At absolute best that will be a quick visual inspection.
A proper inspection and test of that installation would be a full days work and cost £200+
The hob will work fine on that 32A circuit breaker.
CU 32->40a fuse upgrade
- Thread starter nice-but-dim
- Start date
A proper inspection and test of that installation would be a full days work and cost £200+
The hob will work fine on that 32A circuit breaker.
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The RCD like the MCB comes in different flavours, the two sizes normally refereed to at 300 mA used to protect from fire, and the 30 mA used to protect from shock, but the 100 mA was very common to allow the use of a TT supply in relative safety, back in the days before RCD's were required for personal protection.
The equipment used in the house has changed over the years, I look at my own house, inverter fridge/freezer, freezer, washing machine, and induction hob, plus of course loads of other switch mode supplies, and I have realised my type AC RCD
is not good enough, and I had had to order type A RCD
to replace it, both are 30 mA at 40 mS but because I am using items like the induction hob it's possible they will not trip when they should.
However I had a read of the Electrical Safety Council best practice guide 4 issue 5 and there is nothing about checking type of RCD used, it seems we now know the danger, but as yet have not caught up, so not included in an EICR (Electrical Installation Condition Report) which has also been the subject of debate of late as now a legal requirement with some rented property, so it was up to the electrician to consider what required testing and inspecting who was guided by his course and exam C&G 2391 but now it seems he needs to follow some laid down criteria which to date I have been unable to find.
The BS 7671 is considered as the standard most work by, and with a few exceptions each time a new version is released it states it is for new work done after the date it comes into force, so a house built in 1960 could still be used today as long as owner occupied, there is no need to update, however any updates must comply with the latest edition, so we get the situation where to fit some thing which seems rather minor, becomes major because the system needs updating before it is fitted.
We see phrases such as like for like, but in real terms that rarely exists, some thing has changed, if only the manufacturers instructions. And clearly in 1960 no one had an induction hob fitted. So in real terms your old fuse box has reached its use by date, the changing of the fuses to MCB's did extend its life, but if you want to use modern appliances then the box needs to be upgraded.
If the supply is TN then there is not really that much danger using a type AC RCD with this
logo, the RCD is a secondary protection, and likely I am going OTT in changing mine, however if the supply is TT (means it uses an earth rod) then the type of RCD fitted is far more important, you want to see
logo (Type A) or better like this
(type F) or this
(type B) although as far as I am aware the latter two only seem to be used with domestic with electric car chargers and solar panels.
As to size of cable the idea of using a micrometer and calculating the cross sectional area seems too complex, I have some red, blue, and yellow crimps, plus uninsulated 10 mm and 16 mm, and I simply try a crimp on the cable, is the yellow 6 mm crimp will not fit assuming the wire not crushed, then likely it is 10 mm or 16 mm, however it is unlikely to be anything better than 6 mm² it was so much easier before we went metric, I was taught in the age of 7/0.044 cable I could easy measure 0.044 inches with micrometer and can count to 7.
In real terms we don't use a shower for long, so a 7.5 kW shower may be just on the limit of 32 amp, and an 8.5 kW is 37 amp, but we tend to have finished showing long before the MCB or cable reaches a temperature where likely to type or get hot, 9.5 kW at 41 amp is stretching it is little too much, but unless colouring their hair, even then it tends to work most of the time without too much of a problem, however the continual over heating of the MCB tends to make them go weak, and the time you can shower for slowly reduces, but with a 32A MCB it does its job and protects the 6 mm² cable tripping before the cable gets too hot, the only real problem is when the cable warms and cools it can compress in the terminals and over time become loose, and once it get loose it gets a bad connection and heats up to a very high heat, causing fire. We had a service schedule to stop this, torquing up the screws, however it did not really work, as this also compressed the cable and had some cables break at the terminals, but at least no fire. I have never seen anyone do a service on a house. There are units that are claimed to disconnect the supply it is detects sparking, but personally having the RCD trip is bad enough, fitting a surge protection device (SPD) OK when it goes it just shows red in the little indicator window, but there has to be a limit.
