100A OR 200A Zinsco box

[macs shop]

This should be a basic question, but I have had 2 different answers. The main breaker is a 2 pole 100A breaker. So, you would think its a 100a box. How can I tell if the wire to the meter box needs to be upgraded?

I am building a 30x28 garage, planning to run a 100a box in the garage fed from the house.
The current box in the house is a Zinsco, so I need to go ahead and replace it now. However, do I need to upgrade the service?

 

[EOC_Jason]

Usually you can see the wire gauge going to your main breaker if you remove the panel cover. That will at least tell you the size between your meter & main panel...

Now for the size between your meter and the power company... That will vary... Some areas have ringless so you can remove the cover and look, others have rings (or even locking rings), which in that case you will probably need to call the Poco to come out, pull the meter, then inspect the wire.

 

[macs shop]

Okay, well its #3 , 3-3-3 aluminum wiring. So I am guessing it is a 100a service.

 

[wyliesdiesels]

If its #3 then yes 100a service.

Looks like you have a split bus panel.

The feed comes into the top lugs then bus feeds 6 breakers then the main which feeds the lower section.

Definitely replace the panel.

As far as upgrading the service goes, you would need to do a load calc to determine that.

 

[Norcal]

The wire going to the main lugs looks larger then 3AWG. I am viewing it on a phone so it can be misleading.

 

[macs shop]

The wire going to the main lugs looks larger then 3AWG. I am viewing it on a phone so it can be misleading.

The cable insulation has a 3/0 on it. I am assuming that means 3AWG

 

[wyliesdiesels]

The cable insulation has a 3/0 on it. I am assuming that means 3AWG

no 3/0 is a lot larger than #3.

but the other wire you need to check is the wire in the riser that goes to the meter.

 

[macs shop]

Okay, well, I just had another guy come out, actually 2 guys. They assured me it is a 200a feed. So, the old Zinsco box of course needs to be replaced, but the service does not need to be upgraded.

the price to switch out the panel seemed a bit steep, he said off the top of his head, about $2,400.

 

[Bert_]

I'd want to see the inside of the meter box before I assumed I could just slap in a new panel. A 40+ year old meter box is likely to have issues even if it is big enough.

Somebody is making darn good money if they want 2400 to swap a panel. Price is sure to vary depending on your location but still...

 

[macs shop]

House was built in '69 so yeah a 50yr old meter box. I also called the electric company this morning, they are supposed to send a guy out to take a look on their side as well. So he should take a look at the meter and box.

i was hoping for about half that price,

 

[Norcal]

Is the 3/0 copper or aluminum? If copper then it’s 200A.

 

[macs shop]

It is aluminum

 

[Norcal]

It is aluminum

Then it’s not 200A, if it had been 4/0 AL then it’s good for a residential 200A service. Can’t remember what 3/0 AL is good for, think 175A. It’s not something I use.

 

[Stuart in MN]

Is it actually aluminum (the marking on the sheath should say) or are you going by the color of the bare wires at the main lugs in the panel? It may be copper wire with a plated surface.

 

[wyliesdiesels]

Okay, well, I just had another guy come out, actually 2 guys. They assured me it is a 200a feed. So, the old Zinsco box of course needs to be replaced, but the service does not need to be upgraded.

the price to switch out the panel seemed a bit steep, he said off the top of his head, about $2,400.

Dont know how they could make this determination without checking the wire between service the drop and meter pan.

However, under the old table 310.15(B)(7), 3/0 AL would be too small for 200a. 4/0 AL would be required for 200a. 3/0 AL is good for 175a. So, if it is INDEED AL, then those guys that came over are wrong.

That table is now gone, so load calcs are required.

And $2400 is a bit steep. Get some more quotes.

Does your meter pan have a lock seal on it?

can you post some pics of the meter and exterior panels?

What do you have on the outside? Just a meter pan?

 

[macs shop]

Then it’s not 200A, if it had been 4/0 AL then it’s good for a residential 200A service. Can’t remember what 3/0 AL is good for, think 175A. It’s not something I use.

according to this, you are correct

http://encorewire.com/wp-content/uploads/amp%20voltage.pdf

He stated it was good up to 225, but apparently only for copper according to that chart

 

[macs shop]

Will get some pics real quick of the meter, its locked.

I assumed it was copper based on the color of the wire.

 

[wyliesdiesels]

Will get some pics real quick of the meter, its locked.

I assumed it was copper based on the color of the wire.

look at the label on the insulation of the wire. should say either AL or CU

pic of wire in lug looks like AL but pics can be deceiving.

If its copper then youre good.

