Ring main.

[JKMRK1]

Question I have is, is it ok to have x2 ring main circuits on one 32amp type B MCB??

If so does this meet the current regs.

TIA.

 

[Mike Johnson]

Hmm my French house has a TT supply and a 3M rod, resistance value is 56Ω should I panic now?

 

[LastManOnline]

Hmm my French house has a TT supply and a 3M rod, resistance value is 56Ω should I panic now?

No absolutely not. The issue is actually with TNC-S and the widespread (but erroneous belief) that the rod plays the same role in this supply system as it dies in a TT system. By the way a res of 56 ohms?? That's a dream come true over here
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No absolutely not. The issue is actually with TNC-S and the widespread (but erroneous belief) that the rod plays the same role in this supply system as it dies in a TT system. By the way a res of 56 ohms?? That's a dream come true over here☺

Did you test that rod isolated from other earth's?

 

[davesparks]

Yes. Unterminated and taped off in a JB, but obviously accessible. The utility is the location of choice.

So in the future, if it is needed as the customer has bought a new appliance and overloaded the 16A circuit you installed, they have to call you back to connect this other cable and make more current available?

That sounds like a terrible installation design to me, and I'm sure the customers will agree

 

[Mike Johnson]

Did you test that rod isolated from other earth's?

This is on the outside of most rural properties in France for exactly that purpose.

 

[LastManOnline]

So in the future, if it is needed as the customer has bought a new appliance and overloaded the 16A circuit you installed, they have to call you back to connect this other cable and make more current available?

That sounds like a terrible installation design to me, and I'm sure the customers will agree

How is that the wisest course of action? Limiting socket circuits to 16A does not seem like a sensible plan.
If you had said you calculate cable size as if there was more insulation than there actually is I could understand it. But to make an arbitrary decision to put all socket circuits on 16A OCPDs seems daft to me.

What size cable do you use for the 16A socket circuits usually?

Do you make the circuits smaller and run more of them to compensate for the reduction in available current?

Yes. Simple run in more circuits. Not complicated. You will find most continental countries have their socket Circuits at 16 amps. Appliances generally have their own curcuits.

DAVE SPARKS "if you had said you calculate cable size as if there is more insulation..". That's exactly what I said. The decision was, spe ifically made in relation increasing insulation. Reread my post.
I use 2.5 t&e for socket circuits.

Now, an exercise. Check the tables for current carrying capacity of a 2.5 t&e in insulation. Use the appropriate derating factors and see if you are still comfortable using a 20amp mcb?

By the way how many appliances, in your home will trip a 16 amp mcb.

Lastly, no decisions are set in stone. We play what's in front of, but always erring on the side of caution.

 

[davesparks]

Now, an exercise. Check the tables for current carrying capacity of a 2.5 t&e in insulation. Use the appropriate derating factors and see if you are still comfortable using a 20amp mcb?

By the way how many appliances, in your home will trip a 16 amp mcb.

That is a ridiculous exercise as it does not follow the rules for calculating cable size.
You apply rating factors to the nominal current and then select a cable size based on that calculation.

Your 'exercise' suggests starting with a cable size and working backwards to a nominal current, this is incorrect.

I am well aware that a 20A circuit wired in T&E through insulation will require a minimum of 4.0mm, but that is irrelevant to the point.

On their own i don't think any appliance with a plug will trip a 16A MCB unless faulty. However a combination of 2 or more on the same circuit will trip a 16A MCB quite easily.

 

[Mike Johnson]

Yes. Simple run in more circuits. Not complicated. You will find most continental countries have their socket Circuits at 16 amps. Appliances generally have their own circuits.

Ah ha Edmond you have been listening.

 

[davesparks]

Yes. Simple run in more circuits. Not complicated. You will find most continental countries have their socket Circuits at 16 amps. Appliances generally have their own curcuits.

I use 2.5 t&e for socket circuits.

I am aware that most continental European countries have their socket circuits on 16A MCB's, and they run more circuits than we normally would. That is largely irrelevant as they are following their regulations and standard practices, we follow our regulations.
Most continental countries drive in the other side of the road and use Km instead of miles, that does not mean we need to change to match them.

Surely you use the cable size selected as a result of the standard calculations, stating that you use 2.5 for socket circuits is daft.