Anyway interested in the SSE testing, how long does it take them, that's a good indication on how much tested.
The equipment used in the house has changed over the years, I look at my own house, inverter fridge/freezer, freezer, washing machine, and induction hob, plus of course loads of other switch mode supplies, and I have realised my type AC RCD
However I had a read of the Electrical Safety Council best practice guide 4 issue 5 and there is nothing about checking type of RCD used, it seems we now know the danger, but as yet have not caught up, so not included in an EICR (Electrical Installation Condition Report) which has also been the subject of debate of late as now a legal requirement with some rented property, so it was up to the electrician to consider what required testing and inspecting who was guided by his course and exam C&G 2391 but now it seems he needs to follow some laid down criteria which to date I have been unable to find.
That does not sound like a full EICR, it sounds more like the type of checks the suppliers use to do before connecting you up.[SIZE=4][B]SSE Electrical Wiring Cover [/B]advert[/SIZE] said:
[SIZE=4][B]SSE Electrical Wiring Cover [/B]advert[/SIZE] said:
[SIZE=4][B]SSE Electrical Wiring Cover [/B]advert[/SIZE] said:
The BS 7671 is considered as the standard most work by, and with a few exceptions each time a new version is released it states it is for new work done after the date it comes into force, so a house built in 1960 could still be used today as long as owner occupied, there is no need to update, however any updates must comply with the latest edition, so we get the situation where to fit some thing which seems rather minor, becomes major because the system needs updating before it is fitted.
We see phrases such as like for like, but in real terms that rarely exists, some thing has changed, if only the manufacturers instructions. And clearly in 1960 no one had an induction hob fitted. So in real terms your old fuse box has reached its use by date, the changing of the fuses to MCB's did extend its life, but if you want to use modern appliances then the box needs to be upgraded.
If the supply is TN then there is not really that much danger using a type AC RCD with this
As to size of cable the idea of using a micrometer and calculating the cross sectional area seems too complex, I have some red, blue, and yellow crimps, plus uninsulated 10 mm and 16 mm, and I simply try a crimp on the cable, is the yellow 6 mm crimp will not fit assuming the wire not crushed, then likely it is 10 mm or 16 mm, however it is unlikely to be anything better than 6 mm² it was so much easier before we went metric, I was taught in the age of 7/0.044 cable I could easy measure 0.044 inches with micrometer and can count to 7.
In real terms we don't use a shower for long, so a 7.5 kW shower may be just on the limit of 32 amp, and an 8.5 kW is 37 amp, but we tend to have finished showing long before the MCB or cable reaches a temperature where likely to type or get hot, 9.5 kW at 41 amp is stretching it is little too much, but unless colouring their hair, even then it tends to work most of the time without too much of a problem, however the continual over heating of the MCB tends to make them go weak, and the time you can shower for slowly reduces, but with a 32A MCB it does its job and protects the 6 mm² cable tripping before the cable gets too hot, the only real problem is when the cable warms and cools it can compress in the terminals and over time become loose, and once it get loose it gets a bad connection and heats up to a very high heat, causing fire. We had a service schedule to stop this, torquing up the screws, however it did not really work, as this also compressed the cable and had some cables break at the terminals, but at least no fire. I have never seen anyone do a service on a house. There are units that are claimed to disconnect the supply it is detects sparking, but personally having the RCD trip is bad enough, fitting a surge protection device (SPD) OK when it goes it just shows red in the little indicator window, but there has to be a limit.
Anyway interested in the SSE testing, how long does it take them, that's a good indication on how much tested.
I suspect his RCD is so old it doesn’t use those symbols.
Interesting that you point out Type A is important for TT and ind hobs.
I had considered the kitchen was an area that didn’t need type A !
Interesting that you point out Type A is important for TT and ind hobs.
I had considered the kitchen was an area that didn’t need type A !
