AC Disconnect Switch Interrupting Rating

[hocheung20]

I have a air-conditioning unit that is protected by a Safety Disconnect switch that is rated for 240V/60A. This device is further protected upstream by a two-pole circuit breaker that is rated for 240V at my panel. I have 2 questions.

1) The two-pole CB has 30 on each half of the handle. Does this mean the CB is rated for 60A total?
2) Since the Safety Disconnect is already protected by the CB, does it matter what "Interrupting Rating" I need to purchase for the Safety Disconnect?

 

[templdl]

I have a air-conditioning unit that is protected by a Safety Disconnect switch that is rated for 240V/60A. This device is further protected upstream by a two-pole circuit breaker that is rated for 240V at my panel. I have 2 questions.

1) The two-pole CB has 30 on each half of the handle. Does this mean the CB is rated for 60A total?
2) Since the Safety Disconnect is already protected by the CB, does it matter what "Interrupting Rating" I need to purchase for the Safety Disconnect?

Interrupting rating is with reference to The automatic opening of a device and its ability to "interrupt" a fault. With a disconnect switch it is opened manually and it is not intended that it be opened to interrupt a fault. But what it does have is a "withstand rating" which is its ability to hold together when subjected to fault current.

 

[augie47]

In general terms, the breaker would be considered a TWO POLE 30 AMP 240v BREAKER.
(Although one could technically connect 30 amps of 120 v load to each phase, multi-pole breakers are referenced by the amperage on one phase).

I'm guessing your concern with"interrupting rating" is more likely concern with the 60 amp rating which is not actually "interrupting rating"
As templdl noted, interrupting rating is a whole different ball game. A breaker or disconnect will have a amperage rating, a voltage rating and an interrupting rating. Determing the required interrupting rating can be an involved engineering task on its own.
With your disconnect being used as a downstream device on a 30 amp circuit it is highly unlikely, almost impossible, that you would need a disconnect with a rating higher than 10k which I believe is about the lowest rating you would find.

As far as your disconnect being rated at 60 amps on a 30 amp circuit... no foul. Any rating over the required is fine.

 

[cadpoint]

I have a air-conditioning unit that is protected by a Safety Disconnect switch that is rated for 240V/60A. This device is further protected upstream by a two-pole circuit breaker that is rated for 240V at my panel. I have 2 questions.

1) The two-pole CB has 30 on each half of the handle. Does this mean the CB is rated for 60A total?
2) Since the Safety Disconnect is already protected by the CB, does it matter what "Interrupting Rating" I need to purchase for the Safety Disconnect?

While I have no problems with the answers given I will say;

1) No, the 30 Amp breaker is protecting (whats to follow); The circuit breaker is protecting the wire to the equipment the 30 Amp fuses is protecting each line of a circuit.
2) no again (see above) , one Breaker two pole is protecting the Wire (even what the wire might see), the Fuses are protecting what
action might happen beyond and after it's fused.

The fuses handle (must with dual listing) in this one case are for what will happen after a fused application.

 

[hocheung20]

Interrupting rating is with reference to The automatic opening of a device and its ability to "interrupt" a fault. With a disconnect switch it is opened manually and it is not intended that it be opened to interrupt a fault. But what it does have is a "withstand rating" which is its ability to hold together when subjected to fault current.

It does say 10,000A Interrupting Rating embossed on the side and on the front that is a sticker on the face that says 10kA. My only conclusion is that the previous owner on the house elected to install a 60A two-pole CB instead of a normal switch. Sorry about my confusion.

In general terms, the breaker would be considered a TWO POLE 30 AMP 240v BREAKER.
(Although one could technically connect 30 amps of 120 v load to each phase, multi-pole breakers are referenced by the amperage on one phase).

Ah, so if the current on any pole exceeds 30A, it will trip even though the total current going across the device maybe e.g. 45A, thus we cannot call it a 60A breaker.

While I have no problems with the answers given I will say;

1) No, the 30 Amp breaker is protecting (whats to follow); The circuit breaker is protecting the wire to the equipment the 30 Amp fuses is protecting each line of a circuit.
2) no again (see above) , one Breaker two pole is protecting the Wire (even what the wire might see), the Fuses are protecting what
action might happen beyond and after it's fused.

The fuses handle (must with dual listing) in this one case are for what will happen after a fused application.