Types of RCD's and breaker size

[campyk]

1. In this article RCD types explained it says that any electronics or inverter motors will potentially leak DC current into your AC network and blind AC type RCD's.

They are obsolete and even are prohibited to use in some countries.

In Thailand on the other hand one would struggle to find a top brand RCD other than type AC.

Can someone clarify whether DC current leakage is a real issue with average domestic installation? Eg. lots of led lighting, computer, laptops, inverter AC's, fridge, induction hob etc.

Is it worth getting mid-range Chinese type A or B RCD's instead of top brand (ABB, Schneider) type AC ones?

What if I plan to go solar? Does it change things?

 

2. Another question I have is related to sizing breakers.

I'm going to use reference method A (first column). Is it correct for wires in conduit running through AAC blocks?

 

3. Should we cover wire capacity from the table with (1) breaker nominal rating or with (2) breaker tolerance rating of 113% or 145%?

Does it change with planned continuous vs noncontinuous load?

[sometimewoodworker]

1 hour ago, campyk said:

In Thailand on the other hand one would struggle to find a top brand RCD other than type AC.

I don’t know where you are getting your information from but you are wrong, all my ABB MCBs are “Input Voltage Type: AC/DC”, Schneider are no different and yes of course you have to be concerned with DC leakage.

 

1 hour ago, campyk said:

2. Another question I have is related to sizing breakers.

I'm going to use reference method A (first column). Is it correct for wires in conduit running through AAC blocks?

As that is “Method A enclosed in enclosed in thermally wall or in insulating wall” and AAC blocks are thermally insulating naturally that is the one to use.

[OneMoreFarang]

2 hours ago, campyk said:

Should we cover wire capacity

1.5 sqmm is used with 16A breakers since forever. And in lots of tables that is recommended.

IMHO 16A and 1.5 sqmm is sufficient from most devices and installations.

 

Any device which needs more power like hobs, heater, etc. are obvious.

[sometimewoodworker]

28 minutes ago, OneMoreFarang said:

1.5 sqmm is used with 16A breakers since forever. And in lots of tables that is recommended.

IMHO 16A and 1.5 sqmm is sufficient from most devices and installations.

 

Any device which needs more power like hobs, heater, etc. are obvious.

I’m not sure what you are smoking but 1.5 sqmm is a little high for lighting and not suitable for any power circuit. That will be a minimum of 2.5 sqmm.  

[Crossy]

10 minutes ago, sometimewoodworker said:

I’m not sure what you are smoking but 1.5 sqmm is a little high for lighting and not suitable for any power circuit. That will be a minimum of 2.5 sqmm.  

 

My reason for using 1.5mm on lighting (10A breaker) is purely for mechanical strength, 1mm is a little too easy to break.

 

 

[OneMoreFarang]

1 hour ago, sometimewoodworker said:

I’m not sure what you are smoking but 1.5 sqmm is a little high for lighting and not suitable for any power circuit. That will be a minimum of 2.5 sqmm.  

Maybe you should work more with electricity instead of wood...

 

I am not smoking anything.

In Germany 1.5sqmm is used in houses for 16A breakers if the cable is not longer than about 17m.

If that is good enough for a country with at least a million security rules and regulations then it's good enough for me - even in Thailand.

 

 

Edited November 21, 2022 by OneMoreFarang

[sometimewoodworker]

39 minutes ago, OneMoreFarang said:

Maybe you should work more with electricity instead of wood...

 

I am not smoking anything.

In Germany 1.5sqmm is used in houses for 16A breakers if the cable is not longer than about 17m.

If that is good enough for a country with at least a million security rules and regulations then it's good enough for me - even in Thailand.

 

 

The breaker size for the cable is not the relevant point & I agree that for 1.5mm a 16A breaker (or if you are @Crossy A 10A breaker) the point is that a 1.5mm circuit is undersized for power and only really suitable for lighting.

 

Virtually all power circuits have more than a single outlet so 2.5mm minimum.

