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keithl1967 12-15-2013 11:00 AM

Basebouard hot water heat "humming"
Had a question for the gurus...

At the end of last year, I noticed that the baseboard heat in the master bedroom upstairs (the upstairs is on its own "zone") started to hum...It had always 'snap, crackled, and popped" when the heat came on, but this humming was new.

it is doing it again this year.

it seems like it only happens when the heat first comes on (that could be just when I notice it, though), and it seems lie it is only on one "run" of the baseboards in the master bedroom...

I just now noticed the same thing on the main floor (separate zone), where it had never happened before--it was very brief).

1. Given that I have lived in the house for 9 winters now, and the newness of this sound--should I be worried?

2. What would cause this "humming/vibrating" sound?

Last time this happened, i ran down to te boiler to see if the circulator pump was making any noise--it was not...

747 12-15-2013 11:03 AM

circulator pump more then likely. Its humming and traveling through copper pipe.

Bearings going bad/coupler.

keithl1967 12-15-2013 11:09 AM


Originally Posted by 747 (Post 1278684)
circulator pump more then likely. Its humming and traveling through copper pipe.

Bearings going bad/coupler.

that was my initial thought...but now it is happening on a separate zone (perhaps coincidental, I suppose) but why would it only happenon a particular run, and not all of the baseboards?

And also, why would I not be able to hear/feel it right at the circulator pump itself?

Bondo 12-15-2013 11:26 AM

Ayuh,... Sounds like Air in the run to me,... Bleed 'em out,....

Bob Sanders 12-15-2013 11:27 AM

Is the zone valve 24 volt electric?

Check the transformer and the motor head(s). The plates inside these devices can loosen up over time and cause a (60hz) humming noise.

how 12-15-2013 11:42 AM

Bleed the air valves on all of your baseboards and check the auto bleed at the boiler.
Use a long handled screwdriver ( handle against the ear & working end against the part you want to test) as a stethoscope.
Test the baseboard, and then the pump, zone valve and transformer to search out which is the source.

keithl1967 12-15-2013 04:48 PM

Ok--may sound like a rookie question (it is) do I bleed the system?

jmon 12-15-2013 07:30 PM


Originally Posted by keithl1967 (Post 1278796)
Ok--may sound like a rookie question (it is) do I bleed the system?

Depending on how it's plumbed, you may be able to do this right at your boiler with a garden hose as suggested above. Can you post a couple pics of your boiler to include all zones so the techs can better help you out? Thanks.

Additionally, look for bleeder valves on your baseboard heaters as suggested above. They are all a little different some use a special key, screwdriver, or have a t-bar, etc. Start at lowest level then work up. Video attached if needed. Careful water may be hot if boiler has been running. Post results back here. Thanks.

bleeding baseboard heater

look for something like this.

keithl1967 12-15-2013 08:31 PM

OK--there are no bleeders on any of the pipes upstairs... below are some photos of the boiler--the red circulator pump and the black are upstairs and down (not labelled which is which)--the only one I can determine for sure is the gray pump, which is for the basement and has not exhibited any of the issues noted... do I bleed the pipes?

Does water automatically refill for any that is removed in the bleeding process?

mj12 12-15-2013 08:54 PM

I believe the bleeders are on the baseboards themselves. Sometimes you have too remove the covers, sometimes there will be a small access hole.

Bob Sanders 12-15-2013 09:10 PM

I'm not sure air in the rads is the issue here so I wouldn't bend over backwards trying to bleed. It certainly wouldn't hurt but I would suspect other things first.

Air in rads doesn't usually make humming sounds. It gurgles and if enough air exists it would cause an air lock and stop the rad from heating.

jmon 12-15-2013 09:53 PM


Originally Posted by keithl1967 (Post 1278845) do I bleed the pipes? Does water automatically refill for any that is removed in the bleeding process?

For safety, turn off boiler, leave ball valves open on the zone you're bleeding, close all other zone ball valves, attach garden hose to hose bib on zone you're bleeding and run it to a bucket or drain, open hose bib, drain until all gurgling/spit & sputting stops, close hose bib, repeat this process for the other zones.

Go low to high. You said basement zone pump is fine (gray one), do a call for heat to figure out the main floor zone pump (do that next), then do the top floor zone last. When done, be sure that all zone ball valves are open and all hose bibs are closed, turn boiler back on, and recheck the system for proper operation.

Yes the water will auto fill as you bleed it. The green valve by your vent is a pressure regulator/water auto feed valve.

Post another pic of the top of your expansion tank. Additionally, you may have an auto bleeder valve (see pic) that's not set or working correctly. Check and make sure the thumb screw cap on top of bleeder valve (circle in red) is loose so air can exit the system and it's not tightened all the way down. Make sure it's working properly. Remove cap and press relief valve with a small finishing nail or screwdriver, water should come out. This will bleed your system automactically if it's set and working properly. Sometimes they do go bad/fail and need to be replaced, you can pick one up at any box store for a couple bucks.

How old is the boiler and when was the last time it was serviced, inspected, and cleaned by a qualified tech? The reason I ask is because during this important service a qualified tech would be able to check the entire system and tell if there's another cause for this issue. Just a thought.

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