Not todays job, but I would ask how old your wiring is, thaet fact you have fuses, not CBs, is a worry as CBs have been standard for over 20 years now.

 

Even if the house wiring isnt too old, I would still consider having the old wire fuse C.U. swapped out for a modern CB board.

Not todays job, but I would ask how old your wiring is, thaet fact you have fuses, not CBs, is a worry as CBs have been standard for over 20 years now.

 

Even if the house wiring isnt too old, I would still consider having the old wire fuse C.U. swapped out for a modern CB board.

The Consumer unit, although dating from the construction of the house (1984), is in very good condition and  I can't remember when a fuse has ever blown. That also might be an indication of the condition of the  house wiring (which also dates from 1985) I could always stick in one of those after market circuit breakers for fused consumer unit jobbies - but quite honestly, I don't think that's needed. If anything the problem lies elsewhere.

 

My concern is that the cooker circuit, which has its own fuse, is over fused @ 30 amps. Quite honestly the cooker could be run off of a 13 amp plug if the label on the back of the unit is anything to go by - which says the power grill is rated at 2.4 Kw, and although there is no information about the oven element rating, the replacement suppliers are recommending a 2.3Kw one.  (Although the red consumer information label I removed from the front door of the unit when new (And saved) states that the max power consumption of the oven to reach and mainatain 200C for one hour is 1.3 Kwh !!!! - a printing error, Shirley ?). And, the configuration of the switches on the facia means that you cannot have the grill and oven elements operating at the same time and the fan doesn't operate on the grill setting, so max draw is probably occurs when using the oven element + fan @ lets say at worst 3 Kw. That's well within 13 amp plug limits.

 

Interestingly, the flash and the muffled bang that occurred in oven the other day and which killed the oven element left the 30 amp fuse in the Consumer Unit intact. So much for protection !

 

Secondly, my other concern would be that the circuit run is too long before a fuse (Or CB) comes into play. I'd prefer having one either in the BRS or perhaps adding a fused socket on a spur on the cooker feed from the BRS, perhaps located in the cooker cabinet enclosure. So then you'd have a fuse in the 13 amp fused  plug, a 13 amp fused socket, BRS (Fused if you like) and then a reduced value, say 15 amp fuse wire in the consumer unit.

 

Thirdly, the oven has, unnecessarily in my view, whacking great 30 amp cable coming out the back. This could be swapped for 15 amp heat resistant/pyro - must assume that either the fitter didn't have anything more suitable on the van or was attempting to be consistent with the consumer unit fuse rating. I think this 30 amp marlarky is a left over from the 1950s when turning on the hobs and oven on the freestanding unit could darken the lights in the rest of the street. Are there any regs governing this.  I see many of the newer cookers are plug-in i.e. 13 amp nowadays

 

I'm going to take the back off of the unit today and take a look at the internals, particularly the wiring to the oven element (Which looks shot, as said above), if that needs replacing, I presume I'll have to use some heat resistant/ mildly pyro cable. Any recommendations, bearing in mind the max temp achievable in the cabinet is 220C - but as the cable is directly behind the fan and the fan always operates when the oven is on, the "Wind chill" temperature will probably be a lot lower.

 

 

Nick

Edited 23 April, 201610 yr by Clunkclick

Possible solution.

All the gas ovens appear to have a significantly reduced depth requirement circa 43 Cm upwards.(Why, you ask, intuitively you would think the reverse is true)That would easily fit without the need to move the gas pipe.. And that's gas ovens with an electric grill.

But they are £100 more expensive than the electric equivalents.

There's a few on AO that would fit and they do a fitting service inclusive.

Optimistically, I'm thinking that all that's required is the fitting of a T-piece in the gas supply and a flexible hose - surely the householder can do that ?

The electric grill can be wired back into the existing 30 amp junction box.

Question is could the existing 15mm gas pipe supply enough for both a gas oven and the hob simultaneously - seem to recall in the old days that the flexible connectors to free-standing ovens were one inchers.

Nick

Fitting service is replacing a a like for like, not installing a new gas point/fitting - for which you'll need a gas safe engineer.

