How is this legal? (12AWG taps off a 125A fused circuit)

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Jon456

Jon456

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I am still working on correcting all the violations on this pump house I've been upgrading. One thing has me puzzled...

The two 3-phase 230VAC pump motors are large (100A and 60A respectively), so they are on 125A fused branch circuits with 4AWG conductors (the conductors for the 100A motor are currently undersized, but that's a separate problem I'm addressing).

The part that has me concerned is that, for each motor circuit, there are 12AWG taps (230VAC) off two of the hot phases of the motor branches; these taps are for controlling the starters for the motors. That means the hot 12AWG conductors have no overcurrent or short-circuit protection other than the 125A TD fuses that protect the motor branch circuits. How can this be code compliant?

On the 100A pump motor, this 12AWG wiring appears to have been installed at the factory inside the panel containing the fuses, starter, and motor overcurrent device. However, the wiring was modified... the control wiring was extended to a third-party automated pump controller.

So the "unprotected" 12AWG control circuits for both pump motors now pass out of their respective motor starter panels to a separate "master" pump control panel mounted several feet away. If it's a consideration, the pump installer used moisture-tight flexible (nonmetallic) conduit to route these control wires (without any ground).

It just seems wrong to me that 12AWG conductors are tapped off a 125A fused circuit.
 
Jon456 said:
...

It just seems wrong to me that 12AWG conductors are tapped off a 125A fused circuit.
Click to expand...
Quite common in manufactured motor starters... but typically the other ends of these tap conductors go to a fuse block within the enclosure, wire length as short as is feasibly possible.
 
ron said:
What do the #12's land on, and how far do they travel in linear feet of conductor length before they terminate? Do they terminate on a set of fuses or breaker?
Click to expand...

The #12 conductors form a loop between the starter and the controller, Inside the controller, they land on a relay. The controller energizes the relay, which in turn energizes the pump motor starter, which in turn energizes the pump motor.

There are NO fuses or breakers anywhere on the #12 conductors. The only "protection" they have are the 125A TD fuses that protect the pump motor conductors.

The length of the #12 conductors is approx 4 feet for one pump starter, and maybe 10 feet or more for the other.
 
You didn't mention anything about there being a transformer in the motor controller so I assume (correctly I hope), that the contactor coil is line voltage.

If this is in fact the case, are you altogether certain that what you think you saw is actually what is?

Me thinks there is an embedded fuse probably 1/2 amp or so, protecting those #12 control wires. Look closely.
 
Smart $ said:
Quite common in manufactured motor starters... but typically the other ends of these tap conductors go to a fuse block within the enclosure, wire length as short as is feasibly possible.
Click to expand...

I figured there must be some exception that allows for a short length of "small gauge" tap conductor within the starter control panel for the starter controls (since the 100A motor starter panel appears to have been factory wired that way, albeit with NO additional fuse blocks or in-line breakers).

But it seems that whatever exception would allow that was probably tossed out the window when the pump installer ran additional #12 conductors off those same 125A fused taps to go to the remotely mounted pump controller.

Furthermore, on the older pump there is a drip oiler for the pump shaft. That oiler has a solenoid valve that flows the oil when the pump motor is energized. The 22VAC to that solenoid is tapped directly off the motor branch circuit conductors (where they are connected to the motor leads). I can see no markings on the wires to that solenoid, but they look like #14 stranded.

I'll post photos of all this.
 
Looks like it need s to be a #10 to be legal if staying in the enclosure. Table 430.72(B), Motors aren't my strong suit but this seems to apply.

Tom
 
yucan2 said:
You didn't mention anything about there being a transformer in the motor controller so I assume (correctly I hope), that the contactor coil is line voltage.
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I'm not sure I understand your assumption. There is NO transformer. The contactors in the pump controller are just relays (one per pump) that complete the "loop" in the #12 wires coming from the motor starter panels.

