Cable Size

[Sidewinder]

Dave,

I often measure ZL-N at the origin and various points in the install.

This is what I note it as!

I realised what you are on about to be honest.

There is a lot of mis-information and poor information in the general domain wrt a lot of electrical stuff, including solar!

BTW, think about it Ze & ZL-N at the origin, on a TNC-S would be the same...

 

[steptoe]

Dave,I often measure ZL-N at the origin and various points in the install.

This is what I note it as!

I realised what you are on about to be honest.

There is a lot of mis-information and poor information in the general domain wrt a lot of electrical stuff, including solar!

BTW, think about it Ze & ZL-N at the origin, on a TNC-S would be the same...

well, it should be,

but I suppose you could have a bad connection on the N inside the HED.

 

[Sidewinder]

No Steps, not possible mate, the DNO would never leave a job like that! O) :innocent

 

[batty]

an R1R2 on the supply cable would be good, but not maybe quite so easy as it feeds another consumer unit,this is the big problem Im trying to get my understanding of,

the solar PV should be on a dedicated circuit, which it obviously isnt.

This is what is confusing me with this thread. The suspect cable was already installed. I understand it shouldn't have been connected to the PV but it was already there.

 

[newman]

NAPIT have got back and said if the volt drop along the cable is 5% or less,then this conforms to the BS7671 which they say with the figures supplieded it does do, the 1% recommendation is ONLY a recommendation.Seems to me then why fit a recommended 50mm cable for a 150meter run when you can get away with a 12mm cable.

Better get some one in to check the figures

 

[Sidewinder]

I suggest you ask NAPIT how this complies with MCS requirements, as they certify their "entities" for MCS approved work also.

 

[davetheglitz]

NAPIT have got back and said if the volt drop along the cable is 5% or less

Why not 3% - surely there is lighting in the barn?

I've lost jobs by conforming to this rule - it seems that mostly you can get away away with this as most appliances are very tolerant of voltage variations and the supply doesn't vary to the extremes.

 

[newman]

Why not 3% - surely there is lighting in the barn?I've lost jobs by conforming to this rule - it seems that mostly you can get away away with this as most appliances are very tolerant of voltage variations and the supply doesn't vary to the extremes.

Yes there is lighting in the barn

 

[ivor dispatch]

I would also ask napit how 3 or 5% complies with mcs rules, posted earlier the quote that an mcs install must comply with the DTI guide (which is 1%)

Could you post a link for the DTI guide you are quoting from. You might find the 2006 one agrees with Napit

Thanks

 

[Jono Pashley]

Except once you take into account the rest of the load on the distribution circuit it quite probably wont even comply with BS7671. Never mind the fact they have ignored the double ticked item above the VD information in the DTI guide and the information in MIS3002.

 

[newman]

I suggest you ask NAPIT how this complies with MCS requirements, as they certify their "entities" for MCS approved work also.

This is there answer to above question

The DTi Guide Paragraph 2.3.1 states that a volt drop of 1% or less is recommended (not a requirement). In this case the DTi Guide states that the voltage drop must remain within the limits as prescribed by BS7671. In this case it would be the current edition which is BS7671 2008 Appendix 4, Section 6.4, Table 4Ab

 

[Jono Pashley]

and as said in the post above that arguement is flawed as it isnt just the 16A for the inverter being pulled.

 

[ProDave]

I think the only way you are going to move forward is to employ your own electrician to do a detailed test on the whole of that cable run to determine the impedance of each leg, then look for the section with the highest impedance and work out a way to reduce it.

Alternatively, go back to the PV supplier. It is they who your contract is with. they should have sold you a system that works. It doesn't. Just tell them you want them to fix it. you don't care HOW they fix it, you just want it fixed.

Tell them if THEY don't fix it, you will employ your own competent electrician to fix it, and forward the bill for that work to them.

Throw in a mention of Trading Standards and that will hopefully kick them into doing something.

By the way have the DNO installed their voltage monitor yet?

 

[newman]

I think the only way you are going to move forward is to employ your own electrician to do a detailed test on the whole of that cable run to determine the impedance of each leg, then look for the section with the highest impedance and work out a way to reduce it.Alternatively, go back to the PV supplier. It is they who your contract is with. they should have sold you a system that works. It doesn't. Just tell them you want them to fix it. you don't care HOW they fix it, you just want it fixed.

Tell them if THEY don't fix it, you will employ your own competent electrician to fix it, and forward the bill for that work to them.

Throw in a mention of Trading Standards and that will hopefully kick them into doing something.

