Need help planning an electrical renovation

Question

I live in Thailand and I am renovating a small townhouse. I want to do the right thing and plan the circuit breaker with the correct amps.

After a little reading it seems we should use 1.5mm cabling for lighting and power outlets and 2.5mm cabling for a/C and water heater. I'm not sure about fridge, 17kilo washing machine, and microwave. I am assuming they are also OK with 1.5mm cable.

Anyway I think I need a 15amp circuit for each of the 3 bedrooms. I am reading it's also better to have a separate circuit for the lighting and sockets. So does that mean I need 2 x 15amp Siemens breaker for each bedroom? There will be "standard stuff" in the rooms - 4 down lights, probably no computer, maybe a TV in the future. Powering a phone at night. Really nothing special. And how about the living room. Should I have 2 circuit breakers the as well.

I will also have

• 20amp for each a/C in the house (18000 BTU)
• 15amp for the fridge
• 15amp for micro
• Maybe a 15amp for kettle
• 20amp for 2000w water heater

Any other suggestions?

Answer 1

Your planning is a bit...off

Thailand, like most places in the world that aren't in North America, uses IEC style nomenclature and wiring, from what I can tell (the actual standards aren't available in English, but the two threads I found on the topic on a Thai expat forum are thoroughly steeped in IEC terminology, such as RCD/RCBO, metric wire sizing, 400Y/230 LV distribution everywhere, and so on). As a result, 15A isn't even considered a standard breaker size, and Thai wiring rules apparently limit 1.5mm² to 10A anyway, with 16A circuits requiring 2.5mm² wire instead.

Given this, and the fact that Thailand, while having a legacy of using NEMA 1-15/5-15 plugs/receptacles (which is wrong, since those are a 120V config, not 220-240V), now uses its own plug standard (considered a "Type O" in the IEC taxonomy) rated for 16A/230V, you'll want to run your general appliance branch circuits as 16A circuits with 2.5mm² wire. You may be able to use 10A circuits for lighting, though, so do check with someone locally knowledgeable about that.

Wet area receptacles (kitchen/bath/outside) as well as water-heater type appliances will need RCD protection, although it may or may not required panel-wide, best I can tell. Eurostyle consumer units with DIN rail breakers may be permissible, although if you're going above about 24 breaker spaces, special IEC-rated versions of North American panelboard construction are available and may be preferable to the more traditional "consumer unit" construction.

Likewise, your service sizing will be...small by US standards. It seems that 30/32A and 50A are common service sizes in Thailand, with larger services delivered as three-phase. Speaking of large loads, note that that 2kW water heater will be perfectly happy on a 16A circuit, although the air conditioner may or may not require something larger.

Other than that, and any provisioning requirements the Thai standards provide, I'd provision:

• two lighting circuits (so that one trip doesn't wipe out the whole house's lights)
• a dedicated spur for the fridge
• two kitchen receptacle circuits
• a bathroom receptacle circuit
• a circuit for washer + dryer
• your water heater and AC circuits
• and circuits for bedrooms and living spaces as Harper describes (basically, splitting each room across 2 receptacle circuits shared between adjacent rooms)

Last but not least, Thailand apparently uses TN-C-S grounding, similar to what we do over here in North America.

Answer 2

I'll provide a partial answer. In summary: You don't plan the wiring in a renovation by examining your own personal needs right now. You plan them for the high end of what the next person might need.

For air conditioners rather than guessing (sure, 20A sounds good for 18K BTU) install the greatest of (a) what your A/C requires, (b) what local regulations require (c) what a typical large room unit requires. You should actually look at the requirements for the A/C you plan to install rather than guessing.

Same approach for water heaters and all large permanently installed devices.

For bedrooms, forget about lights and computers. Assume there will be simultaneous use of a vacuum cleaner, hair dryer, a couple of space heaters, etc ... just assume someone in each room will plug in something big. The formulas and regulations that are used by professionals in your area will take these things into account. Just because you don't use these things today doesn't mean you should build a building where the next person can't use them.

There really might be some local variations on how things are done. In the US it is normal to put lights and outlets on the same circuit. In the UK it is not but it is normal to use wires that are undersized by 30% by arranging them in a particular way. In Thailand .... I just don't know.

As for the kitchen, in the US and UK you need to plan in a way that allows toasters and kettles to be plugged in in various different places and used simultaneously. You don't plan "a kettle outlet". And the approaches to do this are, again, very different and we just don't know how it's done in Thailand. Maybe you do have kettle outlets.

Without knowing the actual regs, I think I can safely say that you don't need, and should not install, a separate 15A breaker for each bedroom light. At least I can answer one of your questions with some, authority conviction.

All this is just to try to convince you to get local help.

Answer 3

Outside of rooms like kitchen or bathroom, where North American NEC requires dedicated circuits... I'm really not a big fan of "1 circuit per room" or even "2 circuits per room".

I mean, I like the versatility of being able to power, say, a gaming PC and a laser cutter on 2 circuits. But if you think about how you would wire that, it means you will have 2 different room's circuits passing right by each other in the same wall. Well, that's silly.

And besides... most rooms will be very light load (unless you are madly heating with those cheapie portable heaters). It will only be 1 or 2 rooms that become the home office or child's PC gaming room. Of course, you never know which that will be.

I vastly prefer the concept of (coarsely) "1 circuit per wall line". A typical room has 4 walls, so it will be in contact with 4 circuits.

So e.g. 1 circuit per outside wall... 1 circuit running along the dividing walls between a series of rooms... how it works on interior walls is fairly particular to the layout of your home, but don't feel it must rigidly be 1 circuit per wall. You'll get 3-4 in most cases and that's good enough.