Trying to upgrade house fuse to 100A

[Entropy]

I am after some guidance and I know what I am asking for is a 'finger in the wind' guess as estimating a cable's capacity is not necessarily related to the cables diameter.
I arranged to have my main house fuse upgraded last week. I requested a 100A fuse but due to the size of the tails the engineer could only upgrade the fuse to 80A. I recieved a post upgrade call from UK Power Networks and the very nice lady said that she would keep the job open in case I wishto still upgrade to a 100A fuse. She said if the tails are upgradedThey can send out someone to see if the supply into the house is capable of taking a 100A feed.

So my question is. Can I approximately guess if my power supply can take 100A feed from measuring the diameter of the cable? If so what diameter would indicate that it can carry 100A? The current cable runs along the side of the house and due to its stiffness I am assuming it is armoured and has a diameter of 13mm.

Secondly if the cable is currently capable of taking 100A what are the chances that I can persuade the inspector to state that the cable needs replacing? I am asking this as the cable upgrade work is provided for free by UKPN if it is not capable of carrying 100A and a replacement of the supply would allow me to move the meter board when the supply is schanged without me bearing the cost.

Thanks

 

[EFLImpudence]

Which cable are you talking about - before or after the meter?

The size of cable is measured in cross-sectional area of the copper bits - not the diameter although of course that can be approximately calculated.

 

[securespark]

The tails are from the meter to your consumer unit or units, via Henley blocks or a double pole switch if you have them

100A tails are 25mm².

The supply cable may be smaller in cross section, but it's up to the DNO what size fuse they use on their supply cables.

 

[Murdochcat]

OP - What makes you think you need 100A

 

[AndyPRK]

what cable is between the meter and your CU ?
Black SWA ?
2 Tails. grey/brown/blue ?


photos help.

 

[ericmark]

My supply has a 100 amp isolator that I provided, without that isolator difficult to do any work without breaking the seals. The CU also needs to be at least 100 amp, or your own fuses, the old Wylex fuse box was 60 amps,

which I think is the reason I only have a 60 amp supply, even though the CU has now been changed, but also my inverter is 5 kW = 21.6 amps, so total supply is 81.6 amps, so 80 amp would be my limit, unless I fit a 100 amp fuse to feed the CU.

There is some debate about CU like this

two 80 amp RCD's so the sum of the MCB's should not exceed 80 amps, 3x6A, 1x16A, 4x32A can be arranged 82 amps and 80 amps 3 x 6 + 2 x 32 and 1 x 16 + 2 x 32 the two blanks could have RCBO's fitted, picture shows 4 + 4 can't do that unless 80 amps or under supply. I have used one of these

in the past to split supply to 2 or 3 consumer units, but that needs sorting before you call the DNO.

How strict the DNO are I don't know, years ago we did not seem to worry about an under sized RCD, and I look at my house, and we are no where near the limit with actual use, it depends on how perdantic the installer is.

 

[EntropyUK]

For clarification I am referring to the main power supply into the property which runs into the main fuse.

I was looking at going to 100A to futureproof the house for cars etc. and it was a free upgrade so wanted to get it done before someone decides to charge for it.

 

[Murdochcat]

For clarification I am referring to the main power supply into the property which runs into the main fuse.

I was looking at going to 100A to futureproof the house for cars etc. and it was a free upgrade so wanted to get it done before someone decides to charge for it.

Unless you have electric space heating 80A will be more than enough for future EV point etc

 

[flameport]

requested a 100A fuse but due to the size of the tails the engineer could only upgrade the fuse to 80A. I recieved a post upgrade call from UK Power Networks and the very nice lady said that she would keep the job open in case I wishto still upgrade to a 100A fuse. She said if the tails are upgradedThey can send out someone to see if the supply into the house is capable of taking a 100A feed.

The tails are the wires between the DNO fuseholder and the meter, and the wires between the meter and your consumer unit.

The cable into the property before the fuse is unrelated, and they don't need to send someone to look at that because they already have.
The 100A option was cancelled because the tails you have are probably 16mm² instead of 25mm².

If you want the 100A then the wires between fuse and meter need to be replaced, theoretically by your energy supplier.
Those between the meter and consumer unit are your responsibility, but due to the mess of how these things are arranged, in theory you will need the energy supplier to connect the new tails to the meter after you have already arranged someone else to provide them - but that electrician is not permitted to open the meter so can't disconnect the old ones, and the energy supplier can't connect anything to consumers equipment.

Therefore the 'proper' way to do things would be for the energy supplier (who you pay for electricity) to visit and replace the tails between fuse and meter, then add some new ones between the meter and a new isolator that they provide, and they can then shove the old tails into the other side of that new isolator, and then some electrician can attend and replace those between the isolator and the consumer unit.
If your meter is an old one, then perhaps they can attend and replace that and the tails at the same time for no cost. The electrician will have to be paid for in any case.
After that the tails from meter to isolator and the isolator itself will be the energy suppliers property which must not be tampered with, until the isolator fails or needs to be relocated and then it magically becomes your responsibility once again so you can pay for it.

Other, non-proper ways of achieving the tails replacement are available.

 

[SUNRAY]

What I've known work several times now has been to provide and fit the isolator, terminate new tails into it, a pair plenty long enough for both sides of the meter but just hanging. Plus a pair prepared to be fitted between the isolator and the CU.
DNO has arrived and simply completed the installation as far as the isolator, just leaving the CU side to be fitted which they can see laying there.

 

[AndyPRK]

and supply Tea and Jaffa Cakes ?

 

[SUNRAY]

and supply Tea and Jaffa Cakes ?

Of course!!!


Does that need questioning?

 

[securespark]

It has to be Hob Nobs!

 

[Taylortwocities]

It has to be Hob Nobs!

Chocolate Hob Nobs. accept no substitutes!

 

[SUNRAY]

Chocolate Hob Nobs. accept no substitutes!

Not even the Lidl version (which I think are better)?