What size breakers

[Orinoco]

Hi All, got a question, new house build single story

 

What size breakers should be used for the below list.

18,000 BTU,  LG inverter  air con                      

12,000 BTU,  LG inverter  air con   x2

9,000 BTU,   LG inverter  air con

150 Hitachi water pump

3500, watt sharp shower. X2

8 power plugs per zone, ( single circuit ) 4 zones  3 bed rooms and lounge, normal fans tv, pc.

8 power plugs, 1 zone, kitchen, wash machine, toaster, micro wave, fridge. Coffee machine.

Lights 3 zones, complete house inside. Front and rear external lamps 6 each.

All  run on 2.5 wire.

All lights 1.5 wire. ( no wire run is more then 10 meters

Been looking at Square D Shndeider consumer unit 18 breakers

Plus 63 amp MCB with RCBO built in. but the breakers are 6 x 32amp , 6 x 20amp , 6 x 16 amp

Do they seam a bit high. The unit comes populated with the breakers .

 

Just trying to get an idea about this before the spark starts connecting stuff up in the next month.

I don’t know much about electrics, but always get the wife to hold my hand when doing anything.

 

Any help would be most welcome.

Thanks

 

 

 

[bankruatsteve]

The light circuits can go on 10A breaker.  The rest should use 20A.  Consider going with 32A breaker to the shower unit along with 4mm² for potential future upgrade.  Also, it is recommended to go with two 20A circuits to the kitchen to allow for diversity when multiple appliance running.

[Orinoco]

6 minutes ago, bankruatsteve said:

The light circuits can go on 10A breaker.  The rest should use 20A.  Consider going with 32A breaker to the shower unit along with 4mm² for potential future upgrade.  Also, it is recommended to go with two 20A circuits to the kitchen to allow for diversity when multiple appliance running.

Hi  Bankruatsteve 

Thank you for your reply.

20A ok for air cons ?

 

Thanks again

[Crossy]

To expand on @bankruatsteve  excellent notes.

 

20A on 2.5mm² cable will do all your small power including the aircons (which should each have their own breaker). The 16A breakers on the lights will be OK on 1.5mm² cable. Run 4mm² on the 32A breakers for your water heaters.

 

Keep any outside lighting and outlets on their own breakers so you can isolate when the wet gets in (it will) so your RCBO will at least stay on and keep the rest of the house working.

 

[Orinoco]

5 minutes ago, Crossy said:

To expand on @bankruatsteve  excellent notes.

 

20A on 2.5mm² cable will do all your small power including the aircons (which should each have their own breaker). The 16A breakers on the lights will be OK on 1.5mm² cable. Run 4mm² on the 32A breakers for your water heaters.

 

Keep any outside lighting and outlets on their own breakers so you can isolate when the wet gets in (it will) so your RCBO will at least stay on and keep the rest of the house working.

 

Hi Crossy

Thank you for your reply.

all good.

Just one fly in the ointment, the wires to the shower are already in the pipes

in the walls !!!!!!! oh no. will 2.5 wire be ok, there will be no add on's to this circuit.

 

[bankruatsteve]

Well, you can't use the 32A breakers then.  3500W on 2.5mm² is good.

 

Suggest you go with unpopulated CU and go with breakers sized to your plan.

[Crossy]

5 minutes ago, Orinoco said:

Hi Crossy

Thank you for your reply.

all good.

Just one fly in the ointment, the wires to the shower are already in the pipes

in the walls !!!!!!! oh no. will 2.5 wire be ok, there will be no add on's to this circuit.

 

Limit your shower heaters to <4.5kW and you'll be good to go. You should  replace the heater breakers with 20A.

 

[Orinoco]

Just now, Crossy said:

 

Limit your shower heaters to 4.5kW and you'll be good to go. You should really replace  heater the breakers with 20A.

 

Thank you

got a bit worried then !!!!!!!!!!!!

All good

Thank you.

[MJCM]

9 minutes ago, Crossy said:

Keep any outside lighting and outlets on their own breakers so you can isolate when the wet gets in (it will) so your RCBO will at least stay on and keep the rest of the house working.

 

DC, wouldn't it better if he uses these one for his outside lighting and outlets?

 

But the total price tag will be a bit higher

 

https://www.lazada.co.th/products/rcbo-1-pole-10a-50a-30ma-schneider-circuit-breaker-earth-leakage-i2345807881-s7919449767.html

[Crossy]

2 minutes ago, MJCM said:

DC, wouldn't it better if he uses these one for his outside lighting and outlets?

 

Yes!