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Thank you. ISTR that when I first subscribed to the Shield cover I had to have a thorough wiring test by the SSE engineer since they only want to insure properties which are properly wired and protected from the outset.
Good to know I can swap my one 40amp MCB into the shower circuit if the wiring is compatible. I'm still going to wait for a response from Wylex who I've asked to confirm that my old board officially supports 40amp loops.
I'm also now dithering on the shower upgrade after advice above that a 9.5kW model won't noticeably improve the shower and specifically the volume of water coming through it. Maybe the 8.5kW upgrade with integral pump might do a better job for me, albeit I gather it's quite noisy. Upgrade or not, I'll give the shower a 40amp MCB as long as the board supports it (although it has never once faltered on the 32amp MCB in over 20 years).
Photo shows the existing 8.5kW shower.
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Thanks for an interesting post ericmark. I'm beginning to think that you have hit the nail on the head and I should let sleeping dogs lie rather than spend a fortune on multiple refurbs/upgrades just to get one new appliance.
My house is over 100 years old and the wiring is over 25 years old albeit parts of the CU, meter, RCD etc were installed or upgraded in 2001. My earth goes to a rod in the ground if that's what TT is. And my RCD, pictured below, doesn't seem to carry any of your symbols - but it definitely works (for now).
My house is over 100 years old and the wiring is over 25 years old albeit parts of the CU, meter, RCD etc were installed or upgraded in 2001. My earth goes to a rod in the ground if that's what TT is. And my RCD, pictured below, doesn't seem to carry any of your symbols - but it definitely works (for now).
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I have tried to work out the real danger using wrong type of RCD after I made a mistake and fitted 14 RCBO's type AC in my own house. As far as I can work out if appliances are working correctly there is no problem. However if a rectifying diode goes faulty so you have not got full wave rectification many switch mode controlled items will still work and show no signs of being faulty, but due to the uneven draw on positive and negative half cycles can saturate the iron core of the RCD and so stop it tripping.
On this forum we had a discussion about them, and one report seems to say no problem and another is demonstrating that there is, and it seems some countries have banned the use of AC RCD's. The problem is when we test a RCD we turn everything off, so if we have a faulty item we will likely have turned it off before pressing a test button.
However with a TN supply the RCD is the belt and bracer's approach, so even if there is an earth fault that will not trip the RCD it will likely still trip the MCB as long as the earth loop impedance (ELI) is low enough. But with a TT system the ELI is not low enough so we rely on the RCD.
I have and also others have told people if you have a RCD in the consumer unit then it is pointless having a second one for garden equipment etc. However I realise I was wrong with this advice, as the lawn mower is unlikely to be switch mode controlled so even if the RCD in the consumer unit fails to work the plug in type likely will still work.
However even firms with a good reputation like Farrnell who provide a data sheet the data sheet does not say a word as to which type of RCD it is. So what is the point in buying this
when it does not say which type it is? And my RCBO's were clearly marked type B, but it turned out they were type AC curve B. This really cheap one shows the back
and the logo shows it is type A, but data sheet shows nothing.
Some day there will be a court case if the type AC RCD is ineffective, it surprises me there has to my knowledge at least not already been one, as if they are so dangerous you would think some one would have been killed as a result, and that does not seem to be the case. Not that I think we should wait until some one dies before we start correcting the problem, and it is hard enough to get people to fit any RCD never mind telling them that £250 you paid out last year for a new consumer unit populated with 14 RCBO, well it's no good, you need to pay another £300 to have them all swapped to type A.
Oh you fitted type B, sorry sir that was not type B even when it said type B on the box, it was type AC it was curve B we printed type B on the box in error. How would that go down?
On this forum we had a discussion about them, and one report seems to say no problem and another is demonstrating that there is, and it seems some countries have banned the use of AC RCD's. The problem is when we test a RCD we turn everything off, so if we have a faulty item we will likely have turned it off before pressing a test button.
