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New "copper top" cartridge fuses


Charlie R
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Pulled this out of the A/C disconnect yesterday. Scary thing was that the client's father wanted to argue that there was nothing wrong with this because his A/C kept blowing fuses so he had done the same thing at his house. A/C data plate stated maximum breaker size at 25, inside main panel breaker was a 40. (Lotta rust in the disconnect box also)

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Multimotor equipment is an exception to the rule that the branch circuit breaker must be sized to protect the ampacity of the dedicated circuit which serves that equipment. Since a condenser has 2 motors in it and is equipped with a nameplate that lists the manufacturer's specs on ampacity and fuse/breaker rating, it is permitted to be served by a circuit in which the fuse/breaker rating may actually be higher than the ampacity of the branch circuit conductors.

To answer your question: it would have been ok if the branch circuit ampacity was 25 amps or higher. It's likely a #12, 20 amp ampacity.

If you reduce the breaker rating to 20 amps, the condenser will likely trip the breaker occassionally when it starts, which may be normal.

Marc

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Why wouldn't the copper tubes in the exterior disconnect have been okay, if the circuit breaker in the main panel was 25 amps or less?

NO the copper pipe installed in place of the fuses would not have okay.

Even if the interior circuit breaker was of the proper size, the installation of copper pipe in place of the fuse violates the listing of the exterior disconnect. Yeah it works but it's not correct.

If they didn't want fuses out at the HVAC equipment they could install a non rated enclosed breaker ( made by Square D) or a basic pull out type disconnect.

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Why wouldn't the copper tubes in the exterior disconnect have been okay, if the circuit breaker in the main panel was 25 amps or less?

It would be just fine as long as you used copper tubing that was listed for the purpose and as long as the fused disconnect was listed to accept copper tubing. . .

- Jim Katen, Oregon

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Why wouldn't the copper tubes in the exterior disconnect have been okay, if the circuit breaker in the main panel was 25 amps or less?

NO the copper pipe installed in place of the fuses would not have okay.

Even if the interior circuit breaker was of the proper size, the installation of copper pipe in place of the fuse violates the listing of the exterior disconnect. Yeah it works but it's not correct.

If they didn't want fuses out at the HVAC equipment they could install a non rated enclosed breaker ( made by Square D) or a basic pull out type disconnect.

To all that I would add that if there's ever a fire, that guy's insurance is void if the investigator finds that in the fuse box. You've bypassed a safety device, you're SOL with the insurance co.
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