Double Lug Connection at Ckt Breaker?

[Designer69]

I have the following question where I need to tap 2 ways from the service main ckt breaker as shown in the pic below.

My question is.. is it better to add the wireway or is it just fine to tap right from the CB using a double lug connector (is this even doable?)
There are only the 2 feeders going to the ATS's so I don't know if the wireway is overkill for this.

Thank You

better pic here: https://ibb.co/b2Q8u8

 

[petersonra]

I think you should do whatever is more convenient for you. However you have to also consider if the double lug on the breaker is something you can just change out. Some people think you can't. It kind of depends on what it is you're trying to do.

I'm not sure there's any real need to add a wire way. You can put some Polaris connectors in the circuit breaker enclosure.

 

[infinity]

I would guess that a 400 amp CB terminal that's only suitable for up to 500 kcmil would be suitable for the connection of more than one conductor so I would go with that.

 

[petersonra]

Seems to me that the overcurrent protection device rating of the transfer switch will help to determine what he can and cannot do and how far the run is from the circuit breaker to the transfer switches. It seems to me this might be a tap conductor of some sort and the tap rules would apply. I'm kind of afraid of answering questions like this where the question naturally leads to 10 other questions.

 

[infinity]

I agree with Bob there are many variables when choosing either option #1 or #2. For me if the CB has terminals suitable for two conductors I would just use that and then follow the appropriate tap rule.

 

[Designer69]

Seems to me that the overcurrent protection device rating of the transfer switch will help to determine what he can and cannot do and how far the run is from the circuit breaker to the transfer switches. It seems to me this might be a tap conductor of some sort and the tap rules would apply. I'm kind of afraid of answering questions like this where the question naturally leads to 10 other questions.

Thank You.

I wasn't planning on having additional OCPD's for the ATS's. Are you saying I can't have both protected by the Service Main Circuit Breaker?

Does it really have to be like this then?



Thanks so much.

Edit: The ATS's are both right next to the Service Main Ckt Breaker in the same room.

 

[kwired]

Seems to me that the overcurrent protection device rating of the transfer switch will help to determine what he can and cannot do and how far the run is from the circuit breaker to the transfer switches. It seems to me this might be a tap conductor of some sort and the tap rules would apply. I'm kind of afraid of answering questions like this where the question naturally leads to 10 other questions.

If taps to transfer switches (like if this were a 400 amp main then two 200 amp taps) then transfer switches would need to be a type that includes overcurrent protection to properly end the "tap".

 

[infinity]

Thank You.

I wasn't planning on having additional OCPD's for the ATS's. Are you saying I can't have both protected by the Service Main Circuit Breaker?

Does it really have to be like this then?

View attachment 20775

Thanks so much.

Edit: The ATS's are both right next to the Service Main Ckt Breaker in the same room.

If the conductors feeding the ATS's are of the proper ampacity (based on the CB) then you do not need the additional OCPD because the tap rules would not apply.

 

[Designer69]

the calculated load is just under 400A. One transfer sw. needs to be rated for 400A because it's going to handle essentially the entire load and the other one is minimal, literally barely 1KVA on it.

 

[jaggedben]

You don't necessarily need a separate wireway to splice two conductors into one, but it depends on fill limits and the space available in your equipment. Devil is in the details.

 

[Designer69]

If the conductors feeding the ATS's are of the proper ampacity (based on the CB) then you do not need the additional OCPD because the tap rules would not apply.

Thanks. Any help with a code section where this is described?

I was going to have a 500KCMIL going to the 400A ATS and a #10 going to the smaller ATS.

 

[Designer69]

If the conductors feeding the ATS's are of the proper ampacity (based on the CB) then you do not need the additional OCPD because the tap rules would not apply.

Can you please elaborate on this a bit. Proper ampacity? IE, the conductors feeding the ATS's must be the same size?

 

[kwired]

Thanks. Any help with a code section where this is described?

I was going to have a 500KCMIL going to the 400A ATS and a #10 going to the smaller ATS.

Then you have a feeder tap if it is coming off a 400 amp circuit, and would need to terminate at an overcurrent device. Since you have given a little more detail on your installation, looks like you need a 30 amp overcurrent device between the 'feeder tap' and your smaller transfer switch

Feeder tap rules are in 240.21(B).

 

[Designer69]

Now I'm thinking this is the better design but I'm now not sure if I'd need a MAIN service disconnect to disconnect all downstream feeders?

 

[kwired]

View attachment 20776


Now I'm thinking this is the better design but I'm now not sure if I'd need a MAIN service disconnect to disconnect all downstream feeders?

You can have up to six service disconnecting means, they must be grouped in same location. See 230 part VI.

 

[Designer69]

You can have up to six service disconnecting means, they must be grouped in same location. See 230 part VI.

Oh right I almost forgot about that. Thank you so much Kwired.

So then this design as shown, is fine then with the service entrance cables right to the wireway then split to two different service disconnects which protect the individual ATS's?

Thank you!

 

[kwired]

Oh right I almost forgot about that. Thank you so much Kwired.

So then this design as shown, is fine then with the service entrance cables right to the wireway then split to two different service disconnects which protect the individual ATS's?

Thank you!

yes

 

[Designer69]

yes

Awesome thanks. Last question...

How come on this graphic the Main CB splits to two different ATS's without any additional OCPD's. Is it because, as was mentioned earlier, it is likely the ampacity of the feeders is such that this is acceptable?

 

[kwired]

Awesome thanks. Last question...

How come on this graphic the Main CB splits to two different ATS's without any additional OCPD's. Is it because, as was mentioned earlier, it is likely the ampacity of the feeders is such that this is acceptable?

View attachment 20777

Yes. In your case with a 400 amp feeder you would need 400 amp conductors run to both transfer switches, and switches would both needed to be 400 amp. OR tap the 400 amp feeder and hit a 20 amp (think that is what you needed) overcurrent device before the smaller transfer switch. Another option would be service rated transfer switch (which will have overcurrent protection within though you probably won't easily find one with pre-installed 20 amp breaker.

 

[Designer69]

OR tap the 400 amp feeder and hit a 20 amp (think that is what you needed) overcurrent device before the smaller transfer switch.

Like this?



I kind of feel the option to the wireway first then to two service CB's seems cleaner. (Although this way eliminates the wireway)