 

So the statement 

Quote

16A and 1.5 sqmm is sufficient from most devices and installations.

Suggests ingestion of products from ThaiGreenLab

Edited November 21, 2022 by sometimewoodworker

[OneMoreFarang]

3 minutes ago, sometimewoodworker said:

The breaker size for the cable is not the relevant point & I agree that for 1.5mm a 16A breaker (or if you are @Crossy A 10A breaker) the point is that a 1.5mm circuit is undersized for power and only really suitable for lighting.

 

Virtually all power circuits have more than a single outlet so 2.5mm minimum.

Thanks for your reply.

16A x 230V = 3,680W

That is a LOT of light!

 

Maybe our misunderstanding is just about the word "power". What is in your opinion a "power circuit"?

I guess we agree that a heater, with maybe 5kW or 7kW, needs a lot of power and we can call it a power circuit.

But how about a fridge? Or a fan? Or a big stereo? All these devices don't need much power.

[campyk]

2 hours ago, sometimewoodworker said:

I don’t know where you are getting your information from but you are wrong, all my ABB MCBs are “Input Voltage Type: AC/DC”, Schneider are no different and yes of course you have to be concerned with DC leakage.

 

As that is “Method A enclosed in enclosed in thermally wall or in insulating wall” and AAC blocks are thermally insulating naturally that is the one to use.

ABB:

https://shop.bangkokab.com/products/2CSR275051R1164

https://shop.bangkokab.com/products/2CSR256040R1164

https://shop.bangkokab.com/products/2CSR255051R1164

 

Schneider:

https://shop.sirichaielectric.com/product/ลูกเซอร์กิตเบรกเกอร์-กันดูด-1P-16A-30mA-6KA-QO116C06RCBO30-SCHNEIDER

 

There are also Siemens and others but only AC type.

If your RCBO's are A+ type could you share which models did you use?

 

 

[sometimewoodworker]

6 minutes ago, OneMoreFarang said:

Thanks for your reply.

16A x 230V = 3,680W

That is a LOT of light!

 

Maybe our misunderstanding is just about the word "power". What is in your opinion a "power circuit"?

I guess we agree that a heater, with maybe 5kW or 7kW, needs a lot of power and we can call it a power circuit.

But how about a fridge? Or a fan? Or a big stereo? All these devices don't need much power.

As I said 1.5mm is a bit overkill for lighting. 
 

A power circuit is probably anything that isn’t lighting, since power circuits typically have several outlets connected rather than just 1 that is why the standard is 2.5mm.

 

For anything like a stored water heater or instant heater shower they would usually be on a dedicated supply and that could well be 4mm or more.

 

I doubt that even Germany suggests anything smaller

[campyk]

5 hours ago, OneMoreFarang said:

Maybe you should work more with electricity instead of wood...

 

I am not smoking anything.

In Germany 1.5sqmm is used in houses for 16A breakers if the cable is not longer than about 17m.

If that is good enough for a country with at least a million security rules and regulations then it's good enough for me - even in Thailand.

 

What you are missing is that a current carrying capacity is directly dependent on the ability of the wire to dissipate heat.

So Thailand installation in the case of insulated wall and +40 C° would be very different from Germany with reference temperature +25 C° (idk what installation method is used in the table).

[bluejets]

1.5sq mm is fine for lighting.

 

Breaker size , as well as type, is determined by application, not cable size alone.

 

Both are determined by the earth loop impedance measured or calculated.

 

Under the above conditions, a 16A breaker usually fails to meet the requirements and a 10A would be used.

 

Same conditions apply to power circuits where in some cases even a 16A breaker is too large for the conditions to be met.

 

Currently in Aus they are looking at the possible introduction of 12A breakers for 2.5sq mm power circuits.

 

Best approach to avoid possible problems, is keep runs short, use several final sub circuits in place of just one or two,  use larger (4sq mm ) earth on the final sub circuit.

 

[sometimewoodworker]

1 hour ago, bluejets said:

1.5sq mm is fine for lighting.

 

Breaker size , as well as type, is determined by application, not cable size alone.

