Solar panel circuit MCB size?

[netblindpaul]

This forum never ceases to amaze at the lack of understanding of some members, and their total denial when it comes to absolute engineering and scientific facts, and proven data.

 

[shanky887614]

same as isis solar and home sun apart from a lot of these were fitted with fronius inverters.

i thought some of the fronius inverters came with a 15 year guarantee?

 

[Gavin A]

dont forget that is internal temperature and the internals will hit 30oC quite easily inside the inverter so i doubt it would make a huge difference, throw as many charts at me as you like

I know, but the rate of cooling is directly proportional to the ambient air temperature.

I also know that we get virtually every job where the other companies quoting have opted to install the inverter in the loft when there was a cooler option available after we explain this point to them, particularly when the customer is more technically literate.

 

[Leesparkykent]

i thought some of the fronius inverters came with a 15 year guarantee?

yea i think so

 

[Gavin A]

i thought some of the fronius inverters came with a 15 year guarantee?

Fronius offers a 5-year manufacturer warranty on all inverters as standard. You also have the option of extending the warranty period to 10, 15 or 20 years. If a claim is made, Fronius bears the costs for original replacement parts, transportation and work undertaken. The extended warranty therefore protects against any fluctuations in price for the entire warranty period. In addition, free support is on hand from our competent and easy to reach hotline team for the entire duration of the warranty period.

but extended to 10 years as of 1st January apparently

 

[davesparks]

dont forget that is internal temperature and the internals will hit 30oC quite easily inside the inverter so i doubt it would make a huge difference, throw as many charts at me as you like

If the ambient temperature is less then the cooling of the unit will be more efficient,

 

[Gavin A]

So to conclude, the only reason not to put the inverter in the garage is some personal preference based on some vague fear of permanently live dc cables despite them being mechanically protected, and protected as an electrically separated circuit, and via RCMU and start up insulation resistance tests by the inverter.

The reasons in favour of it are based on sound scientific and engineering principles.

Think I'll stick to our methods and reasoning tbh.

 

[shanky887614]

no fear of live cables in walls, i would just rather put it in the loft unless customers wants it else where, let the customer choose where they want it

 

[Leesparkykent]

i understand your point on mechanical protection. but you keep banging on about start up insulation tests etc,this is irrelevant as the dc cables will still be live before, during and after regardless if the inverter starts up or not due to the insulation resistance test carried out by the inverter

 

[shanky887614]

i understand your point on mechanical protection. but you keep banging on about start up insulation tests etc,this is irrelevant as the dc cables will still be live before, during and after regardless if the inverter starts up or not due to the insulation resistance test carried out by the inverter

what are you talking about?

the panels themselfs are always generating electricity the inverter only checks for supply on ac and switches dc accordingly

 

[Leesparkykent]

what are you talking about?

the panels themselfs are always generating electricity the inverter only checks for supply on ac and switches dc accordingly

im quoting Gavin A. and this is my point exactly, Panels are always producing under daylight hence cables will always be live to dc isolator

 

[shanky887614]

im quoting Gavin A

ah i didnt see a quote

 

[Leesparkykent]

ah i didnt see a quote

sorry mate should of quoted Gavins post #67

 

[Gavin A]

i understand your point on mechanical protection. but you keep banging on about start up insulation tests etc,this is irrelevant as the dc cables will still be live before, during and after regardless if the inverter starts up or not due to the insulation resistance test carried out by the inverter

not irrelevant as if the inverter doesn't start up, or cuts out, then even on a TL inverter the circuit stays / becomes an electrically separated circuit with no potential to earth, so even if the cables did somehow get damaged and exposed despite the mechanical protection it would only be dangerous if someone actually grabbed hold of both + and - exposed cables at the same time, and only life threatening if they were holding one bare wire in each hand. ie they could touch the positive or negative cable while also touching an earth bonded radiator and feel absolutely nothing.

It'd also alert the customer to the fault as the inverter wouldn't be working, and the inverter would be somewhere easily accessible for them to notice this.

 

[driverman]

Read thread with great interest after my original question, thanks very much. I did chat to the customer last night and the reason for the inverter sited downstairs was..... cooler position.....which some you of mentioned earlier. If inverter sited elsewhere in the modern home and away from the mains position then I would of thought most homes would have 30ma RCD protection. Does that have any impact on solar panel installations?

 

[BruceB]

Wow, this thread took off a bit.

Personally I would be happy with dc cables running through my house properly protected/signed and prefer to have the inverter sited in a cool, convenient position rather than say in the loft.

If a customer still managed to drill into them, then put it down to Darwin's theories being played out.

Returning to the original topic as per the title, then for example the Schneider guidance is that when multiple mcbs are in a small enclosure then a 20% reduction in rating should be applied to determine the maximum service current. So for sustained operation at 16A, you should use a 20A mcb. In a hot environment the reduction increases.
http://www.schneider-electric.co.uk.../en/local/rti-catalogue-sections/SE7860_8.pdf
page 8/3

 

[driverman]

Not that I'm into design as such, but I can remember reading somewhere that MCB's should be down-rated if mounted sideways on within an enclosure. Also it makes sense not to put heavily loaded MCB's / fuses side by side. I've grown up with Wylex Boards whereby it was always the standard heaviest load near to the main switch then decreasing sizes away from the switch.

 

[driverman]

OK to re-capp. MCB side of things OK. Generally, are you guys OK with Solar Panel circuits being protected with 30Ma RCD's? One person on here said it was not an issue although he had changed a couple re nuisance tripping. Another said his company never install them. Thanks

 

[Richo77]

Yes solar PV should be protected by an RCD. Some manufacturers state 30Ma some state 100Ma. The solar array is outside, usually roof mounted so it requires RCD protection. I always install a new 2 way RCD board separate from the domestic CU to avoid nuisance tripping. The PV installation can have quite a lot of earth leakage and if it's connected to the same RCD as the house it can cause problems. Separating the two installations can make life a lot easier with regard to nuisance tripping.

 

[Gavin A]

Yes solar PV should be protected by an RCD. Some manufacturers state 30Ma some state 100Ma. The solar array is outside, usually roof mounted so it requires RCD protection. I always install a new 2 way RCD board separate from the domestic CU to avoid nuisance tripping. The PV installation can have quite a lot of earth leakage and if it's connected to the same RCD as the house it can cause problems. Separating the two installations can make life a lot easier with regard to nuisance tripping.

no it doesn't require an RCD.

The inverter manufacturers give specifications for RCD fitting where required by local regulations - ie where required by BS7671, so an RCD is only needed where it's required under BS7671.

All you're doing is adding a source of nuisance tripping to the system by adding an RCD where it's not needed.