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Old 12-29-2012, 11:08 AM   #1
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50 amp sub panels from 100 amp main


I worked as a electrical apprentice so I am no stranger to residential wiring. First off I just bought my house which has a G.E. main panel with a 100 amp main breaker. I am more of a square D fan and I am also wanting to run two 50 amp sub panels so I am wondering if I could use a 150amp Square D in place of the 100 amp GE. I have very little in the way of amp hungry appliances or tools. My refridgerator is the only electrical appliance along with a Microwave. The Mechanicals are the furnace and the central air. The central air is running off of a seperate sub panel and meter but come off of a cross connection to the main meter.

I want a 50 amp panel in the garage that will contain all of the garage circuits. These will power garage door opener, table saw, miter saw, drill press, air compressor (a 220 hookup but draws only 15 amps) and two 8 foot long florescent fixtures. I want to be able to shut off the power to the electrical tools when not in use for obvious safety reasons.

The second 50 amp panel will be located in the basement where I have a small recording studio. The circuits will carry only amplifiers, mixers, and lighting and will need to be run through a conditioned main circuit.

Can I do this without running into problems on the electric companies side of the equation? Will code allow me to have two 50 amp breakers inside the 150 amp main panel? Can I replace the 100amp with the 150 amp main breaker? I don't see where I would ever exceed the rated amperage that is in the house now. My concern is that second meter and the 30 amp breaker that come off of the main meter.

The electric company supplies this house with a cable attached between two poles (in the middle so to speak) and there is no connection to a 220 transformer.

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Old 12-29-2012, 11:26 AM   #2
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50 amp sub panels from 100 amp main


You can't replace a 100 amp panel on an electric service with a 150 amp. Have you thought about upgrading to a 200 amp service?

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Old 12-29-2012, 12:13 PM   #3
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50 amp sub panels from 100 amp main


You can use any size panel you like as long as its fused for the service entrance conductors. Meaning you could install a 200 amp MLO or breaker panel inside with a 100 amp disconnect feeding it. Not a smart way to do it, but you can do it.
The house sounds fine on a 100 amp service. But your future additions may warrant a service upgrade.
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Old 12-29-2012, 12:26 PM   #4
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50 amp sub panels from 100 amp main


I think what he wants to do is replace his 100amp main breaker panel with a 150amp panel. That is why I said it is probably a good idea to upgrade to 200amp for the future expansion since you can't just replace the main panel or breaker with a larger one. Unless maybe the service wires and meter socket are large enough to support it.
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Old 12-29-2012, 03:07 PM   #5
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50 amp sub panels from 100 amp main


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I think what he wants to do is replace his 100amp main breaker panel with a 150amp panel. That is why I said it is probably a good idea to upgrade to 200amp for the future expansion since you can't just replace the main panel or breaker with a larger one. Unless maybe the service wires and meter socket are large enough to support it.
The house was built in 1967. The service cable looks to be 100 amp judging by the size. The A/C cable (added after house was built) is 60 amp and not much smaller than the main service cable it self. By running the 50 amp cable to each of the two 50 amp panels I would be removing 2 circuits from the garage and 16 circuits from the basement out of the main panel. The previous owners built out part of the basement and have 9 recepticals running through a 20 amp breaker and 5 flourscent light fixtures, with ballast units, through another 20 amp breaker. Needless to say the house is not up to code now. I am guessing that there is going to have to be an upgrade now with a new service cable. Guess it will cost me more bucks. The original wiring is the old cloth coated wire. This house is starting to remind me of that "Money Trap" movie. Guess I have to call DTE and see what they are going to hit me with.
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Old 12-29-2012, 04:05 PM   #6
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50 amp sub panels from 100 amp main


you can install whatever size panel you want. you just have to size your over current protection (breaker) to the wire you are using. sounds like you want to add more spaces to what is there now. if you are not adding any new loads, just spacing them out you should be okay. if you are adding any new loads, upgrade to 200 amp and take care of your potential problem with overloading your circuit and this will also prepare you for future expansion. if you don't know what your getting into, make sure your rod is grounded.
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Old 12-29-2012, 10:25 PM   #7
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50 amp sub panels from 100 amp main


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Originally Posted by smithdavidp View Post
The house was built in 1967. The service cable looks to be 100 amp judging by the size. The A/C cable (added after house was built) is 60 amp and not much smaller than the main service cable it self. By running the 50 amp cable to each of the two 50 amp panels I would be removing 2 circuits from the garage and 16 circuits from the basement out of the main panel. The previous owners built out part of the basement and have 9 recepticals running through a 20 amp breaker and 5 flourscent light fixtures, with ballast units, through another 20 amp breaker. Needless to say the house is not up to code now. I am guessing that there is going to have to be an upgrade now with a new service cable. Guess it will cost me more bucks. The original wiring is the old cloth coated wire. This house is starting to remind me of that "Money Trap" movie. Guess I have to call DTE and see what they are going to hit me with.
During late 60's-early 70's the third cable drop sometime it called A/C cable as you stated if you really count the numbers of conductor at the attachement point either at the top of mast or weather head and if you have 4 cable.,

Then it is a good chance that you have 3 phase delta there but you will find a single oddball breaker which not a normal item while the rest of breakers are standard size as you may noticed.

As long it still engerized you may want leave it there or convert to single phase and get rid the three phase drop If you have single phase A/C unit but if still have three phase A/C unit still running then leave it alone.

