Circuit Breaker sizes.

[StraightTalk]

The country/village electrician just completely rewired the entire house of my in-laws. He incorporated ground wiring, installed a 8' copper rod, a 'Safety-Cut' circuit breaker box, new power points and electrical on/off switches for lights and fans.

The refurbished house is a 2 floor building.

Upstairs:
8 ceiling lights (15 Watts Compact Fluorescent Light (CFL) bulbs.);
8 power points (for wall-mounted 16" Hatari oscillating fans, fridge, TV, computer etc.);
1 (bathroom) hardwired water heater;
3 10000 BTU airconditioners.
He dedicated 1 breaker @ 15 amps for the 8 ceiling lights;
1 breaker @ 20 amps for the 8 power points; and
1 breaker @ 30 amps each for the water heater and airconditioners.

Downstairs:
10 ceiling lights (15 Watts Compact Fluorescent Light (CFL) bulbs.);
3 ceiling fans (Hitari 18" orbit-type);
10 power points (for fridge, TV, washing machine, water pump, hot water urn, rice cooker etc.);
He dedicated 1 breaker @ 15 amps for the 10 ceiling lights and 3 ceiling fans; and
1 breaker @ 20 amps for the 10 power points.

I am unsure if the breaker are correctly/safely sized and apreciate expert advise if changes to this electrical setup need to be done. TIA.

[stubuzz]

What size is the wiring?

[StraightTalk]

What size is the wiring?

I think he used 1.5 mm for the ceiling lights and fans and 2.5 mm for the power points, water heater and air conditioners.

[StraightTalk]

What size is the wiring?

I think he used 1.5 mm for the ceiling lights and fans and 2.5 mm for the power points, water heater and air conditioners.

CORRECTION - He definitely used 1.5 mm for the ceiling lights and fans and 2.5 mm for the power points, water heater and air conditioners.

[bankruatsteve]

Circuit breakers protect the wire from over-current and the size of the wire determines how much current (amps) it can handle. For 2.5mm2, 20a breaker is OK but 30a is NOT. If the A/C's are on their own individual circuit, it's probably not a worry though.

You didn't say how big the house is but sounds like way to few "power points" which will lead to plugging almost everything into those atrocious extension cords and probably defeating any ground. The US NEC requires receptacles no more than 6' spacing. Here there is no code for that and I am continually amazed to see even new construction sometimes with only 1 outlet per room. I have 7 outlets just in the kitchen.

[StraightTalk]

Circuit breakers protect the wire from over-current and the size of the wire determines how much current (amps) it can handle. For 2.5mm2, 20a breaker is OK but 30a is NOT. If the A/C's are on their own individual circuit, it's probably not a worry though.

You didn't say how big the house is but sounds like way to few "power points" which will lead to plugging almost everything into those atrocious extension cords and probably defeating any ground. The US NEC requires receptacles no more than 6' spacing. Here there is no code for that and I am continually amazed to see even new construction sometimes with only 1 outlet per room. I have 7 outlets just in the kitchen.

Okay then, as stated in my original post, "1 breaker @ 30 amps each for the water heater and airconditioners".

I didn't state that the power points are in fact 'double-power points' - sorry about that. The number of double power points seem at this stage more than adequate.

We all have different requirements; We can easily manage with less than 7 single outlets in our kitchen.

But we digress slightly, I wish to be certain if the breakers for the individual circuits are correctly sized as am unsure if an 'oversized' breaker is safe to utilize, e.g. 1 breaker @ 15 amps for 8 x 15 Watts CFL bulbs (ceiling lights).

[bankruatsteve]

10a -15a breaker is normally used for 1.5mm2 wire. That could power over 100 20W lights although that wouldn't be a sensible thing to do.

20a breaker is normally used for 2.5mm2 wire.

The 30a breaker is oversize for 2.5mm2 wire.

BTW: I don't know why single plug outlets are even made. All mine are double. Anyway, it's more about the convenience (not having to use extensions for anything) than the quantity.

Edited May 28, 2015 by bankruatsteve

[Crossy]

+1 on the above ^^^.

What size water heaters do you have?

There are times when an breaker oversized for the cable is acceptable (e.g. if a cable overload is deemed impossible and the breaker is only required to provide short-circuit protection), but I would be changing the 30A for 20A units.

