220v. 230v, 240v, 250v?

John-SJW · Jun 6, 2021

I saw an oven that was rated at 3,100 watts. Now most would say that cannot be fitted on final ring circuit as rule of thumb. But:
3,100 watts draws amps of:
14.09 amps @ 220v
13.47 amps @ 230v
12.91 amps @ 240v
12.4 amps @ 250v

If the installation is 240v or 250v then it safely inside the 13 amp of a final ring circuit.

The question is, and the regs aficionados can help here, what is the voltage that should be used to assess, as maybe the voltage will vary in an installation over the years.

DPG · Jun 15, 2021

John-SJW said:
Nope.

I don't think lastmanonline has denied the advantages of the UK plug though.

Lucien Nunes · Jun 15, 2021

BS1363 is not the only type with shutters or insulated pins these days. Although, insulated pins are not so important where the plug mating face engages in a deep pocket in the socket front, such as CEE7/3 Schuko.

BS1363 is a good plug that benefits from being of more recent design than most, engineered to meet a specification based on experience of other good plugs including BS372 and derivatives. But the fuse is an Achilles heel due to its heat dissipation and its requirement for fuse contacts of excellent design and manufacture. If these are in any way lacking in quality, and many are (compared to say the original MK Safety Plug) they are markedly unreliable on high load and prone to thermal runaway. This is not a fault with the design as such, but nonetheless it gives rise to a range of common failure modes that would not exist if there were no fuse.

In contrast, a moulded unfused plug with spot-welded leads has no pressure contacts internally and unless of genuinely faulty manufacture cannot exhibit significant resistance or generate significant heat even under overload. Only the socket and switch contacts dissipate significant heat, and if you have spent much time dissecting and testing typical sockets from around the world, you will know that run-of-the-mill BS1363 socket contacts are not always the lowest-resistance offering out there. A well-made Schuko socket will handle 20A continuously, giving a useful safety margin to avoid thermal runaway at 16A.

No one design currently in use has all the best features. Some have very few of them. Some locales tend not to use plugs at all, preferring to push wires into sockets. Shutters are a real nuisance here and well worth avoiding.

LastManOnline · Jun 15, 2021

Lucien Nunes said:
BS1363 is a good plug that benefits from being of more recent design than most..... But the fuse is an Achilles heel.
.

Firstly, your objective analysis is as always...very refreshing. My view of the "achilles heel" is a simple one. Get rid of it. It can be done easily and inexpensively

Replace the kitchen ring (plus other rings) with 2 x20amp radials.

The immediate benefits are...

1) an extra 2kw capacity compared to the 32 amp ring

2) two circuits protecting kitchen rather than one

3) a maintenance free plugtop (fuses no longer necessary)
..... issues re heat dissapation sorted
..... Issues regarding wrong size fuse inserted sorted.
...... safety issues due to shorting out fuse sorted

4) electrical testing simplified (radials versus rings)

nicebutdim · Jun 15, 2021

Regardless of the relative merits or disadvantages, I don't think that getting rid of the BS1363 plug is a great suggestion.

The people of Ireland might be open to this suggestion, but there'd be revolt on the streets of GB.

LastManOnline · Jun 15, 2021

nicebutdim said:
Regardless of the relative merits or disadvantages, I don't think that getting rid of the BS1363 plug is a great suggestion.

Not suggesting we get rid of it. Have already stated my personal preference for it. I firmly believe it should be retained. Just advocating "upgrading"

nicebutdim said:
The people of Ireland might be open to this suggestion, but there'd be revolt on the streets of GB.

Believe me, my views are not overwhelmingly popular there (either). I was removed from 2 local electrical forums last year.

static zap · Jun 15, 2021

LastManOnline said:
I was removed from 2 local electrical forums last year.

Oh dear , this forum was a bit .. Baptism of flaming bitumen in the past.
--We have a be nice policy now ! --
(observe how others behave , and be nice .. don't want to bust a Covid blood vessel , with ambulance waiting times )

LastManOnline · Jun 15, 2021

John-SJW said:
It says:

This hob is equipped with a UK 3 pin plug for an easy plug & play installation. The plug limits the maximum power output to 3.7 KW. For higher power output, please select a hob without plug and ensure installation is carried out by a qualified electrician

Anyway. Back to the thread. The above instructions are lifted directly from Bosch, s own struction manuel. I had a telephone and email exchange with them over the weekend. They confirmed that there is a power limiting device in the hob as Lucien suggested. There is however no mention of this device in the manuel (I stand to be corrected here). Regarding the 3700 watt max rating I raised the issue of a 15 amp load on a 13 amp fuse. However the service personnel could not offer any opinions on this

nicebutdim · Jun 15, 2021

LastManOnline said:
Believe me, my views are not overwhelmingly popular there (either). I was removed from 2 local electrical forums last year.

I don't always always agree with you, but certainly like the manner in which your thinking is clearly laid out and the question you raise. No harm in challenging conventions, especially when reasons for that challenge are clear.

Should add that you also contribute significantly to the overall knowledge this forum allows me to tap into.