If you want to upgrade this with 150 amp you can if the POCO allow it but the POCO may want to know what is your load demand caluations and they may ask you if you are still running the three phase A/C unit or not.

Just be aware that you will not able find new " delta " breaker anymore that is no longer legit for safety reason due that delta breaker the two pole is feeded off from single phase side while the third pole aka wild leg or delta leg ( there are quite few names for this ) will feed directally from the meter socket ( not useing anything from the bussbar ) so that is the issue right there.

If you do have delta breaker in there the best answer you may not want to heard it but you will have no choice but get a electrician in and deal with it ( if you keep the triphase A/C unit if not then you can ditch it )

Merci,
Marc
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Old 12-30-2012, 04:02 PM   #8
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50 amp sub panels from 100 amp main


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Originally Posted by frenchelectrican View Post
During late 60's-early 70's the third cable drop sometime it called A/C cable as you stated if you really count the numbers of conductor at the attachement point either at the top of mast or weather head and if you have 4 cable.,

Then it is a good chance that you have 3 phase delta there but you will find a single oddball breaker which not a normal item while the rest of breakers are standard size as you may noticed.

As long it still engerized you may want leave it there or convert to single phase and get rid the three phase drop If you have single phase A/C unit but if still have three phase A/C unit still running then leave it alone.

If you want to upgrade this with 150 amp you can if the POCO allow it but the POCO may want to know what is your load demand caluations and they may ask you if you are still running the three phase A/C unit or not.

Just be aware that you will not able find new " delta " breaker anymore that is no longer legit for safety reason due that delta breaker the two pole is feeded off from single phase side while the third pole aka wild leg or delta leg ( there are quite few names for this ) will feed directally from the meter socket ( not useing anything from the bussbar ) so that is the issue right there.

If you do have delta breaker in there the best answer you may not want to heard it but you will have no choice but get a electrician in and deal with it ( if you keep the triphase A/C unit if not then you can ditch it )

Merci,
Marc
There are only three wires into the mast head. This goes directly to the main meter. There is a 100amp cable comming from the main meter jumping over to the meter for the A/C system. This is what has me so confused. I was a electrical apprentice in the mid to late 70's and every house that had Central Heat and Air had a 200 amp service or should I say that every house we pre wired we installed a 200 amp service panel. The A/C broke out of the 200 amp panel into a 40 amp panel (220) and then feed the A/C compressor and fan. The A/C was added to this house January 28, 2000 or that is what the date is on the A/C unit. The seperate meter had to be approved by DTE Energy or they would not have installed the meter. The A/C circuit does not run through the meter for the house but is jumpered around the main meter into the A/C meter. From there it is terminated at a 40 amp breaker which feeds the compressor and fan. It appears to me that this is only a two phase system as there is no third wire required for three phase. The mast head does have the opening (plugged) for 4 wires but only three are utilized.
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Old 12-30-2012, 08:42 PM   #9
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50 amp sub panels from 100 amp main


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Originally Posted by smithdavidp View Post
There are only three wires into the mast head. This goes directly to the main meter. There is a 100amp cable comming from the main meter jumping over to the meter for the A/C system. This is what has me so confused. I was a electrical apprentice in the mid to late 70's and every house that had Central Heat and Air had a 200 amp service or should I say that every house we pre wired we installed a 200 amp service panel. The A/C broke out of the 200 amp panel into a 40 amp panel (220) and then feed the A/C compressor and fan. The A/C was added to this house January 28, 2000 or that is what the date is on the A/C unit. The seperate meter had to be approved by DTE Energy or they would not have installed the meter. The A/C circuit does not run through the meter for the house but is jumpered around the main meter into the A/C meter. From there it is terminated at a 40 amp breaker which feeds the compressor and fan. It appears to me that this is only a two phase system as there is no third wire required for three phase. The mast head does have the opening (plugged) for 4 wires but only three are utilized.
Then it pretty much you got single phase right there.

And you mention the new A/C was installed in year of 2000 so therefore that time majorty of resdentail A/C units are single phase due they get much more effeiecy on them and second reason is the cost it getting cheaper as well ( That one part I am not too crazy but that the way it goes I rather run this on three phase because the lights will NOT flicker when the unit kick in. That what I have in my house three phase A/C )

Is there a way you can post the photo of the meter box and breaker box soem way we can able indentify it pretty quick.

Merci,
Marc
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Old 12-31-2012, 12:01 PM   #10
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50 amp sub panels from 100 amp main


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Then it pretty much you got single phase right there.

And you mention the new A/C was installed in year of 2000 so therefore that time majorty of resdentail A/C units are single phase due they get much more effeiecy on them and second reason is the cost it getting cheaper as well ( That one part I am not too crazy but that the way it goes I rather run this on three phase because the lights will NOT flicker when the unit kick in. That what I have in my house three phase A/C )

Is there a way you can post the photo of the meter box and breaker box soem way we can able indentify it pretty quick.

Merci,
Marc
I put the pictures under the Photo section and the Titles (Albums) are A/C Setup and Electrical Goof. They are public and smithdavidp is the owner.
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Old 12-31-2012, 12:20 PM   #11
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50 amp sub panels from 100 amp main


You may already know this but the two boxes above the A/C meter is an interupt circuit. DTE can interupt the A/C power when ever there is a chance of overload on the grid. They can shut the power off for the A/C, remotely, when ever they are reaching grid overload situations. Then all you can do is turn on the fans because you have no power to the A/C system.

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