[NextNewell]

The auxiliary solenoids are a safety device to prevent connecting the shorepower and the generator together if a relay jams.

Yes, but then the fuse would blow and cut off the power.

Not necessarily, an example would be if the shorepower went down and you switched to generator power. At that point, your generator could be backfeeding the shorepower, a situation you never want to occur.

The Auxiliary Relay in my 1992 is a Square D D9999D01 Transfer Switch Interlock.  http://www.alliedelec.com/square-d-9999d01/70060531/

If a main contactor gets stuck the interlock keeps the manual switch from causing simultaneous engagement on the opposing main contactor. It is not highly likely this will occur, but is worth preventing.

Thanks Jon. My example was based on an assumption, unfortunately an unstated assumption, that the main shorepower contactor stuck closed, such as from an overload welding the points together or the internal contactor springs breaking, but I didn't say that in the post so I really appreciate you clarifying my post.

So, would it be relatively safe to assume that in an emergency situation the interlock switch could be bypassed?

[Richard]

Yes anything can be done in an emergency, but you would be far safer to simply wire around the xfer switch in an emergency.

As others have said, the safety system is there to prevent back feeding the power grid. There is another thing that has not been directly mentioned. If you were to have the genny running and close the contacts to the grid, the genny WILL come into phase with the grid. That would be the cause of weeping wailing and the grinding of parts that was mentioned.

Forgive me for being as diplomatic as a brick, but you have said multiple times that electricity is not your strong suite. Can you appreciate why we are discouraging you and any future readers of this post from defeating the interlock system?

[NextNewell]

Yes anything can be done in an emergency, but you would be far safer to simply wire around the xfer switch in an emergency.

As others have said, the safety system is there to prevent back feeding the power grid. There is another thing that has not been directly mentioned. If you were to have the genny running and close the contacts to the grid, the genny WILL come into phase with the grid. That would be the cause of weeping wailing and the grinding of parts that was mentioned.

Forgive me for being as diplomatic as a brick, but you have said multiple times that electricity is not your strong suite. Can you appreciate why we are discouraging you and any future readers of this post from defeating the interlock system?

Absolutely, the harder the brick the better.  And I really don't intend on bypassing anything, I just have a need to learn "what if" which is usually followed by "yes, but?"

[77newell]

Yup, the number of things I've done that were subsequently deemed "really stoopid" is mind boogling. Well, at least the count boogles my mind.

[NextNewell]

Yup, the number of things I've done that were subsequently deemed "really stoopid" is mind boogling. Well, at least the count boogles my mind.

Well it's said that we don't become old and wise unless you're young and stupid first: and I'm full of wisdom.

And today I finally figured out what was causing my electrical issue and I detail it next.

[NextNewell]

I discovered that I had a issue with each contactor that may not have been an issue if they had been used alone or in another application. And I now understand how they work and why the transfer interlock switch should NEVER be bypassed. 
To recap, I replaced both original contactors with new ones. Contactor "A" was the one and attached to shore power:  Contactor "B" was the one attached to generator.  After I installed them, fuses blew whenever I flipped the switch above the driver to select a power source. I called Newell and they determined that both contactors were wired correctly but they just didn't know what to tell me. 
 
One problem was relatively easy to solve when I found low resistance in the coil of contactor "B," which I figure caused the fuse blowing.  
What wasn't so easy to find was why when I flipped the switch to generator above the driver, nothing would happen. The switch sent power back to the transfer interlock switch on contactor "A", but the interlock would not engage and send power to the coil on contactor "B." 

That's when I started asking questions here about connecting directly to the coil and by-passing the transfer switch.

I disassembled the transfer interlock switch from the old contactor just to see how it worked. Let me tell you, there is not much there, which only made the mystery more mysterious to me.  I then took out the interlock switch from contactor "A" and disassembled it too. The two were pretty much constructed the same except for one almost unnoticeable difference. The transfer interlock switch required in my application has part in it that when contactor "A" is engaged, it pulls it up and the transfer interlock switch creates an open circuit that prevents power from energizing the coil on contactor "B". But the part in that particular interlock did just the opposite. When contactor "A" was engaged, it pulled it up but closed the circuit. Then when contactor "A" disengaged, it dropped it back down but, instead of being closed, it created an open circuit that stopped power from getting to the coil on contactor "B."  

I'm sorry if all this sounds confusing, but the end result is that after I installed the old transfer interlock switch, everything pertaining to this problem now works as it should. Now there's issues with the air pressure system ;-(

[77newell]

Your description is awesome, I completely understand it. And you said you didn't understand electricity

[NextNewell]

Thank you all for your invaluable advice to help me resolve my issues with my contactors. I think I have one more issue that might be related though. The gauges above the driver that measure incoming power, L-1 and L-2, don't seem to work. So before I start chasing that issue, is there anywhere I should start checking first?

[Fulltiming]

Check to make sure the breakers for the Air Conditioning units are turned on. My front L-1, L-2 meters are wired through a couple of the Air Conditioner breaker.

[Richard]

Outstanding detective work! And thank you for taking the time to explain the culprit. I think this makes you the xfer switch guru.