Buzzing in Honeywell Aquastat 8148A

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Old 10-06-11, 07:30 AM
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Buzzing in Honeywell Aquastat 8148A

I have a Honeywell Aquastat 8148a on my Weil-Mclean boiler which is making a loud buzzing sound after 20 years of good service.The buzzing is coming from the black phenolic block that is part of the contactor assembly. I can stop the buzzing by lightly touching
the black plastic block which seems to move quite freely but it seems that it needs some time of a dampener. There does no appear to be any way to tighten up the block in its place on the relay.
any suggestions as to what I can do to stop this buzzing. Thank you for any help you can provide.
 
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Old 10-06-11, 11:44 AM
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It's 'normal' for any control with a transformer to hum a bit, or even buzz quietly... but you say this is a LOUD buzzing? Is it loud enough that you can hear it say 3 feet away?
 
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Old 10-06-11, 02:53 PM
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I can hear it upstairs in the living area from the basement as long as the basement door is open at least 10 feet from ttop of stairs to furnace
 
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Old 10-06-11, 04:17 PM
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I'm sure you are aware, but I should have mentioned:

BE CAREFUL ! EXPOSED 120VAC INSIDE THE AQUASTAT ! YOU CAN BE KILLED !

That loud of a buzzing don't sound right... do you hear it all the time? even when the thermostat isn't calling for heat?

If it's actually coming from the contactor and not the transformer next to it, it should not be making the noise when there is no heat called for because the contactor is not energized at that time.

It's usually the transformer that makes the buzzing noise.

There's a small spring at the top of the contactor, is that still in place and intact ? It should be right in the center of the pivot point on the contactor. I wonder if that spring broke?
 
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Old 10-06-11, 04:24 PM
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It only is noticeable when the unit is running and calling for heat. And yes the spring is still in place. Could it be a weak spring and can
it be purchased separately? It seems the spring would be the only thing that would keep the black block from vibrating in it mounting.
 
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Old 10-06-11, 04:36 PM
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Turn power off... with a bright light and some type of inspection mirror take a look to see if there is an insect or something stuck between the 'core' of the electromagnet that pulls the contactor in and the plate on top. It's not going to be easy to see though... but it's a possibility! If the contactor can't pull in all the way because of some obstruction, it will buzz like crazy.

Highly unlikely that you can purchase just the spring. I've never seen them anywhere. I sorta doubt that's the problem though.
 
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Old 10-06-11, 04:45 PM
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If it is the relay itself that is making the noise, it will only buzz during a call for heat, then it has a rusty armature or core keeping the armature from making a solid contact with the magnetized core.

I doubt that you can do much other than replace the entire control but depending on the relay itself there may be a fix. If the relay has a solid plastic top as you describe you might be able to use a piece of fine garnet (NOT EMERY!) sandpaper to clean the rust that is keeping the armature and core from making good contact when the relay is energized.

TURN OFF THE POWER FIRST!

Pass a folded piece of the sandpaper under the moveable part and towards the back away from the electrical contacts. Take several strokes back and forth with upward pressure to clean the armature portion and several strokes with downward pressure to clean the core section. Remove the sandpaper and blow out thoroughly with compressed air. Re-energize the system and see if it helped.

If you have a newer control with the solid metal armature, forget it and buy a new control. The relays with the solid metal armature are junk.
 
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Old 10-06-11, 04:48 PM
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Thank you for the shock warning. Rest assured that I stay well away from the connections and the coil wires and I am using insulated tools.
Having said that, I noticed that there appears to be some dust or similar matter in the slots where the black block is held to the spring.
It has been my experience that dirt cause more problems than anything other than bad soldering. So my thought is, to spray the block
contact points and the underside of the block where it rests on the coil and the vertical switch and spring with "Electrical Contact Cleaner",
let it sit for an hour or so and then try it...Is that an acceptable plan? Of course the power would be off throughout the process.
 
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Old 10-06-11, 05:28 PM
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The sandpaper did it.......the lower surface was somewhat rusty and the contact on the block appeared to be covered with
a patina of sorts....I ran the sandpaper through it and not only does it not vibrate but it shuts down clean instead of buzzing for
minutes after the shut down. Thank you Thank you Thank you.....you guys are good!!
 
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Old 10-07-11, 04:45 PM
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Need to be real careful cleaning the contact points on them relays. The patina won't hurt anything, but removing the plating with sandpaper could! I usually recommend a matchbook soaked with contact cleaner... nothing abrasive.

Glad it's working for ya!
 
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