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Ranger29 · Jan 22, 2007, 09:42 AM

Hello All,

For starters I've searched this topic and haven't found anything that can apply to my situation.

To set this up. We have a boiler/baseboard heating system that makes loud banging noises when it cycles off, on the first and second floor zones. When heating up it makes a creaking noise. That being said, we recently added a garage with master bedroom/bath (separate zone) above to the house.

To the best of my knowledge the system has been purged of air and the expansion tank is working. The working pressure is running between 12 and 14 psi.

Is it possible that the circulation pump could cause this banging? I know that the creaking at the beginning is the pipes expanding from the heat but the shut down banging is the worst.

Any help would be appreciated.

Phil

rickdb1 · Jan 22, 2007, 09:50 AM

10-15 Lbs is normal. Sounds like there is still air in the system... Is it a rapid banging? You might try lowering the pressure to 10 Lbs and see if that helps...

Ranger29 · Jan 22, 2007, 10:01 AM

Hey Rick,

Thanks for the quick reply. And yes it's a pretty quick banging (3 to 5) at shut down of that zone.

I originally bleed the zone(s) by connecting a water hose to the hose bib on the return side of a zone (while the other zones were valved off), manually opened the thermostatically controlled valve and ball cock on the supply side, then manually opened the pressure regulator forcing 50 to 60 psi into that zone while letting it drain into a bucket (air and water). I did this on each zone until the air stopped on each.

Since then I've opened the air bleeders (one on the expansion tank and one on the boiler) on occasion to bleed off any other trapped air.

Does this sound like a correct method? Is there a better way to bleed the air?

Or

Is there something else I should look at?

Thank again

rickdb1 · Jan 22, 2007, 10:07 AM

Do your radiators have bleeders?

Ranger29 · Jan 22, 2007, 10:09 AM

It's all baseboard and no bleeders. Sealed except at the boiler and stand.

Ranger29 · Jan 23, 2007, 07:02 AM

Other idea's... anyone please

garykempen · Feb 5, 2008, 11:37 AM

Hey Rick,

Thanks for the quick reply. And yes it's a pretty quick banging (3 to 5) at shut down of that zone.

...
Or

Is there something else I should look at?

Thank again

Yes, I'd look to see the valve type. I saw on another site that Honeywell, Erie, and the smaller White Rogers valves can close fast enough that they shut before the pump spins down. That will cause a pressure wave that echoes through your system (Bang-bang-bang... ) Taco and the large White Rogers are apparently slower-closing. All hearsay, but it might be worth looking at if you're still having the problem.

hkstroud · Feb 5, 2008, 04:13 PM

I'm not very knowledgeable here but I believe that the valve on the expansion tank is for putting air into the tank, not letting it out. If you bleed here you let all the air out and the expansion tank is now water logged. The purpose of the expansion tank is to hold air, which can be compressed, when the water is heated and expands. Drain tank and allow to fill with air. Surprised your blow off valve isn't blowing off.

tsa7man · Feb 5, 2008, 04:25 PM

The cause of the banging is the zone valves slamming shut at the end of a call for heat, and your circulator is still running (other zones still calling for heat, so the circulator is still running). I would believe that you have a multi-zone system in your house. Depending on your type of zone valve... such as Honeywell, you can move and lock the actuator lever "open" on the zone that has the banging noise, to test this theory. Some makes of zone valve close faster than others. Post the make of zone valves when you get time, they are marked with either a model number or make of the shell of the valve.

tsa7man · Feb 6, 2008, 05:45 AM

An added point... If you go to the Taco zone valves such as the 510G or the 556G valve they are the slowest opening and closing zone valves on the market, and if you look up spec's they are designed to eliminate water hammer issues.

tsa7man · Feb 6, 2008, 06:31 AM

Last added point... before you start changing all of your zone valves, like earlier posts questioned and made comments on; be sure that you have all of the air out of your zones. In reading your original post again, the new bedroom is the highest point in your system?? If so, you would need a bleed port at that location to bleed air out of that zone, the circulator will never be able to push the air bubble that could be in that line back to your boiler air eliminator device. A simple coin type valve added to one of your baseboard ends under the end cover for one of the runs would work well.

NickFromMass · Feb 23, 2010, 05:47 PM

I had this same problem for years, and it especially got worse when a zone valve wore out and I had to install a new one. The banging was so bad that a couple of baseboards units came loose from the wall. I finally soeved it a few weeks ago: replaced all zone valves with circulator pumps. Expensive, but now I can sleep at night,