You cannot do this work yourself.

http://webcache.googleusercontent.com/search?q=cache%3Awww.gassaferegister.co.uk%2Fadvice%2Fgas_safety_in_the_home%2Fdoing_diy.aspx&oq=cache%3Awww.gassaferegister.co.uk%2Fadvice%2Fgas_safety_in_the_home%2Fdoing_diy.aspx&aqs=chrome..69i57j69i58.4416j0j4&client=ms-android-google&sourceid=chrome-mobile&ie=UTF-8

The Consumer unit, although dating from the construction of the house (1984), is in very good condition and  I can't remember when a fuse has ever blown. That also might be an indication of the condition of the  house wiring (which also dates from 1985) I could always stick in one of those after market circuit breakers for fused consumer unit jobbies - but quite honestly, I don't think that's needed. If anything the problem lies elsewhere.

 

My concern is that the cooker circuit, which has its own fuse, is over fused @ 30 amps. Quite honestly the cooker could be run off of a 13 amp plug if the label on the back of the unit is anything to go by - which says the power grill is rated at 2.4 Kw, and although there is no information about the oven element rating, the replacement suppliers are recommending a 2.3Kw one.  (Although the red consumer information label I removed from the front door of the unit when new (And saved) states that the max power consumption of the oven to reach and mainatain 200C for one hour is 1.3 Kwh !!!! - a printing error, Shirley ?). And, the configuration of the switches on the facia means that you cannot have the grill and oven elements operating at the same time and the fan doesn't operate on the grill setting, so max draw is probably occurs when using the oven element + fan @ lets say at worst 3 Kw. That's well within 13 amp plug limits.

 

Interestingly, the flash and the muffled bang that occurred in oven the other day and which killed the oven element left the 30 amp fuse in the Consumer Unit intact. So much for protection !

 

Secondly, my other concern would be that the circuit run is too long before a fuse (Or CB) comes into play. I'd prefer having one either in the BRS or perhaps adding a fused socket on a spur on the cooker feed from the BRS, perhaps located in the cooker cabinet enclosure. So then you'd have a fuse in the 13 amp fused  plug, a 13 amp fused socket, BRS (Fused if you like) and then a reduced value, say 15 amp fuse wire in the consumer unit.

 

Thirdly, the oven has, unnecessarily in my view, whacking great 30 amp cable coming out the back. This could be swapped for 15 amp heat resistant/pyro - must assume that either the fitter didn't have anything more suitable on the van or was attempting to be consistent with the consumer unit fuse rating. I think this 30 amp marlarky is a left over from the 1950s when turning on the hobs and oven on the freestanding unit could darken the lights in the rest of the street. Are there any regs governing this.  I see many of the newer cookers are plug-in i.e. 13 amp nowadays

 

I'm going to take the back off of the unit today and take a look at the internals, particularly the wiring to the oven element (Which looks shot, as said above), if that needs replacing, I presume I'll have to use some heat resistant/ mildly pyro cable. Any recommendations, bearing in mind the max temp achievable in the cabinet is 220C - but as the cable is directly behind the fan and the fan always operates when the oven is on, the "Wind chill" temperature will probably be a lot lower.

 

 

Nick

 

The recommendation used to be get the wiring checked after 25 years, and changed at least after 35- 40 years.

 

Retro fitting a modern board - even if the wiring is good, is highly recommended, it reduces the chances of a fatal electric shock to near zero, protects from "slow" overloads and damaged earthing.

 

A 30Amp fuse DOESNT blow at 30amps, it will happily take 50 Amps for days/weeks, only instantly blowing at currents above 100Amps - which in theory should never happen.

 

A 30Amp circuit breaker will trip out AT 30Amps, and wont reset if there is still an overload on the circuit.

 

In addition, a modern board will have a Residual Current Breaker - this measures the current supply on both the live and neutral and trips out if they become imbalanced (current going to earth) at levels so low, and so fast, you can grab a live cable and not feel it.

 

Your house should have one fitted if you have an electric shower, but that one will ONLY cover the shower, a modern CU will have one protecting all of the power circuits - and possibly the lighting circuits as well; although this can cause the whole house to trip out when a bulb blows.

 

As for your cooker, that 1.3KW* is the USAGE over 1 hour, the 2.3KW is the MAXIMUM it will draw when heating up; so perhaps it will draw only 1KW to KEEP the oven at 200C, after using 2.3KW to get it there.  * It should read 1.3KWh for KiloWatt hours.