[StraightTalk]

+1 on the above ^^^.

What size water heaters do you have?

There are times when an breaker oversized for the cable is acceptable (e.g. if a cable overload is deemed impossible and the breaker is only required to provide short-circuit protection), but I would be changing the 30A for 20A units.

What size water heaters do you have?

The size of water heater is 4.5kw.

There are times when an breaker oversized for the cable is acceptable (e.g. if a cable overload is deemed impossible and the breaker is only required to provide short-circuit protection)

Do I understand correctly that "1 breaker @ 15 amps for 8 x 15 Watts CFL bulbs (ceiling lights)" falls under this criteria and therefore is safe?

but I would be changing the 30A for 20A units.

Could you please elaborate on your suggestion changing from 30A to 20A?

Thanks.

[Crossy]

4.5kW equates to 20.5A, on the line for 2.5mm² cable, the cable will get quite warm. It will be ok but no room for installing a bigger heater in future.

Your 15A lighting breaker is not oversize for the 1.5mm² cable, one would normally replace it with a 5A unit in case a CFL fails catastrophically (potential for fire), but there's no immediate hazard.

A 30A breaker is oversize for 2.5mm² cable, if that cable only supplies only the a water heater or aircon and is short enough that the 30A breaker can provide short-circuit protection then, again, there's no immediate hazard (this is a time an oversize breaker is permitted). BUT if some bright spark adds something to that circuit in future a cable overload and potential fire is possible.

Breakers are cheap!

Note, all bets are off if there's a bunch of taped joints hidden in the roof space or elsewhere, lots of hotspots waiting to cause problems.

[StraightTalk]

4.5kW equates to 20.5A, on the line for 2.5mm² cable, the cable will get quite warm. It will be ok but no room for installing a bigger heater in future.

Your 15A lighting breaker is not oversize for the 1.5mm² cable, one would normally replace it with a 5A unit in case a CFL fails catastrophically (potential for fire), but there's no immediate hazard.

A 30A breaker is oversize for 2.5mm² cable, if that cable only supplies only the a water heater or aircon and is short enough that the 30A breaker can provide short-circuit protection then, again, there's no immediate hazard (this is a time an oversize breaker is permitted). BUT if some bright spark adds something to that circuit in future a cable overload and potential fire is possible.

Breakers are cheap!

Note, all bets are off if there's a bunch of taped joints hidden in the roof space or elsewhere, lots of hotspots waiting to cause problems.

Thanks for elaborated and educational response.

As mentioned in my orignal post, the house is being completely refurbished (incl. new roof, windows, wall/roof/ceiling insulation etc.) and had been rewired completely. In fact, since there is still other work to be done the in-laws haven't moved in yet.

I take your advice and ask the electrician to replace the 2 x 15A lighting/fan breakers with 2 x 5A units.

Although there seems to be no immediate fire hazard, I am going to ask the electrician to replace the 2.5mm dia cable with a 3.+mm dia cable also.

And I am absolutely certain that there aren't any other "taped joints" hidden anywhere in the house nor will anybody add anything to the circuit in the distant future. I intend marking the breaker box panel in Thai indicating the purpose of all existing circuit breakers and try to educate the in-laws accordingly.

Also, the electrician used proper junction boxes covered by a lid and the all joints in junction boxes and on/off switches have been fastened with twist-on (cone) wire connectors.

Thanks again, I feel much more confident about this particular electrical setup.

[Crossy]

Yeah ^^^, use 4mm² cable on the water heater and drop the aircon beakers to 20A and all should be good.

Note that the cable sizes are not diameter but cross-sectional area. Standard sizes are 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35 etc. mm², you can get the current ratings off the manufacturer's website.

[Crossy]

As this is a rewire has the contractor included:-

3-pin outlets with the ground terminals actually connected to a proper ground rod.

A ground connection to the water heaters.

A Safe-T-Cut type breaker (RCD, RCBO) in the distribution board.

The latter is essential for the safety of water heaters particularly.

[StraightTalk]

Yeah ^^^, use 4mm² cable on the water heater and drop the aircon beakers to 20A and all should be good.

