Found this on another board and it seemed interesting so I copied and pasted it.
A Great Electrical Find.
There I was, inspecting a contemporary house built in 1960. It was one heck of a house built into the mountain near a ski lodge. It had a walk out basement on a slope with a one story house above and a flat roof to boot. The air was cold that morning, colder than the windy beach at night in southern Florida during a President’s Gala. The ice in the driveway forced me to use the four wheel drive to make it up the windy way.
The view was spectacular, over the mountains, out into the valley we could see for more than 20 miles. My inspector trainee was with me that morning. He is a soft spoken gentleman in his mid to late fifties, with gray hair and a goatee that matches. He always wears a hat to cover his male pattern baldness. Baldness from years of thinking and stress in his all American life.
OK, never mind, let me get to the juicy details of the technical problem at hand. Here we go.
The main panel was a 200amp older GE panel with a double handled fuse block with breakers below located on the main level in the dining room. The wall it was against was now an interior partition wall but was once an exterior wall prior to the addition. The sub panel was located in the basement inside a large utility room that housed the well pressure tank, furnace and sewage lift pump.
The service mast was located about twenty feet from the house on a pole that housed the meter base and fed into the structure underground.
I had my trusty trainee pull the cover off of the main panel. Let’s call him Greg. When we looked inside we immediately noticed that there were several double taps on non-rated breakers and the bonding screw was properly installed in the buss bar that connected both the neutrals and grounds. There were two 4/0 copper service cables that fed the main bus from the bottom of the fuse block. So far we found a minor defect with the double taps, otherwise normal conditions for this age panel.
The panel was rated for 200amps but was also labeled for less by reducing the number of allowable circuits to 36. We noticed the circuits were maximized, not to mention the double taps. This is where it gets interesting. When I looked at the top of the fuse block to see what was feeding the panel I noticed that it was only fed by a 4-awg stranded aluminum SEcable. What? Was I seeing right? Turns out I was, no mirage there. I turned off every single breaker in this main panel (OK, no comments. I have extensive electrical experience and if I want to exceed the SOP then let me be) and noticed that the furnace still continued to run. How could the furnace run when every single breaker was turned off in the main panel? I had “Greg” go down to the basement and turn off every single breaker in the sub panel and finally the furnace was off. At this point I pulled the double fuse block out (Again, no comments please, to each their own) and noticed that the fuses were both 150amp, much higher than what the SE cable was rated for. But why was the sub panel still hot when the main panel was shut off? I immediately went downstairs to look inside the sub panel and saw that the sub panel was fed by a 4/0 stranded aluminum SE cable that was coming from a conduit out of the basement slab. Huh? There were 10 single pole circuit breakers and 1 double pole 100amp breaker that had the 4-awg SEcable that fed the main panel. Confused yet?
The 4/0 aluminum that fed this “sub panel” (alleged sub panel now) was too big for the lugs on this 100amp rate panel so they conveniently clipped about half of the strands off so they would fit. The 100amp breaker was actually now a feed to the once main panel now considered a sub panel as the sub panel is now the main panel. The 100amp breaker was too hot to touch and the SE cable feeding the 200amp panel upstairs (now a sub panel) was extremely hot.
This means that there are a few major problems here:
The main panel is undersized and has no disconnect means with more than 6 breakers.
The SE cable was illegally reduced to fit the new “main panel”
The former main panel is now a sub panel and the neutrals and grounds need to be separated with the neutrals being isolated from the grounds.
The main panel is overloaded if it is now being used as 100amp sub panel. The breaker at the new main is only 100amps so that is the size limit of the former main panel and 40 circuits are way too many.
This is a complete unsafe cluster of an electrical mess.
The nice part is that there was a very large and proud sticker from an electrical company who is servicing this vacation house.
So what exactly happened? Here is my best educated answer:
- The main panel upstairs was originally the main panel and always was until the addition came along.
- The basement panel was added when the addition was put on for more circuits.
- That basement panel was originally a main shut off because of the remote location of the main panel upstairs.
- Because the main panel was imbedded into the framing with rock lathe they had a hard time accessing the perimeter of it to add a feed to a sub panel.
- They removed the main disconnect and replaced it with a sub panel that feeds the main panel by using the old service cable to fish the new 4-awg SE cable.
*]Someone was a complete idiot.