Earthing a church

[colin durning]

Hi all,
I had been asked to look at the flourys in a church hall as they have problems getting new lamps.
When testing earth cont.(mettalic fittings) i detected 137v between fitting and MET.
I stopped there and inspected the system, free of charge of course, and found 2 100A supplies, 4 sub DB's, 2 water and 2 gas supplies. No bonding whatsoever,only 1 main earthing conductor that feeds 1 sub DB.

I have advised them to get it earthed pronto and they would like me to give quote.

Would it be acceptable to run the bonding to a sub DB, or will i have to run them to the SOURCE???
Not sure if a sub DB is regarded as the source.
Will i have to run main earthing conductors to each sub DB.

Any help would be much appreciated

 

[Adam W]

Re: Earting a church

For TNS and TNCS main bonding should be wired back to the MET (OSG section 2, p15).

 

[malcolmsanford]

All bonding must be connected to the MET which is normally at the origin of the Installation. You can though have a MET anywhere within the installation, it means is that you will need to label it with a BS 951 label indicating that it is the MET this under Reg 514.13.1. So you could reposition the MET if you wish, but becasue of testing it better to be near the origin

Dont the sub DBs have CPC now

 

[colin durning]

Re: Earting a church

Yes. MET in the sub DB or at the source? if you catch me drift.
I'm not sure if the Sub DB is acceptable.

 

[Engineer54]

Are all these Sub DB's at the same location?? if not you need to ascertain the main incoming supply DB and have your MET in that location. All other DB's will then have there earthing connection point as EMTs.

Is this an old church with a bell steeple or the like?? If it does have a highish steeple and is located in a fairly open area, it may also have a lightning protection system in place. So now we need to know what the supply earthing arrangement is TT, TN-S TNC-S(PME)

 

[colin durning]

Malcolm; at the origin there is no MET.
The 10mm T+E(tails) with earth snipped run from the meter to an isolating switch suppling 1x10mm and 1x6mm T+E feeding 2 sub DB's. Effectivley there is no earth, the supplies that feed the sub DB's still have CPC intact but they connect to nothing in the isolating sw.
My thougts were to run the bonding conductors back to the origin and install new MET and MEC to isolating sw as iam not sure if a sub DB's MET is regarded as the origin.
What do you think?

 

[colin durning]

Eng54;
Its old 150 ish, origonal supply feeds the church and vestry.
Supply 2 feeds newer (100yrs) church hallx2, kitchen toilets etc.
Tallest building about, 75-100ft, no sign of lightning cond.
Supply is TNS lead sheath
Origonal supply has a 2 way board adjacent and sub DB 15 mtrs away (8 way all rewireable)
Newer supply has a sub DB 8 mtrs away and the other sub is approx 40 mtrs away.

 

[colin durning]

I have a few photos(nice), dunno how you get them onto this. I'm not clued up that way

 

[Engineer54]

Go through photobucket.com

 

[Engineer54]

Choose one of the main supplies to be your MET point, and bond the other supply point to the MET. All other DB's earthing bars, will then effectively become EMT (earth marshaling terminals) All extraneous bonding conductors from water gas etc will then be taken to the MET.

 

[colin durning]

Ok i've got a few snaps on photobucket, the next big mystery is how do you get them on here ?
I'm sure somebody will tell me soon...

 

[IQ Electrical]

You can just post the links to the pics if you like.

Or hit 'Reply', then 'Go Advanced' and sample the joys of the file uploader by way of the paper clip attachment icon.

 

[colin durning]

This is the supply to the newer part of the churchhttp://i1088.photobucket.com/albums/i332/dubf8t/utf-8BSU1HMDA3MjctMjAxMTA0MjEtMTMyOC5qcGc.jpg

 

[colin durning]

http://i1088.photobucket.com/albums/i332/dubf8t/utf-8BSU1HMDA3MjUtMjAxMTA0MjEtMTMyOC5qcGc.jpg
http://i1088.photobucket.com/albums/i332/dubf8t/utf-8BSU1HMDA3MzAtMjAxMTA0MjEtMTMyOS5qcGc.jpg
http://i1088.photobucket.com/albums/i332/dubf8t/utf-8BSU1HMDA3MzEtMjAxMTA0MjEtMTMzMC5qcGc.jpg
http://i1088.photobucket.com/albums/i332/dubf8t/utf-8BSU1HMDA3MjctMjAxMTA0MjEtMTMyOC5qcGc.jpg

A few more..need to get a new camera

 

[colin durning]

This supplies the church and vestry; needs further investigation.
http://i1088.photobucket.com/albums/i332/dubf8t/utf-8BSU1HMDA3MzQtMjAxMTA0MjEtMTYyOS5qcGc.jpg

 

[colin durning]

http://i1088.photobucket.com/albums/i332/dubf8t/utf-8BSU1HMDA3MjUtMjAxMTA0MjEtMTMyOC5qcGc.jpg

 

[colin durning]

Had a look at the last Periodic from 7 years ago, numerous Code1+2's. Several circuits with IR under 1Meg. VIR everywhere. It's a pity THE big man's skint

 

[Engineer54]

Thanks for the snaps, but too late for me to study ..... I'm sure you'll get some help here from others like Malcolm before i get back here tomorrow...

One of those service heads, is as old as that church, never seen one quite like that, looks as if there's something missing!!!! ...lol!!!

 

[colin durning]

Cheers.
Was thinking of ringing the DNO. You would like to think they would do summit with that.

 

[malcolmsanford]

That does not look like a quick tidy up job and walk away I think you have a bit of work there old mate.

Safety as got to be your first concern and that is the earthing and bonding. I would take a few more pictures and put togehter a plan for the church.

Highlight

The age of the header and advise that the DNO should be contacted. Personally I would be telling the DNO that you can sometimes smell burning and that there is sometimes a buzzing coming from the head, there is a good chance that will be a free upgrade on something that old.

The head at the belfry, is it redundant? it looks to me as if those carriers are empty?

That meter with all those tails .................that is a pure work of dedication getting all that lot in, I bet a few of those conductors have had a shave. If it were me I would when the DNO came to change the head take all that that lot out and fit say 25/35mm one set of tails. Now you could utilise that 3 phase grey board as it still looks ok but big and bulky, If there was money in the pot I would be looking at getting a nice 3 way ryefield to fit.

Once that is sorted again you will have to change the T+E to the sub boards. Personally I would not re-run T+E me I would use MICC, but again it's money, so SWA or even singles in some Plastic trunking. So from the Ryefield/existing board a sub mains 10/16mm depending on calcs to the sub boards.

That should sort out the earthing troubles. Me I would be fitting a 8 way MET at the origin there. The system looks like a TN-s, when the DNO upgrade they may fit a TNC-S for you. So whichever a 16mm main earth from the head to the MET. Then a 16mm from the MET to your Ryefield, and of course then onto your sub boards.

Bonding then you can sort out as you go.

That would be my suggestions to the church board. I reckon also they will have to get the local Building office involved as it may be listed, and then there is the Diocise which may want a say. I think your going to have to stress the safety issue and cover this in writing, you know how boards and comitees love a written missive.