furnace makes a couple of booming sounds as fan turns on


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Old 10-19-10, 06:40 AM
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furnace makes a couple of booming sounds as fan turns on

The furnace has been working fine for the last 20 years and the only change was the addition of a Humidifier by honeywell a couple of years ago. The problem is that as the fan comes on a series of large Boom sounds or noises is made by the furnace.

I m not sure as to the origin of the problem , it is like the switch that controls the fan goes on , then off in a series for a couple of restarts. I cannot see the fan inside the furnace as to if it turns on or off during these incidents, can you give me any idea what this might be ?

thanks
 
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Old 10-19-10, 10:52 AM
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It could be a couple of things. It could be a simple flexing of the duct where the connections to the humidifier removed some of the bracing, this should be fairly obvious watching the duct at that place when the furnace blower starts.

However, at 20 years of age you could be getting delayed ignition due to a number of factors. My old furnace had severely deformed burners at 17 years of age and it would fill the combustion chamber with raw gas and then light with a terrific boom. Once it went so far as to blow off the service panel. I won't describe how but I was able to patch the burners to eliminate the problem for the couple of months before I had the entire furnace replaced.
 
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Old 10-19-10, 06:11 PM
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In relation to the fan coming on, when does the blower start up?

If I were you, I'd sure like to learn, and quick, what is causing this. You would not want something as sever as say some chunk missing out of the heat exchanger and having the blower blow out the fire and reignite. Never seen such a thing, but as I said..................

I'd sure be taking a look at the fire......off to the side.
 
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Old 10-20-10, 10:16 AM
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I have looked into the burner and it starts fine, just like normal , whisper quiet and a nice controlled blue flame. no explosions but ---- Once the fan / blower starts there is a booming sound, well correction ---- but only if the fan was already blowing .

Now either the furnace ie heat or the humidifier can turn on the blower.

Initially the blower starts ok and is running , it then goes boom if the humidifier tries to start the fan or vise versa , if the humidifier started the fan which is running and then the furnace will start and then the fan goes boom boom boom like on and off suddenly

to me its seems as if the switch that controls the fan is turned on then off in rapid sucession a few times , but only once the fan is already running. Could the fan on/off switches be fighting or suffering from stutter ?

Hmm if I disconect the Humidifier fan wire or better just unplug the unit that will tell if this is the case for sure

 

Last edited by geoimpala; 10-20-10 at 10:21 AM. Reason: another thought
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Old 10-20-10, 03:46 PM
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Lettuce know if that stops the boom.

Other than that, your furnace sounds like it has the same problem my car was having, with it's sudden on and off, which would cause such horrific bucking, the transmission gears would bang.
 
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Old 10-23-10, 07:50 PM
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I think I found the problem

In the picture the humidifier terminals GF RT and C are noted fully contacted

These were pressed in fully and I think that fixed the musterious booming sound as to poor electrical contacts

 
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Old 10-24-10, 12:15 PM
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Originally Posted by geoimpala
I think I found the problem......These were pressed in fully and I think that fixed the musterious booming sound as to poor electrical contacts
??? It was bad that they were pressed in fully? Or did you press them in more fully and just didn't say it right in your post?
 
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Old 10-24-10, 12:53 PM
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in the picture you are looking at the side electrical terminal of a truesteam humidfication unit. The wires going in are from the furnace and the control humidistat.

In order to put a wire into the contact you have to presses the white conector tab to the right. This loosens the wire holder so you can put the correct wire in the unit. All the wires are correct but the colors are not due to the number of wires used . The spring in the connector should push out the tab to the left for full contact with the wire and terminal.

In this case the Conectors C Rt aand Gf can be seen to be just a few millimeter short of closing, ie the result is poor or no contact with the wire in the terminal.

In my case this resulted in restricted current flow when turning on/off the fan and most likley intermitent monitoring of the furnace power supply by the humidifier.