 

If you dont get that, consider a 1KW microwave - your jacket potato takes 10 minutes to cook, so that is 1/6th of a hour or 1KW/6 = 166Wh

The recommendation used to be get the wiring checked after 25 years, and changed at least after 35- 40 years.

Retro fitting a modern board - even if the wiring is good, is highly recommended, it reduces the chances of a fatal electric shock to near zero, protects from "slow" overloads and damaged earthing.

A 30Amp fuse DOESNT blow at 30amps, it will happily take 50 Amps for days/weeks, only instantly blowing at currents above 100Amps - which in theory should never happen.

A 30Amp circuit breaker will trip out AT 30Amps, and wont reset if there is still an overload on the circuit.

In addition, a modern board will have a Residual Current Breaker - this measures the current supply on both the live and neutral and trips out if they become imbalanced (current going to earth) at levels so low, and so fast, you can grab a live cable and not feel it.

Your house should have one fitted if you have an electric shower, but that one will ONLY cover the shower, a modern CU will have one protecting all of the power circuits - and possibly the lighting circuits as well; although this can cause the whole house to trip out when a bulb blows.

As for your cooker, that 1.3KW* is the USAGE over 1 hour, the 2.3KW is the MAXIMUM it will draw when heating up; so perhaps it will draw only 1KW to KEEP the oven at 200C, after using 2.3KW to get it there. * It should read 1.3KWh for KiloWatt hours.

If you dont get that, consider a 1KW microwave - your jacket potato takes 10 minutes to cook, so that is 1/6th of a hour or 1KW/6 = 166Wh

I'm sorry but this contains so much nonsense.

A 30Amp fuse will blow above 30 amps (fused wires can be 10-15% over the rating). It won't take 50amps,it'll have burned out long before that. But for more accurate protection we've moved onto RCD breakers.

A bulb blowing on a lighting circuit would only take out that circuit. If it's taking out the whole CU then you have some serious issues with your electrics.

And oven won't use 2.3kw then drop down to 1kw. It'll always be pulling 2.3kw with the stat switching it on/off. It's either on or off.

And the microwave comments - where do I even start.

The only credible part is about the shower & cooker having its own circuit.

I'm sorry but this contains so much nonsense.

A 30Amp fuse will blow above 30 amps (fused wires can be 10-15% over the rating). It won't take 50amps,it'll have burned out long before that. But for more accurate protection we've moved onto RCD breakers.

A bulb blowing on a lighting circuit would only take out that circuit. If it's taking out the whole CU then you have some serious issues with your electrics.

And oven won't use 2.3kw then drop down to 1kw. It'll always be pulling 2.3kw with the stat switching it on/off. It's either on or off.

And the microwave comments - where do I even start.

The only credible part is about the shower & cooker having its own circuit.

 

I am a trained industrial electrician, even though I gave it up, I am not BS'ing; if you dont believe me, go talk to ANY competent electrician and he/she will confirm EVERYTHING I have said.

 

 

A bulb blowing on a lighting circuit would only take out that circuit. If it's taking out the whole CU then you have some serious issues with your electrics.

 

I said if the lighting circuits were covered by the RCB/RC;, one RCB/RCD can cover a number of circuits, not just one - but since you dont believe anything I said, again, go ask a competent electrician who you trust.

 

 

And oven won't use 2.3kw then drop down to 1kw. It'll always be pulling 2.3kw with the stat switching it on/off. It's either on or off.

 

I thought I explained KWh to you, but since you didnt get the microwave analogy, I will refer to the above response again.

 

 

One of my shared Queens Awards can be found listed here https://www.thegazette.co.uk/London/issue/50493/supplement/3

 

The above isnt very specific, it was for the development of the 165S Spin Necker - there are/were other spin neckers in use around the world, but this was the fastest and used the least metal per can (and is now used by most canning companies around the world for making soft drinks cans).

 

Not sure where to look for the others as Exports dont seem to be listed, and the Sentinal System I worked on was covered as NHS, even though the NHS never had much to do with the project - other than cancelling it when the work was already in final testing.

I thought I explained KWh to you, but since you didnt get the microwave analogy, I will refer to the above response again.

My job involves working with heating elements and fused circuits

My job involves working with heating elements and fused circuits

 

Obviously, you havent been taught very well..