 

Both are determined by the earth loop impedance measured or calculated.

1 & 2 should be self evident, but certainly worth noting.

 

However as this is Thailand not the U.K. vanishingly few lighting circuits have an earth (probably true for many power circuits as well, but we will ignore them for the moment) so in these cases how can loop impedance be measured or calculated?

 

i understand that in the U.K. the situation is different today but in the past, and probably in older instances, it was the same AFIK.

[bluejets]

28 minutes ago, sometimewoodworker said:

so in these cases how can loop impedance be measured or calculated?

Could only be assumed, not calculated, and best assumption would be many megohms, in which case, any breaker type is never going to trip. 

Different story if you use an rcd as it works on imbalance between active and neutral. However, these should never be relied upon as being an alternative to good earthing practices, as the elcb is an electronic device, and electronic devices do fail from time to time.

With a good earthing system in place, if the above fails, and the earth loop impedance is at the correct levels, the rated breaker for the job will trip.

Note .......it is assumed this instance to be an earth fault.

Edited November 23, 2022 by bluejets

[sometimewoodworker]

47 minutes ago, bluejets said:

Could only be assumed, not calculated, and best assumption would be many megohms, in which case, any breaker type is never going to trip. 

Different story if you use an rcd as it works on imbalance between active and neutral. However, these should never be relied upon as being an alternative to good earthing practices, as the elcb is an electronic device, and electronic devices do fail from time to time.

With a good earthing system in place, if the above fails, and the earth loop impedance is at the correct levels, the rated breaker for the job will trip.

Note .......it is assumed this instance to be an earth fault.

So given that the overwhelming majority of people here are living in Thailand and rely on people who are actually trained for advice, yours while AFIK is correct, is not of much use, is confusing and seems rather dated. 

There are few RCDs the majority are RCBOs.

ELCBs from my reading are deprecated in domestic installations in favour of the RCBO. Probably, specifically because correct earthing is not assumed

 

You seem to say, from the first sentence, that installing any breaker type on a (line and neutral only) lighting circuit is pointless as it’s never going to trip.

 

it’s quite likely that you abbreviated your explanation but if so it became, like an IBM manual, only intelligible to some one who know exactly how to wire circuits correctly.

[OneMoreFarang]

3 hours ago, bluejets said:

Breaker size , as well as type, is determined by application, not cable size alone.

The breaker Amp size must be lower than what the cable can handle. The cable should never fail. It's the job of the breaker to break the connection before the cable fails/overheats/melts.

Obviously a breaker can be a lower number, i.e. 10A instead of 16. But never higher.

[bluejets]

1 hour ago, sometimewoodworker said:

ELCBs from my reading are deprecated in domestic installations in favour of the RCBO. Probably, specifically because correct earthing is not assumed

Elcb is an earth leakage circuit breaker, a part component of your rcbo so directly relative. Call it what you will, safety cut, earth leakage, all work the same.

1 hour ago, sometimewoodworker said:

You seem to say, from the first sentence, that installing any breaker type on a (line and neutral only) lighting circuit is pointless as it’s never going to trip.

 

No, what I said was , without a low earth loop impedance, no circuit breaker size or type will trip on an earth fault.

So if you have a lighting circuit with fittings requiring an earth and are not earthed, and the fitting develops an earth fault, the breaker on its own will never trip.

It will simply sit there with a live framework waiting for someone unsuspecting to touch the now live frame and get their <deleted> kicked at best.

If there happens to be an earth leakage attached to the circuit, be it in the form of an rcbo or a seperate breaker and elcb unit, the circuit will trip if the imbalance is 30mA or more, depending on the unit and its settings.

 

Maybe you should stick to wood chipping I think.

 

 

[Crossy]

Certainly, in the UK the term "ELCB" is now reserved for the older Voltage-Operated ELCB devices (not permitted for new installations) or for earth-leakage devices in HV systems.

 

But we all understand the terminology.

 

Since we seem to have descended into anarchy this thread is Closed.