The ONLY source of power in the motor starter panels are the 3-phase 230VAC on the 125A TD fuses.

yucan2 said:
are you altogether certain that what you think you saw is actually what is?
Click to expand...

Yep!

yucan2 said:
Me thinks there is an embedded fuse probably 1/2 amp or so, protecting those #12 control wires. Look closely.
Click to expand...

Nope... nothing (unless one considers #12 stranded copper THHN wire to be a fusible link). Hence my concern.
 
OK,

Then were it I, I would install an in-line fuse block(s) to protect the control components. Protecting the conductors are of no concern as any appropriately sized in-line will be far less than 15 amps.
 
Davis9 said:
Looks like #12 is good for up to a 120A fuse/OCP inside an enclosure.

Tom
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That's a blanket statement.

Is that assuming the factory wiring isn't UL listed already? The 200 HP 480v pump panels I was in on Thur had 250 amp breakers and #14 control wire. If I was modifying the factory control wiring, then I'd probably agree that the NEC would want us to fuse it down, like in the OP's case.
 
Cow said:
That's a blanket statement.

Is that assuming the factory wiring isn't UL listed already? The 200 HP 480v pump panels I was in on Thur had 250 amp breakers and #14 control wire. If I was modifying the factory control wiring, then I'd probably agree that the NEC would want us to fuse it down, like in the OP's case.
Click to expand...

The NEC allows a # 12 as I stated with NO additional protection.

Tom:confused:
 
Davis9 said:
The NEC allows a # 12 as I stated with NO additional protection.

Tom:confused:
Click to expand...

I was just making the point that the factory wiring in pump panels appears to be smaller than the NEC recommendations. Which shouldn't be a problem, since it's listed, until you modify it. So his #12's might of been alright, until someone tapped off of them and ran them out of the pump panel enclosure with no additional overcurrent protection.
 
Davis9 said:
Looks like it need s to be a #10 to be legal if staying in the enclosure. Table 430.72(B), Motors aren't my strong suit but this seems to apply.
Click to expand...

Thanks Tom for the code reference. It's starting to make sense. Although I'm not sure how the manufacturer could wire the control circuits inside the enclosure with #12 wire when the panel is rated to 200A. Seems to me it would have to be #8 wire (to gain 400% protection per Note 2 in Table 430.72(B)).

In any case, since the control wiring has been extended beyond the enclosure, now Column C applies. But that's impractical for the ampacities I'm dealing with. So it seems I must apply separate protection and comply with Column A.

I was thinking I'd just get rid of the motor branch circuit taps and put separate breakers in the pump house subpanel for the motor controls. This would be advantageous because it would also allow me to protect the oiler solenoid valve on the older pump (which I'm sure does NOT quality as motor control wiring of any kind). But if I want to place control circuit breakers in the subpanel, I think I will run afoul of 430.75 (Disconnection) which states: "Where separate [disconnecting] devices are used, they shall be located immediately adjacent to each other."

I guess my only other option is to leave the taps but mount an inline fuse or breaker within the disconnect/starter enclosure.
 
Jon456 said:
Thanks Tom for the code reference. It's starting to make sense. Although I'm not sure how the manufacturer could wire the control circuits inside the enclosure with #12 wire when the panel is rated to 200A. Seems to me it would have to be #8 wire (to gain 400% protection per Note 2 in Table 430.72(B)). ...
Click to expand...
The manufacturers do not build to the NEC, they build to the product standard.
 
fwiw

fwiw

Jon456 said:
Nope... nothing (unless one considers #12 stranded copper THHN wire to be a fusible link). Hence my concern.
Click to expand...
296.8 amps for 10 seconds is the melting time for #12 at 104 deg F ambient.
Davis9 said:
Looks like #12 is good for up to a 120A fuse/OCP inside an enclosure
Click to expand...
61.2 seconds is the melting time for #12 at 104 deg F ambient and 120 amps.

Add: 244.7 seconds is the melting time for #12 at 104 deg F ambient and 60 amps (for beyond enclosure).
 
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