Author Topic: mistral air con went smoke...boom!  (Read 1193 times)

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Offline clucas

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mistral air con went smoke...boom!
« on: July 02, 2018, 11:50:57 am »
naw not really but there are some scorched bits :)
Mistral MSS8.0INV split system unit just turned off so I checked the indoor unit board and fuse, all ok, so checked outdoor unit and found this..



Its' a 32amp/500v fuse holder and connecting wire that basically shit itself. I'm replacing it with a 32amp/6kv circuit breaker I have in stock. Given it's probably a surge protector from the mains I still wonder why it failed so miserably. The line in is wired back to the fuse box into a separate ceramic fuse. Should it be upgraded as well to prevent a repeat or at least tripping the breaker and is there anything else I should consider to prevent an ongoing problem.
 
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Offline envisionelec

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Re: mistral air con went smoke...boom!
« Reply #1 on: July 02, 2018, 01:59:53 pm »
It appears the connection to the fuse block may have been improperly torqued. It shows prolonged heat damage to the connector as well as the wire. Replace the wire and the fuse block and you should be back in business.
 
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Offline ignator

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Re: mistral air con went smoke...boom!
« Reply #2 on: July 02, 2018, 02:07:20 pm »
Is the fuse in the fuse holder really 32 amps? Or is the fuse holder rated for that as a maximum. Better check that, as the wire does not look large enough for 32 amps. Locked rotor amps surge should be covered by a fuse rated for that.
I agree with envisionelec that the root cause is a loose connection that caused this failure.
 

Offline clucas

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Re: mistral air con went smoke...boom!
« Reply #3 on: July 03, 2018, 08:48:13 am »
It appears the connection to the fuse block may have been improperly torqued. It shows prolonged heat damage to the connector as well as the wire. Replace the wire and the fuse block and you should be back in business.

aah that's what I was hoping for and it makes good sense. It's been running hot alright...

 

Offline clucas

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Re: mistral air con went smoke...boom!
« Reply #4 on: July 03, 2018, 08:54:26 am »
Is the fuse in the fuse holder really 32 amps? Or is the fuse holder rated for that as a maximum. Better check that, as the wire does not look large enough for 32 amps. Locked rotor amps surge should be covered by a fuse rated for that.
I agree with envisionelec that the root cause is a loose connection that caused this failure.

yeah it really is rated at 32amps and it didn't blow! It's still intact. So a loose connection and possibly wrong gauge or rated wire? Damn Mistral, I thought they were better than that.
 

Online wraper

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Re: mistral air con went smoke...boom!
« Reply #5 on: July 03, 2018, 09:14:01 am »
There is nothing wrong with wire gauge.
 

Offline clucas

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Re: mistral air con went smoke...boom!
« Reply #6 on: July 04, 2018, 02:58:23 am »
^^^ the wire is rated at 12AWG. According to the table below it should be 10AWG or lower. Whether it is passing 30 amps is questionable but it should still have been rated to the 30 amp fuse value. This unit was in storage for the first 8yrs + of it's life. It was installed 18mths ago and worked for a summer and a half b4 the fail. I think the manufacturer just dun goofed with the wiring but I hope that's all they did. I also found a popped cap on the main board rated at 450v but don't know if it's related or coincidence.

« Last Edit: July 04, 2018, 03:02:47 am by clucas »
 

Online blueskull

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Re: mistral air con went smoke...boom!
« Reply #7 on: July 04, 2018, 03:08:33 am »
I had a Carrier (ICP) AC system which died at year 7 into service. Apparently, if a Carrier dies in 7 years, it must be the contractor who screwed up.
And it turns out to be they didn't fully evacuate the tube before filling and water corroded the indoor unit over time. Talking about workmanship.
I ended up replacing the whole AC, not just the indoor unit -- who knows what other stupid things the builder did back then.
I'd rather get someone who does AC and AC only for a living to work on my system, not some random "handyman" with an online certificate.
 

Online wraper

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Re: mistral air con went smoke...boom!
« Reply #8 on: July 04, 2018, 07:43:07 am »
^^^ the wire is rated at 12AWG. According to the table below it should be 10AWG or lower. Whether it is passing 30 amps is questionable but it should still have been rated to the 30 amp fuse value. This unit was in storage for the first 8yrs + of it's life. It was installed 18mths ago and worked for a summer and a half b4 the fail. I think the manufacturer just dun goofed with the wiring but I hope that's all they did. I also found a popped cap on the main board rated at 450v but don't know if it's related or coincidence.
You confuse house wiring installation requirements with equipment. In your case it was bad contact with high resistance, it has nothing to do with wire gauge. You may notice that other end of the wire and all other wires of the same gauge passing the same current were not damaged.
Quote
This unit was in storage for the first 8yrs + of it's life.
I wouldn't be surprised if the contact was damaged by moisture.
« Last Edit: July 04, 2018, 07:47:25 am by wraper »
 

Offline clucas

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Re: mistral air con went smoke...boom!
« Reply #9 on: July 04, 2018, 09:52:16 am »
I had a Carrier (ICP) AC system which died at year 7 into service. Apparently, if a Carrier dies in 7 years, it must be the contractor who screwed up.
And it turns out to be they didn't fully evacuate the tube before filling and water corroded the indoor unit over time. Talking about workmanship.
I ended up replacing the whole AC, not just the indoor unit -- who knows what other stupid things the builder did back then.
I'd rather get someone who does AC and AC only for a living to work on my system, not some random "handyman" with an online certificate.

I too had a dodgy installer who didn't have the right connectors for his vacuum pump so just opened the valves to evacuate the system and thought that would do. Suffice to say I refused to pay him. After much wrangling and fist shaking I bit the bullet and paid him half of what he had asked for.  He was an employee of a supposedly professional installer. I'm expecting the same problem as you sometime down the track.
 

Offline clucas

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Re: mistral air con went smoke...boom!
« Reply #10 on: September 09, 2018, 01:43:08 pm »
unit has been repaired and is now working after replacing the wire, installing a cut-off switch and replacing some bad caps on the control/power board. just thought I would add this since it is the best explanation of what probably happened

« Last Edit: September 10, 2018, 12:19:26 am by clucas »
 

Offline drussell

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Re: mistral air con went smoke...boom!
« Reply #11 on: September 09, 2018, 05:17:42 pm »
Is the fuse in the fuse holder really 32 amps?

That's my question too...  What rating of fuse is actually IN that fuse holder?
 

Offline amyk

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Re: mistral air con went smoke...boom!
« Reply #12 on: September 09, 2018, 05:24:52 pm »
This is what a thermal camera is useful for :)
 

Offline clucas

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Re: mistral air con went smoke...boom!
« Reply #13 on: September 09, 2018, 11:37:43 pm »
Is the fuse in the fuse holder really 32 amps?

That's my question too...  What rating of fuse is actually IN that fuse holder?

for the sceptics...

 


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