 

Looking at his image in the OP I don't actually see and RCBO/RCD included, which would be a fail on his MEA/PEA inspection!

 

[Orinoco]

2 minutes ago, Crossy said:

 

Yes!

 

Looking at his image in the OP I don't actually see and RCBO/RCD included, which would be a fail on his MEA/PEA inspection!

 

Wow Thought it was in a single combined unit with MCB.

 Just shows what i don't know !!!!!!!

[Crossy]

2 minutes ago, Orinoco said:

Wow Thought it was in a single combined unit with MCB.

 Just shows what i don't know !!!!!!!

 

It might be but it's not obvious from the image and I don't see RCBO mentioned. Do you have an actual link to the item?

 

[MJCM]

5 minutes ago, Orinoco said:

Wow Thought it was in a single combined unit with MCB.

 Just shows what i don't know !!!!!!!

You have them for example:

 

https://www.lazada.co.th/products/6-rcbo-stc-gold-32a-50a-63a-100-i2754774848-s10005481575.html

 

but we looked and they are limited in size (slot wise) so we bought the individual Schneider ones.

 

But the price of those is significantly higher then regular ones (see previous link I posted they are around the 8xx THB Mark per piece)

[bankruatsteve]

1 minute ago, Crossy said:

It might be but it's not obvious from the image and I don't see RCBO mentioned

The image I see in the OP says "RCBO 63A" but it looks like regular breaker to me.

[Orinoco]

10 minutes ago, Crossy said:

 

It might be but it's not obvious from the image and I don't see RCBO mentioned. Do you have an actual link to the item?

 

Here you go

oops updated now

 

https://www.lazada.co.th//products/i1644272481-s4551520557.html?spm=a2o4m.cart.0.0.30bf6108fBwMQs&urlFlag=true

[bankruatsteve]

Obviously, the image doesn't match the description given.  Again suggest you go to your local "Home" place and DIY for the configuration.

[Crossy]

OK, it definitely says RCBO in the description but as Steve notes it doesn't look like one in the image.

 

[Crossy]

9 minutes ago, bankruatsteve said:

The image I see in the OP says "RCBO 63A" but it looks like regular breaker to me.

 

Yeah, I made the mistake of reading the text description 

[Orinoco]

I'm off to Global house tomorrow and they stock them so can have a look at MCB/RCBO, i will let you all know.

Thanks for you help guys.

 

[Crossy]

If there's a really good price on the configured unit then spare MCBs of a more appropriate size are not expensive.

[Cardano]

Ok, first some fundamentals;

1. Cable is sized to provide the required full load current at rated voltage for the end consumer.

2. MCB is sized to protect the cable (not the end consumer)

3. All cables have a maximum current carrying capacity based on voltage divided by resistance per Km (R1+R2). Cables are then derated based on ambient temperature (typically standard ratings are based on 20 degs C), type of insulation and installation method.

 

So for your 1.5mm 2 core PVC insulated cable recommended maximum load after derating for temperature at 30 degs C (because we're in Thailand) PVC insulation and installation in conduit enclosed in a wall is 12.64A. As stated above the MCB needs to protect the cable so MCB should be either 10A or less.

Similarly your 2.5mm cable maximum load should not exceed 20.6A and be protected by 16A MCB or less.

 

Maximum load for 1.5mm circuit = 220V*10A= 2.2kW 

Max load for 2.5mm circuit = 220V*16A= 3.52kW

All MCBs are designed to operate without trip up to 1.15% of their rating

Hence all your loads that you have stated will be okay based on 10A and 16A MCBs.

 

As for earth fault/leakage protection this is another ball game in Thailand, first you need to ensure you have installed a functional earth system with enough earth rods to achieve a earth loop impedance of less than 5 ohms to enable your RCDs or RCBOs to trip in less than 0.4 seconds when installed in circuits requiring personnel protection (showers, hand held appliances etc.). Suggest you get a reputable sparky who knows what their doing to check this for you otherwise consequences could be.......well not good. 

 

My advice would be to buy consumer unit with enough capacity for all consumer circuits plus 25% spare. Fit all socket, shower and water heater circuits with dedicated RCBOs, all other circuits standard MCBs. Alternative is split phase board with RCD protection and standard MCBs.

DO NOT buy one of those Safe-T boards, use only good quality reputable branded products.

 

Hope the above is some help.

[Orinoco]

52 minutes ago, Cardano said:

Ok, first some fundamentals;

1. Cable is sized to provide the required full load current at rated voltage for the end consumer.

2. MCB is sized to protect the cable (not the end consumer)

3. All cables have a maximum current carrying capacity based on voltage divided by resistance per Km (R1+R2). Cables are then derated based on ambient temperature (typically standard ratings are based on 20 degs C), type of insulation and installation method.

