# Best answer: How do you size a transformer wire?

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## How do you calculate cable size?

Divide the voltage running through the cable by your target current. If, for instance, 120 volts will act on the cable, and you want 30 amps to run through it: 120 / 30 = 4. This is your target resistance, measured in ohms. 30,000 x 1.724 x 10^-8 = 0.0005172 ohm sq.

## Do you need a disconnect on the secondary side of a transformer?

240.21(C)(4), an OCPD is not required at the secondary side of the transformer. The conductors are protected from physical damage in an approved manner. … The disconnect means for the conductors is installed at a readily accessible location complying with one of the following: a.

## How do you size a transformer?

Calculate an example as follows. A 120-volt motor has a load amperage of 5 amps. Multiply 120 volts times 5 amps this equals 600VA now lets multiply the 125 percent start factor. Take 600 times 1.25 this equals 720VA and most transformers are sized by a factor of 25VA or 50VA.

## How much load can a 1 sq mm wire take?

Current Carrying Capacity: 11 A 1.0 Sq.mm Finolex Electrical Wire

Brand Finolex
Current Carrying Capacity 11 A
Color Red, Yellow
Insulation Material PVC
Packing Type Carton Box
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## How far can a disconnect be from a transformer?

Yes, 25 feet would be the limit without secondary over current protection. Also, 450.14 requires a primary disconnect at the transformer.

## How do you size a transformer disconnect?

Size the Secondary Side of the Transformer.

Using the example numbers: Isecondary = (20 x 1000)/240= 20,000/240 = 83.3 amps. Note: If you had a 3-phase transformer, the formula would be Isecondary = KVA x 1000/(Vsecondary x 1.732).

## What size breaker do I need for a 45 kVA transformer?

For a 45kVA transformer, 125A×1.25=156A, so use a 175A protection device.

## Do you ground XO in a transformer?

xo is the neutral, and the earth is used as a ground reference. by bonding the xo to ground in this fashion, you are establishing the earth as a reference voltage.