Note that the cable sizes are not diameter but cross-sectional area. Standard sizes are 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35 etc. mm², you can get the current ratings off the manufacturer's website.

Yeah ^^^, use 4mm2 cable on the water heater and drop the aircon beakers to 20A and all should be good.

Okay, will do.

Do you consider the circuit breakers for the power points are sized adequately?

Note that the cable sizes are not diameter but cross-sectional area. Standard sizes are 1, 1.5, 2.5, 4, 6, 10, 16, 25, 35 etc. mm2, you can get the current ratings off the manufacturer's website.

I knew you'd pick on that; I used 'dia' because I couldn't generate the small '2' after the mm.

[StraightTalk]

As this is a rewire has the contractor included:-

3-pin outlets with the ground terminals actually connected to a proper ground rod.

A ground connection to the water heaters.

A Safe-T-Cut type breaker (RCD, RCBO) in the distribution board.

The latter is essential for the safety of water heaters particularly.

1. Yes, 8' copper rod was installed together with 3-pin outlets (power points); The copper rod is connected to the 'Safe-T-Cut' Circuit Breaker Panel Box.

2. No. I thought connecting the water heater to the 8' copper rod via the 'Safe-T-Cut' Circuit Breaker Panel Box would suffice. If not, would installing an additional ground rod dedicated to the water heater be adequate?

Please note, the water pipe is non-metallic PVC.

3. The electrician installed a new 'Safe-T-Cut' Circuit Breaker Panel Box which only contains one (1) 'Main' breaker and eight (8) circuit breakers. I thought dedicating one 30A (1) breaker for the water heater would be sufficient. Please advise on how to rectify if this is inadequate.

[Crossy]

1. OK

2. What you have is correct.

3a. Does the panel have a 'Test' button, Safe-T-Cut make standard breakers as well as RCBO's, just need to clarify what you have (or post a photo).

3b. Yes, dedicating the 30A to the water heater is correct.

[StraightTalk]

1. OK

2. What you have is correct.

3a. Does the panel have a 'Test' button, Safe-T-Cut make standard breakers as well as RCBO's, just need to clarify what you have (or post a photo).

3b. Yes, dedicating the 30A to the water heater is correct.

Re: 3a. I am pretty that the panel has no 'Test' button and guess it is just a basic version incorporating only a 'Main' switch followed by a number of circuit breakers. Is it possible adding a 'Test' button to the existing panel?

[Crossy]

If you have no "Test" button then you have no earth leakage protection.

This is a serious omission for a rewire as it could save you from electrocution in the shower or if you get hold of a live wire somewhere.

Do check what you have, it may be possible to replace the main breaker with an RCBO, or if not possible, add a front end RCBO in a separate box. Ask your sparks or (probably better) your local Safe-T-Cut rep. Something like this http://www.safe-t-cutrangsit.com/index.aspx?pid=2ffefa8a-0f2c-47c3-9f21-d811b2be61d7&iid=5cf93687-393c-4de2-917d-ceba28ba17dd

[StraightTalk]

If you have no "Test" button then you have no earth leakage protection.

This is a serious omission for a rewire as it could save you from electrocution in the shower or if you get hold of a live wire somewhere.

Do check what you have, it may be possible to replace the main breaker with an RCBO, or if not possible, add a front end RCBO in a separate box. Ask your sparks or (probably better) your local Safe-T-Cut rep. Something like this http://www.safe-t-cutrangsit.com/index.aspx?pid=2ffefa8a-0f2c-47c3-9f21-d811b2be61d7&iid=5cf93687-393c-4de2-917d-ceba28ba17dd

I am going to go back to the construction site soon. If there is no 'Test' button I'll definitely instruct the electrician to implement your advices.

Thanks again for all the valuable information provided.

Cheers...

[StraightTalk]

If you have no "Test" button then you have no earth leakage protection.

This is a serious omission for a rewire as it could save you from electrocution in the shower or if you get hold of a live wire somewhere.

Do check what you have, it may be possible to replace the main breaker with an RCBO, or if not possible, add a front end RCBO in a separate box. Ask your sparks or (probably better) your local Safe-T-Cut rep. Something like this http://www.safe-t-cutrangsit.com/index.aspx?pid=2ffefa8a-0f2c-47c3-9f21-d811b2be61d7&iid=5cf93687-393c-4de2-917d-ceba28ba17dd

I am going to go back to the construction site soon. If there is no 'Test' button I'll definitely instruct the electrician to implement your advices.