 

So for your 1.5mm 2 core PVC insulated cable recommended maximum load after derating for temperature at 30 degs C (because we're in Thailand) PVC insulation and installation in conduit enclosed in a wall is 12.64A. As stated above the MCB needs to protect the cable so MCB should be either 10A or less.

Similarly your 2.5mm cable maximum load should not exceed 20.6A and be protected by 16A MCB or less.

 

Maximum load for 1.5mm circuit = 220V*10A= 2.2kW 

Max load for 2.5mm circuit = 220V*16A= 3.52kW

All MCBs are designed to operate without trip up to 1.15% of their rating

Hence all your loads that you have stated will be okay based on 10A and 16A MCBs.

 

As for earth fault/leakage protection this is another ball game in Thailand, first you need to ensure you have installed a functional earth system with enough earth rods to achieve a earth loop impedance of less than 5 ohms to enable your RCDs or RCBOs to trip in less than 0.4 seconds when installed in circuits requiring personnel protection (showers, hand held appliances etc.). Suggest you get a reputable sparky who knows what their doing to check this for you otherwise consequences could be.......well not good. 

 

My advice would be to buy consumer unit with enough capacity for all consumer circuits plus 25% spare. Fit all socket, shower and water heater circuits with dedicated RCBOs, all other circuits standard MCBs. Alternative is split phase board with RCD protection and standard MCBs.

DO NOT buy one of those Safe-T boards, use only good quality reputable branded products.

 

Hope the above is some help.

Hi Cardano

Thank you for your very detailed help 

Will get dedicated RCBO breakers for the 2 showers, got to be good.

Off to Global House tomorrow, so will check what they have.

Thanks again.

 

 

 

[cliveshep]

Thais seem to have mental blocks with polarity and earthing and when we bought our 20 year old house and started alterations and extensions that was the first thing we found. Our builder professed to be a qualified sparkie, stuck us in a new 10-way box without turning off outside, not sure how he handled the live pair coming in, managed to connect the incoming pair the right way round but screwed the box back shorting it out. 

 

We ran a pair of 2.5's on a 32A out to a separate breaker box in the workshop, a pair of 2.5's to the kitchen which I made into a ring main on a 32A a la UK style using those Thai sockets that also accept UK plug-tops. We have an American side-by-side fridge freezer, A 6 cu ft chest freezer, microwave and kettle, coffee maker, washing machine, and all the usual gadgets, food processor, blenders, rice cooker etc.

The lighting we pretty much just altered to suit which was when we found those light switches with sockets combined with polarity reversed on many.

 

The builder ran two 1.5 singles as an earth to an outside earth rod that was utterly ineffective. Outside has a thinnish layer of top soil over 18 inches of sand fill over the mud of a former rice field. The ground floor is a suspended floor of concrete planks concreted over with a 3 inch screed and 20mm thick granite tiles. Underneath is a water filled void down to the rice-field mud. The outside earth-rod was a wonderfully useless 2 feet long! The workshop machines were live when running - the neutrals carrying earth leakage from somewhere and I had to use gloves when using them. 

 

The new and existing wiring in the new box was connected brown to the neutral bus and blues/blacks to the breakers. The builder insisted that was correct so I stopped him doing any more electrical work and took it on myself. I used a ratchet crimper and crimps to extend all the brown wires the muppet had cut short and re-wired the box correctly. The air-con man had walked off refusing to connect any of the 6 units insisting that the set-up was dangerous - it was! I had to re-wire all the outside units to get correct colour codes and polarity!

 

Next was the earthing, I cross-bonded everything I could, structural steel, ceiling grids, you name it and ran 4 separate pairs of 1.5 singles (I had loads of green 1.5 single to use up!) out to the 4 outside corners of the property connected to the earth bus in the breaker box. Using my Kango hammer (Chinese copy of course, this is Thailand after all) I drove down 2 metre copper-coated earth rods in all 4 corners outside in an attempt to create an equipotential enclosure.

 

Finally having problems with our breaker box tripping even with a new main switch I got in a proper electrician thinking I had a neutral fault with rats chewing the wire somewhere - nope - it was the main breaker. Sparkie sold me a new one of a different pattern and cross-bonded the neutral and earth together. Voila - all our problems vanished then. So we have the Thai equivalent of the UK PME system now with a good earth system.

[Orinoco]

On 11/15/2021 at 2:27 PM, Crossy said:

If there's a really good price on the configured unit then spare MCBs of a more appropriate size are not expensive.

