This is the second episode of the adventures of Polish electrician in UK
Thanks for all the subscriptions and thumbs ups so far
Today we'll venture into crypts and dark places under the stairs
where, among other scary things, one may find the source of the domestic electrical supply
"Not sure if you've heard Greg, but rumour has it, that old English basement are haunted by a Deedco Made of Hay"
"Deedco what?"
"Deedco Made of Hay"
"And what does that Deedco do, in the basement?"
"Well, the stories vary wildly - some say it's a mischievous creature, others recon it’s very helpful"
"What was that?"
"I don't know - maybe creaky doors upstairs"
My nick is Regan and you're watching The Resistance channel...
I'll see you right after this:
The Resistance presents: Polish Electrician in UK
Episode two: Main supply and meters
Welcome back
As far as most local electricians are concerned - main supply, meter and fuse box in a typical English home
is almost always in a place that's very cramped, forgotten and full of cobwebs.
Down here in Kent, where we make our videos
the supply lines run underground and most towns were built between 1930's and 1950ies
and so majority of fuse boxes are located either under the stairs or, in the basement, if one exists.
In Britain the task of providing energy to domestic premises through the infrastructure is taken care of by the energy supplier
while sales of the energy to the occupier and metering duties are left to the energy companies
Typical owner of the house doesn't see a difference between energy supplier and energy company
But let's start from the beginning
To overwhelm you with technical detail – a typical domestic energy supply equipment found in British properties can be divided into the following three basic parts:
The fugly thing-a-ma-jiggy you can prop your storage boxes against
The box that robs your bank account
And the dirty thing with a flap on the front that can be utilised as a shelf for your torch light.
That thick, dirty cable pokeing out of the floor under the stairs or wall in the basement of your two bedroom terraced mansion
and the bakelite can with a seal on its end
is 100% owned by your local energy supplier known as District Network Operator
They also own that shabby looking piece of chipboard the bakelite can is attached to.
The cable is your main incoming power cable and the can on the end is a service head.
Indigenous islanders call the service head - a "cut-out"
Inside the cut out, one will find a main fuse
Well, not that kind of fuse
Slightly bigger
Bigger still
That's the one!
For all the electricians watching us from Poland and frowning in disbelief
What you're looking at is a hybrid setup performing tasks of the continental
incoming and outgoing mains switch with overcurrent protection, distribution cabinet and metering cabinet in one disorganised place.
and similar setup exists in every domestic premises on the island.
In some cases, where access under the property was not practical, the supply and metering part often resides in a hole in a wall outside
Often in quite a state and protected from nefarious acts of strangers by this kind of high-tech service key.
In UK regardless of the age of installation, the main supply fuse is a passive, cylindrical, single use affair with a fusible wire inside
No mechanical, resettable over-current devices are ever used in the incoming supply before the meter
There are no power limiters either
In terms of amperage limits, it's actually the other way round
a BS1361 fuse is designed to withstand power draw far exceeding its rating for up to an hour before it eventually gives up
For DNO - a blown fuse in the incomer head means that we must have done something stupid and now pose a risk to the rest of the street
so in UK, protective device on the incoming side doesn't just switch us off for a few minutes and it can't be reset by an electrician with a universal supply cabinet key
because it is designed in such a way that
if you blow a main fuse, you'll have to call District Network Operator to replace it and they will really want to know how it happened.
District Network Operator
or DNO for short
is a function, not a company name.
"DNO" equivalent in Poland would be a company like Enea, Energa or Tauron
while Britain, to counteract monopolist tendencies, elected 14 of such "Taurons"
But for some inexplicable reason, all 14 of them now belong to only 6 corporative motherships.
DNOs are tasked by law with taking good care of the regional electrical infrastructure
Which also includes maintenance of cut-outs and supply cables to each and every property.
I'll explain a bit later why this regulation is extremely helpful.
Unlike in Poland, nearly all domestic supplies in UK are single phase
Three phase supplies of course do exist, but they are very rare in single dwellings across British towns and cities.
While a typical domestic distribution board serving 20 circuits in Poland looks somewhat like this:
In UK consumer unit serving 20 circuits is noticeably more compact
As if its dimensions were proportional to the difference in size of the properties between both countries.
