Identification of dropline max amps by line gage?

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Old 01-14-08, 01:12 PM
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Identification of dropline max amps by line gage?

I have a confusing situation I am trying to get squared away. I will try to give as much information as I can without making it confusing. I have a house built about circa 1919. All knob and tube wiring has been upgraded sometime ago. I have an oldschool fuse box that I suspect was probably high dollar at one time. It has a total of 4 handle pull circuits up top, with old school tube fuses in each pull, each pull has two fuses. One is labled main w/two 60 amp fuses. One pull is just for 220 circuits, and the other two pulls each run 4 twist in fuse type circuits, eight twist in fuses of various amps, 15-20 amps. This is where it gets confusing. I want to go to atleast a 100 amp breaker box service, not that the current service is overloaded now, but I want to upgrade to a 50,000 btu heating system and add a couple of rooms to an unfinished attic.
I have installed a digital 200 amp meter, with no cut-of between the main fuse box and this meter. The fuse box is probably just with in 10 feet of the meter. I am unsure of the amperage capability of the drop line from the meter to the current fuse box. I can read 75 c rhw on the two feedlines coming into the box but can't make out anything else. Each line has about a half inch or better diameter with 6 strands of what appears to be aluminum wire in each. I would guess the gage of each one of these wires to be perhaps 10 gage or a hair larger. Of course these lines are constantly live, which makes the idea of working with this box dangerous to say the least. I though of coming off the 60 amp main with a temp line to the new breaker box and slowly moving lines over till I am ready to change the whole drop line to the new box and abandon the old. My question is can I use this existing drop line (it is totally enclosed in metal conduit running from the meter to the current fuse box by the way, which makes proper identification of the line difficult to say the least), or am I likely to have to replace this line, and if so, can I put a cut off in between the meter and breaker box, or would I be better off to stick with a main breaker box with a master breaker? The local codes here in idaho are very vague on this, and I would like to play it safe if at all possible. Any suggestions would be most helpful, thanx for your time wallace.
 
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Old 01-14-08, 02:45 PM
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Originally Posted by lazarus1328 View Post
I want to go to atleast a 100 amp breaker box service, not that the current service is overloaded now, but I want to upgrade to a 50,000 btu heating system and add a couple of rooms to an unfinished attic.
A 100A service is the minimum legal size for a home now. You need to do a "demand load calculation" (google this term for instructions) to determine if 100A is adequate or if you need a larger service.

I am unsure of the amperage capability
Doesn't matter. It should be replaced when the service is upgraded. I'd give a 99.9% chance it's too small for 100A anyway.

Of course these lines are constantly live, which makes the idea of working with this box dangerous to say the least.
They aren't live after you have the power company come out and disconnect the old service. You should never work on a service unless it has been disconnected by trained personnel.

I though of coming off the 60 amp main with a temp line to the new breaker box and slowly moving lines over till I am ready to change the whole drop line to the new box and abandon the old.
Some inspectors will allow this, others will not. You'll have to check with your local building department.

The most common upgrade path is to disconnect the service first thing in the morning; rip out all the stuff; install new panel, conduit, meter base, mast and grounding electrode system; have the power company back out before the end of the day. An electrician can do this in a couple hours, unless you have a lot of experience you could be without power for a few days.

Another procedure would be to install the new service up to code all at once and feed the old panel as a subpanel of the new main. Then you can migrate circuits from the old panel to the new panel, or you can simply remove the "guts" from the old panel and use it as a large junction box to extend your circuits to the new panel.

The local codes here in idaho are very vague on this
What code (NEC version or other) do you follow?
 
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Old 01-14-08, 05:18 PM
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Hey lazarus1328, I'm from Idaho too! I looked at the state's building safety site, they are on the 2005 code. That's all the advice I can give, I'm no expert. Good luck.
 
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Old 01-14-08, 08:51 PM
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Thanx for the reply and this is the cruix

Originally Posted by ibpooks View Post
A 100A service is the minimum legal size for a home now. You need to do a "demand load calculation" (google this term for instructions) to determine if 100A is adequate or if you need a larger service.



Doesn't matter. It should be replaced when the service is upgraded. I'd give a 99.9% chance it's too small for 100A anyway.



They aren't live after you have the power company come out and disconnect the old service. You should never work on a service unless it has been disconnected by trained personnel.



Some inspectors will allow this, others will not. You'll have to check with your local building department.

The most common upgrade path is to disconnect the service first thing in the morning; rip out all the stuff; install new panel, conduit, meter base, mast and grounding electrode system; have the power company back out before the end of the day. An electrician can do this in a couple hours, unless you have a lot of experience you could be without power for a few days.

Another procedure would be to install the new service up to code all at once and feed the old panel as a subpanel of the new main. Then you can migrate circuits from the old panel to the new panel, or you can simply remove the "guts" from the old panel and use it as a large junction box to extend your circuits to the new panel.



What code (NEC version or other) do you follow?
2005 is the current code for idaho as I understand it from another reply. I will have to look up the specifics to be sure. I realize the only way to kill the power is to have the power company come and pull the meter. There is a brand new digital power meter in place 200 amp max.. the service up to it is all correct. The drop line is my big question. I have wired a whole two story victorian house back east a few years ago, but had a pro electrician help me with main power service and such. I'm just not to the point yet where I'm ready to pull the main meter, and thought about going off the fuse box to the breaker box for now, till I was ready to totally switch to the new breaker box and drop the fuse box altogether. I'm not sure what website I might be checking into as far as specific codes becouse alot of stuff I'm finding is for new construction and doesnt really explain much about existing wiring in an existing house. Any pointing in the right direction would be most helpful.. (specific website?) thanx much .. wallace
 
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