interview / dual rcd circuit distribution

[electrosparks]

Hi sparkys. Just wanted some feedback on a interview I attended recently for a sparks in the maintenance social housing sector.
After meeting the qualifying supervisor he left me to complete an elcr and schedule of inspections and tests etc as a test to see my competence in completing paperwork which is fair enough. He also left me table from regs of max permissable values for type b 60898 mcb photocopied straight from regs book. I asked him if he wanted me to tabulate them I.e. divide value by 1.2 and he said no he only uses 100 percent values in his reports.
I filled out paperwork in reasonable time and when qs returned he went through report.
All was fine until we got to schedule of results. He noted that the 7 circuits that i had selected and spread over dual rcd 17 th edition db was not to his liking as I had put ltg on one rcd and power on the other rcd. Saying that if there was a fault you would lose all power or all ltg which would be a nuisance so it would be better if each rcd protected some power and ltg. Now I am not unreasonable I can see his point but this is not a reg a good idea maybe. So as a good sparky a tried to qualify my answer in unoffensive manner. (we do work in an industry where expressing your knowledge can be daunting for all parties so great care was taken to put my point over.)
I said that this is not always acheiveable . Especially in social housing properties which is where this contract is and when the circuits involved may have down ring , kitchen ring and down lts.
if you have for example a downstairs lts cct and kitchen power cct and downstairs power cct the only way you can split ccts so no light and power in the same room are protected by the same rcd on a dual rcd board is to but the two power circuits together on rcd1 . And lights on rcd2.
This is a reg.
Now I could put everything on rcbo put that would be an unnecessary expense especially for a company that operates in social housing sector where winning the contract is all about pricing for the minimum amount of material/labour costs.
Now I wasn't trying to come over as a know it all but I feel on this occasion I was correct and as i was in an interview i felt quite awkward about the whole thing especially as I recently sat 2382 and 2391which is also a requirement for vacancy as is for nearly all jobs nowadays.
The thing is what are you supposed to do when you are asked for your professional opinion , the whole point of all these course tickets is to retain some of the info so you don't have to get outo the regs bs7671 and guidance note 3 to prove your self right.
After further info was discussed i came realize that it didn't suit me as 6 hour days were all that was offered as that is all they will pay per job is the hours it takes to change db fit smoke detection and other minor upgrades. All this and a qualifying supervisor who you cant talk to are absolutely no good to me.
Also the non use of tabulated max permissable zs values. Says it all.
Just for record wasn't offered job so
I think this was the probably the best outcome for all.
What do people think and what would you say do different/better.
Thanx for your time .

 

[Jay Sparks]

I would have put Kitchen skts & down lights on rcd 1, then down skts on rcd 2. That way, if rcd 1 goes, you still have power to plug in lamps etc and if rcd 2 go's, you still have power & lights...just good practice and comon sense really. I put the measured or calculated Zs readings on the test cert. If you want to compare the results/readngs you have with the ones in the regs book, you need to multiply the ones in the regs book by 0.8 but on some certs, you need to put down the MAX Zs allowed.

 

[Grommit]

The problem appears to be not that you couldn't talk to the QS, but that the deaf eared QS wasn't listening. Was he Eastern European ? What was the rate of pay on offer ?

 

[electrosparks]

Hi jay sparks grommit cool name by the way thanx for comments.
He is not eastern european .And he would pay15 to 16 pounds per hour.
And jay sparks the point I am making if you put kitchen sockets and down lights on same rcd you are contravening regs by both circuits are in same room as kitchen power is down stairs as well.
As regards the max permissable zs value this is actually the tabulated value.
E.G. b type mcb bsen 60898 the value is 7.67 ohms
To tabulate= 7.67÷1.2
=6.4 ohms this is value that should be used as max permitted value of zs.and no other and this is the value used for guidance by niceic.not the value in table of regs which is the original figure 7.67 ohms.
This value 6.4 ohms is recorded on test sheet before you get to the actual measured impedance (zs ) of circuit impedance.
I do realize that it is sensible to split load power and lighting (as long as they are not in same room area) as you suggested but sometimes its just not possible to do so as lighting and power circuits would have co-ordinated so circuits are wired to include the same area all the time. This is not the case in most social housing properties.
Thanx again for your response
Electrosparks

 

[telectrix]

disagree. the sotr column asks for the max. permitted Zs, not the corrected for 70deg. value in the osg. and i can't understand his gripe over division of circuits. in your OP you stated that he gave you an EICR to do. the division of circuits, therefore must have been done by someone else, so all you can do is test and complete the report.

