Power cord access while TM is closed

[Bill]

Back on August 12, Wade started an interesting thread titled 2720 Wish List for his then-new TM. The third item on his wish list - a wish shared by many - was to engineer access to the power cable for battery charging and refridge operation while closed. The group kicked around a number of thoughts, looking for a method that was both convenient and SAFE. Consensus was that a small auxiliary cord would be OK - no need to use the big 30 amp cable, which isn't normally accessible when the TM is closed. In this discussion, I was the safety guy - I couldn't figure out a way to have two power cords without creating an electrical hazard. (I am an EE and sometimes electrician.) The thread eventually petered out for lack of a solution.

I have thought about the question off and on since then, and the solution - a convenient and SAFE solution - finally popped into my head. And it is easy, and parts cost only about $10-15.

The desire is to put the plug end of a small AC power cord in some spot that is accessible when the TM is closed. My choice would be the back bumper compartment. If this cord is plugged into a source of AC power, then it will provide AC power to the refer and to the battery charger, and nowhere else. If the cord is unplugged, then the refer and charger AUTOMATICALLY revert to the big 30amp power cord. The word AUTOMATIC is important - with AC power projects, nothing should depend on the memory of a weary traveller. And furthermore, if BOTH the big cord and the little cord are plugged in, there must be no hazard.

The solution? In my 2720, anyway, one of the 20 amp circuit breakers in the AC power distribution panel feeds both the refer and the power converter. At the output of this breaker, we insert a changeover relay. The relay is wired up so that this circuit is normally fed from the big 30amp cord, but if the small cord is plugged in, the relay activates and feeds this circuit (and this circuit only) from the small cord. Voila - the function is accomplished.

If anyone is interested in doing this, I will provide a diagram and source for the relay by email. (The board's server doesn't seem to be accepting graphics during the site change.) WARNING: I do not encourage you to undertake any AC power project yourself if you are not throughly comfortable with AC power wiring, house wiring, etc. The job is not hard, but as you know, the consequences of doing it wrong can be severe.

Bill