Cutler Hammer 400 Amp Bus Plug
It would be more accurate to say the Square D bus plug became a mouse hotel, but Rat Hotel sounds more dramatic. MIDWEST field services runs into some pretty bizarre circumstances. Some funny, some tragic, and some a little of both. In this case MIDWEST was called to replace a Cutler Hammer 400 amp bus plug that had smoked, code for faulted with some arcing and smoking action. The location was a storage warehouse, damp, with minimum heat. It was easy to spot the damaged bus plug because it was partially discolored, or maybe the dust all over it was just toasted. When MIDWEST opened the bus plug to see how much damage there was and to get the exact catalog number, they discovered the remains of a mouse hotel, or colony, or habitat. A smelly little mess. Apparently mice got into the bus plug through an unplugged knockout on the top side of the old bus plug. It wouldn’t make any difference if this was a 400 amp Squared D bus plug or 400 GE General Electric Bus plug, the problem was caused by the missing knockout closure. A few cents cost a couple thousand dollars before the job was all done. The mice got in through the knockout opening, built nests, and seemed to be doing okay until one of them “crossed the phases,” so to speak. There was one toasted mouse, plus other fatalities, and burnt up debris in the bus plug. The guys removed the bus plug, installed a replacement from MIDWEST’s Switchgear Services, and then brought the damaged bus plug back to the shop. The only remaining problem was finding a volunteer to cleanup and check out the damaged bus plug to see if it was worth full reconditioning. It wasn’t. Rats
We received a question from Fred…Hi from Texas. I have a problem and I’m looking for a blogger to help me, if possible. We hit a 200 amp bus plug with a pallet being lifted by our fork truck. Nothing happened, but it is crooked and I’m worried, because my experience is this stuff will go bad on Memorial Day, the 4th of July. Just the way things seem to work out. To check the damage to the bus plug we have to turn a line off and that can only be done on a weekend and that costs overtime, which is invisible these days. Anybody out there with real experience that can tell me whether or not I should check this out. I don’t know how bus plugs are made or how they attach the main line. If I do shut the line down, what should I look for? What would typically go wrong if you hit one of these things and it moves about 2 inches? The pipe coming out the top looks okay, but I’m really concerned by how this thing connects to the hanging metal enclosure that runs the length of the room. Anybody been through this? Any ammo to take to my supervisor to justify the work? And what should I look for. Any help would be appreciated. Thanks, Fred Jenson
Answer: Fred, here are the easy answers. First, you need to check this out soon. The main bus duct that this bus plug connects to, could fail with a catastrophic fault that could destroy the main bus duct and the bus plug and possibly get someone hurt. Recommend to check it out at your first opportunity. Do you have a spare? Many electrical problems are actually just mechanical. So shut her down, Lock it out, Tag it out, Check voltage and then have your best electrician and mechanic investigate the damage. Take a good look at the connections between the old bus plug and the bus duct. Be safe Walt