View Full Version : Main Panel upgrade from 200 amp to 300 amp

July 23rd, 2007, 04:12 PM
This is just a general question in research of upgrading. Does the utility company have to get involved with the overhead power lines coming into the home when upgrading the main service panel from the existing 200 amp to a 300 amp?

July 23rd, 2007, 05:09 PM
Depends on your location. The utility service drop would have to be removed then reinstalled after the service has been upgraded. Some areas require a utility service man to disconnect the service drop then a permit is required, inspector visit and approval, power reconnected.

Some areas require a permit, self inspection, self disconnect and reconnect of service drop.

Check with your power company. First they will ask why you are upgrading from 200 to 300 amps. This will tell them if they need to upgrade the service drop and transformer for their info.

You speak of upgrading from 200 to 300. Normally with such a small difference in cost the electricians will jump from 200 to 400. Check the cost factor of 300 or 400. Might find you may as well go to 400 if you are going bigger. Your choice depending on the demand load calculation answers when you did a demand load calculation to find minimum service size. Are you guessing or sure you need to upgrade to larger service.

Good Luck


July 23rd, 2007, 10:49 PM
Thank you for the info on the service drop. I beleive the utility co. does have to do the disconnect. Do they generally charge for this service and the upgrading of the feed if neccessary? It sounds like the best bet is to have them come out.

I have not done any major calculating. I have been upgrading and fixing many yeras of poor wiring. The interest in the higher amperage panel comes from a reccomendation from the power company since they stated the load was pretty high. We have three seperate liveable units on our property each with full refrigerators and microwaves and so on. We have had dimming issues and such.

Im definately going to look into the 400 amp since we will be remodeling soon and adding many new electrical features.

July 24th, 2007, 12:08 AM
Definitely call your power comany and determine the following:

Do they have a website or published a book specifying their residential power requirements? If not, find out what the current rules are for meter placement, mast construction, grounding restrictions, service size, meter types, and inspection requirements prior to reconnect.

Know the locked rotor current (LRA value on the nameplate) of your largest air conditioner compressor or other motor.

Know how long your service drop is and ask them what size wires they'll give you for a 320 amp service. If you don't like the answer, see if you can pay to upgrade the size and what that cost is.

Look to see what size transformer you have and whether you share it with neighbors. Ask what size they'll provide and what it will cost if you don't like that answer.

For a 320A service with a service drop over 50' long, I'd want 1/0 aluminum triplex and a 25 KVA transformer (maybe even a 37.5 KVA transformer). If your transformer is shared with someone else, I'd want even bigger (probably 10 KVA more for each additional house). If you go with a full up 400A service, I'd want a 4/0 aluminum drop and a 37.5 or 50 KVA transformer. I had to pay $1500 for my 50 KVA transformer (all they'll provide for free is 25 KVA around here).

Learn the local and NEC rules for upgraded services. Usually, your new panels will have to meet current rules, but the rest of the house circuits are grandfathered (no AFCI upgrades, or 20A minimum circuits to certain places). You may need an additional grounding rod, and your ground electrode conductor and water pipe bonding wire will have to be larger than what you have now.

July 24th, 2007, 11:56 AM
My neighbor and I had an issue with dimming lights and it was entirely the power company's fault. We share a transformer and whenever they or I would run our dryer (electric) the light brightness would oscillate throughout our houses. Called the power co., and they placed a recording meter on our line. They found significant voltage drops over the course of a few days. They looked at the transformer and found it was only capable of producing 100A even though I have 150A service and my neighbor had 100A service. They replaced the transformer and all is well.

Don't be afraid to call the power co. I've found them to be the most responsive, punctual, and prompt utility around. I had them change my service entrance from aerial to buried and they did their part of the work absolutely free. They dug a 60 ft trench 2 ft deep, repaired the gutter drainage pipe they ruptured, laid power cables AND phone cable, and covered up the trench in under three hours. The electrician I hired to install the new meter base/main shutoff and run the cable through the basement to the new main panel cost much more, of course, but it was money well spent. Around here, an "inspection" is necessary to have power re-connected. I say "inspection" because you go to the building department at the courthouse and pay $50 for a "permit", but noone actually comes to inspect anything. They then give a thumbs up to the power company to reconnect your service. Nice little scam.


July 24th, 2007, 05:14 PM
In my neighborhood we have 6 houses (3 with 200 amp service, 3 with 100 amp) all powered by one 40 year old 25 kVA transformer. The power company says thats plenty big. Whatever.