Gutter derating

[Brandon Loyd]

I am installing a new 4000 amp breaker and SWG to use as a manual transfer switch, utilizing a Kirk Key system for safety. We are feeding the existing 4000 amp SWG through the new 4000 MTS, and tapping onto the load side bussing to supply power should it be required. The new MTS will be installed 30' from the existing SWG, and all cableing will be parralleled 7 times and routed through gutter. I have 2 questions about this installation.

1. Using 535 DLO cable (420 amps), parraled 7 times, gives me 28 Current Carrying Conductors in 1 gutter. Do I need to derate these wires?

2. Since the bus tap will be used to FEED the existing SWG, would this be considered a "Bus Tap", in which case I would be violating the 25' tap rule?

 

[A/A Fuel GTX]

Regarding question 1, 366.23 states as long as the number of conductors is 30 or less, derating is not required. Not sure about question 2.

 

[petersonra]

I am installing a new 4000 amp breaker and SWG to use as a manual transfer switch, utilizing a Kirk Key system for safety. We are feeding the existing 4000 amp SWG through the new 4000 MTS, and tapping onto the load side bussing to supply power should it be required. The new MTS will be installed 30' from the existing SWG, and all cableing will be parralleled 7 times and routed through gutter. I have 2 questions about this installation.

1. Using 535 DLO cable (420 amps), parraled 7 times, gives me 28 Current Carrying Conductors in 1 gutter. Do I need to derate these wires?

2. Since the bus tap will be used to FEED the existing SWG, would this be considered a "Bus Tap", in which case I would be violating the 25' tap rule?

I would be rethinking the part in red. Unless it is dual rated as something else you can't use DLO cable at all. Keep in mind if you do use it, you will have to replace all the existing connectors with connectors that are compatable with fine stranded wire.

I don't think you can use the manufacturer's ampacity ratings either. I think you have to use what is in the code.

It is only a tap if it is not protected at its ampacity.

 

[renosteinke]

I always derate my gutters, to allow for leaf fill

 

[infinity]

I am installing a new 4000 amp breaker and SWG to use as a manual transfer switch, utilizing a Kirk Key system for safety. We are feeding the existing 4000 amp SWG through the new 4000 MTS, and tapping onto the load side bussing to supply power should it be required. The new MTS will be installed 30' from the existing SWG, and all cableing will be parralleled 7 times and routed through gutter. I have 2 questions about this installation.

1. Using 535 DLO cable (420 amps), parraled 7 times, gives me 28 Current Carrying Conductors in 1 gutter. Do I need to derate these wires?

2. Since the bus tap will be used to FEED the existing SWG, would this be considered a "Bus Tap", in which case I would be violating the 25' tap rule?

As Jim mentioned you need to check on your use of DLO cable.
Question #1- no derating required.
Question #2-25' tap rule applies to the conductor length of the tap. Not sure where you getting the term bus tap.