 

Perhaps you could read the Wiki entry; it states "A standard fuse will take DOUBLE its rated capacity for 1 second before blowing"; at lower levels of overload it will take progressively longer for the fuse to blow; for example - you can run a 15Amp device on a 13Amp plug and fuse for many months - perhaps years, before the fuse will pop.

 

From your original statement, I am guessing you have either an NVQ or GCSE in the subject; both of which are heavily dumbed down ( I used to teach the GCSE many years ago at Evesham College).

Double capacity for 1 second isn't days or weeks as you quoted earlier.

15A on 13A is within the 10-15%

But anyway it's made my Cousin chuckle (Sparky)

Thanks for the interlude gentlemen.

 

(If this was the GP's you be getting a double-stripped warming letter  )

 

I seem to recall  from days gone by, circa 1960s, before central heating was omnipresent, that portable 3 Kw domestic electric  fires could be run from 13 A sockets and cabling without problem. Have the regs changed ?

 

From the "Discussion" above, is it safe to conclude that fitting a CB to a circuit effectively increases the safety margin on a circuit so that either more or higher draw appliances can be run off of  it or, alternatively any built-in  "Safety margin" for short-circuit by way of over-sized cabling can be reduced by fitting reduced capacity cabling ? Or does that breach good practice and the regs ?

 

Again, any suggestions for cabling for the run inside the oven between the transformer/control unit and the replacement element would be appreciated.

 

Otherwise, its just me relying on Morley and Hughes.

 

 

Nick

Thanks for the interlude gentlemen.

 

I seem to recall  from days gone by, circa 1960s, before central heating was omnipresent, that portable 3 Kw domestic electric  fires could be run from 13 A sockets and cabling without problem. Have the regs changed ?

 

I've a 3Kw kettle that runs off a 13A plug so no different I'd imagine.

P=VxI

I've a 3Kw kettle that runs off a 13A plug so no different I'd imagine.

The difference would be that a kettle would only be drawing current for a few minutes at a time, whereas a heater could be drawing current for hours if left switched on and the thermostat did not cut the power, or was faulty. This can be a risk to the cables if they are old or not rated highly enough.

The modern 3kw heater can still be ran from a socket though, quite safely.

 

A slightly different note, but my neighbours left their water heater switched on (unintentionally) and went away on holiday. The water in the cylinder boiled due to a failed thermostat, the water rose up the vent pipe, and the water in the tank (in the airing cupboard only just above the cylinder) got to such a temperature that the steam collapsed the plasterboard ceiling just above. Luckily for them, they arrived home before anything more serious happened.

The tank did not have a cover either - as all tanks should, to prevent contamination.

Double capacity for 1 second isn't days or weeks as you quoted earlier.

15A on 13A is within the 10-15%

But anyway it's made my Cousin chuckle (Sparky)

 

 Go back and read my original post, I didnt say it could take double for weeks, I said a 30Amp fuse wouldn't blow at 30Amps (which you now admit), but would take up to 50Amps before blowing, 50 isnt double; at 50 the fuse would last for minutes, giving the cable it was "Protecting" enough time to get very hot and perhaps set the insulation on fire; certainly enough time for you to be killed if touched anything live as the insulation melted off.

 

In contrast, a CB will switch the power off in fractions of a second, protecting you and your home.

 

I've seen a 100A rated armoured cable overloaded to 280Amps, the paint on the wall caught fire before the cable melted (some idiot kept upping the fuse size when it kept blowing, and reached 300Amps before I got there - GUS distribution warehouse in Droitwich)

 

Your cousin a domestic sparky?? They dont teach them very well either. My training was good enough that control kit I built is/was fitted to RN SSNs, and several multi-national companies would ask for me specifically, when they wanted rectification work carried out on MB A&C supplied equipment.

 

A 30Amp fuse DOESNT blow at 30amps, it will happily take 50 Amps for days/weeks, only instantly blowing at currents above 100Amps - which in theory should never happen.

 

 

 

 Go back and read my original post, I didnt say it could take double for weeks, I said a 30Amp fuse wouldn't blow at 30Amps (which you now admit), but would take up to 50Amps before blowing, 50 isnt double; at 50 the fuse would last for minutes, giving the cable it was "Protecting" enough time to get very hot and perhaps set the insulation on fire; certainly enough time for you to be killed if touched anything live as the insulation melted off.

