The rules are pretty strict as far as transfer equipment especially ones that handle the whole service.
702.6 Transfer Equipment.
Transfer equipment shall be suitable for the intended use and designed and installed so as to prevent the inadvertent interconnection of normal and alternate sources of supply in any operation of the transfer equipment.
Transfer equipment and electric power production systems installed to permit operation in parallel with the normal source shall meet the requirements of Article 705.
Transfer equipment, located on the load side of branch circuit protection, shall be permitted to contain supplementary overcurrent protection having an interrupting rating sufficient for the available fault current that the generator can deliver. The supplementary overcurrent protection devices shall be part of a listed transfer equipment.
Transfer equipment shall be required for all standby systems subject to the provisions of this article and for which an electric-utility supply is either the normal or standby source.
230.82 Equipment Connected to the Supply Side of Service Disconnect.
Only the following equipment shall be permitted to be connected to the supply side of the service disconnecting means:
(1) Cable limiters or other current-limiting devices.
(2) Meters, meter sockets, or meter disconnect switches nominally rated not in excess of 600 volts, provided all metal housings and service enclosures are grounded.
(3) Instrument transformers (current and voltage), high-impedance shunts, load management devices, and surge arresters.
(4) Taps used only to supply load management devices, circuits for standby power systems, fire pump equipment, and fire and sprinkler alarms, if provided with service equipment and installed in accordance with requirements for service-entrance conductors.
(5) Solar photovoltaic systems, fuel cell systems, or interconnected electric power production sources.
(6) Control circuits for power-operable service disconnecting means, if suitable overcurrent protection and disconnecting means are provided.
(7) Ground-fault protection systems where installed as part of listed equipment, if suitable overcurrent protection and disconnecting means are provided.
As you can see transfer equipment is not listed, the only way to install transfer equipment that switches the entire service is to get a transfer switch that is also rated/listed as a service disconnect.
I could not put together a couple of contactors or even one contactor that was double throw to make my own transfer switch.
Many panel makers produce a panel with two mains that are mechanically interlocked so only one can be on at a time and are listed as service equipment.
Trumpy I know you know the dangers here but I think many people do not realize that under the right conditions that their little generator can back feed a POCO transformer and produce some high voltages.
[This message has been edited by iwire (edited 12-28-2003).]