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.

 

[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.

 

[LastManOnline]

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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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.

The more you mull it over, the less unconventional it will seem. Believe me, by nature I, m very cautious and "doing things once and doing it right" is my natural way. In the electrical Industry we are taught to follow the regs rigidly. Correct. However, breaking with convention in order to improve matters is in my experience not really encouraged. It tends to be a case of "that's, how we have always done things". However, it's clear that someone somewhere is doing this, otherwise we would never have new regs and new improvements. I never challenge convention for the sake of it. There must be a very definate practical goal.

 

[Cbuk2k2]

Just a point.
Two rings or not, in general, what are FIRST thoughts on four (or more) cables in a circuit breaker terminal, whilst carrying out an EICR?
How long is a piece of string, maybe?

Is that any worse than a multi stranded 6mm or 10mm cable?

Always seems strange to me sparks dont bootlace these.

 

[davesparks]

Is that any worse than a multi stranded 6mm or 10mm cable?

Always seems strange to me sparks dont bootlace these.

Yes it is different to a coarse stranded cable. Coarse stranded cables have the strands compacted tigether at manufacture and they are further compacted together by the termination. Multiple seperate conductors terminated together can, if not done properly, result in one conductor not being clamped at all.

Ferrules are only required for fine stranded cables as screw terminals can cut through the strands or spread them out so that good contact is not made.
Coarse stranded conductors don't suffer from these same issues if correctly terminated.

 

[Cbuk2k2]

Yes it is different to a coarse stranded cable. Coarse stranded cables have the strands compacted tigether at manufacture and they are further compacted together by the termination. Multiple seperate conductors terminated together can, if not done properly, result in one conductor not being clamped at all.

Ferrules are only required for fine stranded cables as screw terminals can cut through the strands or spread them out so that good contact is not made.
Coarse stranded conductors don't suffer from these same issues if correctly terminated.

Just looks strange to me where I’d almost always see some sort of crimp even on corse stranded cables.

 

[davesparks]

Just looks strange to me where I’d almost always see some sort of crimp even on corse stranded cables.

When/where would you always see some sort of crimp on coarse stranded?

 

[Cbuk2k2]

When/where would you always see some sort of crimp on coarse stranded?

Offshore oil and gas/petrochemical is where I work mainly.

Seems to be fairly standard practiceon the sites I’ve worked on.

 

[davesparks]

Offshore oil and gas/petrochemical is where I work mainly.

Seems to be fairly standard practiceon the sites I’ve worked on.

OK, so that's a specialised industry with its own rules and regulations, not really something you can compare to general installation work.

What type of crimps are used on coarse stranded cables? Are you talking about ferrules or something else?

 

[Cbuk2k2]

OK, so that's a specialised industry with its own rules and regulations, not really something you can compare to general installation work.

What type of crimps are used on coarse stranded cables? Are you talking about ferrules or something else?

We work to the same BS7671 rules as everyone else, I’m not aware it’s driven by any of the ATEX regulations etc. It’s just how I’ve always known it be done. Could be an American thing or a marine thing as there is a lot of crossover there.

Depends on the application but non insulated lugs and bootlace crimps are probably the most common.

 

[stevethesparks]

Will also be seen on all BMS panels

 

[davesparks]

It just seems weird to me that bootlace ferrules are being used on coarse stranded cables.
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Will also be seen on all BMS panels

Any idea why?

 

[ChipFanDave]

Not seen it on gas production systems so not ATEX as far as I can see.

Also on all the lighting and power distribution panels for our BMS non of the SWA has ferrules on. The control cables obviously are.

 

[stevethesparks]

It just seems weird to me that bootlace ferrules are being used on coarse stranded cables.
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Any idea why?

Not sure, at the time (approx 11-9 years ago) we were undertaking work for around 3 BMS firms, and all their panels had it, even the panels internal 13amp socket outlet.

 

[Ian1981]

It just seems weird to me that bootlace ferrules are being used on coarse stranded cables.
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Any idea why?

Bootlace Ferrules on say 6 mm conductors seams to be the new YouTube electricians fad, one does it they all do it, spacing rcbo’s when the circuits are likely to be lightly loaded is another, monkey see monkey do.

 

[stevethesparks]

Not such a bad idea on screw terminals that are not quiet big enough for a folded 6mm, but not in cage clamp type terminals.

 

[Mike Johnson]

They do make the installation look neat, but I wished they had harmonised colours in the different sizes.

 

[Ian1981]

I don’t think it makes it look any neater, a bit of coloured plastic showing on the conductor, they are a necessity on fine stranded conductors but make no impression on me when used on standard coarse conductors, I just think why when connected to a circuit breaker inside a CU?

 

[Mike Johnson]

If the circuit breaker has a cage connector I agree, but not when putting a multi strand cable into a standard screw connector, can't guarantee the whole of the cable is connected securely the strands that are not under the screw are a potential ark point.

 

[Ian1981]

If the circuit breaker has a cage connector I agree, but not when putting a multi strand cable into a standard screw connector, can't guarantee the whole of the cable is connected securely the strands that are not under the screw are a potential ark point.

Yeah true but like I say , I mostly see this at CB terminals

 

[Mike Johnson]

I'v been retired for over ten years so I don't see it at all, except for any work I do for myself, so if I see it it's my fault. I have just put in a set of Aico multi detectors and the 1.5mm cable I used was multi strand so both ends have bootlaces, and I thought it looked good even if I do say so myself.

 

[ackbarthestar]

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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.

May I be the devil's advocate?
2 small ring final circuits could be connected in series to provide one rfc and thus could be connected to one OCPD. Quote Reply Report Edit
Source URL: Ring main. - https://www.electriciansforums.net/threads/ring-main.185730/

 

[nicebutdim]

May I be the devil's advocate?
2 small ring final circuits could be connected in series to provide one rfc and thus could be connected to one OCPD. Quote Reply Report Edit
Source URL: Ring main. - https://www.electriciansforums.net/threads/ring-main.185730/

Surely two ring finals connected in series would no longer constitute two circuits and, as such, would only be once circuit connected to the MCB?


To be clear; I'm asking a question, rather than telling you that you're wrong

 

[DPG]

Trying to get my head around how you wire 2 RFCs in series.