Well he turned out to be a bit of d1ck. He sorts of reminds me of someone, but can't quite put my finger on it.
Replacing an old CU with a new one
- Thread starter Naz1977
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Well he turned out to be a bit of d1ck. He sorts of reminds me of someone, but can't quite put my finger on it.
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Perfect.
Will do that. i will ring northern power grid and see what they say.
I will probably get this one:
http://www.screwfix.com/p/bg-4-pole-rotary-isolator-switch-63a-230-400v/8536r
It is 4 pole as since it is a TT circuit, this is all that is needed.
and whilst i am fitting this, might as well change the tails to 25mm cables as currently they are 16mm.
Who is in charge of the tail between the fuse and the CU? Will it be me or the board?
The setup will in effect end up as:
Meter to Fuse
Fuse to Isolator
Isolator to the CU
Also, the main fuse has been upgraded to 80A at the moment. Do I get them to change this to 100A for future extension? Or is it easy enough to get them to come out and replace when the extension is built?
They came and changed my meter few months ago to smart meter. Shame they didn't talk to me then as otherwise would have asked them to stick a 100A in there.
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You keep saying this.
Please have another look.
ok.
I have a TT setup. The meter is outside the house in a small cupboard ...
Actually better to post a picture.
Give me 5 minutes
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ah, sorry my bad.
Fuse is before the meter
Question still stays the same though
Their demarcation point ( I know Demarc is for network but what is the equivalent for power companies? ) is the meter I assume? So anything before the meter is their responsibility and anything after the meter is the customers?
The tails from fuse to meter has been upgraded to 25mm by the meter company
The tails from the meter to the breaker are 16mm - Original meter tails
From breaker to the CU is 16mm - Original meter tails
I can replace the ones from the breaker to the CU to 25mm when I am at it. No problem there.
It is from Meter to the breaker ( and soon to be the new Isolator ) that I won't be able to replace unless the supply has been isolated from the fuse.
Fuse is before the meter
Question still stays the same though
Their demarcation point ( I know Demarc is for network but what is the equivalent for power companies? ) is the meter I assume? So anything before the meter is their responsibility and anything after the meter is the customers?
The tails from fuse to meter has been upgraded to 25mm by the meter company
The tails from the meter to the breaker are 16mm - Original meter tails
From breaker to the CU is 16mm - Original meter tails
I can replace the ones from the breaker to the CU to 25mm when I am at it. No problem there.
It is from Meter to the breaker ( and soon to be the new Isolator ) that I won't be able to replace unless the supply has been isolated from the fuse.
Not sure they would be prepared to liven up there meter tails into that isolater.
As previously asked have you allowed for whats needed to terminate the TT tails into a METAL Cu
As previously asked have you allowed for whats needed to terminate the TT tails into a METAL Cu
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You only need a double pole isolator for a single phase supply, 4 pole is only needed for three phase and neutral supplies.
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The rating of the iso switch needs to match or exceed the rating of the main fuse. To save any unnecessary expense, fit a 100A one.
Why do you need 4P?
Why do you need 4P?
If both of those are true, the existing installation is unsafe. A fault to earth will not trip any of those MCBs, and will leave exposed metalwork with dangerous voltages.
Sorry it was my mistake, thinking about 4P as being 2ins and 2 outs, rather than 4ins and 4outs.
Yes it will only be a double isolator to brake the Neutral and Live
The only problem with the double pole isolators is that the only ones I can see that are rated at 100A are DIN rail ones to go inside the CU. I wanted to have an isolator BEFORE the CU so if anything goes wrong, I can isolate and change what is needed.
Well, it is a TT for sure
And there is no earth going into the isolator which is outside the box. But this only works as an isolator switch as there is another isolator switch inside the CU.
There is an earth going from CU to the spike outside. There is also internal bonding to gas and water pipes.
The CU at the moment is a plastic unit and not metal
Why would a fault to earth not cause the MCBs to trip as there is the earth link to the spike. I think the isolator outside the CU, only works as a physical isolator. There is a test button on it, I guess I could test that to see if it trips when pressed or not!
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I think you have a lot of learning to do before you can create a system you know is safe.
The fundamental principle of eebads is that all the metal work that goes into your house is connected to an earth, which has a low enough impedence to trip your protective device. With tt your impedence will be tens or even hundred of ohms, and it's impossible to get it to a level that would trip the MCB on your socket circuits.
So if you do have a fault, the metalwork in your house will increase to 240v, and a moderate current will flow through earth. But if you touch anything that is earthed, you'll get a nasty shock. Also the earth electrode will probably warm up and dry out the earth a bit, further increasing its resistance.