Well went Global House and Mega home, no 18 set unit, max was 14 same type. as Op. ( schneider ) or go up to a big metal box at 5000, starting price, with no breakers inside at all, no thank you.

But you were right about the picture and not being a RCBO , its a standard MCB. and that is what comes with the 14 set 

at Global House.  also no  no 10 amp breakers of the same type in stock.

Had a better look online when got home, and found an 18 set blank box and just ordered the correct breakers for it all.

with x2 , 20 amp RCBO for showers and a 63 amp  MCB / RCBO combined breaker.

I should be ok now..

 

[bankruatsteve]

12 minutes ago, Orinoco said:

20 amp RCBO for showers

Virtually all shower units come with "ELCB" which, although a misnomer, is RCD protection at the unit.  IE: RCBO on those might be redundant.  Better use would be circuits with outside outlets and any outlets in the bathrooms (the latter could chain to the shower and use the RCBO for both.)

[Orinoco]

28 minutes ago, bankruatsteve said:

Virtually all shower units come with "ELCB" which, although a misnomer, is RCD protection at the unit.  IE: RCBO on those might be redundant.  Better use would be circuits with outside outlets and any outlets in the bathrooms (the latter could chain to the shower and use the RCBO for both.)

I got them on order now, won't hurt to have it in the consumer unit will it ?

I'm not very up on electrics.

 

Edit, ok i got it now, just trying to get the spark to do that, will be the hard bit !!!!!!!!

Will try when the day comes.

Thanks for your time and help

 

[NanLaew]

Little bit of a hijack here since I am rewiring a small outside structure as my man-cave. I will be using the same brand Schneider CU as the OP but with only 4 single-pole breaker slots; one each for lights, internal wall sockets, outside wall sockets and a single aircon. It's only 4m x 4m so no need for spares envisaged.

 

 

With LED down lights, computers, a small work bench, small fridge, fan and the aircon, what size dual-pole MCB/RCBO will suffice? I was thinking 32A? My understanding is the RCBO is mandatory for MEA/PEA inspections so I could go with a regular MCB since this won't be inspected?

 

What gauge of input wire do I need to feed this. I will be taking a L/N spur from the main external house breaker.

 

I was also thinking of using one of those RCBO single-pole breakers for the external outlet. Am I right in thinking if there's an earth-leakage issue on that outlet, the single-pole breaker will trip but the main RCBO (if I use one) will stay on?

 

 

Here's the MCB/RCBO since the graphic in the OP's post indicated a regular MCB instead of the RCBO that was in the spec.

 

 

Thanks

NL

 

[sometimewoodworker]

5 hours ago, NanLaew said:

I was also thinking of using one of those RCBO single-pole breakers for the external outlet. Am I right in thinking if there's an earth-leakage issue on that outlet, the single-pole breaker will trip but the main RCBO (if I use one) will stay on?

That’s a definite maybe. Depending on the sensitivity of the main RCBO and the RCBO feeding the spur it’s possible if they are the same that either one, or even both, will trip, if however the main is set to be less sensitive than the spur it’s more likely than not that the spur will trip first. Don’t forget that age can have an effect so things may change over time.

[sometimewoodworker]

5 hours ago, NanLaew said:

My understanding is the RCBO is mandatory for MEA/PEA inspections so I could go with a regular MCB since this won't be inspected?

Deciding not to use an RCBO because it won’t be inspected is in my opinion the hight of stupidity. 

[NanLaew]

11 hours ago, sometimewoodworker said:

16 hours ago, NanLaew said:

My understanding is the RCBO is mandatory for MEA/PEA inspections so I could go with a regular MCB since this won't be inspected?

Deciding not to use an RCBO because it won’t be inspected is in my opinion the hight of stupidity.

The house was wired over 15 years ago by an unsupervised, 'stupid' and usually drunk electrician before RCBO's were invented. The whole house that has been safely inhabited by a dozen, arguably 'stupid' people all this time needs a total rewiring. That's NOT going to happen.

 

The 'spur' I speak of comes off the live side of the 100A main breaker that is mounted in a box on an outside wall between the city power pole and the main house. The spur is not from the non-RCBO provisioned CU inside the house.

 

This is so you understand that no RCBO has ever been seen anywhere near the whole 'stupid' installation. Ever.

 

Getting back to making my man-cave as safe as possible, I will have an RCBO as the main breaker in the new, bespoke CU. Will 32A be the correct size for the load I suggested earlier?

 

I will also invest in a single RCBO/CB for the external sockets. The rest will all be regular CB's.

 

Where should I place the ground spike and do I need more than one?

 

Thanks!

NL