Check with an electrician concerning the amount of amperage you will need. Also check with the power company as to what is allowed. Other questions must also be asked. How do you plan to heat and cool your your house, to heat water, wash and dry clothes, and cook food? How many rooms and square feet do you have? More information is needed before any suggestions are possible.
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If it is a new house that is getting built, plan for the future. Go with the 200 amp 42 circuit panel. With all of the new appliances coming out these days the old 100 amp panel is just not enough. The interim 125 amp panel was supposed to be a stop gap and have enough capacity to handle power demand for the next 10 years. Demand outstripped capacity. The bare minimum these days is a 200 amp panel. Some larger homes have 300 amp services and I have installed one 400 amp service in a single family dwelling.
You have more capacity. If you are starting from scratch you want to size the service for what you might grow into in terms of appliances and so forth. For example, a swimming pool in the future may require more capacity. If you are talking about converting from 100 to 200 amps, you would need to consider if you really need the extra capacity given the cost of a new panel or main breaker and whatever the power company might require to increase service.
For a 125 amp sub panel located less than 200 feet away from a 200 amp panel, you would typically use a 2 AWG copper wire or 1/0 AWG aluminum wire to safely carry the current load. It's important to follow local electrical codes and regulations when selecting the wire size.
For a 125 VDC battery feeding a 200 amp main breaker, you should use at least 2/0 AWG wire size to ensure proper current carrying capacity and safety precautions. Larger wire sizes could be used if the distance between the battery and breaker is substantial to minimize voltage drop.
Electricians use the tables in the electrical code book. The table consists of wire sizes and insulation factors. The insulation factors include temperature ranges of 60, 75, 85-90, 110, 125, and 200 degrees C. To use the table, an amperage is selected, for example the wire size for a 200 amp service. Look down the list for 200 amps. There are two listings, one for 75 degree C wire at 200 amps and the second for 90 degree C wire at 210 amps. Local electrical code amendments, based on climate and weather, usually stipulate which of the two degree wires are to be used.
In a 200 amp service panel, the ground wire is typically a bare copper wire or green insulated wire. It is connected to the ground bar within the panel. Make sure to consult the manufacturer's instructions or a licensed electrician for guidance specific to your installation.
For a 200 amp service, it is recommended to use at least a 3/0 copper or 4/0 aluminum wire. These wire sizes can safely handle the current and provide necessary voltage drop considerations for a 200 amp service.
200
125 and 200=25
For a 125 amp sub panel located less than 200 feet away from a 200 amp panel, you would typically use a 2 AWG copper wire or 1/0 AWG aluminum wire to safely carry the current load. It's important to follow local electrical codes and regulations when selecting the wire size.
This is a voltage drop question. To give an answer the voltage must be stated.
As a percentage 125 out of 200 points = 62.5%
For a 125 VDC battery feeding a 200 amp main breaker, you should use at least 2/0 AWG wire size to ensure proper current carrying capacity and safety precautions. Larger wire sizes could be used if the distance between the battery and breaker is substantial to minimize voltage drop.
1.6
0.625
3/0 wire 3/0 wire
Not evenly. 200 divided by 125 equals 1 with a remainder of 75.
125/200 = 5/8 in simplest form
200/125 = 8/5 = 13/5 or 1.6