Single disconnect for two appliances?

[S'mise]

I'm wondering if I can use a Single fused disconnect to feed two small motor driven appliances sitting side by side in an industrial setting. (Hardwired into same disconnect)

Appliance one has 1.5hp motor with controller and has thermal ol's.

Appliance two has a 3hp motor with manual starter w thermal protection.

My thinking is that I'm sizing the ocpd for the smallest motor (using the next size-up rule puts me at 15amps) 15amps will start both appliances no problem.

As I understand it; The manual starter is also considered a disconnect.

Do both appliances need separate disconnects or is this fine?

 

[Little Bill]

I'm wondering if I can use a Single fused disconnect to feed two small motor driven appliances sitting side by side in an industrial setting. (Hardwired into same disconnect)

Appliance one has 1.5hp motor with controller and has thermal ol's.

Appliance two has a 3hp motor with manual starter w thermal protection.

My thinking is that I'm sizing the ocpd for the smallest motor (using the next size-up rule puts me at 15amps) 15amps will start both appliances no problem.

As I understand it; The manual starter is also considered a disconnect.

Do both appliances need separate disconnects or is this fine?

Assuming your voltage is either 208 or 230, since if it is 110V the 15A is too small for either motor. There may be other requirements that I'm not thinking of but 2 that come to mind are: the disconnect would need to be in sight of the motors, and you said you were sizing the OCPD for the smallest motor but you would need to size the conductors for the largest motor. Without looking it up, that's all I can think of.

 

[S'mise]

1.5hp@460 from table is 3amps. 3x175% (fuse)=5.25 next standard size is 15amps.
The other motor appliance has a 3hp which is 4.8amps x 1.75=8.4 next size up is 15amps.

So my 15amps is fine for ocpd and wite size. My question is; Is it ok to feed two appliances from the same disconnect located about 2ft above (4 feet off ground)

 

[Buck Parrish]

Do you have to add 1.25 according to the table after adding them both plus 1.75 ? Because 1.25 will put you over 15 but the 1.75 may have covered it.

 

[augie47]

1.5hp@460 from table is 3amps. 3x175% (fuse)=5.25 next standard size is 15amps.
The other motor appliance has a 3hp which is 4.8amps x 1.75=8.4 next size up is 15amps.

So my 15amps is fine for ocpd and wite size. My question is; Is it ok to feed two appliances from the same disconnect located about 2ft above (4 feet off ground)

Better check 240.6. For your 1.5 hp the 5.25 is correct, but, one of the "standard size" fuses listed is 6 amps so that would be you max.
Also if you check your starter I think you will find with a FLA of 1.5 amps it will call for a smaller fuse than 15.

 

[S'mise]

Do you have to add 1.25 according to the table after adding them both plus 1.75 ? Because 1.25 will put you over 15 but the 1.75 may have covered it.

Thats for ampacity of conductors; Largest motor is 4.8x1.25+3=9amps

The 175% is because I'm using fuses

I dont have NEC in front of me, but it was somewhere around 430.53 that said single disc was ok if ocpd calculated to smallest motor.

 

[S'mise]

Better check 240.6. For your 1.5 hp the 5.25 is correct, but, one of the "standard size" fuses listed is 6 amps so that would be you max.
Also if you check your starter I think you will find with a FLA of 1.5 amps it will call for a smaller fuse than 15.

Ahhhh..."Additional standard ampere ratings for fuses shall be 1, 3, 6, 10, and 601." I missed that part. (btw, the 601 is confusing, does that mean there is also a 101, 103,...501,503 size? or just the oddball 601?)

Thanks Augie, I guess I will have to add a second fused disconnect.

 

[iwire]

(btw, the 601 is confusing, does that mean there is also a 101, 103,...501,503 size? or just the oddball 601?)

The 601 is basically a 600 amp fuse that has the outside dimensions of an 800 amp fuse so that it will fit in 800 amp fused switches.

I don't think there are others but you never know.

 

[kwired]

So far the discussion has been primarily about overcurrent protection.

Lets assume that rules for overcurrent protection are met.

422.30 General.
A means shall be provided to disconnect each appliance from all ungrounded conductors in accordance with the following sections of Part III. If an appliance is supplied by more than one source, the disconnecting means shall be grouped and identified.

Disconnecting means could possibly be cord and plug or unit switches.

 

[pfalcon]

... My question is; Is it ok to feed two appliances from the same disconnect located about 2ft above (4 feet off ground)

I'm wondering if I can use a Single fused disconnect to feed two small motor driven appliances sitting side by side in an industrial setting. (Hardwired into same disconnect)

Appliance one has 1.5hp motor with controller and has thermal ol's.

Appliance two has a 3hp motor with manual starter w thermal protection.

My thinking is that I'm sizing the ocpd for the smallest motor (using the next size-up rule puts me at 15amps) 15amps will start both appliances no problem.

As I understand it; The manual starter is also considered a disconnect.

Do both appliances need separate disconnects or is this fine?

430.102(A) One disconnect per controller. Exception for when they are all part of the same machine.
430.87(c) One controller for several motors where all are in sight.

Each appliance has its own separate controller. Therefore by 430.102(A): No.

 

[kwired]

430.102(A) One disconnect per controller. Exception for when they are all part of the same machine.
430.87(c) One controller for several motors where all are in sight.

Each appliance has its own separate controller. Therefore by 430.102(A): No.

OP said this is feeding two appliances. You need to look in Art 422. 422 does send you to 430 in some places.

 

[S'mise]

So far the discussion has been primarily about overcurrent protection.

Lets assume that rules for overcurrent protection are met.

Disconnecting means could possibly be cord and plug or unit switches.

Thanks for everyones input, I learned a few things

 

[guschash]

Reading 430.53 I would say you are ok. 430.53(B) if smallest rated motor protected....

 

[S'mise]

430.53

430.53

Reading 430.53 I would say you are ok. 430.53(B) if smallest rated motor protected....

Thats what I first thought, but then Iwire corrected me that 15 is not the next size up fuse. (It is for a breaker but not a fuse) I have to use a 6a ocpd for the small motor and need a larger fuse for the other. I added a second fused disconnect since I needed the second set of fuses.

I'm left with two thoughts; first, 430.53 must be rarely used for smaller loads unless a disconnect has more than one set of fuses to satisfy the different ocpd needed for the motors.
Secondly; If I decide to use a 15a circuit breaker instead of a fuse its ok to serve smaller loads. ? I know your supposed to follow manufacture instructions but realisticly they are often not available.

 

[S'mise]

430.53

430.53

deleted duplicated post

 

[pfalcon]

OP said this is feeding two appliances. You need to look in Art 422. 422 does send you to 430 in some places.

Sent by 422 or not, 430 still applies.

Reading 430.53 I would say you are ok. 430.53(B) if smallest rated motor protected....

Can't reach 53(B). OP said there are separate disconnects. Only 53(A) applies under 87. To reach 53(B) the OP will have to combine the controllers to get around 102.