Alternative solar supply available at point of use Domestic kitchen

TNS  Have heard : In general  this DNO supply cable is ageing and breaking up: Its earth connection back to source may no longer be secure So some new recommendation for owners to install this very earth rod for future reliability ? So that implies approval ? 

I think there's been a bit of Chinese whispers on that one. There is indeed a recommendation for an additional electrode these days on TN systems - but it's less to do with ageing TN-S cables, than with the ability of a simple fault on the 'new' TN-C-S (PME) system that can make the "Earth" connection hazardous live. (A problem that was previously mitigated by bonding to metallic water and gas pipes, but these have mostly been replaced by plastic). And no, no chance of getting the DNO to pay for it!

Can this proposed system ( as attached ) pass muster to be in accord with " the regs" 

In my option, yes it can be done. The details will have to be right (some of what you suggest might need adjustment), but nothing fundamental to object to I think. There are plenty of dual supply and off-grid system out there.

Underground Cabling would be SY semi armoured run in pvc pipe.

That's another detail that might need adjustment. SY generally isn't intended for underground use (as ordinary PVC sheaths can absorb water) and the steel braid isn't rated for use as a c.p.c. (and it doesn't comply with any recognised BS, EN or IEC standard).

As far as the local sparks is concerned, that rather depends on the individual. What you want isn't a "normal" domestic setup and may well be beyond the experience or even competence of some otherwise perfectly competent installers. Like anyone else no electrician knows everything about everything.  Someone who specializes in off-grid or UPS systems may feel more comfortable.

   - Andy.

SY cabling  It does need to have flexibility for radius bend  Ordinary armoured cable doesnt bend ?  ... OK Know you recommended something before  Can you point me to a supplier for your recommendation . I would run separate " containment pipes for dc / ac / and data cable  ( battery level)  anything wrong with solvent cement drain pipes  already laid some ?  Your comment pvc absorbs moisture I think now I understand old suppliers nervousness over underground pipes 

want to recommend a suitable " sparks/ consultant ? South London Wimbledon area  ( not the posh bit)  Ms O 

AJJewsbury said:

In my option, yes it can be done.

It's worth looking at Chapter 82 and the requirements for this type of system.

There are provisions in place already in British and International standards, and I'm a little concerned we are trying to "crowbar" a different kind of product in here that doesn't meet all of the necessary requirements for that kind of system.

Anne Otis said:

anything wrong with solvent cement drain pipes  already laid some ?

What size are they?

It's worth looking at Chapter 82 and the requirements for this type of system.

Humm, sort of. Chapter 82 seems more to be concerned with grid-connected systems - whereas what's being proposed here is to my mind more like a distinct system sitting alongside but independent of the grid supply - more like a UPS system (but with the battery charged from PV rather than the mains) - and 82 makes the point that UPS system aren't considered to be PEI (823) because it "is only to supply downstream critical loads and not capable of reverse feeding into the public network and/or current-using equipment in the upstream part of the electrical installation".

I think most of us here are of the opinion that a grid-connected system would be a more "modern" and "user-friendly" approach in a general domestic situation, but in this case it's not what the customer wants. The proposed system may have some definite advantages that the customer thinks valuable - a relatively simple system that more open to education and experimentation. It would be much more obvious how it's working (or not working); and side-steps some of the complexity (G98,G99 etc) needed for grid-connected systems. It might even work out a little cheaper as some of the complexities of having to deal with grid-fail etc aren't needed.

In some other situations, the proposed system would make perfect sense - I've seen something very similar on a narrow boat - providing 230V a.c. to a few appliances when moored somewhere that doesn't have a shore supply hookup (although that one was charged by a dynamo on the main engine, rather than PV). Some more modern units have an auto bypass so supply things from the shore supply if it's available, but I don't see any need to force people down that route if a simpler arrangement is satisfactory to them. I can imagine a caravan or camper van wanting a similar setup - and you really wouldn't want to go for a grid-tied situation there, when it can be plugged into a random installation that likely has no provision for accepting reverse feeding (let alone via a plug that would have its pins exposed when unplugged).

