Consumer Unit basics

[wpcoe]

I just moved into a townhouse and one of my first concerns was evaluating the electrical system. I like to have earthing to as many items as possible, and I noticed a (thin) earth wire coming down the front wall and going through the tiles of the front parking area, presumably to a ground rod. So, hoping to find an intact and populated earth bar in the consumer, I took the cover off:

Much of what I know about consumer units I've learned here on the forum, so my exposure to various types of systems is not great. I thought my last townhouse had an "A" section with all the green earth wires and a wire leading off to the ground rod, and "C" had the live wires for each circuit, with a vertical neutral bar to the left of the main breaker. This unit is clearly different.

1. What are the wires attached to "A"? I thought black wires were live, but are those black wires actually the neutrals?

2. What are the wires attached to "B"? Are those yellow and grey wires the live wires?

3. Is the left bottom wire on the main breaker the neutral (leading to the "A" bar?) and the right bottom wire the live, leading to "C"?

Don't worry, I'm not planning any surgery within the consumer unit, I just want to understand how it's wired. I see nothing in the consumer unit to indicate the ability to easily earth any more outlets without running wires directly to what I hope is a ground rod out front of the townhouse.

[RichCor]

It's important to remember that electrical wires are color-blind (or at least color neutral) when it comes to what runs over them, though your box certainly looks color confused.

What the heck is up with those four YELLOW wires on the first three MCB and the Neutral Bar.

Your MAINS BREAKER seems to be just that, Neutral out fed to the Neutral bus bar. Live out fed to the MCBs.

A would be the common bus for your NEUTRALS

C would be for common LIVE into each MCB (either via a common bus/strip bridged or jumpered common) though you can't see this from the picture

B would be the individual MCB branch circuit LIVE Out

Yea, the box seems to be lacking a dedicated Earth-Ground Bus Bar. No extra Earth-Ground wires in sight.

No Residual Current Device in sight either.

[Crossy]

Rich got there first, +1 on all he says.

[Forkinhades]

I think your biggest concern is to make sure you have a Safety-cut device upstream of that unit.

Please read the pinned thread on how to make your thai electrics safe.

[wpcoe]

It's important to remember that electrical wires are color-blind (or at least color neutral) when it comes to what runs over them, though your box certainly looks color confused.

What the heck is up with those four YELLOW wires on the first three MCB and the Neutral Bar.

Your MAINS BREAKER seems to be just that, Neutral out fed to the Neutral bus bar. Live out fed to the MCBs.

A would be the common bus for your NEUTRALS

C would be for common LIVE into each MCB (either via a common bus/strip bridged or jumpered common) though you can't see this from the picture

B would be the individual MCB branch circuit LIVE Out

Yea, the box seems to be lacking a dedicated Earth-Ground Bus Bar. No extra Earth-Ground wires in sight.

No Residual Current Device in sight either.

Thanks for the explanation. It makes sense, though I wouldn't have quite had it right had I not asked.

So, there is some non-apparent connection running down the "C" bar to deliver the current to each breaker? That's the part I wouldn't have gotten right.

What's your guess is the deal with the taped connection above the "B" bar toward the right end?

I think your biggest concern is to make sure you have a Safety-cut device upstream of that unit.

Please read the pinned thread on how to make your thai electrics safe.

That's my next project: Take a close-up photo of the main breaker to HomePro and see if they have a compatible Safe-T-Cut switch. Then I need to find someone competent to install it. I ain't about to mess with the main wires coming into the box. My guess is it's as simple as unscrewing and pulling the wires from the meter on the pole outside and then replacing the switch, but no way am I going to do that even wearing one-inch rubber soles and insulated rubber gloves.

To later add an air con, how would it be accommodated? Would it tag on to an existing circuit breaker, or would there be an additional circuit breaker installed outside the consumer unit, somehow tied to the main incoming live wire into the box?

[Crossy]

There's a bus-bar running along under the breakers at C, look up underneath.

