Tucked way in the back of every manufactured home installation manual, at the end of the section titled “Prepare Appliances and Equipment” you will find the requirements for electrical testing of the home for continuity, polarity, and operation. So, I thought we should take a closer look at these three requirements so we can better understand how to conduct these important tests. Today we start with Continuity Test.
Ultimately, you are checking to see that all metal parts in the home that could become energized, are bonded (or connected) to the grounding terminal in the electrical panel box.
The intent of this test is to find any electrical shorts that could shock the occupant the home.
To conduct the test, you need a simple “continuity tester” that you can pick up at a building supply store or similar place for under $10 (I bought mine with a 20% off coupon!). Then you need a decent length (50 feet or more) of light gauge wire. I like to use 18 gauge lamp cord. An extra alligator clip might come in handy as well.
Strip about ½” from each end of the insulated wire and attach the alligator clip. Clip the other end of the wire to the alligator clip that comes on the continuity tester. Basically, you want to lengthen the little short cord that came with the tester so you can test the metal parts in a large area.
Once you have added the extra length of wire, you need to test your tester to make sure it works! Just touch the end of the added wire to the probe of the continuity tester. If you made good connections and your battery is fresh, the light in the tester should come on. That would indicate you have a “closed” circuit.
So, you are almost ready to test. First, turn off the power to the home. You don’t want to get zapped when testing the home. Next, if you are installing a multi-section home, the “Bonding Wire” connecting each chassis (or frame) must be connected.
Next, attach the end of the wire to the ground terminal (or bus bar) in the panel box. Now touch the probe to the edge of the panel box. The light should come on, indicating the panel box housing is grounded. Continue to touch the probe to any metal part of the home that may become energized while the other end of the wire is still attached to the grounding terminal. For example, you should check the furnace housing, water heater, chassis, metal heat ducts, any gas piping, any metal siding or roofing, metal light fixtures canopies, metal bath exhaust fans, range hood, waste disposal housing, any metal junction boxes (maybe for a built-in oven or cook top).
Now, when you are checking these metal parts, make sure you touch the probe to bare metal when possible as sometime the paint can hamper your test.
If your wire is too short and you need to move to another source to ground, you can use the ground terminal from a receptacle or attach to a ground conductor. Once you have completed the test, document it on the Installation Checklist.
Ok, I hope this helps explain the process, I would normally tell you to refer to the manufacturers installation instructions or the Manufactured Home Construction and Safety Standards, but they lack detail. If you want to see for yourself, go to 24 CFR 3280.810 (b).
Next time we will talk about polarity testing.