Cable Size

[steptoe]

as a first point,

how do you get your 0.4s disconnection time on a submain?

EDIT, I look forward to your answer.

 

[ivor dispatch]

as a first point,how do you get your 0.4s disconnection time on a submain?

EDIT, I look forward to your answer.

Is a PV AC cable a final circuit or a distribution circuit ??????

I would reckon most would say a distribution or you call it submain

so TN 5 sec and TT 1 s

I look forward to your answer

---------- Post Auto-Merged at 22:43 ---------- Previous post was made at 22:35 ----------

Why ? Does common sense not prevail ??

---------- Post Auto-Merged at 22:00 ---------- Previous post was made at 22:00 ----------

Forgot to ask - Were you the Installer ? (The internets a big place and this is the only thread you have ever posted on ?)

I do not get what you're saying ""Does common sense not prevail"" as you have posted the 1m 3% or 5% VD is OK but a long run with a 3% or 5% is not ok I think you need to do the maths

Am I the installer, maybe?

Thanks

 

[ivor dispatch]

I dont need to do the maths, the maths and thinking isn't straight forward, if you knew what you were doing you wouldn't be asking such a questionMaybe Yes ? Maybe No ? (The internet is a big place no ?)

Perhaps if you are the installer you could explain

1. The whole job in terms of your whys and wherefores as to the way you have done it ?

2. Your calculations?

3. The reasons as to why there is tripping trouble (which i presume is a correct statement from newman the end user) ?

4. As stated by Steps, how and why your installation (if you did it ?) meets the requirement of disconnection times, BS7671 and the MCS rules ?

And just to chuck into the pot, grid impedance (as per your post from SMAs site) has nothing to do with this problem in my opinion, now you may ask who is Canoe, what is his Opinion worth ? Well thats another good question and all i can say is I am a nobody, I make the tea, i sweep the floor, i bring bread to the table, the kids take me for granted, the missus doesnt even notice me BUT in my defence i have never done a job even when i was an apprentice (although i did have a good apprenticeship - i digress) where such appalling mistakes were made.....

I think you are getting carried away mate, please stick to your statement about voltdrop % and cable length.

Thanks

 

[ivor dispatch]

:slap

The installer should have installed a cable with 1% min volt drop, that is why there is a 1% guide, if the run is a meter then 3% is fine maybe even 5% if the run is a long one then 1% is the norm anyone stating otherwise is a muppetThe AC cable should be feeding in at the DNO Intake position not at a sub distribution board

What has been said above about the MCS rules and BS7671 are correct, to be honest NAPIT (some of there tech support dont know much to be honest and you probably spoke to someone who flys a desk) are wrong and if you have any further phone calls from them i suggest in your own interests you record it

The best thing you can do is put in writing (and by all means ask away here so your letter is correct) to both NAPIT and REAL a formal complaint

It will be interesting to see the DNO results but even if there voltage is too high and they drop it to within the required spec your installation probably still wont work due to the volt drop and cable run

The other thing you can do is publicly name the company in question on a nice personal free blog including all that has happened as there is nothing worse than bad advertising on the internet for customers to google and run a mile from the sharks

Another option would be after your complaints and how it goes would be to get another installer to fit the correct cable, do an inspection and report of the whys and wherefores of what was wrong and leave it running properly, after its proved that the proper cable with the proper volt drop is working then issue small claims proceedings against the company who installed it for loss of FIT and the costs incurred for the new cable install and report....

---------- Post Auto-Merged at 21:12 ---------- Previous post was made at 21:11 ----------

And i say it again

The installer was a MUPPET

---------- Post Auto-Merged at 21:12 ---------- Previous post was made at 21:12 ----------

It would be interesting to know exactly what qualifications and experience the installer had.....

:slap

It would be interesting to know exactly what qualifications and experience you think you have?

 

[jameseye12]

:slap :slap

It would be interesting to know exactly what qualifications and experience you think you have?

Obviously, more than you

 

[ivor dispatch]

My question was aimed at the installer - not you.....So are you the installer then ?

Care to answer any questions above ? (Not just mine)

Please do tell us exactly why the inverter is tripping out and how to fix it as i would be interested to know your thoughts (maths equations are welcome)

You may give us grid impedance calculations if you think that will help....

I digress again, i think enough has been said and from the pages above its pretty clear on the problem and how to rectify it so on that note unless someone has some red wine i will leave before i am told i am a moron :slap

Before you go explain your 1m 3% or 5% VD is OK but a """"long run"""" with a 3 % or 5% VD is not OK

Thanks

 

[Jono Pashley]

The best one is when i got sent to north wales to a job PV kit already in needs submain running in......materials delivered to site....okiie dokie....90M run it turns out in 10mm 3 core...called the company i was putting the submain in for they didnt care so just limited my work to the sub and noted on the cert

 

[ProDave]

The installer should have installed a cable with 1% min volt drop, that is why there is a 1% guide, if the run is a meter then 3% is fine maybe even 5% if the run is a long one then 1% is the norm anyone stating otherwise is a muppet

How can a run of 1m with a VD of 3% or 5% work but a """"long run""""""""" with a VD of 3% or 5% not work????????If possible, please post the calculation you are using.

Why ? Does common sense not prevail ??

I have to agree with Ivor on this one. 5% volt drop is 5% volt drop. It doesn't matter if that volt drop is a result of a VERY long 25mm SWA cable, or 6 inches of bell wire, it's still a 5% volt drop and will still give the same volt rise at the inverter and have the same trip problem.

 

[ivor dispatch]

Hello Newman

Just wondering if you have had any progress on your problem?

 

[newman]

Hello NewmanJust wondering if you have had any progress on your problem?