And test buttons don't do any end to end testing, they just test the component in question. You need the right equipment, RCD tester and earth loop impedence tester.
The fundamental principle of eebads is that all the metal work that goes into your house is connected to an earth, which has a low enough impedence to trip your protective device. With tt your impedence will be tens or even hundred of ohms, and it's impossible to get it to a level that would trip the MCB on your socket circuits.
So if you do have a fault, the metalwork in your house will increase to 240v, and a moderate current will flow through earth. But if you touch anything that is earthed, you'll get a nasty shock. Also the earth electrode will probably warm up and dry out the earth a bit, further increasing its resistance.
And test buttons don't do any end to end testing, they just test the component in question. You need the right equipment, RCD tester and earth loop impedence tester.
I am getting confused then!
Because nothing has changed in the wiring at the moment and you are saying it is unsafe? Either I am explaining things wrong or neither electricians, then one who tested last year and the one who did some work this year, both are [EDITED]careless!
So I have a TT setup.
This means the board doesn't supply me an earth and I have to supply earth to my CU. This is done by the means of a earth spike and running a single core earth cable. At the moment it is 6mm, but the previous electrician said this was ok, the new one said it has to be upgraded to 10mm. However looking in 7671 and OSG, it says if the cable is not burried, it can be as little as 2.5mm provided there is mechanical protection!
The main incoming gas and water pipes are also bonded to the earth in the CU.
The ring main, and also lighting circuits have the CPC all connected to the earth point on the sockets and where applicable connected to the earth terminal in the metal boxes.
The RCD should trip as soon as there is a fault, which the new circuit will be protected by. Currently there is no RCD protection at all.
Are we saying this is wrong or are you commenting on the current setup that doesn't have RCD protection on the circuits ?
If it is the latter, this will be rectified by the new CU which has double RCD protection.
But if you are saying the setup is wrong and I need to do something else, please do explain a bit more .
EDIT: Reading your post, I think you are referring to the current setup that it is unsafe if fault happens ? As there is no RCD on some of the circuits. Currently 2 circuits, Electric Shower and Kitchen ringmain have RCBOs so they are ok, but the rest of the circuit has MCB and no RCD.
This was the whole point of the previous who came to replace my CU and then decided he didn't want to do the job properly. I will just go ahead and replace it myself once I have contacted the northern power grid and see what they want to do. If they take too much f**** around, I will just break the seal and remove the fuse and replace the board. If they say why I did it, I will explain my current install wasn't safe anymore as I had metal sockets and this had to be done urgently. They can check my meter readings and see it is still quite a lot. Anyone know what the fine could be nowadays for breaking supplier seals?
Because nothing has changed in the wiring at the moment and you are saying it is unsafe? Either I am explaining things wrong or neither electricians, then one who tested last year and the one who did some work this year, both are [EDITED]careless!
So I have a TT setup.
This means the board doesn't supply me an earth and I have to supply earth to my CU. This is done by the means of a earth spike and running a single core earth cable. At the moment it is 6mm, but the previous electrician said this was ok, the new one said it has to be upgraded to 10mm. However looking in 7671 and OSG, it says if the cable is not burried, it can be as little as 2.5mm provided there is mechanical protection!
The main incoming gas and water pipes are also bonded to the earth in the CU.
The ring main, and also lighting circuits have the CPC all connected to the earth point on the sockets and where applicable connected to the earth terminal in the metal boxes.
The RCD should trip as soon as there is a fault, which the new circuit will be protected by. Currently there is no RCD protection at all.
Are we saying this is wrong or are you commenting on the current setup that doesn't have RCD protection on the circuits ?
If it is the latter, this will be rectified by the new CU which has double RCD protection.
But if you are saying the setup is wrong and I need to do something else, please do explain a bit more .
EDIT: Reading your post, I think you are referring to the current setup that it is unsafe if fault happens ? As there is no RCD on some of the circuits. Currently 2 circuits, Electric Shower and Kitchen ringmain have RCBOs so they are ok, but the rest of the circuit has MCB and no RCD.
This was the whole point of the previous who came to replace my CU and then decided he didn't want to do the job properly. I will just go ahead and replace it myself once I have contacted the northern power grid and see what they want to do. If they take too much f**** around, I will just break the seal and remove the fuse and replace the board. If they say why I did it, I will explain my current install wasn't safe anymore as I had metal sockets and this had to be done urgently. They can check my meter readings and see it is still quite a lot. Anyone know what the fine could be nowadays for breaking supplier seals?
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I never mentioned anything about idiots and I don't think that's appropriate language for the forums. Please be constructive.
Therefore your installation is potentially dangerous and should be turned off until it's made safe.
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