By the way have the DNO installed their voltage monitor yet?

Contacted The DNO again today they said they will ring tomorrow with an appointment ,we will see.

 

[kme]

Sorry -been away from this discussion for a few days...........

Anyroad - just caught up with the happenings, and this lightning-like, thought-type thingie just occurred to me, regarding the initial problem (grid voltage).

Are there other SSEGs in the immediate vicinity; which, "on sunny days", may (help to) raise the apparent supply voltage; which, when combined with the undersized cable, causes the inverter fail??

As for the suggestion that 5% vd is ok for the circuit - sorry, but that is complete & utter testicles, IMO

Without even going into the fact that the cct is not "dedicated", iaw MiS3002

 

[Manator]

Sorry -been away from this discussion for a few days...........Anyroad - just caught up with the happenings, and this lightning-like, thought-type thingie just occurred to me, regarding the initial problem (grid voltage).

Are there other SSEGs in the immediate vicinity; which, "on sunny days", may (help to) raise the apparent supply voltage; which, when combined with the undersized cable, causes the inverter fail??

As for the suggestion that 5% vd is ok for the circuit - sorry, but that is complete & utter testicles, IMO

Without even going into the fact that the cct is not "dedicated", iaw MiS3002

Having done no PV installations, and knowing nothing about it, what you said is double dutch to me, but will make sense to those who do.

 

[newman]

Sorry -been away from this discussion for a few days...........Are there other SSEGs in the immediate vicinity; which, "on sunny days", may (help to) raise the apparent supply voltage; which, when combined with the undersized cable, causes the inverter fail??

Yes, 4kwp solar pv 200 meters away my sub station is 300meters in the oppsite direction fed by overhead wires..............

---------- Post Auto-Merged at 19:53 ---------- Previous post was made at 19:45 ----------

[quote name=

As for the suggestion that 5% vd is ok for the circuit - sorry, but that is complete & utter testicles, IMO

Without even going into the fact that the cct is not "dedicated", iaw MiS3002

The trouble I am having with NAPIT is ,the 1% is only a recommendation, where as the 5% is a requirement

 

[ProDave]

The trouble I am having with NAPIT is ,the 1% is only a recommendation, where as the 5% is a requirement

You could argue that BS7671 has no true legal status, so even the 5% is only a recommendation?

But it appears from what has been said here that the 1% is a requirement of MCS systems, NOT a wiring regs issue.

So your Napit guy is looking at it from the wrong angle. Not only does it have to comply with wiring regulations, but a whole load of other rules AS WELL. That's the issue.

Tell him rather than just arguing about it, to get off his rse and come and look at the installation, find out where the voltage drop (rise) is occuring and find a way to fix it.

All the arguing under the sun does not alter the fact you have an installation that does not work. And this Napit guy can talk till his last breath, but talking won't fix it.

 

[newman]

You could argue that BS7671 has no true legal status, so even the 5% is only a recommendation? But it appears from what has been said here that the 1% is a requirement of MCS systems, NOT a wiring regs issue.

So your Napit guy is looking at it from the wrong angle. Not only does it have to comply with wiring regulations, but a whole load of other rules AS WELL. That's the issue.

Tell him rather than just arguing about it, to get off his rse and come and look at the installation, find out where the voltage drop (rise) is occuring and find a way to fix it.

All the arguing under the sun does not alter the fact you have an installation that does not work. And this Napit guy can talk till his last breath, but talking won't fix it.

I agree with all that has recently been posted,the trouble is my installer still says the inverter is set at G59,(sunny explorea says G83,the disply says G83)I think this is just an excuse so he can go in to the inverter and set the parameters of the inverter so high it will overcome any problems with the undersize cable,thats why I hope the DNO readings come back low.The installer told me to switch of one set of pannels so it would stop tripping,but on sunny days it still does

 

[kme]

We ALL now know the inverter is correctly parametered to G83/1; so he can stuff THAT idea where the sun won`t illuminate it!

My point was, as Prodave put in a better way, that 7671 is not the only set of rules to be followed here - but it DOES need to be looked at, in conjunction with other relevant publications.

Any installer who "tacks on" a PV install, as part of an existing, undersized final circuit, isn`t worth much. Sadly, there are lots of non-compliant installs around, `cos some companies wanted to maximise their instant revenue, by employing inexperienced persons to do their PV electricals - people whom most of us wouldn`t trust to make a cuppa on site safely, without supervision.

I know that doesn`t help you with this specific issue - maybe you need to speak to REAL assurance, or even MCS regarding this?