I wrote a couple months ago about our power pedestal problem and the diagnosis of the failure of the Genset Auto-Transfer Switch.
As I detailed in that post, I needed to hotwire around the transfer switch in order to get power to the coach while I waited to get the new one.
The transfer switch was made by Intellitec and I found that part number (the 300 model) is obsolete. But after talking with Chris at M&M RV Electronics (www.mmrvelectronics.com/) in Ohio I found that the new model 400 was available. Once we got to our winter RV site in Arizona I ordered the 400 from M&M.
This blog post along with the You Tube video (below) explains just what the transfer switch is and how it works (for those of you who might be interested!)
It’s really a very simple device consisting of (3) four post terminal strips, (2) double pole – double throw relays (with 110 vac coils), a small circuit board that is a 15-second delay circuit, and the enclosure.
Each of the three terminal strips have four screws. One for ground, the second for hot leg one, the third for neutral, and the fourth for hot leg two.
Terminal strip one (farthest to the left) is wired to the onboard diesel generator
Terminal strip two (in the center) is wired to the shore power and,
Terminal strip three (far right) is wired to the coach 110v power in.
The only purpose of the assembly is to automatically select EITHER shore power or generator power to supply 110 vac power to the coach.
When there is NO power applied from the shore power connection and the generator is NOT running, the two relays are both in the de-energized position and all four contacts (two on each relay) will pass power (when applied) from the shore power cord to the coach. The relays will stay in this position (de-energized) and each of the four relay contacts (GND, Line1, Neutral, Line2) will provide continuity from shore power to the coach.
If/when the generator is started the small circuit board in the upper left corner starts a 15 second countdown. The purpose of this delay is to give the generator time to come up to full operating speed. After the 15 second delay, the two relays on the board are then energized and power is switched (on all four contacts) from shore power to generator power.
As long as the generator is running these relays stay energized and power to the coach is supplied from the generator (even if shore power is still plugged in and energized).
When the generator is powered down, the relays once again move to the de-energized position and power is once again passed from shore power to the coach.
The video below gives a better visual of how things work.
I’m glad you stopped by to read this post and watch the video, I hope you found some value here.
Thanks again and be safe out there .. we hope to meet up with you down the road!
Herb and Kathy
