Defintion of a motor rated switch

Status
Not open for further replies.
S

shortcircuit1

Senior Member
Location
USA
I am confused with the purpose of a motor rated switch. Lets say if you have a 1/2hp 120v. Can you use a normal 20a toggle switch? Whats the difference between a regular lighting toggle switch and a motor rated switch?
 
shortcircuit1 said:
I am confused with the purpose of a motor rated switch. Lets say if you have a 1/2hp 120v. Can you use a normal 20a toggle switch? Whats the difference between a regular lighting toggle switch and a motor rated switch?
Click to expand...

As an estimator I deal with it this way: Unless they specify a manual motor starter without overloads, or give a part number I consider it to be a Motor-circuit switch per the NEC definition. In order to use a snap switch as a motor disconnect it has to be horsepower rated. 430.109. Standard commercial grade and industrial grade switches have a horsepower rating.
 
Strathead said:
As an estimator I deal with it this way: Unless they specify a manual motor starter without overloads, or give a part number I consider it to be a Motor-circuit switch per the NEC definition. In order to use a snap switch as a motor disconnect it has to be horsepower rated. 430.109. Standard commercial grade and industrial grade switches have a horsepower rating.
Click to expand...
The difference is, it's cheaper to make a switch with a 20A rating for purely resistive loads, but switching an inductive load like a motor means the switch must be capable of interrupting and extinguishing the arc that forms as the inductor tries to keep the current flowing. But just saying "Commercial grade" "Industrial grade" or even "Spec grade" does not necessarily mean you get that motor rating, you must look for it to be explicitly stated on the switch or the spec sheet. For example Leviton Spec Grade 20A toggle, yes, it's rated for up to 1HP. P&S / LeGrand Spec Grade 20A toggle, no HP rating at all.
 
Jraef said:
The difference is, it's cheaper to make a switch with a 20A rating for purely resistive loads, but switching an inductive load like a motor means the switch must be capable of interrupting and extinguishing the arc that forms as the inductor tries to keep the current flowing. But just saying "Commercial grade" "Industrial grade" or even "Spec grade" does not necessarily mean you get that motor rating, you must look for it to be explicitly stated on the switch or the spec sheet. For example Leviton Spec Grade 20A toggle, yes, it's rated for up to 1HP. P&S / LeGrand Spec Grade 20A toggle, no HP rating at all.
Click to expand...

Thanks Jraef.If i understand you correctly its the cost and the contacts for the motor rated switch that makes the difference between a simple toggle switch and a motor rated switch?
 
The physical difference in the switch design is that horsepower rated switches have contacts designed to carry the high inrush current of motor starting as well as interrupt the inductive running current of a motor when opening.

Sent from my XT1585 using Tapatalk
 
Jraef said:
The difference is, it's cheaper to make a switch with a 20A rating for purely resistive loads, but switching an inductive load like a motor means the switch must be capable of interrupting and extinguishing the arc that forms as the inductor tries to keep the current flowing. But just saying "Commercial grade" "Industrial grade" or even "Spec grade" does not necessarily mean you get that motor rating, you must look for it to be explicitly stated on the switch or the spec sheet. For example Leviton Spec Grade 20A toggle, yes, it's rated for up to 1HP. P&S / LeGrand Spec Grade 20A toggle, no HP rating at all.
Click to expand...


I had a little trouble finding this but this is from legrand tech support I think you will find that virtually every switch is actually motor rated or every residential contractor that puts a residential switch in a bathroom with a fart fan is violating code.

