Disconnects

[Jimmy7]

I have a question about disconnect switches. In the past I have used a double pole switch for a 240 V pool pump or a 15 amp 240 V air handler. When do you switch to a traditional disconnect switch ( Side Arm for example) does it depend on the amperage?

 

[LarryFine]

When do you switch to a traditional disconnect switch ( Side Arm for example) does it depend on the amperage?

Of course, in that the switch should be sized for at least the load's current and HP ratings.

You could even use a 2p toggle switch if adequately rated.

 

[Jimmy7]

Do the double pole switches have a HP rating stamped on them?

 

[Dennis Alwon]

I have a question about disconnect switches. In the past I have used a double pole switch for a 240 V pool pump or a 15 amp 240 V air handler. When do you switch to a traditional disconnect switch ( Side Arm for example) does it depend on the amperage?

Well there aren't any traditional snap switches that will handle 40 amps, that I know about, and there are 30 amp DP switches but they can be a bear to install in one gang boxes with #10 wire. I used to used DP 30 amp snap switches for water heaters because they look neater but we basically went over to the small air conditioner type disconnects.

 

[Dennis Alwon]

INteresting that the dp 30 doesn't have a HP rating... at least Levitons doesn't

 

[Dennis Alwon]

I swear they used to be up to 1 hp rating but I don't see it on any of the switches online

 

[infinity]

When is a HP rating actually required on the switch?

 

[Dennis Alwon]

When is a HP rating actually required on the switch?

I believe if it is used for motor loads but I would have to check

 

[Dennis Alwon]

Well according to this is is not necessary

(A) Alternating-Current General-Use Snap Switch.

This form of switch shall only be used on ac circuits and used for controlling the following:

• (1)
  Resistive and inductive loads not exceeding the ampere rating of the switch at the voltage applied
• (2)
  Tungsten-filament lamp loads not exceeding the ampere rating of the switch at 120 volts
• (3)
  Electric discharge lamp loads not exceeding the marked ampere and voltage rating of the switch
• (4)
  Motor loads not exceeding 80 percent of the ampere rating of the switch at its rated voltage
• (5)
  Electronic ballasts, self-ballasted lamps, compact fluorescent lamps, and LED lamp loads with their associated drivers, not exceeding 20 amperes and not exceeding the ampere rating of the switch at the voltage applied

 

[infinity]

Well according to this is is not necessary

I could be wrong but I thought that a HP rated switch could exceed the 80% rule and still be used.

 

[LarryFine]

Do the double pole switches have a HP rating stamped on them?

Some do:

1221-2

leviton.com

https://www.eaton.com/content/dam/eaton/products/wiring-devices-and-connectivity/wiring-devices/switches/construction-grade-switches/heavy-duty-industrial-grade-ac-toggle-switch-spec-sheet-td620032en.pdf?assetID=gmoney

 

[Dennis Alwon]

If a dp switch is rated 30 amps and it is hp rated then if the load of the motor is 24 amps without the 125% added then it can be used because that 125% of 24 is 30 and 80% of 30 is 24. I think that is where this rule comes from

 

[Dennis Alwon]

This makes it interesting

430.110 Current Rating and Interrupting Capacity.

(A) General.

The disconnecting means for motor circuits rated 1000 volts, nominal, or less shall have a current rating not less than 115 percent of the full-load current rating of the motor.
Exception:
A listed unfused motor-circuit switch having a horsepower rating not less than the motor horsepower shall be permitted to have a current rating less than 115 percent of the full-load current rating of the motor.

 

[infinity]

If a dp switch is rated 30 amps and it is hp rated then if the load of the motor is 24 amps without the 125% added then it can be used because that 125% of 24 is 30 and 80% of 30 is 24. I think that is where this rule comes from

Going from memory I thought that there were HP rated switches where the HP rating exceeded the 80%.

 

[Dennis Alwon]

Going from memory I thought that there were HP rated switches where the HP rating exceeded the 80%.

That is what 430.110 , posted above your last post , seems to imply but 115% instead of 125%

 

[Jimmy7]

Can you help me with this example. The circuit is 120 volts for this motor. Can I run a 20 amp circuit with a 20 amp switch (The owner wanted a switch by the motor).

 

[infinity]

Can you help me with this example. The circuit is 120 volts for this motor. Can I run a 20 amp circuit with a 20 amp switch (The owner wanted a switch by the motor).

According to what Dennis posted in post #9 the 20 amp switch would be operating at less than 80% of it's rating so it would be code complaint.

 

[Dennis Alwon]

Can you help me with this example. The circuit is 120 volts for this motor. Can I run a 20 amp circuit with a 20 amp switch (The owner wanted a switch by the motor).
View attachment 2574539

The switch should be hp rated. The ones I see online do not have hp rating written on the switch so I am not sure if the paperwork, if shown, would be acceptable. IMO, it should be fine.

 

[Jimmy7]

Okay, when do you follow the 80% and when do you follow the 115%?

 

[infinity]

Okay, when do you follow the 80% and when do you follow the 115%?

Are you using a general use snap switch?