A DIN mount RCBO will fit in place of your main switch however you may have difficulty finding one (ABB do them). You could add a DIN mount RCD if there's enough room (two unit widths) or maybe combine two of the existing breakers to free up a location.

Failing that, move the main switch into a small DIN box and put the RCD in its place in the CU.

[RichCor]

Thanks for the explanation. It makes sense, though I wouldn't have quite had it right had I not asked.

What's your guess is the deal with the taped connection above the "B" bar toward the right end?

Technically only ONE wire should ever be attached to an MCB 'terminal', though that wire 'circuit' can be daisy-chained or even branched later on -- my guess is it's a Thai-style twisted and taped branch.

I think your biggest concern is to make sure you have a Safety-cut device upstream of that unit.

Please read the pinned thread on how to make your thai electrics safe.

That's my next project: Take a close-up photo of the main breaker to HomePro and see if they have a compatible Safe-T-Cut switch. Then I need to find someone competent to install it. I ain't about to mess with the main wires coming into the box. My guess is it's as simple as unscrewing and pulling the wires from the meter on the pole outside and then replacing the switch, but no way am I going to do that even wearing one-inch rubber soles and insulated rubber gloves.

To later add an air con, how would it be accommodated? Would it tag on to an existing circuit breaker, or would there be an additional circuit breaker installed outside the consumer unit, somehow tied to the main incoming live wire into the box?

An RCD (or Safe-T-Cut device) can be added into your current box, so long as there is room.

But if you plan on adding an Air Con later, it should be on its own dedicated MCB. So, as Crossy suggested, you could combine two underutilized existing breakers into one MCB, then swap out the freed-up MCB with an MCB properly sized for your new Air Con.

If you find you don't have enough room in your box for everything, the suggestion made so far would be to either add a additional box 'upstream' and move the main breaker there or install an external self-contained RCD/Safe-T-Cut box ahead of your box.

While a RCD/Safe-T-Cut device will provide a good fault safety, you may also want to evaluate your Earth-Ground requirements.

Especially for any Class-1 appliances/devices you may be running (ie: Electric Water Heater, Washing Machine, Clothes Dryer, Oven/Cooker, Rice Cooker, Refrigerator, etc.) ...you really want a functioning Earth-Ground anywhere water may spill or a device may melt due to overheat condition. Better the live current finds an Earth Ground rather than find you (previously standing next to the faulty appliance).

[wpcoe]

Okay, I went to HomePro and found the C Team on duty in the electrical section. It was the blind leading the blind. They didn't know what "Safe-T-Cut" was other than a brand of consumer units, and much discussion eruputed when I asked about RCD or RCBO. I kept hearing "CD" like they were discussing a bygone era's music medium.

Finally found ONE gal that knew what I wanted and showed me this:

She said it was 63a and the only other model they carried was 40a, and it was not in stock.

This is my current main breaker:

... and I'm not sure if a 63-amp RCBO (too big?) or a 40-amp RCBO (too small?) would work. She said that mine was 50-amp, but those numbers on the breaker don't clearly say what amperage it is to me -- what is C60N? what is C50? What is 400v~ or 40uv~ ? I do see 10kA. The meter on the pole out side is a 15/45 I think ... need to take another look at it in daylight.

The size of the RCBO looks like it might work as a drop-in replacement for my current main breaker, but until I get it home to compare side by side I won't be sure. If it is the right physical dimension, would either the 63a or 40a RCBO be appropriate?

Regarding the earthing, what initiated this was placing a clothes drier on the front patio. There was a very poorly wired outlet dangling there, with about an extra 2m of loose wire dangling off the other side which was the wire for the water pump. I replaced the outlet with a double, 3-prong outlet fixed to the wall, and we tied in a length of green wire to the existing earth wire in that corner of the patio. We cut off the extra 2m of wire and attached a plug.

I have NO idea what is attached to the earth wire on the patio. All the interior wiring has been put in channels in the wall and plastered over. I need to open the shower water heaters (2) to see if they look like they have an earth wire leading away that *might* lead to that outdoor point.