However with a TN supply the RCD is the belt and bracer's approach, so even if there is an earth fault that will not trip the RCD it will likely still trip the MCB as long as the earth loop impedance (ELI) is low enough. But with a TT system the ELI is not low enough so we rely on the RCD.
I have and also others have told people if you have a RCD in the consumer unit then it is pointless having a second one for garden equipment etc. However I realise I was wrong with this advice, as the lawn mower is unlikely to be switch mode controlled so even if the RCD in the consumer unit fails to work the plug in type likely will still work.
However even firms with a good reputation like Farrnell who provide a data sheet the data sheet does not say a word as to which type of RCD it is. So what is the point in buying this
Some day there will be a court case if the type AC RCD is ineffective, it surprises me there has to my knowledge at least not already been one, as if they are so dangerous you would think some one would have been killed as a result, and that does not seem to be the case. Not that I think we should wait until some one dies before we start correcting the problem, and it is hard enough to get people to fit any RCD never mind telling them that £250 you paid out last year for a new consumer unit populated with 14 RCBO, well it's no good, you need to pay another £300 to have them all swapped to type A.
Oh you fitted type B, sorry sir that was not type B even when it said type B on the box, it was type AC it was curve B we printed type B on the box in error. How would that go down?
That is a 100mA RCD, the wrong rating for additional protection of socket outlets, showers and most everything else.
Some of the MCBs might have been fitted around 2000, but the fusebox is much older.
Doubtful - that RCD is a 1980s part, possibly early 1990s at the latest.
Some of the MCBs might have been fitted around 2000, but the fusebox is much older.
A pumped shower won't change anything - they are only for situations that have low pressure cold water from a storage cistern.
The flow rate of an electric shower is limited by the power rating - the only way to get more flow is to either have a cooler shower, or to put a lot more power in.
With inlet temperature of 5C and outlet of 40C (temperature rise of 35C), the flow rates are
8.5kW = 3.5 litres/minute
9.5kW = 3.9 litres/minute.
0.4 litres per minute extra flow at the same temperature.
Even going to the most powerful electric shower of 10.5kW, which would require new cable and a new consumer unit, it's still only 4.3 litres/minute.
If you want a higher flow rate, then an electric shower is not the solution.
The flow rate of an electric shower is limited by the power rating - the only way to get more flow is to either have a cooler shower, or to put a lot more power in.
With inlet temperature of 5C and outlet of 40C (temperature rise of 35C), the flow rates are
8.5kW = 3.5 litres/minute
9.5kW = 3.9 litres/minute.
0.4 litres per minute extra flow at the same temperature.
Even going to the most powerful electric shower of 10.5kW, which would require new cable and a new consumer unit, it's still only 4.3 litres/minute.
If you want a higher flow rate, then an electric shower is not the solution.
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I looked for the instructions for Triton Ivory II and failed, but all the Triton showers I found said
In real terms the 100 mA RCD is a good isolator so maybe leaving in place is a good idea as saves calling the DNO to fit an isolator. I did have a pumped shower at my parents house, until the combi boiler was fitted which made it illegal, and it had to be swapped for a simple thermostatic shower, it was a good shower, but it also required a 30 mA RCD to be fitted.
I had a look at the instructions for my own induction hob,
BS 7671 is not law, the building regulations are, but not BS 7671, so no one can tell you that the fuse box needs upgrading. But with my house there are 14 RCD's all 30 mA built in with the MCB called RCBO's so if my cooker did stop the RCD from working then the other 13 remain unaffected. Even with a malfunction of some equipment, the chance of some equipment on the same supply giving me a shock and not tripping is very slim. But you have got all yours eggs in one basket.
And the RCD is 100 mA so needs changing, it is well past use by date.Triton said:
In real terms the 100 mA RCD is a good isolator so maybe leaving in place is a good idea as saves calling the DNO to fit an isolator. I did have a pumped shower at my parents house, until the combi boiler was fitted which made it illegal, and it had to be swapped for a simple thermostatic shower, it was a good shower, but it also required a 30 mA RCD to be fitted.
