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Thread: Compressor leads blow out!!
09-12-2012, 09:52 PM #1
Compressor leads blow out!!
Just an interesting story i thought i would share about an air conditioner i encountered yesterday. Customer says the unit trips breaker and she leads me to disconnect ( breaker style), which is tripped. She resets breaker and i hear the compressor begin to slam like a motor that is running into something during revolution and then the breaker trips. I pull the electrical cover panel off the condenser and find the capacitor missing! An 80 mfd capacitor is missing and the loose wires from the contactor and start winding are touching the casing to the unit! Anyways, i install new capacitor and flip breaker to get the same reult. I began to check things to ground but nothing is grounded. Puzzeled, my fellow technician flips the breaker once more. I here the revolution sound once and then it gets quite. Fan is running and i begin to here a slapping sound. I realize quickly that the sound is coming from the metal conduit. The wires were slapping arounf inside the conduit like a water hose with too mush water! I stick my insulated screw driver to the conduit and it sticks with magnitism! All of this happening within about seven seconds i began to reach for the breaker when BOOOOOMM!!!!!! The compressor leads blow out on this 410A scroll commpressor and black gas smothers and blinds the working space.
The loose wires in the cabinet are probable cause for the windings, which i now assume were internally shorted together, to short out. The short caused an extreme overcurent of electricity and the overload blew out the terminals.
You can bet ill be looking deeper into these situations before resetting any breakers from now on. Things could have gotten ugly.
09-12-2012, 09:56 PM #2
if i come to a tripped breaker, i ohm and verify everything before turning it back on
09-12-2012, 09:59 PM #3
Must say never had that happen to me before. I got a call from a lady once she returned from vacation calls me says her furnace wasn't working I get there she tells me where furnace was located and I came back upstairs and told her to show me which room again when we went to room she screams "OMG my furnace is gone". Lol. That was a easy sale for me.
09-12-2012, 11:31 PM #4
Never pump a scroll down under 20 psi.
This is why york does pump out not pump down!
09-13-2012, 01:11 AM #5
Along with replacing the compressor or unit, replace the breaker too, it is fried.
You're lucky that residential electrical service uses relatively low KVA transformers, if you had kept resetting the breaker like that in a commercial/industrial area, you may have gotten a first person experience with an arc flash explosion.If more government is the answer, then it's a really stupid question.
09-13-2012, 02:29 PM #6
What I would want to know is who's the moron who removed the capacitor and left its wire connectors touching the cabinet. No excuse for that. They did not need to pull the old capacitor out in order to take it to a supply house to get a new one to match. Just write down the info or take a snap with a smart phone.
Sounds like a botched DIY try that could have resulted in RIP for you...or anyone else unlucky enough to be in contact with that cabinet when the wires shorted."In this house we obey the laws of thermodynamics!"
- Homer Simpson
09-13-2012, 03:54 PM #7
A good reminder to always work safely. You never know when something bad will happen.Local 597 Service Fitter
Metal Trade Journeyman
PAY ME NOW OR PAY ME LATER
It was working when I left...
09-13-2012, 04:33 PM #8
I got a call from customer who told me that they could spin the fan by hand and the system would cool but once it shut off it wouldn't cool. I pull in the yard and see a fog and his daughter runs around the house saying "it blew up ". Dad was standing over the top of it with a stick trying to start tthe fan when the terminals blew. He was white as a ghost...
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09-13-2012, 05:32 PM #9
I've actually been a witness to two window units that met their maker that way. One of them I had it out of the case inside the house when it blew out. Compressor made a grumbling noise then it let go. I had just moved my face back since I thought something didn't sound right, lucky me I guess. Not so lucky for them. Not only were they in need of a new unit, thy also needed some drywall/paint work done.
09-13-2012, 05:35 PM #10
This is a good Thread to post this in my Refer Teacher has a nasty scare on his wriast where a disconect blew open and sliced it. Always stand to the side when throwing the disconect and don't reach across it to turn it on. You never know what is done. I always bust out the Multi meter and check things out before I reset it.
Had a little old lady call and say she is tired of her Furnace door blowing Off. ever since the " Duct cleaners" Cleaned her furnace it made a loud boom and the door blew off and went across the room. so when I got thier sure enough she raised the T-stat and in about 30 seconds I heard a Crazy whoosh Boom from the Basment. I went down thier and had a look. The last guy that cleaned it mixed up the burners so it wouldn't light across and have a delayed ignition that had a big Roll-out. I fixed the burners and checked the unit over 100%. I cycled it hoping I didn't have to change my underwear and it was all good. How the guy left the unit like that and didn't come back to fix it is beyond me.
09-13-2012, 09:47 PM #11
09-14-2012, 02:16 AM #12
I've actually had a 75A 3ph breaker on a 480v system explode like a grenade.
I found it tripped in the main panel, and turned the disconnect off to the package unit before resetting it.
I checked for shorts to ground at the compressors and motors in the unit, and didn't find any, so I flipped the disconnect back on.
There was a horrible buzzing noise, and the 2 inch conduit running across the roof jumped around for a few seconds, then there was a loud *BOOM* down in the building, then the whole place went quiet.
Turns out the windings in one compressor were shunted together, and I didn't check for that....
Fortunately nobody was in the small room with the breaker panel, because when the breaker blew it blew the latched door open on the panel, and shrapnel from the breaker was actually embedded in the wall and ceiling. It did surprisingly little damage to the panel itself though.
Anyone that had been standing in front of the panel could have been seriously injured, possibly killed.
That happened 17 years ago, and I've never forgotten that lesson.
I turned the thermostat on, and heard the gas valve open, but the combustion box damper hadn't opened yet.
I bent down to pull the damper open by hand, so I could look at the burners.
The fact that the burners hadn't actually lit registered in my brain about the same time the jet of fire belched out through the damper and singed the hair on one side of my head!
A "friend that used to do AC work" had tried to fix it, and had screwed up the wiring so the gas valve was getting powered instead of the damper motor. As soon as I manually opened the damper enough to close the safety switch, the spark ignition control started doing its thing and *WOOOOSHHH*, emergency hair cut time.If more government is the answer, then it's a really stupid question.
09-14-2012, 07:16 AM #13