ISTR mention that sometimes using a condo balcony railing can be a makeshift earth. Would it help if I ran a length of the green wire from a metal point on the water heater and attached it to the metal railing structure separating the townhouses?

[Crossy]

OK the first issue is that the Haco unit is an RCD not an RCBO so it will have to live alongside your current main breaker. The good news is that at 63A it will be fine.

I suspect you'll have fun finding a DIN RCBO outside of a big specialist electrical place

EDIT I see quite a few suitable units on AliExpress which will ship to Thailand.

Something like this http://www.aliexpress.com/item/DPNL-1P-N-63A-230V-50HZ-60HZ-Residual-current-Circuit-breaker-with-over-current-protection-RCBO/1086847618.html?spm=2114.01020208.3.225.w71REf&ws_ab_test=searchweb201556_1,searchweb201644_2_10001_10002_10005_10006_10003_10004_62,searchweb201560_1,searchweb1451318400_6149 would do the trick. Since this is not a new installation (doesn't have to get past a PEA inspection) a 63A unit will be fine (50A seem to be as common as hen's teeth). I've dealt with that seller in the past, known and reliable.

EDIT 2 Whilst the railing may well be a decent earth your neighbours may not understand. If you can access the building steel anywhere that would work, otherwise drill a hole in the patio and bash a rod through.

[canuckamuck]

what's the definition or difference between RCD and RCBO,

[bankruatsteve]

what's the definition or difference between RCD and RCBO,

An RCBO is a combination of over-current breaker (rated in amps) AND an RCD which detects current leakage or ground fault (rated in milliamp).

[RichCor]

... She said that mine was 50-amp, but those numbers on the breaker don't clearly say what amperage it is to me -- what is C60N? what is C50? What is 400v~ or 40uv~ ? I do see 10kA. ...

MCB Nameplate Data

multi9 Multi 9™ is a modular system product line and trademark of Schneider Electric.

All of the products are built in a consistent format with incremental widths of 0.35in. (9 mm) (therefore the name Multi 9)

C60N Unfortunate designation for a Schneider Electric Range of Products of Multi-standard (UL/CSA/IEC) miniature circuit-breakers

'N' designates the breaking capacity type (a, N, H, L)

C50 Curve Code 'C' - 50 A (at 30 °C)

The circuit breaker is labeled with the rated current in amperes, but without the unit symbol "A". Instead, the ampere figure is preceded by a letter "B", "C" or "D", which indicates the instantaneous tripping current — that is, the minimum value of current that causes the circuit breaker to trip without intentional time delay see Wikipedia Circuit Breakers Standard current ratings.

400V~ Rated operational voltage (up to) 400 Volt AC

10kA Breaking capacity: 10kA Icu conforming to EN/IEC 60947-2

IEC157.1 International Electrotechnical Commission

International standards and conformity assessment body for all fields of electrotechnology.

IEC 157 Low voltage switchgear and controlgear, Part 1: Circuitbreakers.

IEC 157-1 = BS EN 60947-2

[10000] Breaking capacity

24207 Schneider Electric product number

see How To Read MCB Nameplate

electricaltechnology.org

[wpcoe]

Not sure what happened. I clearly remember seeing an RCBO -- I showed the letters on the box to the guys who said they "mai mii" RCBO's, but sure enough the 63A one in the photo of is an RCD.

My concern about having 63A replacing 50A was that it would allow overloading of wires/circuits, but since it would be between the main CB and the street side pole, the main CB would still clamp down at 50A. Am I close?

Maybe it's time I made my first purchase from China? Alibaba for US$4.10 isn't much.

Regarding the neighbors not understanding using the railing as an earth, is that because they might get tingles when they touch the railing? If I discretely put a screw on my side, I doubt they'd notice, unless they got shocks.

If I owned this townhouse I would definitely do it right: Install a sturdy earth rod and completely rewire the house. I was looking for ways to take the edge of life-threatening events without a full production that the owner might not approve of.