However, the main difference is that the single-phase supplies in UK
with rare exceptions (more in the next episode)
Are rated at either 100, 80 or in older properties 60 amperes.
In UK, the amperage of incoming supply has no impact on the metering tariff.
and regardless of whether it's a 60A or 100A supply, the basic charge per kWh does not change.
DNOs supply two types of earthing to domestic premises
In newer properties it's usually TN-C-S, where main earth is provided directly from neutral cable through a connector block inside of the cut-out
And among older properties, it's usually TN-S, where main earthing is delivered from the transformer via dedicated conductor or armour around supply cable.
In the oldest versions of TN-S – earthing is provided via metal brace around stripped sheath at the end of the supply cable
Braces used for that purpose should be in form of either a specifically designed for this purpose clamp
or in form of a constant force spring.
For a few years in the sixties and seventies, due to shortage of materials, DNOs used BS951 clamp
originally designed for bonding connections to copper pipes
Such a connection for main earthing is nowadays considered to be incorrect and due for an upgrade.
because it's possible to fasten the clamp so tight that it may squash the lead sheath and possibly create short circuit inside.
The oldest TN-S cables, those that utilise more or less rusty metal tape as a sheath and means of earthing
should never ever be moved, pulled, hit or bent during building work.
Many of these cables despite newer service heads on the end, date back to 1930ies and 40ies
and deep inside, beneath layers of bitumen coated hessian, corroded steel tape and lead waterproofing sheath
live copper cores are insulated by a millimetre thin layer of paper dipped in mineral oil
it's also worth knowing that the oil used to impregnate insulation paper in old cables often contained vile, nasty substance known as PCB.
Ninety years later, the integrity of this insulation may be similar to a moist toilet paper
and any bending or impact may affect this delicate internal balance
And in Britain there are no additional protective devices for your property beside of what you see in front of you
That fugly bakelite box on the wall is the last protective device
The next device upstream may turn out to be an 800A delayed fuse for the entire street
A shortened cable from the times of Churchill theoretically may end up welding itself for hours until it will perish, probably together with your basement and the nearest cable joint
and it may not be possible to stop it without disconnecting half of town
[From The Archives of Construction Industry Nuttery]
Recently during periodic inspection in an HMO we came across bizarre happenstance
At some point in the past the crew tasked with installation of tanking in the basement
moved main supply cable with service head off the wall
and somehow managed to disconnect main earthing conductor for the consumer unit from the arrangement
The ingenious individuals couldn't figure out what exactly that loose earth conductor was originally secured to
so they decided to check how the main earth was connected at their rented accommodation and then simply mirror it
We can safely assume back at home they found 1960ies TN-S arrangement
because they stripped insulation at the end of the cable and attached a clamp, obviously the wrong BS951 one…
and then connected green and yellow cable hanging from the consumer unit to their new means of earthing.
As you can probably predict - things didn't exactly go according to plan
The earthing arrangement supplied by the DNO in this particular property was TN-C-S, not TN-S
so the main supply cable didn't really feature a sheath such clamp could be secured to
The nutjobs simply skinned the incomer cable down to bare, live copper cores
while all they really had to do was to attach the conductor hanging from the consumer unit back to the dedicated earth block on the side of the service head
For safety and to prevent bypassing the meter
main service head and fuses are sealed
and in rougher areas sometimes even covered in bitumen paint
Seals on the service heads are meant to be cut only by the DNO and meter companies.
And the issue of electricians having to remove main fuse during upgrades to consumer units remains unresolved for many decades
Some companies officially allow registered electrician to remove seals and main fuses
while others require them to call in and arrange removal of the main fuse by the DNO
The average waiting time for such service at the moment exceeds three weeks and quite often also several hundred pounds
It's not a surprise then, that statistically, nearly 107% of electricians upgrading consumer units around the country
experience power cuts in main supply by means of supernatural powers and gravitational anomalies
"We are currently at Mrs. Grazyna's property in vicinity of Lutonski Street"
"The service head appears to be sealed so we'll presumably have to replace consumer unit live"
"Not for the first time either"
"I'll grab a tool"
"I don't actually see any seals"
"Oh how odd"
"I could have sworn the seal was there"
"Oh well, I'll grab a screwdriver then"
"Wow, that's properly emo dark..."
"Do we have any light?"
"yeah, we've got a torch. It‘s probably RCD"
"Everything seems to be on..."