 

[macs shop]

Insulation on service cables coming in from the meter up close pics, insulation says 600V, 3/0AWG, THW

 

[alfredeneuman]

Another way to the amperage of Zinsco panels (courtesy of Norcal, I think ) is tell if the buss are that 100A busses are flat bars, and 200A are shaped like a piece of aluminum angle stock.

 

[macs shop]

I cant really see much more on the insulation, it twist and the print is facing the wrong way. I can make out a UM right where the insulation was cut back for the lug.

Here are pics of the bus bar, if that is an accurate way to tell.

 

[macs shop]

Dont know how they could make this determination without checking the wire between service the drop and meter pan.

However, under the old table 310.15(B)(7), 3/0 AL would be too small for 200a. 4/0 AL would be required for 200a. 3/0 AL is good for 175a. So, if it is INDEED AL, then those guys that came over are wrong.

That table is now gone, so load calcs are required.

And $2400 is a bit steep. Get some more quotes.

Does your meter pan have a lock seal on it?

can you post some pics of the meter and exterior panels?

What do you have on the outside? Just a meter pan?

They did look, literally just look up, at the mast where the service line from the pole meets my house and said those wires were 200a feed.

 

[wyliesdiesels]

They did look, literally just look up, at the mast where the service line from the pole meets my house and said those wires were 200a feed.

yeah lol. thats not the proper way to look. they needed to look at the labels on the wire.

 

[alfredeneuman]

That table is now gone, so load calcs are required.

If you do the math, the sizes on the old table are still accurate though.

 

[Charlie K]

It looks like tin-plated copper. If it is 200 amp is good.

 

[macs shop]

I nicked into the neutral 3/0, its Aluminum

 

[macs shop]

I did a quick load calc using a website calculator. I have gas heat, water heater, and dryer. Electric oven and cook top, AC, space heaters, freezer, and a 220g Saltwater reef system. It estimated my load at 80amps. Even if I mulitiply that by 1.5, I still only come up with 120A.

Depending on how expensive it is to change out the service line from meter to panel, maybe I just go with a 150A box instead of a 200?

I can still run a 100A panel to the garage? It is a 1 man shop, so a dust collector, air compressor, and a table saw may be the biggest loads at once. Someday I may get a welder, so thats about 50A, but again only a 1 man shop. It will have gas heat.

You guys have been a great help, any additional things I need to know about? It makes me nervous to think this first electrician(and his partner) planned to upgrade this 3/0 wire to a 200A service. I wouldnt have known any better if I didnt come in here asking for advice

 

[Norcal]

Might be a pain in the **** 175A is a standard size circuit breaker, just replace a 200A main with a 175A breaker or after almost 50 years replace it all. Electrical equipment is not like fine wine, it does not get better with age.

 

[alfredeneuman]

Depending on how expensive it is to change out the service line from meter to panel, maybe I just go with a 150A box instead of a 200?

200 amp bussing is used on all 125-200A panels. In fact, a 200A may be less $ than 125-150A panel because of the greater demand for them.

 

[nadogail]

In my limited residential wiring experience, no body used the name ZINSCO for a circuit breaker; they were called F---ing Zinscos. Given the opportunity, I would send all Zinsco equipment to the shredder and then melt them down for scrap.

My wiring experience has been mostly Marine (shipyards) and Industrial.

 

[Jim greengo]

If you're going to the trouble of upgrading service I'd do a 200a service.
Like others have said,panel is probably cheaper than 125-150,price for service cable isn't that far off between the 2.
Given the choice I'd use copper over aluminum to feed it.

 

[Norcal]

If you're going to the trouble of upgrading service I'd do a 200a service.
Like others have said,label is probably cheaper than 125-150,price for service cable isn't that far off between the 2.
Given the choice I'd use copper over aluminum to feed it.

There is nothing wrong with the use of aluminum conductors. Improperly installed copper conductors is just as bad as improperly installed aluminum conductors.

 

[Jim greengo]

There is nothing wrong with the use of aluminum conductors. Improperly installed copper conductors is just as bad as improperly installed aluminum conductors.

I prefer copper because cables are smaller,easier to work with is all.

 

[Bert_]

I prefer copper because cables are smaller,easier to work with is all.

I guess it depends on the person but I would consider alumninum easier to work with. Even though it's a size or two bigger it's lighter and 8000 alloy is much easier to bend than copper.

 

[Jim greengo]

I guess it depends on the person but I would consider alumninum easier to work with. Even though it's a size or two bigger it's lighter and 8000 alloy is much easier to bend than copper.

Through the same size pipe I'd rather pull copper,no big deal.