I had a look at the instructions for my own induction hob,
It seems to say it will not interfere with the operation of a RCD. It also does not say one must be fitted. © 09.2009 so BS 7671:2008 was in force when this was printed. I also found the Australia version that also has nothing about requiring RCD protection. I had expected it to say must be RCD protected, but nothing.Belling FSE 60i said:
BS 7671 is not law, the building regulations are, but not BS 7671, so no one can tell you that the fuse box needs upgrading. But with my house there are 14 RCD's all 30 mA built in with the MCB called RCBO's so if my cooker did stop the RCD from working then the other 13 remain unaffected. Even with a malfunction of some equipment, the chance of some equipment on the same supply giving me a shock and not tripping is very slim. But you have got all yours eggs in one basket.
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I found the instructions here. They say: "To enhance electrical safety a 30mA residual current device (RCD) should be installed in all UK electric and pumped shower circuits. This may be part of the consumer unit or a separate unit." Since their other electrical instructions all use the word "must", I assume that the 30mA RCD advice is not mandatory. In any event, after 20 years of electricity consumption, nothing has ever gone wrong - including the one occasion when I cut through a live cable and really did need the RCD to work and it did.
Indeed I have had occasions when a single device has tripped the RCD and it's inconvenient, once every 2-3 years. And I do use a portable RCD in any socket I'm attaching a heavy-duty appliance to such as a jet washer or a drill.
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Well, that's what I've got. My shower water comes from the cold water tank in the loft.
It certainly doesn't sound impressive but 0.4L more would be a >10% improvement and that might just be enough to make the shower more fit for purpose. In any event, I won't be investing in new plumbing for a different shower…and the Triton with the internal pump might give me more than 10%.
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Wylex have replied to me (see below), passively confirming that my old 1206 board does take 40amp MCBs and noting that they haven't stocked for four years. They also confirm that the aggregate draw of my active appliances should not exceed 100amps, ie less than half the aggregate max capacity of the installed MCBs. Since my 100amp RCD rarely trips, I assume that I don't normally exceed 100amps but that would be more by luck than judgement. Seems somewhat hit-or-miss but maybe I shouldn't mess with it. It's not uncommon for me to be using concurrently: the hob; the oven; the microwave; the kettle; the washing machine; the tumble drier; the shower(on its 32amp MCB); and a couple of dozen or more small appliances such as PCs, an electric heater, lights, phones, battery chargers, routers, POE switches, security lights, etc, etc and it handles that load without complaint. But maybe I should steer clear of upgrading my shower.
From: "[email protected]" <[email protected]>
Subject: FW: 1206 MCB compatibility
Date: 3 August 2020 at 09:20:28 BST
To: xxxxxx xxxxxx
Hello
The rating of the switch on that is 100 amp max, so when everything is fully running it should not exceed 100 amps, it would be up to the electrician on site to do their calculations, apply diversity etc to see what rating of circuits would be ok.
The B40 would be hard to find, Wylex haven’t sold any now for about 4 years now and there is no stock left of them now, I am afraid.
With best regards, Simon
Estimating Engineer
SI LP ELEC S BD Electrium Sales Limited SI LP ELEC FIN HR Lakeside Plaza
Walkmill Lane Cannock WS11 0XE, United Kingdom Tel.: +44 1543 455020 mailto:[email protected] www.electrium.co.uk Electrium Sales Limited - registered office: Faraday House, Sir William Siemens Square, Frimley Camberley GU16 8QD. Registered No. 02226729
From: xxxxxx xxxxxx
Sent: 02 August 2020 11:03
To: SI LP Electrium Wylex Technical <[email protected]>
Subject: 1206 MCB compatibility
Hello,
I have an old 1206 Wylex fuse board (see photo) in my house. It continues to work well and has been inspected regularly by my local electricity supplier but I have no documentation for it and would be grateful for an answer.
Could you please tell me if this board supports one, two or more 40 amp MCBs? As can be seen from the photo, there is one 40 amp MCB installed in the board but since the protected device (an induction hob) only requires a 32 amp MCB, the 40 amp MCB may not be operating at its full rating.
