly operating. And I would check the pressure regulating valve to be certain that the pressure at the very top of the system is at least 3-5 PSI

 

icesailor

Banging Noises:

You must have a steam system. Steam systems (One Pipe) have one pipe to the radiators and an air vent on the side that will hiss while the air is bled off. Hydronic, Hot Water systems have two pipes and no open air vents. They have a vent on the top of the radiator that you vent and get water out of. You are asking the right questions, But on the wrong type of heating system. Ask about Steam.

MacBosnia

Radiators banging noise

Gordon, we bled all our radiators (about 15 of them in the whole house) and that seems to have done the trick. We didn't hear any banging noises last night. Some of the radiators on the 3rd floor had to be bled several times before any water came out, but now everything seems to be working. And, the house is much warmer. 

Thank you for your timely input and advice! Much appreciated.

Mac

Steve_175

Add water?

Did you add make up water to the boiler after you bled the radiators? When was the last time the boiler was purged of rusty water from the drain?