Incomers and service fuses

[securespark]

Read in Scots accent: "No, but think of the cost!"

 

[kendor]

35mm2!

That's only 1mm larger in diameter than 25mm - no big deal.

If we are talking Current ratings then the Cross sectional area (csa) should be discussed not the diameter and there is a big deal of difference between the current capacity of 25mmsq and 35mmsq

 

[Big_Spark]

Well, now here is the crux of this problem, the rating difference between 25mm and 35mm tails varies depending on the insulation used, however in Domestic situations, which is all we worry about here, we deal with 90C rated thermosetting Insulated cables for tails..and this is the problem.

Most electricity suppliers have always allowed diversity to dictate the size of the incomer tails, normally 25mm, HOWEVER, this only has a maximum rating of 100A anyway, but 35mm is only rated at 124A.

Now it may be that the diversity allowance will still be applied, thus we can be sure that 35mm tails will be sufficient, but if the supliers decide that due to this increased demand the 60% diversity rating they have always applied should be changed, we could be facing the potential of 50mm tails as these are rated at 149A.

 

[ban-all-sheds]

35mm2!

That's only 1mm larger in diameter than 25mm - no big deal.

If we are talking Current ratings then the Cross sectional area (csa) should be discussed not the diameter and there is a big deal of difference between the current capacity of 25mmsq and 35mmsq

Indeed - and it was abundantly clear to the rest of us that 25mm2 etc were csa sizes.

Mildmannerdjanitor exclaimed at the thought of 35mm2 tails, all I was doing was pointing out to him that if you put the two sizes next to each other there would be a barely detectable difference in size. Even the 50mm2 promised by FWL are less than half as thick again as 25mm2.

 

[Big_Spark]

Even the 50mm2 promised by FWL are less than half as thick again as 25mm2.

Hold on a moment, I never promised you a thing

I hope that something can be sorted out about this, trying to get 50mm tails into Consumer units will be a hightmare, especially the plastic ones as they will be bowed out of shape by the cables!!

 

[mildmanneredjanitor]

35mm2!

That's only 1mm larger in diameter than 25mm - no big deal.

My fault for being ambiguous again...

I was actually referring to the supply cable prior to the incoming fuse/meter. I imagine??? this is SWA and rated differently to the tails?

What is this cable rated at (usual domestic scenario - if there is such a thing).

 

[sterose]

Obviously diversity is not being applied properly, because it if drew over 100amps the fuse would simply trip. I find it risible that any house could draw over 100amps at once - even with every single appliance switched on.

It is very easy for this to occur, and it does happen. It is also a bit pressumptious to assume that diversity is not being applied properly.

As your knowledge seems to wildly exceed mine, FWL, I respect that you are the man in the know and I won't argue.

However, it is not presumptious to assume that it's not being applied properly, because, as said, the fuse would simply blow if it got near 100amps.

Although not impossible, how many people have all high-load appliances on all at once. You don't see many houses with a cooker, shower, kettle, hoover, all tv's, all electric heaters on at the same time...

And even then you might only draw about 80amps - which, incidentally, I am aware some company fuses and meters are rated at - but that is besides the point.

 

[Big_Spark]

However, it is not presumptious to assume that it's not being applied properly, because, as said, the fuse would simply blow if it got near 100amps.

Although not impossible, how many people have all high-load appliances on all at once. You don't see many houses with a cooker, shower, kettle, hoover, all tv's, all electric heaters on at the same time...

And even then you might only draw about 80amps - which, incidentally, I am aware some company fuses and meters are rated at - but that is besides the point.

Sterose, on saturday I had my washing machine, Dishwasher and Tumble Dryer on the go, Kettle was boiled to make coffee, girlfriend had the TV on and the garage heating was on at this time due to the temperature outside. For where I live, and many homes in the UK today, this level of loading is not unusual.

Washer 12.8A
Dish 12.5A
Tumble 12.5A
Kettle 12.8A
TV 4A
G-Heat 9.5A
Everything Else about 15A

Total is 79.1A

Now I could load that up even more if it occured at night.

For homes with electric water heating, or electric showers as well, and are a family home, exceeding 100A is actually a real possibility for short periods.

This is why many new heads going in are 125A.

The real problem is that Diversity was great many years ago, but technology has moved on, and the electrical loads we are subjecting our installations to has increased dramatically in the last 10 to 15 years, however the allowance of diversity has not kept pace with this move, although this is the IEE not the sparks.

 

[sterose]

Sterose, on saturday I had my washing machine, Dishwasher and Tumble Dryer on the go, Kettle was boiled to make coffee, girlfriend had the TV on and the garage heating was on at this time due to the temperature outside. For where I live, and many homes in the UK today, this level of loading is not unusual.

Washer 12.8A
Dish 12.5A
Tumble 12.5A
Kettle 12.8A
TV 4A
G-Heat 9.5A
Everything Else about 15A

Total is 79.1A

Now I could load that up even more if it occured at night.

For homes with electric water heating, or electric showers as well, and are a family home, exceeding 100A is actually a real possibility for short periods.

This is why many new heads going in are 125A.

The real problem is that Diversity was great many years ago, but technology has moved on, and the electrical loads we are subjecting our installations to has increased dramatically in the last 10 to 15 years, however the allowance of diversity has not kept pace with this move, although this is the IEE not the sparks.

Youre house is extremely inefficient. A TV that consumes 4amps and a washer at 12.8amps. The wattage on my appliances do not nearly equal that. Even my 25'' telly only takes about 2-3amp.
Perhaps what you mean is that those figures are the maximum that the appliances take. Such as how a motor consumes more at startup than when running.

However, I believe I shall now submit and avoid an embarrasing defeat in this argument...

 

[Big_Spark]

Sterose..36" CRT TV...BIG load mate !!

The Tumble Dryer and the Dishwasher both use heavy loads..the washing machine does when it heats the water....haven't got around to getting a hot supply plumbed to it yet!!

 

[ban-all-sheds]

....haven't got around to getting a hot supply plumbed to it yet!!

RTFM first - I did that plumbing once, and then found that even though it had H&C connections, on anything other than the 90° programme it still took only cold in and heated it up. Why did I bother, I wondered...

 

[Big_Spark]

Ban, I did check before buying the new washing machine a few months back, and it will take hot if available..but it has to be plumbed in first!!

 

[ban-all-sheds]

OK - just would hate to see anyone make the same mistake. Chose a m/c with hot fill. Never thought to ask "will it actually use hot water if it is there?"