@RichCor: Thanks for that detailed explanation of the nameplate info on the main breaker. No way I would have determined that it was a 50A breaker.

All of this would be completely a non-hassle in a western country with enforced electrical codes, and licensed electricians. But, since this is not such a country, I want to have as much information as possible so I can monitor what actually is done.

[Crossy]

If the railing is a half decent ground nobody will get a shock, it's the visibility of a wire connected which may prove worrying.

As to using a 63A breaker, many 15/45 meters are protected by 63A if 50A isn't available.

That AliExpress unit I linked to is an RCBO, you can simply replace your current 50A incoming breaker with it with no danger to the supply or meter.

[bankruatsteve]

Unless I'm confused... the 63amp RCD just means that it can handle 63amps - if just RCD it will not trip on over-current. So, the RCD will have absolutely no effect on your main over-current breaker at 50 amp.

It still seems strange that, if your unit was done by professional, that the ground would not be actually grounded. (?)

[Crossy]

Unless I'm confused... the 63amp RCD just means that it can handle 63amps - if just RCD it will not trip on over-current. So, the RCD will have absolutely no effect on your main over-current breaker at 50 amp.

That is correct Steve, an RCD does not provide over-current protection so must be paired with an MCB. The 63A is the maximum operating current beyond which the RCD may randomly trip or (worse) not trip at all..

RCBOs provide the functionality of an RCD and an MCB in one package, handy where space is limited as in our OP's case.

[wpcoe]

I'm still not clear why a 63A RCBO would be considered a safe thing to install. If my power source is 15/45 (forgot to check before I left on a trip this morning) wouldn't I want an RCBO or conventional CB to clamp down at closer to 45A, like the 50A CB I have now? Or, is the extra 13A that would be allowed through not be a problem at all? I'm not doubting your recommendation, Crossy, just trying to understand the operational parameters.

[Crossy]

Electrical installations are very robust things, your 15/45 meter will happily carry a 100% overload for several hours without flinching (but with some loss of accuracy). Same goes for the incoming cables and your village transformer (which is likely overloaded right now). Many, many 15/45 meters are protected by 63A fuses or MCBs, probably more 5/15 meters have no protection whatever.

If your existing load isn't opening the 50A then there's no hazard involved with using a bigger unit, it wont suddenly go bang, the current draw is no different. Unless you're on a (very) long cable you will still get short-circuit protection.

Replacing a breaker with a bigger one 'because it keeps tripping' IS a hazard, evidently the load is close to the limit (actually well over it, a 50A breaker will take over a minute to operate at 100A).

If you are worried and can't get a 50A RCBO then install a 40A RCBO (it will probably never operate on overload) or use a separate RCD and MCB.

EDIT 50A RCBOs do exist but the only ones I can find on the main sources are 3 modules wide (should still fit with the space you have). Like this one http://www.aliexpress.com/item/high-quality-10A-16A-20A-25A-32A-40A-50A-63A-2-pole-transparent-residual-current-earth/32368380458.html?spm=2114.01020208.3.21.vJH8Wd&ws_ab_test=searchweb201556_1,searchweb201644_2_10001_10002_10005_10006_10003_10004_62_61,searchweb201560_1,searchweb1451318400_6149 you need to tell them what current you need when ordering.

FURTHER EDIT I've been doing more research for 2-module wide RCBOs. We have to be very careful as many of the 2-module units are actually 1 pole with a solid neutral, not what we want as an incomer.

[Crossy]

I'm going to change my recommendation based upon trying to find a decent quality 2 module RCBO from a source available in Thailand.

Go with the original idea in post #6 of a separate MCB and RCD, mount the MCB in an external box if you can't make room in the CU.