"Oh, look - a main fuse is missing! And a straw of hay on top of the service head"
"Probably slid out on its own"
"See - it has slipped out"
"Weird - and the air suddenly got chilly?"
In all seriousness - if you notice any damage, cracks or incomplete elements to your supply cable or service head
then you can report it straight to your DNO by calling 105 from any phone
And due to ESQCR regulations your local DNO must repair their equipment free of charge
Although the guys from our local DNO are notorious for working very long and very hard so nothing gets done
but rumour has it that a platter of stylishly served exquisite biscuits with white tea can sometimes convince them
to, for example, perform spontaneous upgrade of an old 60A service head to new 100A PME setup, while doing some small repairs.
Statistics suggest that around 11 for each 10 of service head upgrades annually, may be performed with in circumstances involving tea and biscuits
Meters and meter tails to the service head virtually belong to energy companies
"Virtually", because metering market in UK is similar to mobile telephony:
It doesn't matter which company installed your meter - but who currently has a contract for that meter number
Despite "British Gas" or "EDF" logo or label on your meter
After just a few minutes on the phone or few clicks on the internet, the new owner of your meter "providing" energy to your home
may be your local supermarket
A petrol station
or a high street shop selling clothes
The size of meter tails nowadays should be 25mm2 minimum
This standard is set by DNOs.
Most meter tails in the older properties are still 16mm2
and yes, they were probably installed by the same DNO that now requires bigger tails
but in terms of electrical regulations, in all the properties with 60 and 80 ampere fuses in service heads
16mm2 is considered safe, within the norm and not requiring any immediate upgrades
To upgrade main fuse to 100A (with help of tea and biscuits) you'll however need 25mm2 tails between cut-out and the meter
In case you wonder how the electricians connect their tails from consumer unit to the meter
then the answer is simple - they don't. Ever.
Nobody except your meter company and DNO should ever touch seals on the meter
And you should point blank refuse any electrician that attempts to change meter tails by removing seals
Removed meter seals immediately look dodgy
and that guy who checks your energy usage on behalf of energy company few times a year won't even think twice about reporting you
It's you, the owner, not the electrician that will be held responsible and chased by third parties for screwing around with meter equipment
It's very simple – there are other ways – so don't let anyone fork around with your meter
Similar to Poland, discounted tariffs also exist in UK
(Oh, not those kind of discounted tariffs)
for example, Economy 7 available at night or Economy 10 available in selective hours during the day
Cheaper tariffs come from the same single-phase supply but through a special switch and to a secondary consumer unit
The switch is somewhat interesting, because in most homes it receives radio signal broadcasted on BBC Radio 4 frequencies.
The box has a built in radio and turns the second fuse box on and off when signalled
Second fuse box mostly powers storage heaters and secondary immersion element
And just a few words about "Anomalies in the system"
In blocks of flats or HMOs, the owner of the property can assign electrician to create a "middle man" setup between DNO and metering company
Such "middle man" setup is known as Building Network Operator
Duties of the BNO include splitting and means of delivery of power from DNOs incomer to multiple bedsits or flats
and creating internal supply infrastructure so multiple locations can be metered separately
BNO is responsible for securing the entire installation to prevent any possibility of energy theft
Additionally, BNO has to make sure that DNO’s incomer doesn't get damaged by the demand
Electricians creating BNO infrastructure should utilise equipment specifically designed for the purpose of the internal distribution
and one that can be permanently locked and sealed
for example Ryefield Boards or Lucy multiservice DBs.
And that's the end of this boring episode
thanks for your patience and endurance
Ask your questions in comments section
I'll read them all and try to answer them in future episodes
I bid you farewell and next time we'll compare British consumer unit types and all the cabling across the last 80 years.
I'm Regan, the guy who protected me from Deedco in the basement is called Greg, and you've been watching The Resistance channel
[Outtakes] "In Kent, where we make our videos, most of the distribution network runs underground"
"and most cut-outs and fuse boxes are either under stairs or in the basement"
"there are exceptions though, sometimes just as we start searching for the door to the cupboard under the stairs the owner shouts:"
'Oh no-no - my fuse box is in the toilet'
"but these are - pardon my expression - stinky subjects"
(and the award for the dryiest joke of 2020 goes to..)