SWA For meter tails?

[Msitekkie]

I need to upgrade my meter tails to 25mm. The existing tails pass along under the pebble dash in plastic conduit (which would be too small), then apparently at an angle through the porch structure (unprotected) then turn sideways into a void & up the void to CU.

I have seen other posts where the use of SWA is suggested but I haven't actually seen SWA with 25mm cores. "25mm SWA" appears to be 25mm "Outside diameter", so I presume that means the cores are smaller.

Any suggestions as to the best approach welcomed. I actually think I will struggle with getting SWA through anyway even if it does exist with suitable cores, because of the bends involved.

NB The meter box is under the window of the house rather than on the side of the porch, but the void inside the porch is set back behind the run of the outside wall so it's not possible to drill directly through the outside porch wall into it.

 

[Spoon]

Don't take offence @Msitekkie . By most of the opinions on here I'm neither an 'electrician' or 'engineer'.... Everyone to their own....

 

[Pete999]

Don't take offence @Msitekkie . By most of the opinions on here I'm neither an 'electrician' or 'engineer'.... Everyone to their own....

Deleted

 

[LeeH]

I was just waiting for somebody to blow up on this thread....and DS was the first.

 

[Msitekkie]

You’re probably getting the calculations wrong then, the average house doesn’t need much more than about 20A.

Out of interest how did you arrive at a figure over 100A for a house?

House+garage+workshop:
Starting with 7.4Kw Induction Hob (1st 10A plus 30% of the remainder) 16.6A already...
3Kw Immersion heater - No Diversity allowed another 13A...
3Ring + 3 Radial Circuits (100% of 1st & 40% of rest) 32+49.6 = 81.6A
+ 4 x 6A lighting - haven't worked out all the lights I'm having yet, so lighting diversity still up in the air (although mostly a mix of compact flourescents & LEDs).
I know diversity is a bit of a black art so any constructive comments/suggestions welcomed. As the immersion is only used in emergencies if CH not working. I'm wondering if there are any options there.
P.S I don't have a clamp meter yet.

 

[Andy78]

Don't take offence @Msitekkie . By most of the opinions on here I'm neither an 'electrician' or 'engineer'.... Everyone to their own....

He was the one that brought up qualification defining his status in fairness

 

[Midwest]

The section on diversity in the OSG, has been the same content for quite some time, and is not reflective in modern appliances. So that guidance for RFC, can be taken with a pinch of salt. Unless your plugging in electric heaters in every socket outlet. Lighting circuits with LED lamps, will be only a few amps, again unless its like Blackpool illuminations. Get a clamp meter & check it out for yourself.

 

[Pete E]

House+garage+workshop:
Starting with 7.4Kw Induction Hob (1st 10A plus 30% of the remainder) 16.6A already...
3Kw Immersion heater - No Diversity allowed another 13A...
3Ring + 3 Radial Circuits (100% of 1st & 40% of rest) 32+49.6 = 81.6A
+ 4 x 6A lighting - haven't worked out all the lights I'm having yet, so lighting diversity still up in the air (although mostly a mix of compact flourescents & LEDs).
I know diversity is a bit of a black art so any constructive comments/suggestions welcomed. As the immersion is only used in emergencies if CH not working. I'm wondering if there are any options there.
P.S I don't have a clamp meter yet.

Re the Hob (and the Oven if electric) won't necessarily draw their full current loads even when on max due to them being thermostatically controlled. Same goes for the immersion heater....

 

[Midwest]

OP's applied the allowed diversity to the induction hob, can't really thin it back anymore, especially round Xmas time

 

[Des 56]

as no answers from anyone on the routing question, although I appreciate that's difficult to visualise on a forum such as this.

PPP

Post pictures please

 

[Mjgriff82]

There’s little chance those ring circuits are going to pull over 80 amps after diversity, why not have a 20a radial upstairs, 20a radial downstairs and a ring for kitchen?
What are other radial circuits,
Think of peak times morning evenings when most load will be consumed should only be short periods when applying diversity,
a bs88-3 (new bs number for 1361) will take 190a for half hour fig 3A1 bs1761
I doubt very much your ever going to come anywhere near this.
I would recalculate put in an 80a kmf

 

[Msitekkie]

There’s little chance those ring circuits are going to pull over 80 amps after diversity, why not have a 20a radial upstairs, 20a radial downstairs and a ring for kitchen?
What are other radial circuits,
Think of peak times morning evenings when most load will be consumed should only be short periods when applying diversity,
a bs88-3 (new bs number for 1361) will take 190a for half hour fig 3A1 bs1761
I doubt very much your ever going to come anywhere near this.
I would recalculate put in an 80a kmf

Radials are sockets in Garage, workshop & new utility room. Upstairs & downstairs are existing rings - don't really want to add work by converting to radials if I can avoid. Splitting kitchen off downstairs ring onto its own.

 

[marconi]

If you consider loads over 1kW, which could over a period of say an hour be on at the same time, some of which are thermostatically/simmerstat cycling on/off or controlled by a programmer, then I reckon your short-lived peak demand is:

Ind Hob 7kW (to take account of Christmas Day type useage)

Imm Htr 3kW

Wash Mach 2kW

Tumb Dry 2.5kW

Dish Wash 2kW

Electric Convection Oven 2.5kW

Total = 19kW = 79A at 240V for which 16mm2 tails and 60A/80A BS88 cut out is perfectly adequate.

Most of the time the load will be far less - I'd estimate the time-averaged power consumption over an hour period to be:

Ind Hob 2kW

Imm Htr 3kW

Wash Mach 0.5kW

Tumb Dry 1.5kW

Dish Wash 0.5kW

Electric Convection Oven 0.5kW

Total 8kW or circa 35A again well within the capacity of a 60A/80A BS88 fuse and 16mm2 tails.

In my home I have 2 TDs, 2WMs, DW, IH, 2 electric convection ovens all supplied by a 80A BS88. The short DNO meter tails are 16mm2 and the CU tails are 25mm2 but 16mm2 would have sufficed.

 

[Mjgriff82]

Completely agree with what Marconi has said, I can’t ever see the house pulling more than about 40 amps.

On your method though, your looking at it from the wrong angle if you have a down ring which is ok, why do you need to split it as this is adding another 14 or so Amps to your calc for an extra ring circuit

 

[davesparks]

House+garage+workshop:
Starting with 7.4Kw Induction Hob (1st 10A plus 30% of the remainder) 16.6A already...
3Kw Immersion heater - No Diversity allowed another 13A...
3Ring + 3 Radial Circuits (100% of 1st & 40% of rest) 32+49.6 = 81.6A
+ 4 x 6A lighting - haven't worked out all the lights I'm having yet, so lighting diversity still up in the air (although mostly a mix of compact flourescents & LEDs).
I know diversity is a bit of a black art so any constructive comments/suggestions welcomed. As the immersion is only used in emergencies if CH not working. I'm wondering if there are any options there.
P.S I don't have a clamp meter yet.

If the immersion is only a backup then ignore it for this purpose.

81.6A of portable/small appliances in a house sounds ridiculous to me, does the total running current of every appliance you own actually add up to that much?

It helps to actually think about the real world rather than getting lost in the numbers written in a book.
What will actually be plugged in and operating during the average day, and will it all be on at the same time?

 

[Midwest]

I've never understood the suggestion of converting an RFC into radials in a property, will somehow reduce electrical consumption? Its still the same house with the same appliances