Size of Micro breaker

[Iggifer]

A 10A breaker on the same line as a 13A fuse will break first. This is rather fundamental stuff. But your mind does wander a little, rambling on about Continental systems and the likes.

No. It won't. THAT is fundamental.

What are these double pole micro breakers you're planning on installing? please do share a link to them

 

[Adam_151]

flameport, a 10A breaker on the same line as a 13A fuse will break first. This is rather fundamental stuff. .

If only discrimination was that easy! Breaking first (which you might find the 10A MCB will do for a reasonable range of fault levels - but not all) is only half the story. You then have to consider whether the total I²t of the breaker is below the pre-arcing i²t of the fuse and of course the outcome will vary with fault current.

 

[EFLImpudence]

Ah but is Ray concerned with fault current?

Isn't he only talking about his appliances rebelling against him and deciding to overload the (oversized) OPDs and self-igniting?

 

[stillp]

Why do you want to use micro breakers and not miniature circuit-breakers like everyone else?

 

[ban-all-sheds]

So as well as having your electrician install all of these circuits, you're also going to need a very large CU with a 2P busbar.

I wonder if you might change your mind when you find out how much that is going to cost you....

 

[Ray Tay]

a 10A breaker on the same line as a 13A fuse will break first. This is rather fundamental stuff

If we are talking fundementals, something in my "basic principles" folder says that it is fundamentally bad practice to have a lower current CPD upstream of a larger one!

Taylortwocities, there are exceptions, and this is one. The point is not to remove a heavy appliance from a unit and superior overall protection of the cable, flex and appliance by sizing the DP MCB/RCBO to suit, not just slapping in a 16A MCB/RCBO because that is what most do. If an appliance only draws say 8A then a 10A MCB/RCBO will be fitted raising the overall protection.

stillp, MCBs is what I mean, sorry.

Igiffer, double pole micro breakers are available. They are more common in Germany and France. Also DP RCBOs are available. A Consumer Unit with DP RCBO's on all circuits is the ultimate protection. The best. One I may aim for. Check out the DP jobs. I am not going to Google for you, but type in 'DP RCBO' and lots comes up. The cheapest is £13 and then upwards. They are there, not in Screwfix, but there.

ABB make a DP MCB that are available in a "single module" width, the same width as a normal single-pole MCB. If space is a problem then these are ideal. I think they are quite expensive, so if space is not a problem then these are the way to go.

ban-all-sheds, the cost of DP RCBOs on a handful of circuits for a flat is not a great cost but the superior protection is worth the cost. Also DP RCBOs divides and rules. Only that circuit trips in the case of a fault not the whole place and the neutral is also switched out. It is also easier to test. I intend to have these DP MCBs or preferably DP RCBOs/DP MCBs also as isolators in the Consumer Unit for heavy appliances, so saving costs elsewhere and eliminating those ugly FSUs on walls. Put it all in the Consumer Unit all at one point.

 

[Ray Tay]

Igiffer, I did a search an this is just one maker of DP RCBOs:
http://www.rapidonline.com/electric...-030-double-pole-rcbo-type-b-10a-30ma-23-4782

For £25.59 each for 5 of them is not expensive at all. Heavy built-in appliances will most probably need the 10A versions:

The range of DP RCBOs:
Type B 6A 30mA
Type B 10A 30mA
Type B 16A 30mA
Type B 20A 30mA
Type B 25A 30mA
Type B 32A 30mA
Type B 40A 30mA
Type C 6A 30mA
Type C 10A 30mA
Type C 16A 30mA
Type C 20A 30mA
Type C 25A 30mA
Type C 32A 30mA
Type C 40A 30mA

Why go for less?

 

[bernardgreen]

I did a search an this is just one maker of DP RCBOs:

Do they fit conveniently to a pair of bus bars ( Live and Neutral ) or is it necessary to use cable between the inputs to the devices and a pair of distribution bars else where in the box.

I do know the answer,

 

[RF Lighting]

Good luck finding a type tested assembly which will accept those devices....

Proof if ever it were needed that a little knowledge is a dangerous thing.

 

[Ray Tay]

I did a search an this is just one maker of DP RCBOs:

Do they fit conveniently to a pair of bus bars ( Live and Neutral ) or is it necessary to use cable between the inputs to the devices and a pair of distribution bars else where in the box.

I do know the answer,

Is this a quiz?

Good luck finding a type tested assembly which will accept those devices....

Proof if ever it were needed that a little knowledge is a dangerous thing.

Another one with attitude. These forums breed them. Why do they bother?

 

[DetlefSchmitz]

I'd still like to know what a 'Micro Breaker' is. I'm clearly missing something!

 

[Iggifer]

That was my point! I'm fully aware what a DP Miniature Circuit Breaker is and I'm fully aware what a DP DCBO is.

If he wants to spend all the that money for no real benefit, let him!

 

[Ray Tay]

I'd still like to know what a 'Micro Breaker' is. I'm clearly missing something!

You are missing something as it was cleared up in the thread.

 

[Ray Tay]

That was my point! I'm fully aware what a DP Miniature Circuit Breaker is and I'm fully aware what a DP DCBO is.

If he wants to spend all the that money for no real benefit, let him!

You should not be in the electrical game (if you are of course) if you think there is no benefit to what I suggest. I actually highlighted the benefits

 

[EFLImpudence]

MCBs is what I mean, sorry.

It seems you have missed the fact that both Micro and Miniature begin with 'M'.