Hence I had a problem manifesting itself as a boom stop/start fan after fan activation as the humidifier could not tell the actuall condition of the furnace.

With the tabs fully retracted to the left like all the others ... ie I tugged them out, there is contact and the unit is no longer "Booming"


Make sure those termials and wires are snug tight !! give em a shot of wd-40

ps a bucking car is usually a bad sensor .....
 

Last edited by geoimpala; 10-24-10 at 01:34 PM.
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Old 10-24-10, 01:10 PM
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Thanks for coming back to fully explain.
 
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Old 10-26-10, 04:36 PM
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Cool

actually I found that my run capacitor was too old ie more than 15 years old , s I replced it and voila it works !!

ie
Run capacitors
Run capacitors are designed for continuous duty, and they are energized the entire time the motor is running.[1] Run capacitors are rated in a range of 370 microfarads (F), with voltage classifications of 370 V or 440 V.[1] Single phase electric motors need a capacitor to energize a second-phase winding. If the wrong run capacitor is installed, the motor will not have an even magnetic field, and this will cause the rotor to hesitate at those spots that are uneven. This hesitation can cause the motor to become noisy, increase energy consumption, cause performance to drop, and cause the motor to overheat.

So now I know why I was getting boomed by the motor...






this was the olde areovox one
'

 
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Old 11-02-10, 08:58 AM
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just to kick this Lennox booming horse thing once more I found the problem !!

So now I know why I was getting boomed by the motor...

well now I know...

This furnace uses a squirel cage to blow the air thru the furnace heat exchanger so that it circulates round the house. The 60l2201 emmerson electric motor is a propriatry, 5 speed motor that is in this furnmace. This is the second such unit and this one is over 15 years old, with get this ----the orginal 20 year old capacitor ( I know cause I saw a pic of the same furnace blower as installed in China had the old grey areovax capacitor.)

Now the motor seemd fine ... er seemed fine . I had a second such motor "lyin round" cause the last time I needed service when the temp hit -40 C the price of an ignitor skyrockedted over $1000.00 smackers ... so what to do ???

I found a video on the net that showed the procedure to replace a motor and it wasn't too bad. So I got the wife to assist me in a saturday morning motor swap.

Well guess what I found with the old motor . It looked goood seemd to run fine , but the main shaft moved ----up to a 1/4 inch in and out along the shaft's axial spin.

This resulted in the squirel cage impacting the cage frame at unpredictible intervals and going BOOM , scrapppppppe , pop and bang . Then the shaft retracted and all was well for a while.

Moral of the story -------the new motor has a rock stead ( good bushings) main shaft that does not let the squirrel cage fly !!!

till its knocked back into line by "keepin her tween the ditches" type of alignment. The new motor is exactly the same as the old but bought just last summer runs whisper quiet and holds the wobboly squirell cage inside of operating clearances in the cage frame. I only use one of the 5 speeds sadly.

So the lennox Boom is solved , I'm getting another motor though this time is gonna be a generic one to hold just in case this one goes out -- and it will start boomin cause of the unbalacned squirrel cage.

Go ahead and balance the squirrel cage , go ahead see how it works for you ha

Three questions arise...

1) Can I buy new bushings and put em in the old motor to rejuvenate it ?

2) Can I use a --- cap 10/370V 1⁄2 1,075 3 115volt 6.5 1⁄2 x 4 6 15.3 AOSDL1056 $200.82 AO Smith replacement motor next time?

3) Can I use a rotary switch by Carson rotary switch. Three speed positions and off. 10A 1/4HP @ 125VAC or 5A @ 277VAC 1/2HP @250VAC to control extra furnace speeds ?

Thanks

now the yummy pics

new motor


specs


old motor


specs


squirel cage


exchanger from underneath


car jack from 1987 dodge lancer that operfectly rasied and lowered the fan cage
 

Last edited by geoimpala; 11-02-10 at 10:12 AM. Reason: editing for easier readablity
 

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