Motor Circuit Protectors & Motor Circuits

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jraef -
Hard to believe you and I are on the same side. The earth's magnetic field must have done and INSTANTANEOUS swap.

Sick pun penalty - Bad dog
 
don_resqcapt19 said:
I would permit that installation as a feeder tap, even if I had to resort to using 90.4. It is not less safe with the MCP in the circuit as compared to a direct connection to the feeder.
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Don - Your argument is extremely persuasive:
"As Chief Mugwump of the swamp, I'm declaring myself god-of-the-NEC-for-a-day. I don't need no stinking book lecturing me on physics."​

It's true there are days when I do think I have a better understanding than the code panels.
This one would not be one of them.

The worm turneth and searches for an event horizon.
 
iceworm said:
Don - Your argument is extremely persuasive:
"As Chief Mugwump of the swamp, I'm declaring myself god-of-the-NEC-for-a-day. I don't need no stinking book lecturing me on physics."​

It's true there are days when I do think I have a better understanding than the code panels.
This one would not be one of them.

The worm turneth and searches for an event horizon.
Click to expand...
Not saying you can use the MCP to protect the conductors, just saying I would treat the load side connection to the MCP as a feeder tap. That feeder tap would be based on the OCPD that supplies the MCC bus. I just don't see any case where making that install would be less safe than making a direct tap to the MCC bus.
 
Jraef said:
No, because as I said, the MCP cannot be listed as a stand alone device for any purpose. It’s ONLY valid use is as a COMPONENT in a subsequently listed assembly.

Even if someone were to have listed it as a “Molded Case Switch”, think about it this way:

If it is not the branch, it’s a feeder. So could you legally put a non-fused disconnect in a switchboard and use it as a feeder just because there is a branch OCPD at the other end? No you can’t. So that scenario with trying to use the MCP as a switch is no different.
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If you used a molded case switch plus fuses (rated as branch circuit devices) you have a branch circuit after those fuses.

I can see the MCP not being listed for branch circuit protection (outside of listing of the assembly) but why can't it just be considered a switch?

Fuses may or may not be economical way to do this and there may be some listing technicalities but I have a hard time saying it is outright dangerous.
 
kwired said:
If you used a molded case switch plus fuses (rated as branch circuit devices) you have a branch circuit after those fuses.

I can see the MCP not being listed for branch circuit protection (outside of listing of the assembly) but why can't it just be considered a switch?

Fuses may or may not be economical way to do this and there may be some listing technicalities but I have a hard time saying it is outright dangerous.
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They are not saying it’s dangerous, it’s just not tested. That listing technicality.
 
kwired said:
I get it, but yet I don't.

If it can pass as a MCP, why can't it pass as a switch? Seems to exceed the listing requirements of a switch to me.:huh:
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I does pass as a switch as it is the disconnect for the motor controller in the combination starter.
 
kwired said:
... If it can pass as a MCP, why can't it pass as a switch? Seems to exceed the listing requirements of a switch to me.:huh:
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don_resqcapt19 said:
I does pass as a switch as it is the disconnect for the motor controller in the combination starter.
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ptonsparky said:
Yes, but nobody has....:)
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kwired said:
I agree.
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Hummm ...
If you are looking for any kind of a "Listing" mark on an instantaneous CB - Save your eyeballs. There is none. No listing of any kind. Never has been.
 
Note to OP: This is not about you. You have it figured out.

don_resqcapt19 said:
Not saying you can use the MCP to protect the conductors, just saying I would treat the load side connection to the MCP as a feeder tap. That feeder tap would be based on the OCPD that supplies the MCC bus. I just don't see any case where making that install would be less safe than making a direct tap to the MCC bus.
Click to expand...

Okay, let's look at what you are suggesting:

OP says the units are installed in an MCC, Buckets will be small the devices are VAVs.

So, here is a normal line up
1000kva, 480V, 5%Z
motor is 10 HP

conductors are #12
Available Short circuit current is 24KA

Hey it is just a tap - just connect them to the bus. Why would it need a TM CB?
Wait, we have a 10A Mag-only CB lets use that.

You are making it too easy to point out the idiocy.
Methinks you are just on a lets make noise mission

enjoy
 
iceworm said:
Note to OP: This is not about you. You have it figured out.



Okay, let's look at what you are suggesting:

OP says the units are installed in an MCC, Buckets will be small the devices are VAVs.

So, here is a normal line up
1000kva, 480V, 5%Z
motor is 10 HP

conductors are #12
Available Short circuit current is 24KA

Hey it is just a tap - just connect them to the bus. Why would it need a TM CB?
Wait, we have a 10A Mag-only CB lets use that.

You are making it too easy to point out the idiocy.
Methinks you are just on a lets make noise mission

enjoy
Click to expand...
Explain to me how a "tap" connection to the load side of the existing MCP, would be less safe than a tap connection to the feeder that supplies the MCC. Of course in either case, compliance with the tap rules in 240.21(B) would be required.
 
don_resqcapt19 said:
Explain to me how a "tap" connection to the load side of the existing MCP, would be less safe than a tap connection to the feeder that supplies the MCC. Of course in either case, compliance with the tap rules in 240.21(B) would be required.
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Using the not-in-any-way-listed part to feed a tap from an MCC strikes me as difficult to be in "... compliance with the tap rules in 240.21(B)..."

Then again, I likely would not drill the MCC bus and feed a circuit outside of the MCC either **. One might find a code section to stretch to allow - don't know, I'm not going to look. However, it would still be bad design. I give it my best to not do that either.

In any case, you have the code sections. There's nothing further I can do to help.

** (edit to add) Unless it was a full size tap to additional sections.

:bye:

The Worm shaking the padded bars, yelling, "Please, Please, let me out. The inmates are running the place."
 
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iceworm said:
Using the not-in-any-way-listed part to feed a tap from an MCC strikes me as difficult to be in "... compliance with the tap rules in 240.21(B)..."

Then again, I likely would not drill the MCC bus and feed a circuit outside of the MCC either **. One might find a code section to stretch to allow - don't know, I'm not going to look. However, it would still be bad design. I give it my best to not do that either.

In any case, you have the code sections. There's nothing further I can do to help.

** (edit to add) Unless it was a full size tap to additional sections.

:bye:

The Worm shaking the padded bars, yelling, "Please, Please, let me out. The inmates are running the place."
Click to expand...
Don't have to drill MCC bus, just tap the incoming feeder conductor in an approved manner. It is still a feeder tap.
 
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