Twin to triple socket converter. Will the fuse blow?

[Taylortwocities]

I see. Just to be sure I understand, there is effectively a ring before the grid and each of the switches (and the socket downstream from it) is effectively a spur, right?

Is there effectively an amp rating on each of these spurs?

It depends on how it has been configured and if there are any fuses built into the grid array.
Personally I think having a grid switch array on a ring final is bad engineering as it means that all of those loads are concentrated at one point on a ring. The point of a ring is that loads are distributed around the ring.
When I’ve done one of these I have used a 32amp radial as the feed.

 

[ericmark]

The official line is

The load current in any part of the circuit should be unlikely to exceed for long periods the current-carrying capacity of the cable (Regulation 433.1.5 refers). This can generally be achieved by:
(i) locating socket-outlets to provide reasonable sharing of the load around the ring
(ii) not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile from the ring circuit
(iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit
(iv) taking account of the total floor area being served. (Historically, limit of 100 m² has been adopted.)

So the washing machine and dish washer should both have a dedicated supply. However historically the washing machine was not a fixed appliance, OK there were some odd ones like the old Bendix front loaded which were bolted to the floor, but in the main we would drag twin tub to centre of floor on wash day, and no other items would be use in the kitchen at the same time, it was hot and cold fill, so even if it had a heater, the total load was low, and I know my son could run a 2.4 kW washing machine on his narrow boat with a 6 amp type B MCB supply to whole boat, with a 40ºC wash, but a 4 amp MCB would trip. As the heater was on for such a short time. Never put an energy monitor on the dish washer, but again the time to heat water is short. So in real terms both from same double socket is not really a problem.

However this would not include a washer/drier with a resistive heater for dryer, the heat pump type would be OK, as long as volt drop is within limits, but not resistive type.

third socket to power something else

This depends on the some thing else, before solar panels were fitted, it was common practice for me to make two cups of coffee at the same time with two one cup boilers both plugged into the same extension, on the odd time the fuse would rupture, but the time they take to boil was so short, in spite of the 6 kW load on a 13 amp fuse it worked OK, not the correct thing to do, and since solar with battery stopped doing it as battery only good for 3 kW so now cheaper to do one at a time, and wife not using milk, so want the larger of the two one cup boilers for us both, but for a short time a socket can be over loaded without any real problem.

The problem is resistive tumble drying, as it runs for such an extended time, we moved to heat pump, which yes means only 650 watt, however the 2.5 hours is a problem as getting two washing loads a day without drawing from the grid is a problem. Today I ran out of battery at 11 pm, we did not get enough late sun to carry us through until cheap rate, we are likely going OTT in trying to spread our load to make max use of sun and cheap rate, but the solar has changed our living style to try and reduce grid use.

This has resulted in being more aware of what power we are using in total, even more than simple smart meter use, and we can draw 3 kW from the battery, and up to 6 kW from solar direct, today our use looked like this the peak was where wife using bread maker at same time as I had dryer on, it is likely we could nearly run whole house under 13 amp except for the showers, in the main highest power use is making coffee.

So although theroy say have dedicated circuits, in practice we can get away without them, on the odd time a fuse may blow, but not enough times to really worry about it.

 

[JohnW2]

Personally I think having a grid switch array on a ring final is bad engineering as it means that all of those loads are concentrated at one point on a ring.

It depends upon where that 'point on the ring' is. If most/all of the loads are connected at, or near to, the mid-point of the ring (which is often roughly the case for those grid switch arrays in kitchens), then that is close to an ideal 'balanced' arrangement, and actually becomes equivalent to a 5mm² radial if all the loads are applied at that point.

The point of a ring is that loads are distributed around the ring.

They don't actually have to be distributed 'around the ring', but they ideally need to be 'balanced' on the two 'sides' of the ring (either side of the midpoint), with none too close to either end, but there's nothing wrong with the loads all being ('symmetrically') fairly near the mid-point, since that optimises the chances of equal current in the two sides of the ring, just as would be the case if they were spread (symettrically) along the entire length of the ring.

When I’ve done one of these I have used a 32amp radial as the feed.

