Enquiry of Ze from DNO.......useless!!

[S60TEM]

OK, I have just completed a PIR on a first school the week before last and didn't want to break the seals which covered the earth terminal at the head (TNC-S)

I decided that I'd give NEDL a call to get the Ze from them. Guess what they said to me?!

DNO - "Sorry, WE don't hold any information like that sir, you will have to measure it and let us know!" EH!!

ME - "is it OK for me to break your seal then?"

DNO - "Oh no sir, your not allowed to do that"

ME - "OK then, can you send someone out today to cut and reseal it after I've took my measurement then?"

DNO - "I'm sorry but we don't have anyone that performs that task"

ME - "So I can cut the seal then?!"

DNO - "Errrrr, yes OK then but can you reseal it afterwards?"

ME - "Yes, I can"

DNO - "Thank you"

Now why the f**k do our forms say Ze by ENQUIRY or Measurement?!

They havn't got a clue!!

 

[ianmacd]

Doesn't the esqcr require them (by law) to advise on enquiry these details?

 

[Andy™]

remind them of their requirements of ESQCR.

although they will probably tell you 0.35

 

[S60TEM]

thats what I was implying when speaking to them (the convo was a bit longer on the phone) but they were just clueless!

 

[a1]

ALL DNOs should have specialised departments for different areas of their business.

IE:

• New connections
  
• Earthing Queries
  
• etc
  
• etc
  

 

[ianmacd]

[quote name='Andy

 

[steptoe]

s'easy really,

TNCS 0.35

TNS 0.80

but why would you have to break their seal to measure it?

surely you could dis-connect the cable at the other end? where it terminates at the MET,

this difference in reading should be for all intents and purposes negligible in most situations.

 

[m4tty]

Last time i rung they didnt have a clue and said they dont hold earthing arrangements on record and couldnt provide anything apart from saying ring the supplier. Going back and forth getting nowhere. Seal ?? what seal (JOKE)

 

[S60TEM]

s'easy really,TNCS 0.35

TNS 0.80

but why would you have to break their seal to measure it?

surely you could dis-connect the cable at the other end? where it terminates at the MET,

this difference in reading should be for all intents and purposes negligible in most situations.

Thing is, the whole installation throughout the school was in metallic trunking and fed via SWA so I wanted an accurate Ze reading without any parallel paths from all the bonded metalwork etc. I agree that I didn't need to break the seal etc but as it hadn't been tested since 2001 on some of the DB's, I wanted to be 1000% on the job as it was within a primary school. Better to overdo a job like this really imo when little intuitive fingers can be poked in dangerous places !!

 

[ADS]

Thing is, the whole installation throughout the school was in metallic trunking and fed via SWA so I wanted an accurate Ze reading without any parallel paths from all the bonded metalwork etc. I agree that I didn't need to break the seal etc but as it hadn't been tested since 2001 on some of the DB's, I wanted to be 1000% on the job as it was within a primary school. Better to overdo a job like this really imo when little intuitive fingers can be poked in dangerous places !!

But surely there is a MET that you would disconnect the 'Earthing Conductor' from and measure your Ze - nothing to do with where it connects in the 'head'??

Or am I mis-reading something?

 

[S60TEM]

But surely there is a MET that you would disconnect the 'Earthing Conductor' from and measure your Ze - nothing to do with where it connects in the 'head'??Or am I mis-reading something?

It was a TNC-S system and to remove the cover from the side of the head to gain access to the MET you have to remove DNO Fuse number 3 on a three phase system. I couldn't have got an accurate reading elsewhere as from there the supply went straight into a main isolator wired in SWA then from that in SWA to a main Submains incomer which fed seperate isolators for each specific Distribution board which throughout the school were wired in bonded trunking and conduit. As you can see, all the SWA armour was bonded to all the metalwork of the installation so the only way for me to have got an ACCURATE Ze was to remove DNO fuse number 3 and remove the MET cover, disconnect the earth, replace fuse number 3, take my Ze using the now uncovered MET and replace everything once done including a new seal for the fuse.

 

[steptoe]

so, you are saying that the bonding is also behind this cover as well?

I would have cut them all off and put an ISCO/HENLEY on.

otherwise how can you test the MEBs?

 

[S60TEM]

there was no bonding mate! That went on my snagging list.

 

[Sidewinder]

Scott,

Are you SURE there was NO bonding?

Remember if there is LOTS of structural steel then you can bond your services to the steel then the steel to the origin db as long as the steel is connected together.

