Can a KW transformer and a PowerHouse share neutral?

Just make sure the neutral is heavy enough to carry all the current that might be supplied at the same time from the KW or PH brick.  If you truly only run them one at a time, it's not an issue.

Yes, you are good to go. Use "U" on the KW as common, and the bottom socket(not the middle) as common on the PowerHouse. Phase the two using common technique(s) rotating the KW plug in the 120 outlet as needed.

Any return capable of the total load should be sized to carry ~ 25 amps for a short(up to 20 seconds) duration if the KW circuit breaker is working properly.

Thanks for the input guys. After giving it some thought, I think I might change course and go with 2 modern 40w transformers instead of the KW. The only reason I would need the KW would be for when my nieces and nephews came over with their conventional locomotives. On top of that, I've already fried a locomotive with a KW.

I just solved my problem!!! I'll use DPDT switches instead of SPDT switches with a common neutral. A DPDT can switch two independent circuits simultaneously, so one circuit will be power, and the other neutral. Now the neutral will return to its respective power source.

Stewart,

   Run your KW thru the DCS TIU, with its built in TVS it will protect your engines,

put a Bank of 7-10 Amp Scott type resettable breakers between both transformers and the TIU to protect the wiring and you will be fine.  You can get a couple of hand held DCS remotes for the girls to both control the trains with, in this manner also.  The KW is not a problem when set up properly, I use 2 of them and 2, ZW's set up in this manner. I have never damaged an engine or any part of my layout running in this manner.

PCRR/Dave