What amp circuit required for 2 ovens and a hob

[JohnW2]

Must admit I have never bought any 4.0 T & E, the price diff was minimal if any and was not always easy to obtain a few years ago. In fasct 10.0 was a rarity until showers got hotter too.

For what it's worth, I have to say that I have bought and used a fair bit over the years, and actually find it nicer to work with than 2.5mm² T+E

Kind Regards, John

 

[SUNRAY]

I beg to differ, unless someone has got their sums or tests wrong then it should do so with a bit of headroom as a safety factor.
The fact we often add a bit on for our own piece of mind probably helps mitigate hotspots, poor quality cable, out of limit o.p.ds and slightly loose connections, after all not every circuit is absolutely 100% perfick in every way is it?

And circuit design/derating factors that so many either don't know about or can't be arsed to bother with?
And that heavily used cooker regularly running >40A on 4mm², maybe >50A?

Yes we all know it will work and yes it gets a bit warm sometimes... but yeah that's OK init?

Just as you yourself have said I have never purchased 4mm² T&E as the negligible price difference makes it a silly option and why muck about with 2 rolls of cable when one will do a better job.

It is possible my industrial/commercial experience, which has vastly outweighed the domestic experience, has given me a very different outlook.

 

[JohnW2]

And circuit design/derating factors that so many either don't know about or can't be arsed to bother with?

When we talk about the 'rating' of a cable, that obviously includes any adjustment for 'de-rating factors'.

However, to the best of my knowledge nothing other than those de-rating factors alters the current that the cable is deemed to be able to carry.

It is possible my industrial/commercial experience, which has vastly outweighed the domestic experience, has given me a very different outlook.

I obviously can't answer that question but, as I see it, "the current carrying capacity (after application of any de-rating factors)" of a cable is "the current carrying capacity (after application of any de-rating factors)" of thst cable, regardless of the environment in which the cable is being used.

Kind Regards, John

 

[SUNRAY]

When we talk about the 'rating' of a cable, that obviously includes any adjustment for 'de-rating factors'.

However, to the best of my knowledge nothing other than those de-rating factors alters the current that the cable is deemed to be able to carry.

I obviously can't answer that question but, as I see it, "the current carrying capacity (after application of any de-rating factors)" of a cable is "the current carrying capacity (after application of any de-rating factors)" of thst cable, regardless of the environment in which the cable is being used.

Kind Regards, John

So you are stating a cable rated at say 37A is suitable for any 37A application if there are no derating factors?

 

[ebee]

yep . why not?
I`m not sure I see the point you are making.
If it`s good for XXA with no derating factors then it`s good for XXA.
If there are derating factors which make it good for YYA then it`s good for YYA.

 

[JohnW2]

So you are stating a cable rated at say 37A is suitable for any 37A application if there are no derating factors?

Yep.

If (as seems to be the case) you don't think the same, then, as I asked, what do you think that (in the absence of de-rating factors) "rated at 37A" means?

Kind Regards, John

 

[ebee]

I think that 37 Metric Amps is probably about the same as 37 Imperial Amps so that can`t be the answer either

 

[martygturner]

I cannot think why this is so vexed...its add the total watts to get of the attached cooking items find the amps by dividing by 240,
start eg 50amps max load take 10 amps away and find 30% of the remainder then add back the 10 amps, mcb sorted...then consult the carrying capacity of the cable according to its method of installation, cable sorted.

 

[Murdochcat]

4mm cable is useful when running 32A radials with a few sockets

Tricky with 6mm

Easier to install and test than a 32A ring

 

[JohnW2]

I cannot think why this is so vexed...its add the total watts to get of the attached cooking items find the amps by dividing by 240, start eg 50amps max load take 10 amps away and find 30% of the remainder then add back the 10 amps, mcb sorted...then consult the carrying capacity of the cable according to its method of installation, cable sorted.

Indeed - give or take the fact that we conventionally undertake calculations at 230V, so (assuming the 'Watts' were quoted for 240V) your figures would need to be multiplied by 230/240 before applying the diversity calculation.

However, as you will have seen, it is "vexed" because some people seem to have the idea (which seems ludicrous to me), that the diversity calculation has to be undertaken separately for each 'cooking appliance' on the circuit. That can result is a much higher calculated after-diversity figure, since each and every 'appliance' attracts thee "10A minimum", whereas that only arises once if the calculation is applied to the total cooking appliance load on the circuit.

Don't ask we to understand, explain or justify why some people think/believe that

Kind Regards, John

 

[JohnW2]

I think that 37 Metric Amps is probably about the same as 37 Imperial Amps so that can`t be the answer either

True. What about US Amps ?

Kind Regards, John

 

[SUNRAY]

Yep.

If (as seems to be the case) you don't think the same, then, as I asked, what do you think that (in the absence of de-rating factors) "rated at 37A" means?

Kind Regards, John

So the 32A feed to the summer house at the end of the garden requiring 40m of cable?

And

i know this is very different to what is being discussed but a while back I was asked to look at a problem with a 28day RSL transmission on band II, the transmitter site being in woodland on top of the North Downs and the studio was some 1/2mile down the hill. I had supplied the cable for the stereo audio (4 pair CAT 2) and as it sounded fine with the transmitter in the studio on a dummy load and crap when in situ the fualt was promptly placed on the audio cable not being screened.

I turned up and met customer in the woods, first test I made was listening to the audio directly on the input terminals with a battery powered amplifier which sounded fine, I'd already heard how bad the radio signal sounded.

Transmitter had 3 leds (power, stereo both lit & alarm not lit) and 2 volume controls, so all looking good.

Next test was measure the mains voltage which was way down, near 150V, transmitter spec ~120W 230V and contained a linear power supply.

Customer had purchased cable to do the same run from the studio. AKA 0.5mm² 3 core flex.

I checked the maximum current by shorting the supply with current range of multimeter, which was only a couple or 3amps.

The quickest fix was a generator followed by 2.5, 4 and 6mm² cables

Circuit design is far too frequently forgotten and not only by non qualified/experienced electricians.

 

[SUNRAY]

I cannot think why this is so vexed...its add the total watts to get of the attached cooking items find the amps by dividing by 240,
start eg 50amps max load take 10 amps away and find 30% of the remainder then add back the 10 amps, mcb sorted...then consult the carrying capacity of the cable according to its method of installation, cable sorted.

Absolutely correct except our nominal voltage is 230V and where we are supposed to do our calculations.

 

[SUNRAY]

4mm cable is useful when running 32A radials with a few sockets

Tricky with 6mm

Easier to install and test than a 32A ring

I dispute running a 4mm² radial is easier than a 2.5mm² ring in a typical house.
And what makes a 6mm² trickier than a 4mm²?

 

[SUNRAY]

True. What about US Amps ?

Kind Regards, John

US Amps are just that... Unserviceable