Loud banging noises

LarryC

Home owner here.

It could be someone anchored the pipes securely and left no room for thermal expansion. When stresses build up to a point of sliding past the anchor, BANG! Happens once on heatup and once on cooldown.

A possible work around is to left the system on constant circulation and control the furnace temperature with Outdoor reset.

Do you still hear gurgling? If so, I think you don't have all of the air out.

Larry C

Leo G_100

Loud banging noises

I have a hydronic heating system with a gas fired boiler and cast iron rads. The house is a bungalow, built in 1949, and has the the original rads on the main floor. The basement has slightly newer cast iron rads - probably from the 1960s. The original pipes are metal, and the newer basement ones are copper. The current boiler was installed in 1981, there is an electric water circulator and no zone valves. There is also a honeywell thermostat on the boiler where I have the max temp set to 140F in the fall and 180F in the winter, and the circulator shut-off set to 110F. Here is my problem: whenever the heat comes on, I hear some light popping and clanging sounds coming from the original rads and pipes, which I guess is understandable. However, after about 30 minutes, I hear a 'muted' loud bang somewhere in the pipes close to the back of the house (the pipes are located between the main floor and basement ceiling). I also hear the sound of water gurgling. However, once the boiler is up to a steady temperature, the system is basically silent. Then, once the heat shuts off, I hear some more light clanging sounds as the system cools off. However, after about two or three hours, I hear a tremendously loud clanging/banging noise coming from the pipes close to the back of the house again. It literally makes me shoot straight up out of bed. It sounds like someone hit a metal pipe with a sledgehammer, and you can even feel the bang if you're standing on the floor. I read a post about zone valves causing this noise, but I don't have any. There are four rads on the main floor (living room, 2 bedrooms and bathroom), and four in the basement (one is turned off). There used to be at least two more rads on the main floor which at some point, were removed.

Sorry for making this so long but I've gone everywhere and no one is sure what the problem is. I had the boiler inspected, the expansion tank replaced, the air bled from all the rads, I turned down the temperature setting on the honeywell t-stat (thinking that maybe the water was just getting too hot), but nothing has worked. My basement ceiling is finished with stucco except for the laundry room, so I can't really access most the pipes to have a look. The pipes I see in the laundry room appear to be OK - solid with no movement, leaks or rust. Has anyone encountered this before? Will I have no choice but to rip up my basement ceiling, or is there something else I'm missing?

Leo G_100

Thanks for your reply! I may have to consider your suggestion. How much 'give' should these pipes have? The ones heading to the bedroom are rock solid and don't move at all, so your analysis seems to be spot on.

Yes, I still hear gurgling, but only for about the first hour, then it seems to go away (or be faint enough that I can't really hear it). There's one rad that won't really bleed - when I turn the little knob, a few drops of water come out, but no air. It seems like it's clogged. I've bled all others but will check again to make sure there's still no air. Do I have to bleed the basement ones too? I thought any air in the system would have gone up to the main floor rads, so I didn't bleed any of the basement ones.

able

noises

What is the water presure in the system.is there a automatic feed valve.I have seen this when waterfeeder is piped into the top of the boiler and there is no automatic air removal a air cushion can form in the top of the boiler and boiler will make pockets of steam wich flash when they hit water and sometimes cause banging noises but you wuld see the needle on the tridicator bouncing up and down also have seen people wire boiler mates to the wrong side of the high limit and burner will not shut off at set temp sounds like you definetly have air in the system or maybe not enough water 12 to 18 psi.how long have you lived here and is the noise something new .

Leo G_100

Thanks for your reply. This is my third winter in the house, and the banging noise has been there since I moved in. There appears to be both an automatic feed valve as well as an air vent in the piping close to the boiler. The water pressure is at approx 12psi when not in use, and goes up to around 18psi at peak (I've seen it as high as 20psi, but very rarely). I've never seen the needle bouncing, but then again I've never been next to the boiler when there has been a loud bang. It just happens twice per cycle - on warm up and on cool down, but the timing varies quite a bit. There was still air in the system: I bled the smallest rad which is on the main floor and air came out for about 10 seconds. This concerns me because I bled it not too long ago. Where could all this air be coming from in a closed system? However, even after bleeding that rad, I still heard a loud bang last night, although it didn't seem quite as thunderous as usual.

LarryC

Auto feed and air

The additional air might be coming from make up water if, ... you have an unseen water leak.

What type of surge volume do you have in this system? Is it a diaphram tank or a tank with a air over water? Is it water logged?

Do you know if the air vents are functional?

Larry C

Leo G_100

Auto feed and air vent

Hi,

I recently had the original expansion tank (1949) replaced with a diaphram tank at the recommendation of a heating guy I hired. I'm not sure what surge volume means. As for the vent, it is located on the incoming pipe (city water supply) before the boiler. How can I tell if it is functional?

As for an unseen leak, I wondered about that and checked every nook and cranny around the house where there are rads and pipes - no leaks that I can see, unless it's in the basement ceiling somewhere and there are no water stains yet...