Residential Power 1

[spammail1000]

I am considering adding an additional 200 amp service to my house that presently has a 200 amp service.

In order to understand the magnitude of the project, I would like to know if new power lines need to be installed to the house (pole to meter).

Is there a standard supply service to residential installations (pole to meter), i.e. 400 amp total, 200 Amp nominal breaker panel, therefore 200 amp overhead, or do most installs match cable size to house rating?

 

[jbartos]

In the past, the Utility usually upgraded 200A service to 400A. Routinely, a new 400A service line is installed from the Utility power distribution to your house and a new meter. The power panel may be replaced for 400A or an addional 200A installed. Usually, the utility inspects the site prior to giving permit to any electrical contractor to work on it.

 

[BESCOJIM]

Typically most utilities will have only a few overhead or underground service triplexes. For example, underground usually comes in 1/0, 3/0, & 350 ugr triplex. The utilites will size the service conductor based on demand and not the service size of your home. A typical service triplex is usually #4, #2, or #1/0 triplex. But that will depend on what type load you have in the house. Do you have gas or electric heat? Do you have a gas or electric hot water tank? Do you have a hot tub, swimming pool, electric driveway heater, etc? You need to contact your local utility and provide the type electrical load and separate the new from the existing equipment. They will do a capacity check to see if their equipment is adequate.

 

[roliver]

As with BESCOJIM response, most utilities size services on demand and from my experience #1/0, #4/0 or #350 UG or OH triplex condutors. Load Shape of your home, determines this demand. Again, most utilities do not supply the meter base (customer interface), but will provide the meter to go into it. For a total 400 amp main meter base, Utilities will use their 320 amp meter. As far as your wiring from that meter base on into your panel, this is handled under the N.E.C. (National Electrical Code). This is also why Utilities use 320 amp meters because of NEC code requirements for your meterbase of not allowing more than 80% loading on it. But the questions can be answered for the design on that side of it. For the Utility design, they will look at your load shape (demand), depending on this, usually the demand is somewhere near .50 to .70 percent. This demand then could be as high as 38 & 58 kilowatts. Most likely the Utility will check their transformer sizing and following the scenario I am presenting may change it out to a 50 kva unit, if it is soley the one serving the resident or increase it, if the additional load is not within or close to its rating.

 

[jbartos]

A small encore to the previous posting: Please, notice that the nominal sizes of conductors and protective devices are per 400A rating for 400A service, 200A rating for 200A service, etc. as the minimum. There will be no disconnection or trip of protective device if the load exceed 80% of the Utility service size. In fact, there are consumers who have their main protective devices actuated because of overloads (maybe they do not have money for upgrades or the upgrade is not so easy).

 

[rhatcher]

Fortunately the NEC and UL have made provisions to protect people from the above misconception. In other words, if you buy a 400A panel w/400A Main Molded Case Circuit Breaker (MCCB) and supply it with conductors rated at 400A, the requirement for overcurrent protection at 80% of conductor rating will be automatically met (it is childproof). As well a 320A utility meter will be appropriate (utility meters are considered "100% rated"...read on).

"Standard UL489 MCCBs are calibrated for operation in a 25C room ambient temperature. Given this 25C room ambient, the enclosure or panelboard designer is required to limit the ambient within his enclosure to 40C. When operated in this 40C enclosure ambient, the breaker is rated to continuously carry 80% of its nominal rating without overheating or nuisance tripping. If the MCCB is marked "100% Equipment Rated", it is capable of continuously carrying 100% of its nominal rating when operated in a 25C room/40C enclosed ambient temperature. For other ambient temperature operating conditions, derating factors must be applied."

Above cut and pasted from :

http://www.geindustrial.com/industrialsystems/support/technical/tip11.htm