[COLOR=#2C2C2C !important][FONT=FFDINWebProMedium !important]Thank you for your question regarding Pass & Seymour switch(Model # CS20AC1W).[/FONT][/COLOR]
[COLOR=#2C2C2C !important][FONT=FFDINWebProMedium !important]This Commerical grade switch is UL20 listed for 1HP at 120V and 2HP at 240/277V.[/FONT][/COLOR]
[COLOR=#2C2C2C !important][FONT=FFDINWebProMedium !important]Pass & Seymour products 1.800.223-4162 opt 3 Mon - Fri: 8am - 8pm EST (excluding holidays)[/FONT][/COLOR]
 
Strathead said:
I had a little trouble finding this but this is from legrand tech support I think you will find that virtually every switch is actually motor rated or every residential contractor that puts a residential switch in a bathroom with a fart fan is violating code.

[COLOR=#2C2C2C !important][FONT=FFDINWebProMedium !important]Thank you for your question regarding Pass & Seymour switch(Model # CS20AC1W).[/FONT][/COLOR]
[COLOR=#2C2C2C !important][FONT=FFDINWebProMedium !important]This Commerical grade switch is UL20 listed for 1HP at 120V and 2HP at 240/277V.[/FONT][/COLOR]
[COLOR=#2C2C2C !important][FONT=FFDINWebProMedium !important]Pass & Seymour products 1.800.223-4162 opt 3 Mon - Fri: 8am - 8pm EST (excluding holidays)[/FONT][/COLOR]
Click to expand...
Well, they can say it all they like but if they don't list that in their on-line specification sheets, or unless it actually says it on the switch body itself, it may as well not be true. An AHJ would want to see proof. Poor marketing if you ask me...
https://www.legrand.us/api/legrand/...h=/passandseymour/switches/hard-use/csb20ac4w
 
Jraef said:
The difference is, it's cheaper to make a switch with a 20A rating for purely resistive loads, but switching an inductive load like a motor means the switch must be capable of interrupting and extinguishing the arc that forms as the inductor tries to keep the current flowing. But just saying "Commercial grade" "Industrial grade" or even "Spec grade" does not necessarily mean you get that motor rating, you must look for it to be explicitly stated on the switch or the spec sheet. For example Leviton Spec Grade 20A toggle, yes, it's rated for up to 1HP. P&S / LeGrand Spec Grade 20A toggle, no HP rating at all.
Click to expand...
Yes. We would differentiate them as AC1 (pf > 0.96) and AC3 typically for induction motors.

From Schneider:

AC-1 category
This applies to all AC devices (loads) with a power factor of at least 0.95 (cos phi greater than or equal to 0.95).
Example of use: resistive load, heating, distribution.


AC-3 category
This applies to squirrel cage motors where breaking occurs while the motor is running.
Example of use: all squirrel cage motors, lifts, escalators, conveyors, bucket elevators, compressors, pumps, mixers, air conditioning units, etc.

The AC3 current rating is less/very much less than than the AC1 rating for the same device.
 
Thanks everyone for your input. Now lets say if you have a cassette or an MCU in the ceiling. These are very low power consumption motors like 60-100w. Per code we need to have a disconnecting means with in sight. For that purpose would you put a normal 15 or 20a toggle switch or would you still use a motor rated switch for this kind of fractional horse power motors?
 
shortcircuit1 said:
Thanks everyone for your input. Now lets say if you have a cassette or an MCU in the ceiling. These are very low power consumption motors like 60-100w. Per code we need to have a disconnecting means with in sight. For that purpose would you put a normal 15 or 20a toggle switch or would you still use a motor rated switch for this kind of fractional horse power motors?
Click to expand...
I think I know exactly what you are talking about and I have connected such systems before. You do not need a disconnecting means within sight, as they are under 300VA/1/8 hp, the branch circuit device is the disconnecting means.

They do not fall under art 440 either, only the compressor unit does.
 
kwired said:
I think I know exactly what you are talking about and I have connected such systems before. You do not need a disconnecting means within sight, as they are under 300VA/1/8 hp, the branch circuit device is the disconnecting means.

They do not fall under art 440 either, only the compressor unit does.
Click to expand...


Understood.Thanks for the code reference.
 
Status
Not open for further replies.
Top