 

I'm confused  

I'm confused

 

OOPs, sorry, please blame the side effects of the antibiotics I am on, amongst other things, they are stopping me from sleeping at all - I am totally strung out and havent felt I was safe to drive.

 

I should have written minutes or hours, as per this quote.

 

 

Class gG fuses

These fuses provide protection against overloads and short-circuits.

Conventional non-fusing and fusing currents are standardized, as shown in Figure H12 and in Figure H13.

Fig. H12: Zones of fusing and non-fusing for gG and gM fuses

 

• The conventional non-fusing current Inf is the value of current that the fusible element can carry for a specified time without melting.

Example: A 32 A fuse carrying a current of 1.25 In (i.e. 40 A) must not melt in less than one hour (table H13)

• The conventional fusing current If (= I2 in Fig. H12) is the value of current which will cause melting of the fusible element before the expiration of the specified time.

Example: A 32 A fuse carrying a current of 1.6 In (i.e. 52.1 A) must melt in one hour or less IEC 60269-1 standardized tests require that a fuse-operating characteristic lies between the two limiting curves (shown in Figure H12) for the particular fuse under test. This means that two fuses which satisfy the test can have significantly different operating times at low levels of overloading.

 

(gG means domestic fuse, gM is industrial) Link to the full page is here http://www.electrical-installation.org/enwiki/Elementary_switching_devices

 

The rest holds true, a wire fuse will take substantially more than its rating, and will do so for a long time - depending on how far over its rating it goes. With a ring main fused at 30Amps, but the devices plugged into it only being rated for 13Amps, the ring fuse should never blow; plus the old coils of wire used in domestic wire fuses is notoriously inaccurate.

 

Which leads me to one of my pet gripes; under the old UK Regs, multiple fuse ratings for 13A plugs were recognised - 1,2,3,5,7,10&13; under the EU unified regs, only 3&13 are recognised; so you could have a 1Amp device "protected" by a 3Amp fuse, or a 4Amp device "protected" by a 13Amp fuse - the device could then actually overload to over 400% before the fuse blows..... (or God forbid, a 1Amp device with a 13Amp fuse - as plugs fitted with a 3A fuse as standard are not common).

I seem to recall  from days gone by, circa 1960s, before central heating was omnipresent, that portable 3 Kw domestic electric  fires could be run from 13 A sockets and cabling without problem. Have the regs changed ?

You're not thinking of the 15amp round pin plugs (and smaller 5amp plugs) that the UK used before the current fused plugs were introduced?

OOPs, sorry, please blame the side effects of the antibiotics I am on, amongst other things, they are stopping me from sleeping at all - I am totally strung out and havent felt I was safe to drive.

 

I should have written minutes or hours, as per this quote.

 

 

(gG means domestic fuse, gM is industrial) Link to the full page is here http://www.electrical-installation.org/enwiki/Elementary_switching_devices

 

The rest holds true, a wire fuse will take substantially more than its rating, and will do so for a long time - depending on how far over its rating it goes. With a ring main fused at 30Amps, but the devices plugged into it only being rated for 13Amps, the ring fuse should never blow; plus the old coils of wire used in domestic wire fuses is notoriously inaccurate.

 

Which leads me to one of my pet gripes; under the old UK Regs, multiple fuse ratings for 13A plugs were recognised - 1,2,3,5,7,10&13; under the EU unified regs, only 3&13 are recognised; so you could have a 1Amp device "protected" by a 3Amp fuse, or a 4Amp device "protected" by a 13Amp fuse - the device could then actually overload to over 400% before the fuse blows..... (or God forbid, a 1Amp device with a 13Amp fuse - as plugs fitted with a 3A fuse as standard are not common).

Except the plug fuse is there to protect the cable, not the device at the far end of it.

Except the plug fuse is there to protect the cable, not the device at the far end of it.

 

That doesnt work, they dont put a cable capable of handling 13-20 amps on a 4Amp device, they put the thinnest cable they can get away with, typically 0.5mm; when you need  2.5mm to cope with 13Amps (technically ~1.75mm, but they dont make that size)

 

(I got about an hours sleep last night, so feeling relatively chipper compared to yesterday!!)