Lucien Nunes · Jun 15, 2021

Replace the kitchen ring (plus other rings) with 2 x20amp radials.
The immediate benefits are...
1) an extra 2kw capacity compared to the 32 amp ring

This is a double-edged sword because of the loss of diversity. Yes the total load capacity is greater, but there is less flexibility about where the loads may be connected. With 20A circuits it is not nearly so much of a limitation as with 16A. It might take four or more of the latter to do the work of one 32A, if nuisance tripping and persistent non-trip overloads are to be avoided due to unfavourable distribution of load.

The above was another economic argument in favour of retaining local OCPD in the IEC60906 retrofit scenario, and mitigation of the admittedly high unit cost of my MCB-equipped sockets. Taking all the benefits into account, in principle I agree with @John-SJW on the advantages of the fuse, although I am rather less specifically in favour of BS1363 having spent a sizeable fraction of my life working with alternatives.

Grant1987 · Jun 15, 2021

LastManOnline said:
Not suggesting we get rid of it. Have already stated my personal preference for it. I firmly believe it should be retained. Just advocating "upgrading"

Believe me, my views are not overwhelmingly popular there (either). I was removed from 2 local electrical forums last year.

I like the fact that you voice your opinion and unless your comments are derogatory or insulting then you should not be removed from any forum. I like the debate and I believe we should be allowed to speak out so good on you keep it going ?

LastManOnline · Jun 15, 2021

Lucien Nunes said:
This is a double-edged sword because of the loss of diversity. Yes the total load capacity is greater, but there is less flexibility about where the loads may be connected. With 20A circuits it is not nearly so much of a limitation as with 16A. It might take four or more of the latter to do the work of one 32A, if nuisance tripping and persistent non-trip overloads are to be avoided due to unfavourable distribution of load.

There is a really easy and practical answer to this. Take a look at the average 3 bedroomed home in ROI, France, Germany, and compare with UK. Appliance use is virtually identical. In ROI, two radials are required in the kitchen. Guess how often I get calls about mcb, s tripping??
The above fears are in practice non-existent

Lucien Nunes said:
The above was another economic argument in favour of retaining local OCPD in the IEC60906 retrofit scenario.

I do remember similar fears in the noughties being expressed in the UK about the introduction of rcd, s. Their was a quite vocal "anti-rcd brigade" who proclaimed their own "project fear" message about the inevitability of nuisance tripping that would be caused by the rcd, s. They omitted to look at countries where these same devices had been in use for many years

Lucien Nunes · Jun 15, 2021

LastManOnline said:
In ROI, two radials are required in the kitchen

In UK, one 32A circuit will do more than a kitchen. I'm not saying that's advisable for reasons of redundancy, but that's a separate consideration. OTOH I did manage to trip a 16A MCB in Germany with two electric heaters that I thought I had plugged into separate circuits but were actually on the same circuit. As I mentioned, there is a noticeable increase in flexibility of the 20A circuits compared to 16A.

In a previous occupation I used to go around venues plugging lots of 3kW loads into 13A sockets. What works in a domestic kitchen won't necessarily suffice in that situation, but any kind of standard plug and socket needs to be suitable for whatever wiring configurations are applicable to both.

John-SJW · Jun 15, 2021

LastManOnline said:
Firstly, your objective analysis is as always...very refreshing. My view of the "achilles heel" is a simple one. Get rid of it. It can be done easily and inexpensively

Replace the kitchen ring (plus other rings) with 2 x20amp radials.

The immediate benefits are...

1) an extra 2kw capacity compared to the 32 amp ring

2) two circuits protecting kitchen rather than one

3) a maintenance free plugtop (fuses no longer necessary)
..... issues re heat dissapation sorted
..... Issues regarding wrong size fuse inserted sorted.
...... safety issues due to shorting out fuse sorted

4) electrical testing simplified (radials versus rings)

Why get rid of a safety asset. Madness to do so.

John-SJW · Jun 16, 2021

nicebutdim said:
Regardless of the relative merits or disadvantages, I don't think that getting rid of the BS1363 plug is a great suggestion.

The people of Ireland might be open to this suggestion, but there'd be revolt on the streets of GB.

There are lots of ring circuits in Ireland. Maybe they want deaths and fires by reducing protection.

static zap · Jun 16, 2021

John-SJW said:
There are lots of ring circuits in Ireland. Maybe they want deaths and fires by reducing protection.

Maybe we need to shame more appliances .
In the 1980-90s it was VCRs that the fire-brigade usually blamed.

I wonder how many fake Iphone chargers are in untidy kitchens
with paper , polythene nearby.
or in bedrooms hidden by bedding. Smoke detectors may save lives,
but at what cost for connected convenience. !

LastManOnline · Jun 16, 2021

John-SJW said:
There are lots of ring circuits in Ireland. Maybe they want deaths and fires by reducing protection.

With respect John. It would be appreciated if you concentrate on electrically analysing the questions being raised rather than making throwaway / unfounded comments.

John-SJW · Jun 16, 2021

LastManOnline said:
With respect John. It would be appreciated if you concentrate on electrically analysing the questions being raised rather than making throwaway / unfounded comments.