I'm a little concerned we are trying to "crowbar" a different kind of product in here

I do share some concerns there - there are certainly a lot of details that have to be got right. I have a decent suspicion that many inverters out there (especially of the smaller/cheaper variety), like many of the smaller petrol generators, are only intended for supplying a single appliance and won't be easily made suitable for supplying multiple appliances through a fixed installation (won't accept an N-PE link etc). I'm sure there is suitable equipment out there (for entirely off-grid homes etc) but suspect it's not cheap.  Likewise the arrangement for long and/or buried cables still needs some work. Lots of information is still missing, but I still have worries about impact/shock protection for any LV d.c. on an unearthed system (whether PV or battery) as well as v.d. to/from the battery if the thought was to have the battery in the outbuilding and the charger and/or inverter in the house. The choice of LV or ELV for the battery, probably helps one problem but hinders the other. Maybe no simple solutions, but that doesn't mean it can't be done.

   - Andy.

AJJewsbury said:

and side-steps some of the complexity (G98,G99 etc) needed for grid-connected systems. It might even work out a little cheaper as some of the complexities of having to deal with grid-fail etc aren't needed.

If you intend to operate the said inverter in parallel with the grid at any point, then G98/G99 must be complied with (according to ESQCR). If the inverter is set up as a simple grid-connected inverter, that may be OK ... but I'm not sure about the consequences for "backup" operation as per earlier posts.

"Side-stepping" something because it's difficult, or doesn't fit with the product as provided, is not really a good enough reason when we have specific legislation and standards (there's a reason things say what they do).

I still think it's worth looking at how the particular inverter is designed and arranged, to determine whether:

• It's possible to actually earth one of the live conductors of the "backup" (I know it's not in some designs); and
• the arrangement conforms to ESQCR for the operation in island mode.

One of the issues with answering questions in forums like this, is we aren't always told all the facts about a particular installation, so please forgive my apparent pedantic approach.

AJJewsbury said:

and 82 makes the point that UPS system aren't considered to be PEI (823) because it "is only to supply downstream critical loads and not capable of reverse feeding into the public network and/or current-using equipment in the upstream part of the electrical installation"

Well, if the inverter is a UPS then it will have a Declaration of Conformity to BS EN IEC 62040 series for that functionality ... otherwise, you would have to consider making a statement about its use in line with Regulation 511.2 ...

Having said all that, there may not be an issue with this particular product/application ... it may well conform to IEC 62040 and be suitable for use as a UPS ... I just don't know at this point.

worries about impact/shock protection for any LV d.c. on an unearthed system ..

Oh please expand  Expecting the solar panel dc will be in order of 100V or so :  48V battery. :   Dont think unusual ? So what normal  protections would be usual please ? 

Reckon I would run earth to solar mount "belt and braces".  Reckon bury a 3 core 10mm cable for ac side with the earth core as  link  inverter N/E to  DNO TNS MET ?  

FYI 

Plastic weld drain  pipe already partially run : 3 lots separated  50mm 30mm and aluminium under floor heating tube for  data cable  

I am going to need local expertise. If any suggestions 

Ms O 

PS reckon the energy future outook  is precarious at best . Reckon some off grid  mix could be wise . And simple maintenance. 

Anne Otis said:

Plastic weld drain  pipe already partially run : 3 lots separated  50mm 30mm and aluminium under floor heating tube for  data cable

Good luck! 

Any bends?

no 90 bends only  120 : Pull throughs going in  Doing it bit by bit letting my lawn grow back  Do you have any advice on what kind of cable for underground  Moisture proof ?   Supplier Ms O 

Personally, and I have no idea/couldn't care less if it it is proscibed by "the regulations", I am absolutely against the use of blue mpde water pipe, brown soil pipe and white/grey waste pipe as cable ducting. And I've come across them all. It is asking for trouble imho. As specific, easily identifiable, cable ducting is readily available why would you use anything else?