Dangers and Problems with "Dirty" Transfer Switch

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This past weekend, I replaced the recalled Iota ITS-50 Automatic Transfer Switch with a Surge Guard 40250 Automatic Transfer Switch. This modification will be posted on the Modifications subject area. It is what I found inside the Iota ATS that is surprising and bothersome!

In the installation manuals of these Automatic or Manual Transfer Switches, one is warned to keep the inside of the switch clean and not even let the trimmed wire insulation to fall inside the transfer switch case. Once I had disconnected all power from my Alpine – shore line removed and the spark plug wires disconnected on the generator – I opened the Iota ATS and got quite a surprise! Sawdust!

In the attached picture, one can still see a mound of sawdust in one corner of the ATS case. That is after I dumped some out to find out "what in the world is that stuff"! The problem is that the sawdust is easy to "kick up" during the process of moving the RV. Bits of this sawdust can come to rest on the contacts that connect either the shore power or the generator power. This sawdust between the contacts presents a resistance to current flow. This resistance causes heat – possibly a lot of heat. And not only can the sawdust cause resistance between transfer switch electrical contacts, it can also provide an ignition source for fire! So, once the sawdust heats up, it burns, but the ash still provides resistance between the contacts. Perhaps the ash stays attached to the contact when it opens and more sawdust gets deposited on the contact. More heat builds on this resistance . . . until finally the transfer switch starts to fail.

This could happen if you installed the transfer switch, if it was factory installed, or added by a RV service shop. And it doesn't matter if it is an automatic or manual transfer switch. What does matter is keeping the inside of the transfer switch free of foreign material and clean per the installation manual. I gather from another source that it is a good idea to check the torque on the electrical lugs once a year. You can have a RV service shop do this, but also ask them to clean out the transfer switch box with compressed air when they check the lug torque.

If you attempt this chore, please be aware that you MUST disconnect ALL electrical connections to the RV and disable the generator! I really can't stress this enough. Disconnect the shore power cable! Pull the spark plug wires off the spark plugs on the generator. Disconnect the batteries – especially if you have an inverter! Failure to take proper precautions could mean an untimely death! But once you assure that all is safe, checking the torque on the RV shore power input, generator input, and output to RV connection lugs is fairly easy, simple, and quick – but use a torque screwdriver or proper torque tool. And getting a "can of compressed air" such as used to clean computer keyboards will allow one to quickly clean out the transfer switch case to insure that it is clean. And safe!

Ron