Overcurrent protection selection

Not sure if it belongs to this forum, but I have no other place to ask. If you know other place - let me know please.
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I am doing minor remodeling in my 40+ years old house and would like to replace old main fuse panel with CB panel.

Few odd thing I found while inspecting the current setup:

1. Air conditioner 1PH, 240V drop wired with 10AWG wires in 20 ft outside conduit protected with 40A breaker. Compressor is 21A, Fan 8A.

2. Drop to another part of the house (secondary breaker box) is 8AWG in conduit about 60FT currently protected with 60A fuses.

3. Lights and outlets wired with 14AWG wires protected with 30A fuses – open air attic wiring with ceramic isolators, covered with house thermal insulation.

What breaker sizes should I get for these circuits?
I have no problem to put 15A CBs for lights and outlets.

I was going over NEC2002 and just got confused even more…

The only wire I can replace is probably AC drop – not sure.

BTW, secondary box was replaced with CB type last year and have all breakers 15A for 14AWG wires and 20A for 12AWG wires.

Any ideas?
Thanks

Ahhhh....A typical older home, why I love a robust economy so all I have to do is sit and play with PLC's and not do rewiring projects.

I recommend that you put in a 200 amp panel. Some areas around here it is required by local ordinance. I am amazed at the old houses that have a 60 amp panel with A/C, microwave, electric range and dryer, etc, and never blows any fuses.

1). The A/C probably won't ever have any problems with the 10 ga. Actual current draw is probably less from the units I've checked (line voltage is usually quite a bit higher around here. I deal with 4 major power companies and 4 local municipal utilities on a regular basis. The 40 amp breaker is high for the wire, but may have been placed there due to inrush tripping the breaker, possibly not. Some guys on here are "Letter of the Law" and will say change it. I could let it slide, especially if all wiring is in conduit. The breaker is good for short circuit protection and compressor overload, and should handle both okay.

2). Drop to second box probably should have been #6, unless there is not much load there. Probably 40 or maybe a 50 amp breaker. 60 is a bit high, but being in conduit, it is safer. I would say this is going to be a consciounce matter. Some Hard-Nosed guys on here won't agree. Figure the actual loads as opposed to the breaker sizes, and go from there.

3). Definitely 15 amps! When the house was wired, a Well-Equiped room had a light and three outlets. A circuit might have had 3 or 4 rooms. As more stuff was added, 15 amp fuses blew, then 20's, so people wound up with 30's or "pennies". Don't exceed 15 here. As soon as possible, try to replace the open knob and tube wiring. It is pre-WW2. When it was new, it had a current rating that may not have been 15 amp, due to a high content of other allows. Some wire was copper coated steel.

Split off as many circuits as possible if you can. Run new circuits for refrigerator and microwave. Bathroom GFI outlet too, if possible, space heaters and hair dryers run a lot of power. Hopefully you don't have to run in conduit. I live in a romex area, and since I wire a lot of houses, really appreciate it. Romex costs less than individual strands. Now that wire has jumped up to 2-3 times what it was 6 months ago, and conduit is up over 60%, I really want to just play with PLC's.

I have tested some old wire, and found that some starts getting warm at 11 amps. Since you normally don't turn everything on simultaneously, it can be very unsafe with a 30 amp fuse. I tested 20 amp fuses years ago, slowly bringing up the current, and not one fuse blew below 36 amps. Figure a 30 amp fuse probably won't blow until at least 50 amps, connected to an old open with covered with ???. Turn on the load, slowly, 1 or 2 amps at a time. Eventually, POOF! Fiberglas bat insulation doesn't burn, but the kraft paper on it does. I have ignited some older fiberglas based insulation that was blown in.

Anyway, enough for now, feel free to ask any questions.

regards....casey

Wow, thanks a lot for this reply.

A couple things I need to make clear: house build in 1960, I got it in 1994.

When I mentioned open air wiring on ceramic tube isolators- it is still inside a walls and on the attic - nothing outside on the walls

I have no intentions to break wall to put romex at least for now.

All outlets in the house replaced with GFCI already - this is NEC2002 if no ground wire present.

This main box covers 3 bedrooms and 2 bath - 2 fuses only for all.
It was no celling fixtures in this house - I have this now.
I will try to split it at lease lights/outlets, and put arc suppressor breakers (NEC2002).

Secondary box covers about 60% area of the house: kitchen, living and dinning rooms, office, laundry and garage.
I have gas stove and dryer.

It is well split and all breakers are 15A, except garage with new 12AWG line with 20A CBs.

Currenly it uses 60A fuse on 8AWG wire and I have no way to replace wires at least for now.
I will put 40A to see if it works.

I will measure AC current this week to see actual load. I will start with 30A breaker - if not I can relplace this line.

I am still debating about 200A main breaker - my service line and meter are 200A already. wires from meter to the main fuse only 2AWG.
Thanks again.

I wouldn't rush out to replace those breakers.

ARC Fault Interupters - Since I am 90 miles from Chicago, and 30-40 miles from most suburds, there is a lot of differnce in local codes. Only 2 localities around here require ARC Fault.

One inspector is part time and a Com Ed employee. He is by the book, and very knowledgable. He soes a good job, and I don't argue with him.

The other is part time, a retired industrial electrician, and recently required the arc faults, probably at the request of the fir chief.

Locally, my fire chief / inspector doesn't want them.

They false trip a lot, and I have had a high fail ratewith them.

I don't recommend them unless it is required.

Whoever (probably a framing carpenter) rewired my house before I bought it, put a 200 amp box on a 100 amp service with 2 ga wire. Been here 8 years. May change it some day. Don't think my load ever gets above 80 amps.

anyway

more regards.....casey

Our city 20miles east of Cleveland is very liberal when it comes to inspections and permits: new construction, major remodeling - for sure. Small house jobs like this - unless contractor does it while I am programming PLC - I am not calling them, but sometimes they are sending reminder letter: "permits required for all houshold work..."

Anyway - I am glad you told me about arc suppressor CBs - they cost a lot. NEC2002 required them for all bedrooms, I will put regular CBs for now.
200A panels I saw are too large to fit in the small space I have.
I will probably buy 100A panel - 60A work really good now.

This is a next weekend project...

contr_conn,

What city are you in, if you don't mind me asking?

If you will do a lot of wiring, maybe is a good idea to run extra cables for telephone, internet, tv, audio, smth else..

Just a thought.

Jnelson: I live near Mayfiled and I-271

Eugen Thanks for the idea, The house is already wired with cable, telephone and network in every room. At this point I am planning to replace box only, nothing else.

The wife works in mayfield for progressive. We are out that way all the time. Nice to know someone else local is on here. I work in painesville.

Sorry for the ot stuff guys?

In actuallity, mayfield has some pretty strict regulations on building codes, as I have worked there. They do enforce them also. Problem is though, that the electrical inspectors are usually from cuyahoga county instead of mayfield city. Mayfield city usually only provides structural inspectors (I do not know why)? I am sure you know how cuyahoga county goes. Anyhow good luck.

It actually city of Highland Heights. I live here for 10 years. They are more liberal than Mayfield and Mayfield Heights. I never had any problems. Inspectors I had a couple times were really nice inspecting mostly grade to avoid complains from a guy next door.