As above, that is essentially what one has if there is a grid switch array at roughly the centre of a ring. However, wiring it as a "2 x 2.5 mm² ring" may be more convenient than as a 4 mm² radial in terms of where one wants to locate a few other sockets in the room (as one usually would)/

 

[plugwash]

As above, that is essentially what one has if there is a grid switch array at roughly the centre of a ring. However, wiring it as a "2 x 2.5 mm² ring" may be more convenient than as a 4 mm² radial in terms of where one wants to locate a few other sockets in the room (as one usually would)/

And also in terms of actually physically getting the wires in there.

 

[JohnW2]

The official line is .... <quote> ... So the washing machine and dish washer should both have a dedicated supply.

That may be your opinion - although I have to say that I cannot recall ever having seen such appliances having dedicated supplies in any UK domestic installation!. However , your "So..." seems to imply that you believe that it follows from the material you have quotes (which is guidance, not a regulation).

If that is the case, do you really believe that a WM or DWM qualifies as an immersion heater, comprehensive electric space heating or loads of a similar profile, or a cooker, oven or hob with a rated power exceeding 2 kW ??

The fact surely is that such appliances (at least one of which exist in nearly all UK domestic properties) are inevitably supplied from multi-socket ring or radial circuits (probably most commonly rings), isn't it?

 

[JohnW2]

And also in terms of actually physically getting the wires in there.

Yes, that, too, if you're talking about the grid switches.

 

[chssvl]

Thanks a lot for the replies! Learned a lot as always.

I think I've found a better solution for the third plug - just use an extension lead from one of the outside plugs and hide it as best as possible. It was to be used with either a coffee maker or a microwave.

And, to be clear, it was not for a hob. We do have an electric hob but that has its own circuit and MCB.

The washing machine is a washer/drier type, but something broke in the drier and I had to physically disconnect the resistance a couple of years ago and disable the drier function to get the machine to turn on - not that we used that function much anyway.

I've checked the smart meter and I don't think I've ever seen the washing machine or dish washer draw anything close to 2kW each - more likely about half that.

 

[ericmark]

As @JohnW2 has implied many do not consider the 4 high load fixed appliances really need to be treated any different to the high load portable appliance. So washing machine, dish washer, dryer and oven treated the same as a kettle.

I would single out the dryer, be it built into a washing machine or as a separate item, an immersion heater with 40 gallons can take 4 hours to raise the temp from 10ºC to 80ºC with a 3kW immersion heater, however mine does not go that deep in the tank, so does not heat 40 gallons, lucky if it heats 10 and it does not heat to 80ºC more like 60ºC so in real terms less than an hour, so in real terms my old vented tumble dryer was a heavier load to the immersion heater it runs for longer than the immersion, and my immersion has a variable load since using an iboost+ so it only uses solar power, so comparing the immersion with a resistive clothes dryer they are about on par with each other.

The others including the oven are thermostatic controlled so the load is unlikely to be any more than the kettle as far as heating effect on cables goes. The being central on a ring final is desirable to stop overload near the origin as the load sharing not as good at the origin of a ring final.

The ring final reading the old literature was designed to allow the home to be electrically heated, I think this was a pipe dream, as an electric fire can be switched on for an extended time, and my parents home built 1954 so one of the first to have a ring final from new, had a single ring final and even with 7/0.029 cable which was slightly thicker than 2.5 mm² and solid brass pins in the 13 amp plug which will conduct heat away faster, and only 30 amp not 32 amp without the coal, coke, then gas fires it would have struggled to keep house warm with just electric without some over heating of cables or fuse rupturing.

I've checked the smart meter and I don't think I've ever seen the washing machine or dish washer draw anything close to 2kW each - more likely about half that.

I have since solar has been fitted also looked at power use, peak of 3471 watts is not shown on the smart meter app and the peak shown on smart meter not shown on solar app under consumption as it does not regard recharging batteries as consumption. The two charts selected to show same day, one would not think related to each other.

I note with the solar there can be a delay of 5 to 10 minutes, and also seems to be some odd readings with the IHD (in home display) my power meter works better for a single items to see what it uses, this shows a battery charger, but problem is time, recent usage is only shown for around an hour, and once one goes to average hourly use it rounds things off, however the point is more does it matter? It takes time to heat up a cable, fuse, or trip, so short peaks hardly matter, what we are trying to avoid is prolonged high power overloads, so really only the immersion heater, room heaters, and tumble dryer of items using 3 kW or less are a problem, the rest either has dedicated supply as over 3 kW or runs for a short time.