[cigar7]

I'd replace the whole main box with a bigger Schneider or Bticino box, with lots of slots for individual breakers, and have a grounding bar built-in. Homepro stocks Schneider 50 and 63 amp double pole RCBO main breakers, but a smaller electric store usually sell them for 300-500 baht cheaper. The Schneider breakers are made in Thailand. The Schneider breakers will also fit into Bticino boxes that are cheaper cost than the Schneider. Schneider also makes individual RCBO breakers at 20 amps. Schneider breakers also fit into old Square D make boxes.

Schneider also makes surge suppressors that fit into the main box and have better overall solutions for residential wiring.

SCHNEIDER - Residental And Building Solutions 2015.pdf

Edited January 13, 2016 by cigar7

[Crossy]

@cigar7

Yes, I agree in part, if our OP was the new owner he would likely want to change the CU to one with more space, ground bar etc. If a renter he would want to make safe at minimal cost.

I have a personal dislike for the plug-in type CUs, mainly because they are difficult / impossible to customise (adding under-volt units etc), I much prefer those with DIN mount modules.

[Forkinhades]

Electrical installations are very robust things, your 15/45 meter will happily carry a 100% overload for several hours without flinching (but with some loss of accuracy). Same goes for the incoming cables and your village transformer (which is likely overloaded right now). Many, many 15/45 meters are protected by 63A fuses or MCBs, probably more 5/15 meters have no protection whatever.

If your existing load isn't opening the 50A then there's no hazard involved with using a bigger unit, it wont suddenly go bang, the current draw is no different. Unless you're on a (very) long cable you will still get short-circuit protection.

Replacing a breaker with a bigger one 'because it keeps tripping' IS a hazard, evidently the load is close to the limit (actually well over it, a 50A breaker will take over a minute to operate at 100A).

If you are worried and can't get a 50A RCBO then install a 40A RCBO (it will probably never operate on overload) or use a separate RCD and MCB.

EDIT 50A RCBOs do exist but the only ones I can find on the main sources are 3 modules wide (should still fit with the space you have). Like this one http://www.aliexpress.com/item/high-quality-10A-16A-20A-25A-32A-40A-50A-63A-2-pole-transparent-residual-current-earth/32368380458.html?spm=2114.01020208.3.21.vJH8Wd&ws_ab_test=searchweb201556_1,searchweb201644_2_10001_10002_10005_10006_10003_10004_62_61,searchweb201560_1,searchweb1451318400_6149 you need to tell them what current you need when ordering.

FURTHER EDIT I've been doing more research for 2-module wide RCBOs. We have to be very careful as many of the 2-module units are actually 1 pole with a solid neutral, not what we want as an incomer.

Yes indeed Crossy, 1 pole can be an issue, but there is nothing further upstream?

[Crossy]

Electrical installations are very robust things, your 15/45 meter will happily carry a 100% overload for several hours without flinching (but with some loss of accuracy). Same goes for the incoming cables and your village transformer (which is likely overloaded right now). Many, many 15/45 meters are protected by 63A fuses or MCBs, probably more 5/15 meters have no protection whatever.

If your existing load isn't opening the 50A then there's no hazard involved with using a bigger unit, it wont suddenly go bang, the current draw is no different. Unless you're on a (very) long cable you will still get short-circuit protection.

Replacing a breaker with a bigger one 'because it keeps tripping' IS a hazard, evidently the load is close to the limit (actually well over it, a 50A breaker will take over a minute to operate at 100A).

If you are worried and can't get a 50A RCBO then install a 40A RCBO (it will probably never operate on overload) or use a separate RCD and MCB.

EDIT 50A RCBOs do exist but the only ones I can find on the main sources are 3 modules wide (should still fit with the space you have). Like this one http://www.aliexpress.com/item/high-quality-10A-16A-20A-25A-32A-40A-50A-63A-2-pole-transparent-residual-current-earth/32368380458.html?spm=2114.01020208.3.21.vJH8Wd&ws_ab_test=searchweb201556_1,searchweb201644_2_10001_10002_10005_10006_10003_10004_62_61,searchweb201560_1,searchweb1451318400_6149 you need to tell them what current you need when ordering.