 

[markc123]

Aye, fair one that tel - how can he criticize you on the deisgn of something you haven't installed?

 

[spark 68]

The way I usually (try) to split 3 rings across a dual board is as follows:

Kitchen ring with U/S ring with downstairs lighting, because the kitchen ring is likely to be the most heavily loaded and so is put on with likely the lightest loaded ring.

D/S ring on with U/S lighting.

And try to balance a cooker and shower (if present) across each side if possible, depending on the loading present.

I am not aware of a reg that specifically says you Must do it this particular way, apart from maybe regs section 314 division of installation.

 

[GLENNSPARK]

Hi sparkys. Just wanted some feedback on a interview I attended recently for a sparks in the maintenance social housing sector.
After meeting the qualifying supervisor he left me to complete an elcr and schedule of inspections and tests etc as a test to see my competence in completing paperwork which is fair enough. He also left me table from regs of max permissable values for type b 60898 mcb photocopied straight from regs book. I asked him if he wanted me to tabulate them I.e. divide value by 1.2 and he said no he only uses 100 percent values in his reports.
I filled out paperwork in reasonable time and when qs returned he went through report.
All was fine until we got to schedule of results. He noted that the 7 circuits that i had selected and spread over dual rcd 17 th edition db was not to his liking as I had put ltg on one rcd and power on the other rcd. Saying that if there was a fault you would lose all power or all ltg which would be a nuisance so it would be better if each rcd protected some power and ltg. Now I am not unreasonable I can see his point but this is not a reg a good idea maybe. So as a good sparky a tried to qualify my answer in unoffensive manner. (we do work in an industry where expressing your knowledge can be daunting for all parties so great care was taken to put my point over.)
I said that this is not always acheiveable . Especially in social housing properties which is where this contract is and when the circuits involved may have down ring , kitchen ring and down lts.
if you have for example a downstairs lts cct and kitchen power cct and downstairs power cct the only way you can split ccts so no light and power in the same room are protected by the same rcd on a dual rcd board is to but the two power circuits together on rcd1 . And lights on rcd2.
This is a reg.
Now I could put everything on rcbo put that would be an unnecessary expense especially for a company that operates in social housing sector where winning the contract is all about pricing for the minimum amount of material/labour costs.
Now I wasn't trying to come over as a know it all but I feel on this occasion I was correct and as i was in an interview i felt quite awkward about the whole thing especially as I recently sat 2382 and 2391which is also a requirement for vacancy as is for nearly all jobs nowadays.
The thing is what are you supposed to do when you are asked for your professional opinion , the whole point of all these course tickets is to retain some of the info so you don't have to get outo the regs bs7671 and guidance note 3 to prove your self right.
After further info was discussed i came realize that it didn't suit me as 6 hour days were all that was offered as that is all they will pay per job is the hours it takes to change db fit smoke detection and other minor upgrades. All this and a qualifying supervisor who you cant talk to are absolutely no good to me.
Also the non use of tabulated max permissable zs values. Says it all.
Just for record wasn't offered job so
I think this was the probably the best outcome for all.
What do people think and what would you say do different/better.
Thanx for your time .

this would depend on how the value of Zs was acheaved....

calculated Zs: Ze + (R1 R2)
this would require the correction factor 1.2 to be applied for tempreture

measured direct Zs: the max tabulated values in the BGB can be used here without correction....

 

[Spark1979]

Personally I'd have let you do the job then asked why you'd done it that way then based on your answers would have went from there. I often put all lights on 1 side all power on other then split shower and cooker etc accordingly. I often ask the householder (private jobs) what they want and explain advantages disadvantages as personally I don't want my sockets going off cos a bulbs blown. Horses for courses and no right or wrong answer personally social housing normally have a spec to follow so you gotta do it their way or the highway

 

[electrosparks]

Thanx fo all you answers you have all ben very helpful all with a different perspective. So nuce one guys