No,waiting for the DNO to respond to the meter readings they have took

 

[steptoe]

Is a PV AC cable a final circuit or a distribution circuit ??????I would reckon most would say a distribution or you call it submain

so TN 5 sec and TT 1 s

I look forward to your answer

---------- Post Auto-Merged at 22:43 ---------- Previous post was made at 22:35 ----------

Am I the installer, maybe?

Thanks

only if nothing else is fed from the same OCPD at the circuit origin,

in this case we know this isnt rue as there are various circuits being fed from the same protective device, never mind the same RCD.

 

[kme]

Right. I can`t take this bitching - If someone was enjoying the baiting, then I`m spoiling the fun.

If its a short run (say 2M), then v.drop isn`t going to be an issue anyway, as the cable correctly sized for the load isn`t going to have much drop - in V, not %

The grid voltage, and indeed inverter voltage, are finite, measurable units. They are not an abstract percentile.

Ergo: a cable sized for a 3% v. drop that was only 1M long would resemble bell wire.

A short cable (v.drop calcs including the "per metre" component) won`t have the inherent "drop" of the longer supply cable.

Part of the overall issue is the number of "installers" ( I refuse to call them sparks, or electricians) who ONLY think of current-carrying-capacity; and NEVER do any other checks on their cable sizes; let alone KNOW that MCS spec. a 1% v. drop.

Albert: It wasn`t any of MY guys - but it sounds atypical of many of the national PV companies.........

 

[ivor dispatch]

only if nothing else is fed from the same OCPD at the circuit origin,in this case we know this isnt rue as there are various circuits being fed from the same protective device, never mind the same RCD.

Steptoe you asked a question "as a first point,how do you get your 0.4s disconnection time on a submain?"

I answered correctly, you are now trying to imply I did not. You did not include newmens installation in your question so why use it now.

---------- Post Auto-Merged at 01:47 ---------- Previous post was made at 01:02 ----------

Right. I can`t take this bitching - If someone was enjoying the baiting, then I`m spoiling the fun.If its a short run (say 2M), then v.drop isn`t going to be an issue anyway, as the cable correctly sized for the load isn`t going to have much drop - in V, not %

The grid voltage, and indeed inverter voltage, are finite, measurable units. They are not an abstract percentile.

Ergo: a cable sized for a 3% v. drop that was only 1M long would resemble bell wire.

A short cable (v.drop calcs including the "per metre" component) won`t have the inherent "drop" of the longer supply cable.

Part of the overall issue is the number of "installers" ( I refuse to call them sparks, or electricians) who ONLY think of current-carrying-capacity; and NEVER do any other checks on their cable sizes; let alone KNOW that MCS spec. a 1% v. drop.

Albert: It wasn`t any of MY guys - but it sounds atypical of many of the national PV companies.........

KME is it possible for you to post some of your calcs as an example of say 1%,2%,3%,4%,5% VD on all different lengths and sizes of cable as it would be interesting to see if you are correct. G83 inverters trip at 260Vish and G59 at 1st stage 250V ish and 2nd stage 260V ish so supply voltage is critical when using the VD/impedance calculations

I do think looking at SMAs guide to grid connection would help you understand the importance of impedance & voltage and its effect / tripping of an inverter.

 

[ProDave]

No,waiting for the DNO to respond to the meter readings they have took

Do YOU know what the readings were, i.e what were the maximum and minimum voltages that were recorded at the supply point?

 

[professional]

The PV array is an alternative source of supply - these feed into the installation UPSTREAM of any circuit protective devices or installation isolation point so as not to impact on the existing installation.

Of course, if the installer wishes to connect said alternative source at a point DOWNSTREAM of CPD`s and/or installation isolation they must be competent to carry out full design calcs on the existing installation to assess the impact of the addition/alteration - but they may be asked to justify the stance that they have taken in a court of LAW, including proof of competence in circuit/installation design.

Come on 5DW`s, do you feel lucky? .... well do ya? ]

 

[steptoe]

Ivor, why wouldnt I be basing my points on newmans installation? This is what this thread is about, is it not?

 

[professional]

712.411 Protective measure: Automatic disconnection of supply 712.411.3.2.1.1 On the a.c. side, the PV supply cable shall be connected to the supply side of the protective device for automatic disconnection of circuits supplying current-using equipment.

and it goes on ....

 

[ivor dispatch]

712.411 Protective measure: Automatic disconnection of supply 712.411.3.2.1.1 On the a.c. side, the PV supply cable shall be connected to the supply side of the protective device for automatic disconnection of circuits supplying current-using equipment.and it goes on ....

agree

 

[professional]

Domestic PV is notifiable under Part P.

Both BS7671 AND Part P require manufacturers recommendations to be adhered to.

I believe that most (if not all) manufacturers of inverters that are used for domestic PV in England and Wales recommend that their equipment is NOT fed from an RCD - so bodging the PV into an existing spare RCD protected way does NOT comply with Part P. Also, since the cable "feeding" the inverter needs to comply with the requirements for RCD protection, all cabling will have to be mechanically protected / at least 50mm into the fabric of the building / SWA.

Discuss .... ]

 

[Jono Pashley]

Domestic PV is notifiable under Pat P.Both BS7671 AND Part P require manufacturers recommendations to be adhered to.

I believe that most (if not all) manufacturers of inverters that are used for domestic PV in England and Wales recommend that their equipment is NOT fed from an RCD - so bodging the PV into an existing spare RCD protected way does NOT comply with Part P. Also, since the cable "feeding" the inverter needs to comply with the requirements for RCD protection, all cabling will have to be mechanically protected / at least 50mm into the fabric of the building / SWA.

Discuss .... ]

SolarEdge inverters installation instructions state that if a rcd is required by local regulations then one must be installed. However it would have to be seperate from any other circuits. Not randomly stuffed into a spare way on the rcd side of a board.