 

[Gigagator]

Thanks a lot for the replies! Learned a lot as always.

I think I've found a better solution for the third plug - just use an extension lead from one of the outside plugs and hide it as best as possible. It was to be used with either a coffee maker or a microwave.

And, to be clear, it was not for a hob. We do have an electric hob but that has its own circuit and MCB.

The washing machine is a washer/drier type, but something broke in the drier and I had to physically disconnect the resistance a couple of years ago and disable the drier function to get the machine to turn on - not that we used that function much anyway.

I've checked the smart meter and I don't think I've ever seen the washing machine or dish washer draw anything close to 2kW each - more likely about half that.

If you are happy to use an extension lead, perhaps a neater solution would be to just cut the plug off your coffee machine or microwave, and extend it with another piece of suitably sized flex and something like this:
https://www.tlc-direct.co.uk/Products/BG458.html

Not the most elegant solution, but if you are okay with using an extension lead and trying to hide it, maybe this would be easier to deal with?

Just a thought!

 

[chssvl]

If you are happy to use an extension lead, perhaps a neater solution would be to just cut the plug off your coffee machine or microwave, and extend it with another piece of suitably sized flex and something like this:
https://www.tlc-direct.co.uk/Products/BG458.html

Not the most elegant solution, but if you are okay with using an extension lead and trying to hide it, maybe this would be easier to deal with?

Just a thought!

Actually, not crazy. But we sometimes upgrade these things and sell the old ones so this might affect the ability to resell. But the idea dis cross my mind!

 

[JohnW2]

As @JohnW2 has implied many do not consider the 4 high load fixed appliances really need to be treated any different to the high load portable appliance. So washing machine, dish washer, dryer and oven treated the same as a kettle.
I would single out the dryer, be it built into a washing machine or as a separate item,

I think "many do not consider ..." is probably a serious under-statement. As I wrote, I've personally never seen or heard of any WM, DWM or dryer being fed from a 'dedicated circuit' in a UK domestic installation, have you?

Dryers are different (even though usually 'plugged in to a multi-socket circuit), but I'm not sure that a WM or DW is much 'worse' (in terms of duration of high load) than a kettle or suchlike, is it, and there are any number of 'portable' cooking appliances that are plugged into multi-socket ring or radial circuits in kitchens, many of which (microwaves, air fryers, fat fryers, soup makers etc. etc.), some of which draw appreciable current for appreciable periods of time

an immersion heater with 40 gallons can take 4 hours to raise the temp from 10ºC to 80ºC with a 3kW immersion heater,...

I think you are probably 'preaching to the converted' there. In dramatic contrast to what I've said above about kitchen/utility appliances, it is (for good reason) extremely unusual to see immersion heaters which are NOT supplied by a dedicated circuit, isn't it?

 

[Risteard]

I think "many do not consider ..." is probably a serious under-statement. As I wrote, I've personally never seen or heard of any WM, DWM or dryer being fed from a 'dedicated circuit' in a UK domestic installation, have you?

Dryers are different (even though usually 'plugged in to a multi-socket circuit), but I'm not sure that a WM or DW is much 'worse' (in terms of duration of high load) than a kettle or suchlike, is it, and there are any number of 'portable' cooking appliances that are plugged into multi-socket ring or radial circuits in kitchens, many of which (microwaves, air fryers, fat fryers, soup makers etc. etc.), some of which draw appreciable current for appreciable periods of time

I think you are probably 'preaching to the converted' there. In dramatic contrast to what I've said above about kitchen/utility appliances, it is (for good reason) extremely unusual to see immersion heaters which are NOT supplied by a dedicated circuit, isn't it?

It's not that uncommon for these sorts of appliances to have dedicated circuits.

 

[JohnW2]

It's not that uncommon for these sorts of appliances to have dedicated circuits.

Maybe not in your country but, as I said, I can't recall having seen that done in a domestic installation over here.

A dedicated circuit might just about be justifiable for a dryer (even though I've never see that done), but to install a dedicated circuit for a washing machine or dishwasher would seem (at least, to me) to be way OTT, and a waste of money and copper.