FURTHER EDIT I've been doing more research for 2-module wide RCBOs. We have to be very careful as many of the 2-module units are actually 1 pole with a solid neutral, not what we want as an incomer.

Yes indeed Crossy, 1 pole can be an issue, but there is nothing further upstream?

We are (were) suggesting replacing his current 2-module incomer with a direct replacement RCBO, so nothing upstream

[Forkinhades]

^^ Just to be clear, if you have individual RCBOs, and a Front end RCD, it is important to make sure your RCBOs are double pole.

Although still effective, the system will give a blackout under fault conditions if the RCBOs are NOT double pole.

With Front end RCD, and double pole RCBOs, only the final circuit with fault will open. Highly recommended if you don't want a blackout.

[wpcoe]

Good thing I went on a trip for a few days. The winds and tides have changed.

I haven't yet researched what is on each circuit for each CB yet, but IF I find something I think can be combined, hence reducing the number of CBs by one, THEN I could safely insert a triple-wide RCBO with a double-pole switch?

When researching if any circuits can be consolidated to one CB, is it good practice to keep each air con on its own CB? Ditto for each shower water heater? If so, that's four out of seven already accounted for, which doesn't look good for any circuit consolidation.

While I was back at the old condo, I took a photo of the consumer unit there:

It has a single-pole RCBO. Is that a cause for concern? Or do condo wiring systems inherently have something upstream to compensate?

[Crossy]

I can't see the part number but that is likely a double pole RCBO specifically intended to be used as a main switch. No issue whatever.

What makes you think it's single-pole?

[wpcoe]

Uhm, only a single wide switch? <blush>

I thought that your original recommendation of this drop-in RCBO was withdrawn because it was single pole, which I extrapolated was due to the single-width switch...

So, now that my obvious ignorance is now out in the open, how do you determine if an RCBO is single-pole?

[Crossy]

Uhm, only a single wide switch? <blush>

I thought that your original recommendation of this drop-in RCBO was withdrawn because it was single pole, which I extrapolated was due to the single-width switch...

So, now that my obvious ignorance is now out in the open, how do you determine if an RCBO is single-pole?

Usually by the part number or by looking at the little diagram on the unit, if it shows two opening switches, 1 in L and 1 in N then it's double pole.

I see what you mean about the Schneider unit, that the switch itself is only 1 unit wide, if we could see the part number it could be confirmed. But IIRC my condo had a Schneider CU with a 2 pole incoming MCB and that still had a narrow switch.

There are also 2 pole MCBs that are only 1 unit wide just to throw confusion into the mix.

Unfortunately the unit I originally linked to shows the double pole labelling but has only a single width MCB (with it's own little diagram). Most misleading which is why it got me It was at least referred to as "1-pole + N" in the description.

[cigar7]

Good thing I went on a trip for a few days. The winds and tides have changed.

I haven't yet researched what is on each circuit for each CB yet, but IF I find something I think can be combined, hence reducing the number of CBs by one, THEN I could safely insert a triple-wide RCBO with a double-pole switch?

When researching if any circuits can be consolidated to one CB, is it good practice to keep each air con on its own CB? Ditto for each shower water heater? If so, that's four out of seven already accounted for, which doesn't look good for any circuit consolidation.

While I was back at the old condo, I took a photo of the consumer unit there:

condo-CU.jpg

It has a single-pole RCBO. Is that a cause for concern? Or do condo wiring systems inherently have something upstream to compensate?

The main breaker, on the left, using the double slot, doesn't look like a RCBO main breaker. See page 25 of the Schneider catalog posted earlier. Usually the RCBO main breaker has a test button (white) in the top right corner, and also states 30mva the shut-off current trigger.

Also consider adding a surge suppressor, as shown on page 25, if you have a grounding wire.

Edited January 18, 2016 by cigar7

[wpcoe]

There is a test button and a rating of 30mA, which I assumed is the level at which it trips? Am I wrong yet again? If that's not a RCBO, is it just a fancy "standard" main breaker?