The main service wire is the cable that carries power from the meter into your home — so choosing it correctly is critical for safety. Undersized or substandard main wire builds up heat, causes voltage drop, and creates a real fire risk. This guide explains how to size the main service wire to Thailand’s electricity-authority (MEA/PEA) standards.
Main Service Wire Size by Meter Capacity
Size the main service wire to your electricity meter’s rating:
| Meter | Copper | Aluminum |
|---|---|---|
| 5(15) A | 4–6 mm² | 10 mm² |
| 15(45) A | 10–16 mm² | 25 mm² |
| 30(100) A | 35–50 mm² | 70 mm² |
Copper or Aluminum — Which for the Main Wire?
Copper cable is preferred for indoor installation: it offers superior conductivity and durability, and it is the only material permitted inside buildings. Aluminum cable is restricted to outdoor aerial installations only.
Why Correct Sizing Matters
Choosing the wrong size or using substandard material causes heat build-up, voltage drop, and a risk of fire. The main wire carries the entire household load, so it must be sized and certified correctly.
Plan for the Future (EV Chargers)
For future-proofing — especially if you plan to add an EV charger — it’s advisable to select one size larger than the minimum requirement, so the wire can safely handle continuous high-load situations.
Choose Standard Main Service Wire from TETA Intertrade
TETA Intertrade is a wire-wholesale specialist supplying TIS-standard copper and aluminum main service cable in every size, matched to MEA/PEA meter ratings. Choosing the correct, standard-compliant main wire from the start keeps your home’s electrical system safe and reliable.
Frequently Asked Questions (FAQs)
What size main wire do I need for a 15(45)A meter?
Typically 10–16 mm² copper, or 25 mm² aluminum for an outdoor aerial run. If you plan to add high-continuous loads like an EV charger, size up one step.
Can I use aluminum main wire inside my house?
No. Aluminum is restricted to outdoor aerial installations. Inside buildings, copper is the only permitted material, thanks to its conductivity and durability.
What happens if the main wire is too small?
An undersized or substandard main wire accumulates heat, causes voltage drop, and creates a serious fire hazard, since it carries the entire household load.
Should I oversize the main wire for an EV charger?
Yes. Choosing one size larger than the minimum gives headroom to handle the continuous high load of EV charging safely, and future-proofs your installation.
