Determining the size of the incoming service cable

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Old 07-18-05, 05:49 PM
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Determining the size of the incoming service cable

Hello: I am a first time poster to this forum.

I am an investor in row homes in my area. Typically, these are 1200 - 1400 square feet with an additional basement and garage built in the late '60s and early '70's. In any case, I have just purchased three of these homes and they each have a circuit breaker panel with a 60 amp main breaker. I have installed 100 amp breaker panels in other homes that I own, but, on those, I had a new service cable (from the utility co to the street side of the meter, and from the meter to the main breaker) installed.
On these homes, the service cable appears to be large enough to carry 100 amps. There is no conduit required for the service cable, so I am looking at the actual cable. How can I tell if it is, in fact, large enough to carry 100 amps? I am not an expert on wire gauge, so I would appreciate it if someone could give me a measurement of the diameter of the wire that would carry 100 amps (i.e 60 amp = 1 inch, 100 amp = 2 inch, etc). If it would not require the running of a new service cable, I would like to upgrade the panel to a 100 amp panel. Any help would be greatly appreciated. Thanks in advance.
 
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Old 07-18-05, 09:05 PM
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in my experience, service cable is sized for the service installed. I have never seen one oversized for future expansion. Now the POCO drops from the pole might be sized for 1 or 200 amps if the old ones were damaged in a storm or something and new ones had to be run. But as far as SE cable down the side of a house, always just big enough for the existing service. Plan on new services if you want to upgrade to 100/150/200 amps.
 
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Old 07-19-05, 09:14 AM
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Originally Posted by JMattero
Hello: I am a first time poster to this forum.

I am an investor in row homes in my area. Typically, these are 1200 - 1400 square feet with an additional basement and garage built in the late '60s and early '70's. In any case, I have just purchased three of these homes and they each have a circuit breaker panel with a 60 amp main breaker. I have installed 100 amp breaker panels in other homes that I own, but, on those, I had a new service cable (from the utility co to the street side of the meter, and from the meter to the main breaker) installed.
On these homes, the service cable appears to be large enough to carry 100 amps. There is no conduit required for the service cable, so I am looking at the actual cable. How can I tell if it is, in fact, large enough to carry 100 amps? I am not an expert on wire gauge, so I would appreciate it if someone could give me a measurement of the diameter of the wire that would carry 100 amps (i.e 60 amp = 1 inch, 100 amp = 2 inch, etc). If it would not require the running of a new service cable, I would like to upgrade the panel to a 100 amp panel. Any help would be greatly appreciated. Thanks in advance.

Wire sizes in the U.S. are not expressed in inches diameter, but rather by AWG. The smaller the number, the larger the wire size. Only until they get past a certain size do they start getting expressed in millimeters.

The first thing you should find out is the distance from the meter to your main breaker panel. If it's, say, greater than 100 feet (someone correct me here if I'm wrong), you might do well to bump up to the next size as a 'just in case' option. For 100A of service, I believe a #2AWG copper should suffice. However, since the cost of installing a 100A and a 200A panel is only perhaps an extra $50, why not go ahead and install a 200A panel? To handle that particular panel, you would need a #3/0AWG copper...this size wire should be able to handle 200-225A safely.
 
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Old 07-19-05, 12:27 PM
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It's very unlikely you can re-use any of the old service except the drop from the utility pole. The utility drop is probably rated for 200A. You will need to replace the panel box, the meter base, the mast (if installing one), and all of the cable in between. An electrician may give you a good deal if you do all three at once.

I understand that as investment properties you want to do the bare minimum 100A service, but a load calculation may require 150A services in these houses. An electrician will be able to tell you that when you get a quote on the services, or post back the electrical requirements. What are the fuel sources of: heat, water heater, cooktop, oven, cloths dryer? Do they have A/C, dishwasher, other electrical appliances?
 
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Old 07-19-05, 03:43 PM
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Followup to my question

Thanks to all who replied.

To answer some of the questions, the distance from the meter head to the panel is about 5 feet. This home has gas fored forced air heat, and gas cooking and hot water. The gas range is new. The only other appliances in the kitchen are the dishwasher and exhaust fan. There is no microwave, although some tenants bring in a countertop microwave. The rest of the electrical needs of the home are basically lighting. Some other tenants put in a room A/C unit. Do I really NEED to upgrade to 100 amp or more?

Assuming that I do NOT need to upgrade, can I add a 220 line for an electric dryer to the existing panel? There are 8 circuits in the panel, and room for 4 more.

Again, my thoughts are as follows... If the line coming from the utility company to the meter is large enough to carry 100 amps I would think about changing the panel to a 100 amp or higher. I have done this in the past with a panel that had rusted out. I would also need a meter head I would guess. I have also done that in the past. Really, the only thing I need to know is how to tell how much ampacity the cable (from the utility company to my meter socket) can carry. Is there a way to measure the cable to tell what the AWG gauge is?

Thanks.
 
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Old 07-19-05, 04:01 PM
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The AWG should be printed somewhere on the cable jacket. Something like "AL SER 4-4-2". It is also important if the cable is aluminum or copper. If you can't see the cable jacket outside, open up the panel and look at the conductors in there; they might have printing on them. You can't really tell by measuring the cable, because older cable is much thicker than modern cable due to different materials used in the insulation. Every type and age of cable is a different thickness depending on a lot of factors.

You could head down to Home Depot and buy a foot each of #2, #4, etc for comparison. The insulation will be a lot thinner in new wire, but you need to compare the actual diameter of the metal in the wire -- that should be the same. Hold up the new little pieces to the SE cables in the panel and see which one is closest; that will provide a good guess.

I think with all gas appliances, you only need to upgrade to 100A services if your insurance company requires it; many do now. I think that FHA requires 100A services also, so you won't be able to sell to FHA buyers with a 60A service.

Personally, I would go ahead with the 30A dryer line without a service upgrade. You have no other major electrical loads. Let your buyers negotiate it as part of the deal if they really want it.
 
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Old 07-19-05, 07:56 PM
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ibpooks

Thanks for the ideas. Since this is a property I plan on renting out for a long time, rather than selling, I think I will leave it at 60 amp for now.

One more quick question ... what size cable do I but for a 30 amp 220 line for the dryer? Is 12/3 romex thick enough? I would guess it is not. Also, does it have to be encased in some type of conduit, or wire mold? This will be going about 20 feet across the finished ceiling of the basement, and then entering into the unfinished laundry area. Where can I find specs so that I won't have to ask stupid questions like these???

Thanks for all of your help.
 
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Old 07-20-05, 05:14 AM
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For a 30 amp dryer yopu need 10 gage wire. To run across a finished ceiling you will need to protect the wire in some manner.
 
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Old 07-20-05, 06:31 PM
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A good question to ask is are you even allowed to do these upgrades as you are not living in the houses yourself. My jurisdiciton will only allow the homeowner to work on their own house (where the live). Any other work must be done by a licensed electrican.
 
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