TT Supply

Conversations 3

First post, long time lurker here.

Right this is confusing me, looking at a domestic board and it has 2 main rcds feeding 2 rows of mcbs.

The earth coming from the meter in the main feed is left hanging at the meter, not connected to anything.

Is this common in older domestic properties?

What should I look out for in the installation?

Haven't done anything yet, boss was just talking about putting me on that job.

Want to be prepared.

2011

Rural installation?

First off you need to determine whether this installation should be TT or not.
Most are now TNCS but there are a few exemptions in some rural areas. I assume that ESB Networks are best placed to advise. Perhaps you could call them with the MPRN number and they can advise.

Conversations 3

2011 wrote: »

Rural installation?

First off you need to determine whether this installation should be TT or not.
Most are now TNCS but there are a few exemptions in some rural areas. I assume that ESB Networks are best placed to advise. Perhaps you could call them with the MPRN number and they can advise.

Yea, a rural installation.
Fed underground from a pole prob 10 mtrs away.

I see TT is popular in the UK, it's the first I've heard of one here.

I'll contact the ESB and see what they say.

Newuser2

That's a UK TT board

Conversations 3

Newuser2 wrote: »

That's a UK TT board

It's in rural Ireland.

Newuser2

https://images.app.goo.gl/kUMq7eXWVri39J9M6

Does it look like that

I think a couple of reasons why you would do this are the supply loop impedance being too high or else bad lines


You could take a L-N loop impedance reading at the board see what it is, should be around 0.35max for TNCS if I recall correctly

Take a look at the supply lines outside see is it a good supply

That will give you an idea of whether it can be changed but you'll probably have to deal with the network

Conversations 3

Newuser2 wrote: »

Does it look like that

I think a couple of reasons why you would do this are the supply loop impedance being too high or else bad lines


You could take a L-N loop impedance reading at the board see what it is, should be around 0.35max for TNCS if I recall correctly

Take a look at the supply lines outside see is it a good supply

That will give you an idea of whether it can be changed but you'll probably have to deal with the network

It's similar to that with circuits spread over 2 rcds.
It's older though so no double pole isolator.

I'll try get a measurement on that if I can.

I'll get onto the ESB as well.

EHP

Alot of rural areas weren't neutralised when first connected so should have a 300ma RCD maximum covering the whole premises and still have a 30ma covering sockets etc. When we come across a situation like this we were told by Safe Electric to report it to the ESB as a fault and that they should come and neutralise the property, but in reality I've found that the ESB require a cert from a REC before doing this.

Conversations 3

EHP wrote: »

Alot of rural areas weren't neutralised when first connected so should have a 300ma RCD maximum covering the whole premises and still have a 30ma covering sockets etc. When we come across a situation like this we were told by Safe Electric to report it to the ESB as a fault and that they should come and neutralise the property, but in reality I've found that the ESB require a cert from a REC before doing this.

Grand, will the whole installation have to be certed?

I don't think they'll want to spend big money on it if it comes to it.

EHP

If just upgrading the tails and neutralising you have to do a IR on the complete installation check all bonding and earthing and test one fixed appliance at a minimum.

Conversations 3

EHP wrote: »

If just upgrading the tails and neutralising you have to do a IR on the complete installation check all bonding and earthing and test one fixed appliance at a minimum.

Cheer's, they might go for that.

Newuser2

You've got to test fault loop impedance for every final circuit too

Rcd trip times as well

Pretty much anything on a test sheet I'd say if it's never been neutralized

meercat

EHP wrote: »

When we come across a situation like this we were told by Safe Electric to report it to the ESB as a fault and that they should come and neutralise the property, but in reality I've found that the ESB require a cert from a REC before doing this.

I’ve come across this numerous times and asked the account holder to report it as a fault directly to the emergency number. Esbn treat this as a serious fault and respond immediately. Usually same day and once within the hour (whilst I was still there). Never have they requested a certificate

Newuser2

meercat wrote: »

I’ve come across this numerous times and asked the account holder to report it as a fault directly to the emergency number. Esbn treat this as a serious fault and respond immediately. Usually same day and once within the hour (whilst I was still there). Never have they requested a certificate

Maybe not but that's wrong

Should be a cert for that change

meercat

Newuser2 wrote: »

Maybe not but that's wrong

Should be a cert for that change

It’s not required. It’s only required for upgrade main cable supply

Newuser2

meercat wrote: »

It’s not required. It’s only required for upgrade main cable supply

I'm not a REC.so I'm not familiar with the paperwork

It goes without saying if you connect a MPC to the supply neutral you have to check all your Zl readings because they've probably never been checked or you dont know if they comply

So at a minimum you've got paperwork to fill out and the installation should be safe, Earthing Conductor sized for TNCS

meercat

Newuser2 wrote: »

So at a minimum you've got paperwork to fill out

Not necessarily. If I replace a socket and test afterwards then no paperwork is required as it’s minor work (unless requested).
Even when quoting for a job it’s a simple matter of plugging test equipment in and checking values whilst talking to prospective clients.