Edited 25 April, 201610 yr by GentleGiant

It's a fact. Fuse rating should scale with (flexible) cable size, thin cable, small fuse, thicker cable bigger fuse.

 

Apparently most of the world doesn't have such requirement for a fuse in the plug because they don't use the ring main concept, so each outlet (and cable plugged into it) has relatively more protection at the distribution board.

 

Look it up. I'm not making it up.

You're not thinking of the 15amp round pin plugs (and smaller 5amp plugs) that the UK used before the current fused plugs were introduced?

No, Square pin, MK design which have been around since the late 1930s.

 

15A and 5A round date from the 1890's ?

 

Nick

Getting ahead of myself (I haven't yet disassembled the oven to see if the wiring issue can be fixed ) I took a look at the Gas Safe Register site - that just in case I have to get a new oven and consequently get the gas pipe moved (All it needs is moving back about 25mm).

 

To those that don't know, its a database of government approved gas fitters/engineers complete with business addresses and names and photos of same. I was surprised, given that the public will be probably accessing this first nowadays (And making judgements) before contacting a firm, on the photo presentations of those on offer. Grim wasn't the word, not a smile cracked by any of them - even when I changed the postcode and put in a local posh area. I know we are not paying them for looks or smiling ability, but, honestly, some of them looked as if they just done 20 on the moor and the rest looked like they were all shagged and ready to depart this place. You might be frightened to let them into your house if you were on your own or had kids. I noticed a couple of entries, for allegedly different one-man band firms, within half a mile of one another, had what looked like the same bloke in the photo - in one shot he was pasty with a beard and in the other he was clean shaven with a tan. By comparison, roofers look half normal.  

 

 

Nick

The recommendation used to be get the wiring checked after 25 years, and changed at least after 35- 40 years.

Retro fitting a modern board - even if the wiring is good, is highly recommended, it reduces the chances of a fatal electric shock to near zero, protects from "slow" overloads and damaged earthing.

A 30Amp fuse DOESNT blow at 30amps, it will happily take 50 Amps for days/weeks, only instantly blowing at currents above 100Amps - which in theory should never happen.

A 30Amp circuit breaker will trip out AT 30Amps, and wont reset if there is still an overload on the circuit.

In addition, a modern board will have a Residual Current Breaker - this measures the current supply on both the live and neutral and trips out if they become imbalanced (current going to earth) at levels so low, and so fast, you can grab a live cable and not feel it.

Your house should have one fitted if you have an electric shower, but that one will ONLY cover the shower, a modern CU will have one protecting all of the power circuits - and possibly the lighting circuits as well; although this can cause the whole house to trip out when a bulb blows.

As for your cooker, that 1.3KW* is the USAGE over 1 hour, the 2.3KW is the MAXIMUM it will draw when heating up; so perhaps it will draw only 1KW to KEEP the oven at 200C, after using 2.3KW to get it there. * It should read 1.3KWh for KiloWatt hours.

If you dont get that, consider a 1KW microwave - your jacket potato takes 10 minutes to cook, so that is 1/6th of a hour or 1KW/6 = 166Wh

Competent electrician here. Some of your statement was incorrect. An mcb will not trip out at its rated current. Hence why theres time current graphs. A type B 60898 will only trip instantaneously at 5In (nominal current)

No, Square pin, MK design which have been around since the late 1930s.

 

15A and 5A round date from the 1890's ?

 

Nick

 

1947 was the switch over  to the square pin plug.

Correct... but.

 

That is the magnetic circuit for dealing with short circuits, mCBs have a thermal circuit as well, for dealing with overloads; this isnt so fast, but will trip out at SUSTAINED current flows above the rating; so yeah I was dumbing down, however the truth is that mCBs operate faster and more reliably than fuses in all situations, in identical situations, a fuse can take x10 rated current before blowing in 20mS while the mCB will trip at x5 in 20mS.

 

It is also the case that a mCB wont reset if the fault is still present, whereas putting a new fuse in can cause a hell of a bang.

 

I see from a quick look that it isnt just fuse sizes they have dumbed down, the older UK mCBs (type 1), used to trip faster as well, at x4 in 20mS and above x2.7 for O/L greater than 200mS, although this did cause nuance trips when lightbulbs blew.

 

SWMBO should be home from work soon, so I can hand over child rearing duties and have another stab at trying to get some sleep. :zzz: