"Pete C." wrote:

Steve Spence wrote:

Pete C. wrote:



I've not seen any transfer switches that switch or isolate the neutral
and I've seen many transfer switches.

Pete C.

My transfer switch switches both hots and neutral.

http://www.green-trust.org/wiki/inde...ransfer_Switch

--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
Contributing Editor, http://www.off-grid.net
http://www.rebelwolf.com/essn.html

The picture is a bit small, but it sure looks like a pair of 2 pole
contactors. I can't tell if they have auxiliary contacts installed for
electrical interlock. It looks rather like the auto transfer switches
I've seen on RVs. If they are indeed 2 pole contactors then you're
either running 120V only or have a solid neutral.

I built a small transfer switch myself with a pair of contactors with
auxiliary contacts installed to allow for electrical interlock of the
contactors coils. When a contactor is energized the NC aux contacts open
the circuit to the coil of the other contactor preventing it from being
energized. Three possible states, one contactor on, the other contactor
on or both contactors off.

Pete C.

Come to think of it, if it is the RV type it could indeed switch the
neutral by using the contactors together and utilizing the NC and NO
sets of contacts with no provision for an "off" state. NC to connect to
one source until the other source is available, cycles the time delay
relay and then energizes both contactors. Of course this type of setup
has the potential for a nasty failure mode if one contactor fails.

Pete C.