SWA For meter tails?

[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

 

[Msitekkie]

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
/QUOTE]
Thanks for that. Fig 3A1(page 319) is most illuminating. Few discussions of diversity refer directly to this time factor and its clearly very relevant.

 

[Msitekkie]

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

Thanks for that. Fig 3A1(page 319) is most illuminating. Few discussions of diversity refer directly to this time factor and its clearly very relevant.

 

[Msitekkie]

PPP

Post pictures please

 

[Midwest]

That is a bit of a lash up, what you want is a bit of swa cable

Could the tails be routed out the back of the meter box, then surface inside in some plastic trunking?

 

[Pete999]

That is a bit of a lash up, what you want is a bit of saw cable

Could the tails be routed out the back of the meter box, then surface inside in some plastic trunking?

saw cable?

 

[Midwest]

saw cable?

Thanks Pete

 

[Pete999]

Thanks Pete

Your welcome.

 

[Mjgriff82]

I would consider using a 16mm split concentric chopped in the wall Covered by an earthed 3mmsteel plate covering, from the incomer connected to a kmf isolator

 

[Msitekkie]

If it's SWA why would I use surface trunking? The problem I'm facing really, is once it reaches the porch getting it through the brickwork and wooden beam to the void. Ironically the supply to the meter appears to originate from somewhere under the concrete floor inside the porch, but moving the meter inside isn't really an option.

 

[davesparks]

If it's SWA why would I use surface trunking? The problem I'm facing really, is once it reaches the porch getting it through the brickwork and wooden beam to the void. Ironically the supply to the meter appears to originate from somewhere under the concrete floor inside the porch, but moving the meter inside isn't really an option.

Trunking looks a little nicer than cleated SWA.

To get through the brickwork and wood drill a hole.

It’s not really ironic, it’s just probably been moved outside from it’s original location inside.

 

[Pete999]

saw cable?

Why is it Old Lee?

 

[Midwest]

If it's SWA why would I use surface trunking?

I was suggesting an alternate to swa, some 6181y and surface plastic trunking?

 

[Msitekkie]

I was suggesting an alternate to swa, some 6181y and surface plastic trunking?

OK. Yes, looks like this is the way I'm going to go, then straight through the wall and cut a channel round the outside of the brick pillar (inside the porch), through into the void.

 

[davesparks]

OK. Yes, looks like this is the way I'm going to go, then straight through the wall and cut a channel round the outside of the brick pillar (inside the porch), through into the void.

When you say cut a channel you don’t mean to bury the tails in the wall do you? Because then they’d need RCD protection which would be unacceptable.

 

[Msitekkie]

When you say cut a channel you don’t mean to bury the tails in the wall do you? Because then they’d need RCD protection which would be unacceptable.

In conduit.

 

[Msitekkie]

When you say cut a channel you don’t mean to bury the tails in the wall do you? Because then they’d need RCD protection which would be unacceptable.

In conduit.

 

[Ian1981]

In conduit.

How will you Earth the conduit?

 

[Msitekkie]

How will you Earth the conduit?

Plastic conduit.

 

[Andy78]

Plastic conduit.

Really ? Please refer to previous comments of concern suggesting you get an electrician in.

 

[Msitekkie]

Really ? Please refer to previous comments of concern suggesting you get an electrician in.

I am involving another electrician... As mentioned previously. Existing tails are in plastic conduit embedded in the wall. This is more like passing through the wall in conduit as does the DNO supply.
If you have feedback on the method based on standards, please refer.

 

[Msitekkie]

Really ? Please refer to previous comments of concern suggesting you get an electrician in.

I am involving another electrician... As mentioned previously. Existing tails are in plastic conduit embedded in the wall. This is more like passing through the wall in conduit as does the DNO supply.
If you have feedback on the method based on standards, please refer.

 

[Andy78]

I am involving another electrician... As mentioned previously. Existing tails are in plastic conduit embedded in the wall. This is more like passing through the wall in conduit as does the DNO supply.
If you have feedback on the method based on standards, please refer.

If another electrician is involved then it would be most appropriate to ask them about installation methods and all other aspects of the installation if they are to be signing certificates. That is what I would expect if I were doing the same favour.

 

[Pete999]

I am involving another electrician... As mentioned previously. Existing tails are in plastic conduit embedded in the wall. This is more like passing through the wall in conduit as does the DNO supply.
If you have feedback on the method based on standards, please refer.

So you have the help of two Sparkies then?

 

[Midwest]

Don't get embroiled in scavenging now.

 

[davesparks]

Plastic conduit.

Not acceptable in my opinion, it would have to be earthed metal conduit to fully comply with the regulations.

 

[Msitekkie]

Not acceptable in my opinion, it would have to be earthed metal conduit to fully comply with the regulations.

I'm actually following the electricians instructions... but thanks for the heads up, I will raise it with him.
(For the benefit of anyone else trying to learn from this thread, the regulations we are discussing here are 522.6.x)
I'm now leaning back towards using 25mm SWA (2 core as I already have a decent earth) with a Henley block once I reach the void (more than 50mm deep) to convert back to double insulated tails and minimise issues with bend radius.

 

[Pete999]

I'm actually following the electricians instructions... but thanks for the heads up, I will raise it with him.
(For the benefit of anyone else trying to learn from this thread, the regulations we are discussing here are 522.6.x)
I'm now leaning back towards using 25mm SWA (2 core as I already have a decent earth) with a Henley block once I reach the void (more than 50mm deep) to convert back to double insulated tails and minimise issues with bend radius.

How will you provide an earth for the armouring on the SWA 2 core?

 

[Toneyz]

From looking at the photo's could you not just box that part in therefore you could use standard 25mm tails further back than 50mm outside run in plastic trunking (could even semi recess into pebbledash).

 

[Msitekkie]

Good point thank you, my thinking hadn't got that far. I could maybe gland off to a galvanised conduit angle box and use Pratley box connectors instead of the Henley block. Plenty of earth's available in the void I could use.
I could use a Pratley box for that matter but seems an expensive option and a bit overkill.
Other than that I would have to put the Henley block in some other sort of box that I could gland off to.

 

[Msitekkie]

From looking at the photo's could you not just box that part in therefore you could use standard 25mm tails further back than 50mm outside run in plastic trunking (could even semi recess into pebbledash).

The bit I am putting in the wall is in the middle between the void and the outside wall, so I don't quite follow you. If you are suggesting I run it on the surface inside the house, yes I could probably do that, but a bit of a cop out as would be rather unsightly.

 

[Toneyz]

The bit I am putting in the wall is in the middle between the void and the outside wall, so I don't quite follow you. If you are suggesting I run it on the surface inside the house, yes I could probably do that, but a bit of a cop out as would be rather unsightly.

From looking at the photo would be only bringing the wall level with the door.