Newuser2

meercat wrote: »

Not necessarily. If I replace a socket and test afterwards then no paperwork is required as it’s minor work (unless requested).
Even when quoting for a job it’s a simple matter of plugging test equipment in and checking values whilst talking to prospective clients.

Point taken

EHP

Newuser2 wrote: »

You've got to test fault loop impedance for every final circuit too

Rcd trip times as well

Pretty much anything on a test sheet I'd say if it's never been neutralized

Yes you have to test all RCDs on the board but and this is on advice from a safe electric inspector you only have to do the fault loop impedance on the fixed appliance circuit on the test, saying that it wouldn't surprise me to get completely different advice from the same inspector the next time I meet him.

EHP

meercat wrote: »

I’ve come across this numerous times and asked the account holder to report it as a fault directly to the emergency number. Esbn treat this as a serious fault and respond immediately. Usually same day and once within the hour (whilst I was still there). Never have they requested a certificate

I wonder is it a different response from different areas because safe electric told me that it shouldn't require a cert and the ESB should treat it as an emergency like you said but twice in the last year they have insisted on a cert before neutralising.

Newuser2

EHP wrote: »

Yes you have to test all RCDs on the board but and this is on advice from a safe electric inspector you only have to do the fault loop impedance on the fixed appliance circuit on the test, saying that it wouldn't surprise me to get completely different advice from the same inspector the next time I meet him.

Could be, I can see how it might be treated as just a fault repair

The main things would be like you said IR testing and tails and main board correct, bonding, earthing

Verify Zl at a circuit

Test RCDs

Also meter and fused cutout and supply good, no risk of neutral inversion

Earthing of supply neutral by the network too

meercat

EHP wrote: »

I wonder is it a different response from different areas because safe electric told me that it shouldn't require a cert and the ESB should treat it as an emergency like you said but twice in the last year they have insisted on a cert before neutralising.

All different Dublin esbn locations. Phoned in as an emergency with an earth left out for esbn to terminate into cutout. Page 2 of this newsletter but I don’t think a hotline was ever setup. I’ve reported at least 20 in the last 3yrs and never required certification.you’d be surprised how many have never been neutralised even with replacement distribution boards!!!

https://safeelectric.ie/contractors/wp-content/uploads/sites/2/2018/09/2016dec_news.pdf

Conversations 3

This is the situation, earth swinging and MEN link open, screws shut.

Waiting for ESB response, some people say connect it some don't.

https://ibb.co/GPDZH05

Can't figure out how to post photo

2011

Conversations 3 wrote: »

Waiting for ESB response, some people say connect it some don't.

The first step is to determine if this is a TT supply or not.
Have you done this yet?

Conversations 3

2011 wrote: »

The first step is to determine if this is a TT supply or not.
Have you done this yet?

Board is fed through a 63a switched fuse, then feeds from the bottom to 2 rcds.

One feeding the sockets mcbs, standard 30ma.
The other is feeding the rest of the mcbs for lights, immersion etc. This is a 300ma RCD.

Going by this, without confirmation from the ESB, it is a TT supply.
How else would you tell?

Risteard81

meercat wrote: »

I’ve come across this numerous times and asked the account holder to report it as a fault directly to the emergency number. Esbn treat this as a serious fault and respond immediately. Usually same day and once within the hour (whilst I was still there). Never have they requested a certificate

I've reported properties not being neutralised to the ESB as well, and like you it has been dealt with immediately as an emergency.

2011

Conversations 3 wrote: »

Board is fed through a 63a switched fuse, then feeds from the bottom to 2 rcds.

One feeding the sockets mcbs, standard 30ma.
The other is feeding the rest of the mcbs for lights, immersion etc. This is a 300ma RCD.

Going by this, without confirmation from the ESB, it is a TT supply.

What you have described certainly suggests that this is a TT supply, but you really need the ESB to confirm. That is the only way to be sure. Back in the good old days plenty of people would install whatever they could lay their hands on.

There are not that many TT installations in Ireland anymore.

2011

Risteard81 wrote: »

I've reported properties not being neutralised to the ESB as well, and like you it has been dealt with immediately as an emergency.

^^^The best course of action IMHO

Conversations 3

2011 wrote: »

^^^The best course of action IMHO

I've been in contact and sent the MPRN number and my phone number.

I'll update when the local engineer is in contact.