Odd Service Setup Auto Transfer Switch

[Mr. Tuttle]

Ok. I have an odd scenario made even odder by having to put in a generator whole house auto backup in.

Here is the current setup. Service 4 ft underground to old 6"x6"x4" jbox (1930's) original. It is then nippled out to a 150 amp main disconnect. From there the load out goes to meter via 2/0 SER and out of meter SER back to a MLO then to another sub panel off that with #4 SER.

Ok. First of all, is that even code? I did not even open meter yet but would the installed have had to put in an isolated neutral bar in meter enclosure and is that even allowed?

Secondly, because I'd rather not deal with POCO for a shutdown at street can I add an automatic transfer switch on load side of 150 amp main disconnect via nipple, then add isolated neutral bar in autotransfer switch?

I understand everything downstream of main is now a sub panel and needs an isolated neutral but not sure how this pertains to meters and automatic transfer switches.

 

[augie47]

250.142(B) would apply to the meter, if the install meets those parameters

 

[Smart $]

Ok. I have an odd scenario made even odder by having to put in a generator whole house auto backup in.

Here is the current setup. Service 4 ft underground to old 6"x6"x4" jbox (1930's) original. It is then nippled out to a 150 amp main disconnect. From there the load out goes to meter via 2/0 SER and out of meter SER back to a MLO then to another sub panel off that with #4 SER.

Ok. First of all, is that even code? I did not even open meter yet but would the installed have had to put in an isolated neutral bar in meter enclosure and is that even allowed?

250.142(B) would apply to the meter, if the install meets those parameters

Secondly, because I'd rather not deal with POCO for a shutdown at street can I add an automatic transfer switch on load side of 150 amp main disconnect via nipple, then add isolated neutral bar in autotransfer switch?

I understand everything downstream of main is now a sub panel and needs an isolated neutral but not sure how this pertains to meters and automatic transfer switches.

Question: Is the 150A main disconnect fused?

If it is, 250.142(B) Exception No. 2 will not apply.

If not, the disconnect may serve as a "main"... but is not the service disconnecting means. Providing there are no more than six breakers (or hand operations), the MLO panel serves that purpose.

Putting an ATS between the "main" disconnect and meter will mean, in addition to paying for the fuel consumed to run the generator, the homeowner will also be charged by the POCO for the generated power :slaphead: (typical optional standby usage may not be much, but an overcharge all the same).

Put in a "suitable for use as service equipment" ATS between meter and MLO panel. You'll have to relocate the Main Bonding Jumper and Grounding Electrode Conductor(s) to this ATS.

If the "main" is fused, install dummy fuses (comments?), and proceed the same way.

 

[Mr. Tuttle]

MLO

MLO

Yes, there is a 150 amp main breaker. Good call on the charge twice. I did not even catch that. I'll install the ATS on the load 2/0 SER out of meter right before the MLO. The MLO was a 30 breaker panel. I'm guessing i'll have to add an isolated neutral bar to the ATS ?

 

[augie47]

Yes, there is a 150 amp main breaker. Good call on the charge twice. I did not even catch that. I'll install the ATS on the load 2/0 SER out of meter right before the MLO. The MLO was a 30 breaker panel. I'm guessing i'll have to add an isolated neutral bar to the ATS ?

THe ATS and the panel... You may find the neutral on the ATS is already isolated.. many that I see are.

 

[Smart $]

Yes, there is a 150 amp main breaker. Good call on the charge twice. I did not even catch that. I'll install the ATS on the load 2/0 SER out of meter right before the MLO. The MLO was a 30 breaker panel. I'm guessing i'll have to add an isolated neutral bar to the ATS ?

Having the meter after the service disconnecting means is odd... POCO's usually not too receptive to that, but not an NEC violation.

Yes, you will have to keep the neutral and grounding separated at that location... but as Gus mentions, many ATS's already are.