Because of the primitive nature of Costa Rican electrician’’s wiring (use a “mother line†down the center of the house and splice off that for all circuits) we decided to wire our own house. We used Rex Cauldwell’s book, Wiring a House, to proceed.
Our system begins at the street meter box where 240 comes onto the property through #6 Aluminum wiring (the standard for the electric co here). It is grounded at this site and has a porcelain knife switch for shut off to the service line. From here on all of our wiring is North American copper wire.
We then buried #4 in PVC electrical tubing and brought 3 wires ( 2 hots and a ground) to our work shop; a distance of about 70 feet.. Here we established another porcelain knife switch (100amp 250v) for the incoming line.
Here the line is split. One set of #6 wires (2 hots and a ground) goes underground in PVC electrical tubing to the house and its breaker box ( distance 30ft). Another set of wires goes from the same knife switch to the shop breaker box. Neither breaker box has an internal main switch.
The house has a Siemans 200AMP 24 space breaker box which is grounded at the house. The shop has a Cutler Hammer 200AMP 6 space breaker box that is not grounded at that point.
The house breaker box is wired as follows:
black(hot) to the breaker
white & copper to neutral/ground bus
Tie bar is in place connecting neutral bar and bus bar
Neutral and ground are grounded outside with a ground rod
panel bond is in place.
I can send a picture if it would help.
The wiring to the house is new this year. In years past our normal kilowatt usage has run about 200 kilowatts per month. This is running several machines on 220 lines from the shop (planers, table saws etc). Since the new wiring in the house and the addition of an electric stove and dryer we are now averaging about 800 kilowatts a month.
The questions I have for the experts are:
1)is our house breaker box wired correctly
2) Because there is a ground at the street does the indoor load center need to be grounded as well.
3) All of the high kilowatt usage is from the 220 lines (when the dryer is running it takes 1.5 sec for a revolution of the meter disc) Why?
4) Is the house load center considered a sub-panel even though it does NOT pass through the panel in the shop?
If any of you kind people have any information it would be greatly appreciated here, and as there are NO qualified electricians in the area I am throwing myself at your mercy. Please keep it simple!
Troubleshooting
Since the high kilowatt readings we have done the following:
1) shut off all knife switches to shop and house, and then checked the meter disc. No movement
2)turned on each knife switch with all breakers in breaker boxes turned off- no movement of meter disc
3) unplugged every electrical appliance and unscrewed every lightbulb.
4) opened and closed each circuit breaker (one at a time) to check for shorts- no movement of meter disc
5) pluggged electrical appliances back in and checked each circuit for speed of meter disc- each 220 circuit sped the meter disc up to about 2 seconds per revolution.
6)The electric company has changed our meter- no change in performance.
Replies
Start here:
#6 aluminum wire has an allowable short circuit current of about 700 amps for 1.667 seconds. 9000 amps for .0167 seconds. That is the energy that could get let thru to your place without damaging the feed from the Utility. It should provide.
In the US in free air a single aluminum conductor should carry no more than 60 to 105 amps
#4 Copper lets thru 2000 amps for 1.667 sec
In the buried conduit (with no more than 3 conductors) 70 to 85 amps max
#2 Copper lets thru 4000 amps for 1.667 sec.
In the buried conduit (with no more than 3 conductors) 100 to 110 amps max
That is a lot of juice that could possibly reach your house or shop. There is a term in the US called "service rated entrance equipment". You don't have it. Your first protection is the branch circuit. Nothing is protecting the wires (4 & 2 Ga from the main to your buildings.
You need a fuse or breaker for service interruption. 22,000 AIC (amp interrupting capacity) is generally the minimum acceptable. factories and spots with high incidence of lightening strikes generally go for larger numbers like 50,000, fuses can take you to 200,000 +.
This is cheap insurance. You have to know that many electrical problems strike when someone turns on an operating switch (knife in your case) with a dead short on the line. What happens is the switch explodes causing burns,defib... bad stuff in short. I'd have to believe there is some fusing at your knife switch if not put some in. It will save your equipment and maybe your life.
I'm suggesting you need a main circuit interrupting device, probably 2. One for the shop and one for the house. Considering the coconut telegraph system there, could be large transient voltages coming down the line from lightening storms. Now unless you have insurance and want to replace all of your appliances everytime the thunder booms you need some interrupting capability. You can buy a "Safety switch" which is a 2 or 3 hot lead device to replace the knife switch. Inside that safety switch put in 100 amp and 200amp fuses rated with an AIC of 200,000 to 300,000 style fuses.
It isn't that much money probably 100 $ for each switch and $30 for each set of fuses.
Knife switches without fusing will be dangerous unless you have some sort of main breaker or fuses to cover your systems.
What you have works no doubt, but there are safeguards needing addressing. You have other issues as well but the service entrance needs help first.