 

[nicebutdim]

Now, an exercise. Check the tables for current carrying capacity of a 2.5 t&e in insulation. Use the appropriate derating factors and see if you are still comfortable using a 20amp mcb?

Do you, like most of continental Europe, run dedicated circuits for fixed appliances or are such appliances running on a single 16A circuit? Your earlier washer/dryer comment led me to believe those appliance are not on dedicated circuits, but on the same 16A circuit as other appliances.

While I like the idea of an electrician wiring homes to take future additional insulation into account, I can't help thinking that I'd prefer that to take the form of more robust infrastructure, rather than less available current.

What way do you run kitchen sockets? I'm inclined to think that these may be 20A radials in 4mm as 6mm would be a bit impractical for installation, but kitchens attract all manner of gadgets, several of which could be running at the same time.

 

[LastManOnline]

That is a ridiculous exercise as it does not follow the rules for calculating cable size.
You apply rating factors to the nominal current and then select a cable size based on that calculation.

Your 'exercise' suggests starting with a cable size and working backwards to a nominal current, this is incorrect.

I am well aware that a 20A circuit wired in T&E through insulation will require a minimum of 4.0mm, but that is irrelevant to the point.

On their own i don't think any appliance with a plug will trip a 16A MCB unless faulty. However a combination of 2 or more on the same circuit will trip a 16A MCB quite easily.

If I had chosen to wire the socket circuits in this particular install in 4mm to SUIT 20 amp MCB's I would be guilty of poor design and wastefulness and cause unneeded expense for the home owner. His 2 heaviest appliances are 1800 and 1500 watts. He has access to 4 separate circuits in his kitchen. I can confidently predict he will enjoy years of hassle free cooking, hoovering etc.

 

[nicebutdim]

Most continental countries drive in the other side of the road and use Km instead of miles, that does not mean we need to change to match them.

ROI did change to KM several years back.

What I'm trying to grasp is whether these installations are going down the route of multiple circuits, where the UK might use one, and the use of much larger CUs to accomodate many extra ways. If that's the case then I can understand lower rated circuits.

 

[davesparks]

If I had chosen to wire the socket circuits in this particular install in 4mm to SUIT 20 amp MCB's I would be guilty of poor design and wastefulness and cause unneeded expense for the home owner. His 2 heaviest appliances are 1800 and 1500 watts. He has access to 4 separate circuits in his kitchen. I can confidently predict he will enjoy years of hassle free cooking, hoovering etc.

4 circuits for the kitchen is wasteful and unneeded expense. It uses more cable and 4x RCBO instead of 1.
One ring circuit is normally adequate for the ground floor of the average house.

With your 16A radial approach how big do your CUs and DBs end up being?

 

[LastManOnline]

I am aware that most continental European countries have their socket circuits on 16A MCB's, and they run more circuits than we normally would. That is largely irrelevant as they are following their regulations and standard practices, we follow our regulations.
Most continental countries drive in the other side of the road and use Km instead of miles, that does not mean we need to change to match them.

Surely you use the cable size selected as a result of the standard calculations, stating that you use 2.5 for socket circuits is daft.

My "" stating that I use 2.5 for socket circuits is daft"" is, pardon me, daft. Worldwide 2.5 is used for socket circuits. For general socket circuits, we don't need to make "standard calculation", we need to ensure that the cable is protected properly under whatever conditions it's been installed.Simple as. That is in my experience how socket cir uits are wired worldwide. Now when it comes to fixed appiances etc, we naturally begin with the load first and work back.

As, regards "this is what the Europeans do and this is what we do" is a mantra I don't support. I much prefer, let's see what "they do" (whoever they may be) and what we can learn from them. They and you (UK) do a number of things we (Eire) can learn from. I As, you have probably gathered I am all for change (positive change that is). I see it as "win, win"
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Do you, like most of continental Europe, run dedicated circuits for fixed appliances or are such appliances running on a single 16A circuit? Your earlier washer/dryer comment led me to believe those appliance are not on dedicated circuits, but on the same 16A circuit as other appliances.

While I like the idea of an electrician wiring homes to take future additional insulation into account, I can't help thinking that I'd prefer that to take the form of more robust infrastructure, rather than less available current.

