main breaker and subpanel size?

[chasebull]

i stumbled across this site and have really enjoyed reading the posts and learning. i have a home owners permit to do my own wiring on my residence that i just purchased. the detatched garage had an old screw in fuse type panel that i wanted to update with a breaker style. the garage is fed through a breaker in the house's main panel with 4 ga aluminum. i have learned that the size of the wire is not sufficient for 100 amp service but have already purchased a 100 amp panel. the sizing of wire should allow for me to put a 60amp breaker in the house main and feed the garage from there. my question is this, do i have to change the main breaker on the garage panel to the same size as the house one feeding it or can i leave the 100 amp in place? it is the convertable type homeline style and they do make one to replace the 100 but is it really necessary?

thanks in advance

[Richard Moore]

Actually, #4 aluminum is only allowed for up to 55 amps in this use. I don't think you will find a 55 amp breaker. As long as you use a breaker of 50-amps or less at the house panel, it is fine to leave the 100-amp breaker at the sub-panel. It will just be acting as a disconnect.

[Jim Katen]

i stumbled across this site and have really enjoyed reading the posts and learning. i have a home owners permit to do my own wiring on my residence that i just purchased. the detatched garage had an old screw in fuse type panel that i wanted to update with a breaker style. the garage is fed through a breaker in the house's main panel with 4 ga aluminum. i have learned that the size of the wire is not sufficient for 100 amp service but have already purchased a 100 amp panel. the sizing of wire should allow for me to put a 60amp breaker in the house main and feed the garage from there. my question is this, do i have to change the main breaker on the garage panel to the same size as the house one feeding it or can i leave the 100 amp in place? it is the convertable type homeline style and they do make one to replace the 100 but is it really necessary?

thanks in advance

It would be very strange if you had an old fuse panel fed by a #4 aluminum wire. Fuse panels were from the age of copper. Look carefully at your feeder wires. Are you sure that they aren't tinned copper? What kind of insulation is on the outside of the wires? Do you have pictures?

- Jim Katen, Oregon

[chasebull]

it is definitaly 4 ga aluminum. i suspect that they pulled wire and just used a left over box they had laying around.

[Jim Katen]

it is definitaly 4 ga aluminum. i suspect that they pulled wire and just used a left over box they had laying around.

In that case, I agree with Richard. Use a 50-amp breaker at the beginning of the circuit and use the panel that you have. You needn't change out the 100-amp breaker in the panel.

- Jim Katen, Oregon