In particular, I’m thinking of upgrading an electric shower which would require another of my MCBs to be upgraded from 32 amp to 40 amp (assuming I can find one).
I will take it as read that you would advise me to replace my CU with a modern one.
Many thanks for your help.
Subject: FW: 1206 MCB compatibility
Date: 3 August 2020 at 09:20:28 BST
To: xxxxxx xxxxxx
Hello
The rating of the switch on that is 100 amp max, so when everything is fully running it should not exceed 100 amps, it would be up to the electrician on site to do their calculations, apply diversity etc to see what rating of circuits would be ok.
The B40 would be hard to find, Wylex haven’t sold any now for about 4 years now and there is no stock left of them now, I am afraid.
With best regards, Simon
Estimating Engineer
SI LP ELEC S BD Electrium Sales Limited SI LP ELEC FIN HR Lakeside Plaza
Walkmill Lane Cannock WS11 0XE, United Kingdom Tel.: +44 1543 455020 mailto:[email protected] www.electrium.co.uk Electrium Sales Limited - registered office: Faraday House, Sir William Siemens Square, Frimley Camberley GU16 8QD. Registered No. 02226729
From: xxxxxx xxxxxx
Sent: 02 August 2020 11:03
To: SI LP Electrium Wylex Technical <[email protected]>
Subject: 1206 MCB compatibility
Hello,
I have an old 1206 Wylex fuse board (see photo) in my house. It continues to work well and has been inspected regularly by my local electricity supplier but I have no documentation for it and would be grateful for an answer.
Could you please tell me if this board supports one, two or more 40 amp MCBs? As can be seen from the photo, there is one 40 amp MCB installed in the board but since the protected device (an induction hob) only requires a 32 amp MCB, the 40 amp MCB may not be operating at its full rating.
In particular, I’m thinking of upgrading an electric shower which would require another of my MCBs to be upgraded from 32 amp to 40 amp (assuming I can find one).
I will take it as read that you would advise me to replace my CU with a modern one.
Many thanks for your help.
It doesn't work like that.
The number and rating of MCBs connected does not cause power used to increase or decrease
It doesn't work like that either.
An RCD does not trip on current usage.
he doesn't "passively confirm" that. He did not answer your question. he just said they are no longer offered. Your CU might have been designed to accept one or more 40A MCBs; this would be seen by the presence of (I think always only one) MCB-socket that was larger than the others and was capable of accepting the intentionally-larger (green?) 40A MCB used at the time. I don't see such a position in your pics.
At the time your CU was made, the MCBs were a different design, with two push-buttons. Yours has the (much) later switch type and perhaps when they were offered the B40 no longer had the protrusions. B40 were always very rare on Wylex Standard CUs.
Last edited:
The 40A way isn't bigger. The green or orange part has an extra tab to prevent it being fitted into a way it is not suitable for easily. Like all fooling tabs they could have been bypassed (i.e cut off)
See here. The orange one has an extra tab at the bottom right.
https://www.ebay.co.uk/itm/WYLEX-C3...046559&hash=item1a33ad6fa3:g:D-sAAOSwe9dZnA2u
The blue one does not (15A in this case)
https://www.ebay.co.uk/itm/15A-Cart...957886?hash=item3da7f68c3e:g:QasAAOSwCNJfH~S0
See here. The orange one has an extra tab at the bottom right.
https://www.ebay.co.uk/itm/WYLEX-C3...046559&hash=item1a33ad6fa3:g:D-sAAOSwe9dZnA2u
The blue one does not (15A in this case)
https://www.ebay.co.uk/itm/15A-Cart...957886?hash=item3da7f68c3e:g:QasAAOSwCNJfH~S0
I might have an old 12-way metalclad on my scrap shelf. If I have, I'll see if it looks like it was designed to fit the 40A MCB. I don't think so, because I've seen Wylex standards where it was separate and clearly identified.