Manual Transfer Switch as Service disconnect

[tbassler_99]

I just read this in Mike's email:


Q3. Can a service rated automatic transfer switch be installed between the utility meter and first disconnect?
A3. Yes, if it is listed as ?suitable for use as service equipment? [230.66]. If it were not listed as such, it could not be used because electrical equipment must not be connected to the supply side of the service disconnect enclosure, except for the equipment listed in 230.82. Transfer switches are not one of the items listed in that section.

This is not a metered installation. I have a mobile skid with a generator and an option for an alternate power supply connection. Either power supply goes through a manual transfer switch to a main circuit breaker panel board. If The manual transfer switch is listed as suitable for service equipment, can I eliminate the fused disconnect switch from the alternate power supply connection?

I thought the alternate service had to terminate in an over current device per 230.90. But reading it again I guess it only says in series.

 

[augie47]

Two things to take into consideration. On the positive side, 230.91 allows the service overcurrent protection to be "immediately adjacent" to the disconnect so a service rated manual switch with OCP adjacent can serve as service. On the negative side, most manual service rated switches have a low AIC rating (10k), so they are not acceptable on a lot of services.

 

[tbassler_99]

Two things to take into consideration. On the positive side, 230.91 allows the service overcurrent protection to be "immediately adjacent" to the disconnect so a service rated manual switch with OCP adjacent can serve as service. On the negative side, most manual service rated switches have a low AIC rating (10k), so they are not acceptable on a lot of services.

Excellent point. Thanks. I will need to put the main panel on the other side of the wall this MTS so that pretty much rules it out.

 

[Pierre C Belarge]

I just read this in Mike's email:


Q3. Can a service rated automatic transfer switch be installed between the utility meter and first disconnect?
A3. Yes, if it is listed as ?suitable for use as service equipment? [230.66]. If it were not listed as such, it could not be used because electrical equipment must not be connected to the supply side of the service disconnect enclosure, except for the equipment listed in 230.82. Transfer switches are not one of the items listed in that section.

This is not a metered installation. I have a mobile skid with a generator and an option for an alternate power supply connection. Either power supply goes through a manual transfer switch to a main circuit breaker panel board. If The manual transfer switch is listed as suitable for service equipment, can I eliminate the fused disconnect switch from the alternate power supply connection?

I thought the alternate service had to terminate in an over current device per 230.90. But reading it again I guess it only says in series.

A SERVICE is supplied from a utility. Your site is not utility supplied, at least not so from what I read (Highlighted).

Your requirements will be found in Article 225, mostly from Part II.