Thanks again for all the valuable information provided.

Cheers...

I have a few more questions, please:

1. Since it appears that I have a very basic version of the Safe-T-Cut panel box, would you know if a RCBO (Residual Current Breaker with Overload protection) could be added to this panel?

Something like displayed here: https://www.google.co.th/search?q=rcbo&sa=X&biw=1087&bih=480&tbm=isch&tbo=u&source=univ&ei=CQJoVYuALYyIuASdq4PYCQ&ved=0CBwQsAQ

This would probably more cost efficient than the box shown here:

http://www.safe-t-cutrangsit.com/index.aspx?pid=2ffefa8a-0f2c-47c3-9f21-d811b2be61d7&iid=5cf93687-393c-4de2-917d-ceba28ba17dd

2. Does a RCBO replace the Main breaker or is it necessary to install both RCBO and Main breakers?

3. How does one test a RCBO for leakage in a less sophisticated environment and what are the recommended frequencies for testing?

I looked at http://www.eaton.com/Eaton/OurCompany/NewsEvents/NewsReleases/PCT_255273

it's all very technical and seems complicated.

4. Do you know of a simple, straightforward way testing for leakages and is there some kind of testing equipment required?

Thanks.

[Crossy]

1. It may be possible, there are a number of different formats (DIN, plug-in), I don't know what format the Safe-T-Cut panel uses.

2. You can use an RCBO as the main breaker if you can get one that fits.

3. The simplest test for an RCBO is to press the "Test" button as recommended by the manufacturer. There are very basic testers around for $100 or so if you want to go a bit further.

4. Testing for leakage can be a difficult and confusing job requiring specialist knowledge and test gear. A methodical approach can be used to locate a leak which regularly trips out an RCD/RCBO but if it's unpredictable you're in for a world of frustration.

EDIT There's nothing to stop you putting a suitably rated RCD / RCBO on a small DIN box and installing it in front of your existing panel in the same way as the big Safe-T-Cut box would be, probably a cheaper solution. Effectively creating something like this http://www.safe-t-cutrangsit.com/index.aspx?pid=2ffefa8a-0f2c-47c3-9f21-d811b2be61d7&iid=7fe6f7c3-e326-41ee-8947-85e908991898

[StraightTalk]

I was unsuccessful sourcing a single RCBO module to fit into my existing Safe-T-Cut panel and decided buying a new unit. The new panel is named "Safe-T-Cut Smart Consumer Unit & RCBO Premier".

A)
The box panel consists of a:-
1) MAIN breaker, model: C010E, (which appears to be a 3-in-1 unit, i.e. the 3 breakers can not be switched on/off individually);
2) 10 Way Circuit Breaker RCBO Module, model: R20 - 63A; and
3) 10 Circuit Breakers - 3 rated at 16 A, 4 rated at 20 A and 3 rated at 32A.

The RCBO module has a Test button and a Sensitivity dial button. The sensitivity ranges are: 6, 10, 20 and 30 mA.

How does one determine the correct the sensitivity setting?


The aircondition I am propose to install is rated at 9000 btu/1000 watt.

I calculated that the circuit breaker needs to be rated at about 5.2amp (watt/voltx1.25).

I therefore propose to replace one of the breakers with a 10A unit for this particular airconditioner as there is no lower rated breaker available for this particular box panel.

How critical is it to the electrical circuit installing an 'oversized' breaker?
TIA

[Crossy]

The 'correct' setting for the sensitivity is the lowest that will stay engaged without nuisance trips during power fluctuations (lightning etc.)

For your aircon I would wire it in 2.5mm² and use a 20A breaker, even though the run current is 5A or so the start surge will be significantly higher and could trip the 10A breaker.

[StraightTalk]

The 'correct' setting for the sensitivity is the lowest that will stay engaged without nuisance trips during power fluctuations (lightning etc.)

For your aircon I would wire it in 2.5mm² and use a 20A breaker, even though the run current is 5A or so the start surge will be significantly higher and could trip the 10A breaker.

Okay, thanks again for advices.