What way do you run kitchen sockets? I'm inclined to think that these may be 20A radials in 4mm as 6mm would be a bit impractical for installation, but kitchens attract all manner of gadgets, several of which could be running at the same time.

Yes. Any load above 1500 watts is recommended to have its own circuit.

 

[nicebutdim]

Yes. Any load above 1500 watts is recommended to have its own circuit.

What about kitchen sockets?

 

[LastManOnline]

What about kitchen sockets?

It's a minimum of 2 circuits. But the key reminder we have gotten here for many years is"the regs are a MINIMUM""requirement.

 

[nicebutdim]

It's a minimum of 2 circuits. But the key reminder we have gotten here for many years is"the regs are a MINIMUM""requirement.

2x20A or 2x 16A?

It's this room, where a plethora of gadgets that draw significant current can usually be found. Would be difficult to guess where a homeowner might plug their kettle and toaster in, when deciding which circuit to power a built in microwave from.

I don't dislike your thinking, but I'm not quite over the line in sharing it. As a homeowner (not an electrician) I'd much rather see a 32A supply for kitchen sockets, regardless of whether that takes the form of a ring or radial. For 364 days of the year I think your ideas would be fine for our household, but I wouldn't want to guide the other half and kids toward specific sockets for that other 1 or 2 days each year when they go mad with baking or whatever else that range of gadgets are used for.

Looking around our modest sized kitchen I see 3 circuits: Oven/hob, fridge freezer and general sockets, of which there are 10 (5x 2g). Splitting those sockets over two circuits would be difficult as there can be appliances that draw considerable current plugged into any of them, although most loads are admittedly very light.

 

[Mike Johnson]

A typical three phase Domestic circuit board in the EU, in fact France, but could be Germany, Norway........................

 

[nicebutdim]

A typical three phase Domestic circuit board in the EU, in fact France, but could be Germany, Norway........................

That's what I was driving at in a previous post - whether this sort of board is being used in Ireland if circuits are run in greater numbers at lower ratings.

 

[LastManOnline]

2x20A or 2x 16A?

It's this room, where a plethora of gadgets that draw significant current can usually be found. Would be difficult to guess where a homeowner might plug their kettle and toaster in, when deciding which circuit to power a built in microwave from.

I don't dislike your thinking, but I'm not quite over the line in sharing it. As a homeowner (not an electrician) I'd much rather see a 32A supply for kitchen sockets, regardless of whether that takes the form of a ring or radial. For 364 days of the year I think your ideas would be fine for our household, but I wouldn't want to guide the other half and kids toward specific sockets for that other 1 or 2 days each year when they go mad with baking or whatever else that range of gadgets are used for.

Looking around our modest sized kitchen I see 3 circuits: Oven/hob, fridge freezer and general sockets, of which there are 10 (5x 2g). Splitting those sockets over two circuits would be difficult as there can be appliances that draw considerable current plugged into any of them, although most loads are admittedly very light.

2 x 20 amps would be the norm. Installing 16 amp mcb, s is not the norm here. Remember I stated this is my first time applying this measure. But I think it will become more common in the future.
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That's what I was driving at in a previous post - whether this sort of board is being used in Ireland if circuits are run in greater numbers at lower ratings.

Very unlikely 3 phase boards will be used here.
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A typical three phase Domestic circuit board in the EU, in fact France, but could be Germany, Norway........................View attachment 59939

Yes. You can add Sweden to that list. 3 phase in domestic situations is in my view a positive developement

 

[nicebutdim]

Very unlikely 3 phase boards will be used here.

I was going to edit that post, but figured you get that I was referring to the use of boards with significant capacity and not 3 phase installations.
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2 x 20 amps would be the norm. Installing 16 amp mcb, s is not the norm here. Remember I stated this is my first time applying this measure. But I think it will become more common in the future.

I'm very much in favour of breaking with convention, when doing so fulfills a need or improves upon convention - whether that be a one off circumstance or in a more widespread manner.

What I struggle with here are the potential limitations placed upon homeowners as that house could have new occupants 2 or 3 years from now, with very different requirements to the current occupant. It may be that you have got this installation bang on the money for the style of property, but I can only consider the issue from my own perspective and limited experiences. Your ideas may not meet with universal approval, but I like that they challenge convention and give me something to think about.