Wire requirements

[alexspencer]

I would first like to say this is my first post and everything I've found on this board has been very insightful.

Conditions:

480V feeder with 4-350mcm + ground in 3" EMT

Included in the feeder conduit listed above is two signal cables (#10 Thhn).

Question:

My boss keeps referring to some code section that does not allow the signal cables to be pulled in with the feeder cables due to the difference in wire sizes (350 + #10). He cannot remember the code section, and my mind is fried on the code today.

Help me please.

 

[iwire]

Can you tell us what exactly the 10 AWGs do?

 

[jumper]

Even if the #10s are allowed-depending on insulation, class type, and what not-the odds of them surviving the pull with the #350s undamaged are slim IMO.

 

[alexspencer]

The #10 wires generate a start signal for an emergency generator.

@jumper I have to agree with you on surviving the pull, that is mainly just the reason I was asking because it just doesn't seem correct

 

[alexspencer]

700.10 (D)(3) ?

 

[don_resqcapt19]

Even if the #10s are permitted in the conduit with the 350s there is a stong possibility of conductor damage to the #10s if there are two or more 90s in the run.

 

[resistance]

Even if the #10s are permitted in the conduit with the 350s there is a stong possibility of conductor damage to the #10s if there are two or more 90s in the run.

I agree!! Seems they have little to no room left. Should have upsized to 3.5-4” EMT—preferably 4”.

 

[don_resqcapt19]

I agree!! Seems they have little to no room left. Should have upsized to 3.5-4? EMT?preferably 4?.

It is not really a space issue. It is where the conductors end up when going around the 90s. If the 10s end up on the outside of the 90 and if they can't slide by the 350s, they will break because the path on the outside of the 90 is longer. They often can't slide by to make of the needed length because they are pinched between the 350s. This will normally happen only when you have two or more 90s in the run.
Our common motor installation is to pull the #14s for the HOA switch in with the motor power conductors, but only where the motor conductors are #4 or smaller. Anytime the motor conductors are larger, the control wires get their own conduit.

 

[Strathead]

I would first like to say this is my first post and everything I've found on this board has been very insightful.

Conditions:

480V feeder with 4-350mcm + ground in 3" EMT

Included in the feeder conduit listed above is two signal cables (#10 Thhn).

Question:

My boss keeps referring to some code section that does not allow the signal cables to be pulled in with the feeder cables due to the difference in wire sizes (350 + #10). He cannot remember the code section, and my mind is fried on the code today.

Help me please.

One person asked what the wires are for, I expect this is to determine if they are Class 2 conductors or possibly current carrying conductors. Class 2 conductors can not be pulled in a conduit with current carrying conductors.

The elephant in the room is whether the #10's are current carrying conductors. As unreasonable as it may seem, the code requires derating to 80% for 4-6 current carrying conductors in a conduit.

 

[qcroanoke]

The #10 wires generate a start signal for an emergency generator.

Then my opinion is no, you cannot pull a generator start signal in with the generator output. Most would say it is a class 2 circuit.
My opinion is the generator and Transfer switch Mfgr. would never allow those wires in the same conduit as the output.

 

[don_resqcapt19]

Then my opinion is no, you cannot pull a generator start signal in with the generator output. Most would say it is a class 2 circuit. ...

Generator starting control circuits are often supplied by the batteries that start the engine. It is unlikely that power source would meet the requirements for a Class 2 power supply. If the power supply is not a Class 2 power supply, then the circuit cannot be a Class 2 circuit.

 

[resistance]

It is not really a space issue. It is where the conductors end up when going around the 90s. If the 10s end up on the outside of the 90 and if they can't slide by the 350s, they will break because the path on the outside of the 90 is longer. They often can't slide by to make of the needed length because they are pinched between the 350s. This will normally happen only when you have two or more 90s in the run.
Our common motor installation is to pull the #14s for the HOA switch in with the motor power conductors, but only where the motor conductors are #4 or smaller. Anytime the motor conductors are larger, the control wires get their own conduit.

I agree, and see your point. But after doing a calculation, it seems the space is close to Nada—where type RHH was used for the 350Kcmil in the calculation!!!

 

[qcroanoke]

Generator starting control circuits are often supplied by the batteries that start the engine. It is unlikely that power source would meet the requirements for a Class 2 power supply. If the power supply is not a Class 2 power supply, then the circuit cannot be a Class 2 circuit.

Agreed, That is why I also stated I have seen a lot of Genset and ATS mfgrs. clearly state the start circuit and other control wiring cannot share the same raceway as the output of the generator.