If you take the fuse out of the plug when on a ring, you will get fires, as an essential safety point has been removed. The farsighted men in 1942 who thought of the fuse in plug, and then regulated for it, were brilliant. We have the best. Why change what does not need changing.

LastManOnline · Jun 17, 2021

Lucien Nunes said:
In summary, I do not think it was the intention of Bosch to imply that a 3.7kW load may be supplied via a 13A plug,

Got an update from Bosch this morning stating that it's hob will "not draw more than 3.7kw when being used".So this would imply a current of 15.5 amp in the UK and 16 amp in ROI on its 13 amp plugtop when the hob is on full load.

The figures don't look great. We are on the wrong side of the plugtop rating. However, (going to stick my neck out here a little). I would have no concern about installing one of these in my own home as my current Induction hob (which by coincidence only ever has 2 rings on at any one time) is constantly cycling in and out and in reality the average load is under 13 amps (probably a, few amps under after initial startup).

Would I install one in someone else's home?. Unlikely unless there is a separate circuit. This particular appliance seems to fall between a rock and a hard place according to our regs. Can't see an inspector being pleased to see it being plugged in.

Bosch I think we're more than a little careless in the way they wrote their instruction Manuel.
Secondly, it was clear to me that the "service personnel" (who were very pleasant to deal with) were struggling a little in answering technical questions. Not their fault.

John-SJW · Jun 17, 2021

LastManOnline said:
Got an update from Bosch this morning stating that it's hob will "not draw more than 3.7kw when being used".

So, what is it set to, if it is settable, as it has a 13A fuse?
Is this a continuous 3.7kW, or a spike?
Something tells me they do not know enough about their own product.

Out of interest, my Smeg induction hob states 7.2 kW. It can be wired 3 or single phase. I assume the 7.2kW is for 3-phase connection. I put on an amp clamp, then put all rings on full with pans full of cold water, on the P setting. It was drawing only 21.46 amps at 247v, which is about 5.3 kW, way below the max of 7.2 kW they state.

LastManOnline · Jun 17, 2021

John-SJW said:
So, what is it set to, if it is settable, as it has a 13A fuse?

As mentioned in earlier posts. A 13 amp fuse will take 15 amps for a significant period

John-SJW said:
Out of interest, my Smeg induction hob states 7.2 kW. It can be wired 3 or single phase. I assume the 7.2kW is for 3-phase.

No. 7.2kw is also suitable for single phase. They have 3 phase on the continent in domestic dwellings and that's why the hobs are configured to be connected both ways

John-SJW said:
put on an amp clamp, then put all rings on full with pans full of cold water, on the P setting. It was drawing only 21.46 amps at 247v, which is about 5.3 kW, way below the max of 7.2 kW they state.

You are probably getting an average as the rings cycle in and out of full power

John-SJW · Jun 17, 2021

LastManOnline said:
As mentioned in earlier posts. A 13 amp fuse will take 15 amps for a significant period

No. 7.2kw is also suitable for single phase. They have 3 phase on the continent in domestic dwellings and that's why the hobs are configured to be connected both ways

You are probably getting an average as the rings cycle in and out of full power

I know it can. I forget how long. Any offers from the group? I recall a 13A fuse blows at about 17A after about an hour. So for intermittent use that is fine, not for a continuous load like a space heater.

I put the large pans of cold water on each ring, then all on the highest P setting, then observed the clamp meter. No switching in and out at that point as all rings were on full belt.

John-SJW · Jun 17, 2021

Look at at a plug. It always says 13A, 250V. That is 3.2 kW.

timhoward · Jun 18, 2021

John-SJW said:
I know it can. I forget how long. Any offers from the group? I recall a 13A fuse blows at about 17A after about an hour.

If this graph is true a BS1362 13 amp fuse won't blow at all until over 20 amps and at least 2 hours.

[ElectriciansForums.net] 220v. 230v, 240v, 250v?

Julie. · Jun 18, 2021

The characteristic curve isn't quite right or the markings are wrong, the characteristic must become asymptotic at a value no greater than 19.5A for a 13A fuse, or it wouldn't comply with the 1.5 rule going back to the 14th for close protection, and they are the same fuses now.

It could take up to 4 hours to operate of course.

timhoward · Jun 18, 2021

Julie. said:
The characteristic curve isn't quite right or the markings are wrong, the characteristic must become asymptotic at a value no greater than 19.5A for a 13A fuse, or it wouldn't comply with the 1.5 rule going back to the 14th for close protection, and they are the same fuses now.

It could take up to 4 hours to operate of course.

Thanks Julie. I've never found a good graph for this question...

220v. 230v, 240v, 250v?

John-SJW

DPG

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Lucien Nunes

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LastManOnline

nicebutdim

LastManOnline

static zap

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LastManOnline

nicebutdim

Lucien Nunes

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Grant1987

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LastManOnline

Lucien Nunes

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John-SJW

John-SJW

static zap

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LastManOnline

John-SJW

LastManOnline

John-SJW

LastManOnline

John-SJW

John-SJW

timhoward

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Julie.

timhoward

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