British gas TT earthing and rcds

[pope]

I have done a few of these jobs for the same client. Install a 315a fused TPN isolator in their new heating centres. All the others I have done UKPN have bought in a PME supply so I have just mounted the fused isolator with tails into the CT chamber ready for me to do the follow up at a later date so the meter man can get his stuff on and get it live. This one I have gone to and no earth has been supplied no problem I say to the client I will put your earth rod in and an rcd unit as the first point, which I was under the impression was required. The client then calls the meter man who has connected the previous five for us where the connections come from the PME on the head and the terminals from the CT chamber but he is saying that there is no need for the rcd unit on the TT system. Am I missing something here?

I have but the rcd unit in as I am sure it needs it just picking people's brains incase there is some reg I am not aware of or is the British gas guy clueless?

 

[SPARTYKUS]

Clueless, youre right.

 

[pope]

Cheers bud. Didn't have my regs book on site with me but I'm going to find the reg stating this just so I can justify the extra cost and materials compared to the others I have done for him.

 

[ImpededLoop]

You're correct, he's clueless!

 

[Richard Burns]

Cheers bud. Didn't have my regs book on site with me but I'm going to find the reg stating this just so I can justify the extra cost and materials compared to the others I have done for him.

411.5.2

 

[Engineer54]

Why do people listen to these meter merchants, most of them know even less than a Electrical Trainee!!

 

[pope]

411.5.2

Cheers bud

 

[pope]

Why do people listen to these meter merchants, most of them know even less than a Electrical Trainee!!

Because in the eyes of the clients they are the gods that turn their power on to their nice new district heating exchange. Which if is not on in time has a £1.9m penalty clause involved.

 

[Deleted member 9648]

Technically he is right and our learned friends above are wrong.There is no reg stating an RCD is required on a TT. 411.5.2 states that an RCD is the preferred means of earth fault protection,not a required means. If a TT provded a low enough Ze value then an OCPD could be used.Of course in the real world......Oh no,hang on,everyone keeps telling me they get sub 1 ohm Ra values so why the RCD?

 

[Engineer54]

Technically he is right and our learned friends above are wrong.There is no reg stating an RCD is required on a TT. 411.5.2 states that an RCD is the preferred means of earth fault protection,not a required means. If a TT provded a low enough Ze value then an OCPD could be used.Of course in the real world......Oh no,hang on,everyone keeps telling me they get sub 1 ohm Ra values so why the RCD?

The Clever arse rises again......lol!!

Unfortunately that sub 1 ohm value can ''only'' be achieved when people put a little effort in and ''TRY''!! It will rarely to Never happen with people like you, (who has never achieved anything even close) who have clearly made it clear on many occasions here, that you have no intention of ever trying because the BGB say's 200 Ohm, and that's good enough for ANY of you lazy buggers out there!!

It's the drose like the above that makes the UK literally the worst country i've ever had the pleasure to work in for TT systems. It's funny how other countries can routinely provide stable single and low double figure Ra values and in UK triple figures are what's aimed for, especially if it happens to be under that somehow magical 200 Ohms mentioned in the BGB!! ....

 

[Knobhead]

The OP did say he was going to put a rod in, what more could it possibly need?

 

[Deleted member 9648]

The Clever arse rises again......lol!!

Unfortunately that sub 1 ohm value can ''only'' be achieved when people put a little effort in and ''TRY''!! It will rarely to Never happen with people like you, (who has never achieved anything even close) who have clearly made it clear on many occasions here, that you have no intention of ever trying because the BGB say's 200 Ohm, and that's good enough for ANY of you lazy buggers out there!!

It's the drose like the above that makes the UK literally the worst country i've ever had the pleasure to work in for TT systems. It's funny how other countries can routinely provide stable single and low double figure Ra values and in UK triple figures are what's aimed for, especially if it happens to be under that somehow magical 200 Ohms mentioned in the BGB!! ....

Just found it interesting that in post #6 the implication is that by stating that the meter man is spouting nonsense,your view is that an RCD is required. Why not say to the OP that a proper TT electrode will provide a low enough Ra to negate that requirement?

 

[Engineer54]

Just found it interesting that in post #6 the implication is that by stating that the meter man is spouting nonsense,your view is that an RCD is required. Why not say to the OP that a proper TT electrode will provide a low enough Ra to negate that requirement?

No, you just thought you'd try being a clever dick again!! lol!!

I stated that most of these metermen know less than a electrical trainee. But i can just guess as to what the earth rod installation is like and the sort of Ra value that has been obtained!!

Now if this district heating project has such a high monetary value, there shouldn't be any financial restrictions to actually providing a sub 1 ohm TT system, but will it ever get such a TT installation?? Very doubtful in the UK, after all there is always an RCD to bung in!!

 

[Deleted member 9648]

No, you just thought you'd try being a clever dick again!! lol!!

I stated that most of these metermen know less than a electrical trainee. But i can just guess as to what the earth rod installation is like and the sort of Ra value that has been obtained!!

Now if this district heating project has such a high monetary value, there shouldn't be any financial restrictions to actually providing a sub 1 ohm TT system, but will it ever get such a TT installation?? Very doubtful in the UK, after all there is always an RCD to bung in!!

Cop out mate.

 

[Engineer54]

Whatever you say!! lol!!

 

[D Skelton]

WP, you're just lazy!

Everybody knows that 10 ohms is better than 200 ohms. Of course, there will be absolutely no difference whatsoever in how the system operates, but 10 is lower than 200, so it must be better?!

;-)

 

[Engineer54]

Someone else that sounds over bored!! lol!!:juggle2:

 

[Nightmare1308]

No, you just thought you'd try being a clever dick again!! lol!!

I stated that most of these metermen know less than a electrical trainee. But i can just guess as to what the earth rod installation is like and the sort of Ra value that has been obtained!!

Now if this district heating project has such a high monetary value, there shouldn't be any financial restrictions to actually providing a sub 1 ohm TT system, but will it ever get such a TT installation?? Very doubtful in the UK, after all there is always an RCD to bung in!!

how can you obtain a steady sub 1 ohm reading which you can guarantee not to fluctuate due to weather drying up ? will the circuit meet its 0.2s or 1s disconnection times depending on circuit design?
just a question...

 

[D Skelton]

how can you obtain a steady sub 1 ohm reading which you can guarantee not to fluctuate due to weather drying up ? will the circuit meet its 0.2s or 1s disconnection times depending on circuit design?
just a question...

In certain areas, subject to ground conditions, it can be done, and very easily. I have done it, as will have any electrician worth his salt. It won't ever have been on a domestic though that's for sure. Last time I did it was at the intake building for a large agricultural installation.

Ten or so underground sub mains fed from the intake position. It was either a decent earthing system or £2k for an up front s-type for the whole complex, which in itself would have been idiotic.

 

[netblindpaul]

TT does not equal hit a single 3/8" dia 4' rod in the ground, just in case some don't realise that.