See interlinear comments. I upgraded my house from 60A service to 350A
service. I'm not an electrician so I had to do a *lot* of research. Was
able after some self education (bought and studied a copy of the NEC) to get
a city permit and do it safely myself. The inspector was impressed, so I
must have done at least a decent job. =) See comments interlinear.

"sparty" wrote in message
oups.com...
I have a 150amp panel in my home, which is decently full, but probably
has space for about another 70amps worth of breakers, but only about 4
spots left.

I HAD planned on running a 70 amp breaker, and then 4 gauge wire to my
garage to a new breaker panel. That will probably max out my panel in
my house. I've done all of the math, and I'm pretty sure it can handle
that.

One of the reasons I am doing this is to run some 230V tools in my
garage. Now recently, I may have come across the opportunity to get a
used cheap Millermatic 250 Welder, which is going to pull 44-45 amps vs
the original 20 amps, I was going to pull with a smaller Welder. This
welder all by itself would require a 60 or 70 amp breaker. So now, I
would like to run 100 amps to my garage instead.

I ended up completely redoing the service to my house. Put in twin 200 Amp
panels to match the large twin lug meter, swapped a 150 into the panel for
the house for a total of 350 amps.

Because of this, I'm thinking I need to increase my House Panel from
150amps to 200amps. What all is involved in this? Does the electrical
company usually do this for free?

In Omaha at least the power company is required by the city to provide
service on their end (appropriately sized transformer, meter socket, meter,
wire from the pole to my wires protruding from the mast thru the roof) at no
charge. Before I started the project, I called the power company and got in
touch with the service designer over my area. He was pretty helpful.
Didn't hurt that I sounded motivated to do whatever my part was and not be a
nuisance. My neighborhood was built in the late sixties. He came out and
looked things over. Said they would have to upgrade the current transformer
that runs the block. Turns out they dug a new hole in my yard, installed my
own utility pole and hung a commercial sized transformer just for my house.
The old can stayed one house over and runs everyone up the block from me
while mine now runs everyone from my house down. It seems they didn't want
the block to brown out when I cranked things up. =) I'm tapped directly off
the big can.

I know I will need to buy a bigger
main breaker, will there be anymore cost involved?

You need to make sure the existing panel is rated for the bigger breaker.
For me to replace the 200A breaker with a 150 in one of my panels it was
actually cheaper to buy another main breaker panel kit with the same style
breaker and use the one it came with.

I realize you are talking a much simpler project, but for mine the basic
order was something like this:
-call the power company to make sure the project was doable and glean what I
could in the way of their special requirements
-get the city permit
-power company issued me a new meter socket, no charge
-power co sends a team to install "my" new utility pole in preparation for
my upgrade, also no charge
-install a complete overhead service about 20' from my old one to place the
new panels directly in the garage
-install new monster grounding rod system sized for the new service.
Interestingly enough the conductor running just to the ground rods is bigger
than the old main service lines
-convert my old panel into a subpanel (just separating neutral from ground,
had to install another ground bus)
-install a single breaker to feed the old house subpanel from the new house
panel
-wire everything literally just short of connecting the new panel to the old
main breaker. I ran the wires all the way and taped the ends to avoid
fireworks before the power company came out to shut off the old and transfer
to the new transformer
-make sure everything is perfect, then have the inspector out to have his
look
-inform the power co that the inspection is complete and approved
-schedule a day for them to come do the switch
-wait around most of the day for them to come =)
-power co. crew arrives and kills power to the block
-with a flashlight i do the final hookup inside between new panel and (old,
now sub)panel
-give the crew the thumbs up that I'm done and everything is squared away
inside. ie: no shorts. =)
-line outside goes live
-check voltages inside before throwin' the switch
-done. From tabulated resistance values, I calculated that at full 350A
load the aluminum wiring between the house and pole becomes an approx. 1000
watt strip heater. The power company does not have to obey NEC for
distribution lines. Even so, the voltage drop at that load should be less
than 4 volts. Better than the guys at the far end of the block get even at
low loading.

The only cost to me was for the permit and inspection, the hardware and wire
inside the house and some of the stuff outside the house. I bought and own
the mast and the copper wire inside. The meter socket is now an integral
part of my house and they tell me it is mine to keep. The meter itself and
the wire going from my mast to the transformer at the corner of the yard are
owned by the power company, provided at no cost to me.

Is 4 gauge NM-B still ok for 100 amps, or is it pushing it too much?

There are so many tables for the various insulation/environment combinations
it takes me a bit to find the right one. Hopefully someone will chime in
with an expert tip.

Pushing that much through it, does that present a fire risk, or is 4
still enough? That kind of distance should be a 2% or less drop, which
is ok, just curious about heat.

This will be through my Basement Ceiling Joists, then up a Garage
finished wall, then through the Garage Attic, then to a Breaker Panel.
Should be about 70-80 feet.

Thanks, James


hth,

StaticsJason