On Fri, 11 May 2007 14:20:29 -0400, George wrote:

Mark Rand wrote:


Has everybody missed the point that fitting proper interlocks is _precisely_
what Iggy is proposing to do? OK he's not buying a nice idiot homeowner retail
kit from home-generators_R_us. He is engineering a solution that is at least
as foolproof and effective. Good luck to him!



Mark Rand
RTFM

No point missed. He isn't engineering anything. He is trying to cobble
stuff together to avoid the use of a proven, approved for the purpose
and readily available DPDT transfer switch.

You design, test and submit for approval alternative devices when a
suitable device is not manufactured.


A double pole double throw switch is _not_ a safe design for a transfer switch
an inductive load that causes arcing on the opening contacts can result in
connecting both sources together or one source onto a fault. A panel that has
pairs of switches tied together can connect both sources to the load if one
switch or the link fails, with no opportunity to verify that the disconnect
occurred before the connect occurred. Neither protect against trying to
synchronise the source network a long way out of phase with the load network

Iggy's solution requires that one source is isolated well before the other
source can be connected.

Oh, and I have, in my role as an electrical engineer, in the last year had to
refuse to connect UL and CE marked equipment supplied by a major (Blue)
manufacturer because it was unsafe as assembled. When the installation
"engineer" claimed that similar equipment had been installed all over the
country, I had to state that it's use would be illegal in each of those
installations. I'm not that bothered about safety except where the lack of it
endangers people, then I get quite particular.

regards
Mark Rand
RTFM