 

[steptoe]

kill the main switch, cut the Earthing Conductor and stick an ISCO on,

you now have your own MET where you can test, plus it gives you somewhere to attach your flying lead to verify MEBs.

 

[S60TEM]

Scott,Are you SURE there was NO bonding?

Remember if there is LOTS of structural steel then you can bond your services to the steel then the steel to the origin db as long as the steel is connected together.

100% mate. Building is a very old stone built circa 1900's with no structural steel. The mains gas was in a small locked outhouse in the corner of the playground approximately 100 metre's from the main building and totally isolated from getting bonding to it, so the next closest place was where the gas main entered the building into the boiler room which there was no bonding and also a tray plate system for all the pyro that was not bolted together and had no cross bonding between the trays. The water intake was in a seperate cellar boiler room. There was a small 3 way DB that had been installed in there last May by an NICEIC contractor to control the lights, water boiler and another circuit....this had been wired in SWA from the main submains DB and to bond the water, they had cut away the PVC sheath of the SWA, put on a standard earth clamp and run a 10mm Earth from that to the mains water!

kill the main switch, cut the Earthing Conductor and stick an ISCO on, you now have your own MET where you can test, plus it gives you somewhere to attach your flying lead to verify MEBs.

Unfortunately I couldn't cut the main power from the isolator as it was an agreed limitation as they had a main server running from the main submains which couldn't be turned off. Fortunately for me this server ran off the red phase (DNO fuse 1 of 3) Everything else was turned off and isolated bar this one feed to the server and that way I could remove the blue phase fuse (with no load) to gain access to the MET.

 

[Sidewinder]

Cool Scott, sorry to doubt you mate but there have been questions asked before, well, you know what I mean!

I can't comment on the 951 on the SWA, that is just appalling!

Gets my back up, suppose it is a limitation of the QS system.

However, the QS should be kicking a5r3 or, if it is a small company should just simply know better!

 

[steptoe]

100% mate. Building is a very old stone built circa 1900's with no structural steel. The mains gas was in a small locked outhouse in the corner of the playground approximately 100 metre's from the main building and totally isolated from getting bonding to it, so the next closest place was where the gas main entered the building into the boiler room which there was no bonding and also a tray plate system for all the pyro that was not bolted together and had no cross bonding between the trays. The water intake was in a seperate cellar boiler room. There was a small 3 way DB that had been installed in there last May by an NICEIC contractor to control the lights, water boiler and another circuit....this had been wired in SWA from the main submains DB and to bond the water, they had cut away the PVC sheath of the SWA, put on a standard earth clamp and run a 10mm Earth from that to the mains water!Unfortunately I couldn't cut the main power from the isolator as it was an agreed limitation as they had a main server running from the main submains which couldn't be turned off. Fortunately for me this server ran off the red phase (DNO fuse 1 of 3) Everything else was turned off and isolated bar this one feed to the server and that way I could remove the blue phase fuse (with no load) to gain access to the MET.

how did that help?

you still couldnt test Ze anyway.

you have to disconnect it to test it, and the only way to disconnect it is to ISOLATE the incoming supply.

BTW, I assume you mean the grey phase,

 

[S60TEM]

Cool Scott, sorry to doubt you mate but there have been questions asked before, well, you know what I mean! I can't comment on the 951 on the SWA, that is just appalling!

Gets my back up, suppose it is a limitation of the QS system.

However, the QS should be kicking a5r3 or, if it is a small company should just simply know better!

no problemo, I was just bemused to what they had done tbh! Needless to say, the quote for the remedial work is pretty hefty for these types of things that I found!

how did that help?you still couldnt test Ze anyway.

you have to disconnect it to test it, and the only way to disconnect it is to ISOLATE the incoming supply.

BTW, I assume you mean the grey phase,

I know what your saying Steps but the only way to get round it was to turn off every DB apart from one feeding the server; luckily enough this DB was single phase and running from the Red phase. So upon removal of the Blue phase DNO fuse, there was no load on it and no risk of any arcing etc. Once I removed the fuse and the cover to the MET and removed the Earth, I refitted the fuse and took my Ze reading from the MET using the nearest DB for my Line & Neutral connections which happily was only half a metre above the head and isolator.

Hope you understand what i'm trying to explain as i get myself confused when typing sometimes LOL

---------- Post Auto-Merged at 22:58 ---------- Previous post was made at 22:57 ----------

Oh and also, yes the grey phase LOL (they were still marked old colours at the time)

 

[steptoe]

Scott, what Im trying to say is,

you mean you left the installation with NO EARTH while it was powered up?!?!?!?!?!?!?!?!?