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Leesparkykent
i give up to be honest, you have your opinions i have mine.
with the power off, and he just happens to be using a metal drill bit rather than a masonry or wood drill bit?
and is going to just keep drilling despite the drill not going in like it should and sounding like it's hit something metal?
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davesparks
Which is unlikely to operate once he's turned all of the power off. Or if he's using a cordless then I doubt a DIY level cordless drill will be man enough to injure galv pipe.
But either way how many diyers actually switch off their whole house before drilling holes? All that will happen if they do is that it won't go bang when they drill through a cable but probably will when they turn it back on.
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davesparks
I have to say there are a fair few who do just keep going after they've hit a buried bit of metal, carpenters are quite good at that trick too, along with plumbers and kitchen fitters
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Leesparkykent
he is a DIY'er after all!
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davesparks
Thinking about it I've been guilty of the 'get the SDS out and give it some proper welly' approach when encountering resistance whilst drilling a hole. I wouldn't be surprised if most of us are!
besides, with the inverter off, even transformerless inverter circuits become protected by dint of being electrically separated.
Switch it back on and the insulation resistance test on start up should detect a damaged cable and not start up, so the circuit stays electrically separated until the fault's repaired.
At the end of the day, it's allowed under BS7671, and it's allowed because it's considered to be safe.
Switch it back on and the insulation resistance test on start up should detect a damaged cable and not start up, so the circuit stays electrically separated until the fault's repaired.
At the end of the day, it's allowed under BS7671, and it's allowed because it's considered to be safe.
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Leesparkykent
exactly this is my point, it has been known lol
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Leesparkykent
and that is why i said IMO
why would the customer need to go into the loft to isolate it anyway.
if the inverter is in the loft just isolating the ac side will turn the inverter off.
the dc cables will always have potential on them unless the customer covers them on the roof or works at night lol
if the inverter is in the loft just isolating the ac side will turn the inverter off.
the dc cables will always have potential on them unless the customer covers them on the roof or works at night lol
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Leesparkykent
hes on about putting the inverter downstairs by the consumer unit
yes but doing it that way would need local isolation for dc side in the loft as well for the solar panels.
This is a graph of failure rates vs operating temperatures for capacitors - not solar inverter capacitors specifically, but indicates the problems associated with operating inverters in lofts as the issue is pretty much generic for all capacitors (though some cope better than others).
Fine if there's no other option, but causing your customer to have to fork out for a new inverter twice as often as they probably would have with the inverter in the garage where that was an option doesn't seem like a good idea to me.
what capacitors were used in that test?
This is a graph of failure rates vs operating temperatures for capacitors - not solar inverter capacitors specifically, but indicates the problems associated with operating inverters in lofts as the issue is pretty much generic for all capacitors (though some cope better than others).
Fine if there's no other option, but causing your customer to have to fork out for a new inverter twice as often as they probably would have with the inverter in the garage where that was an option doesn't seem like a good idea to me.
a lot of chinease caps are crap.
there is a reason good mid-high end psu in pc's use japanise capacitors becauae they last a lot longer.
i have had two cheap nasty power supplies fail on me from leaking capacitors
the capacitors themselves weren't anything like those used in inverters, much lower voltage units, but it was the best graph I could find to illustrate the point about the increase in failure rate / decrease in lifetime with higher operating temperatures.
This effect is fairly universal for capacitors although the specific lifespans for given temperatures will vary depending on type and quality.
Here's another.
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davesparks
Even if you use the best components in the world to build something it will still last longer and work more efficiently if it is installed in a cooler environment
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
yep.
I expect the likes of a shade greener will be in for a very nasty surprise in coming years as they've installed every single inverter they've used in the loft, and used the cheapest possible inverters they could get hold of in bulk from china.
I'd lay odds that virtually all of their inverters will need replacing within 10 years.
Oh yeah, and they also use 2.5mm2 t&e cable on every job, and only install 3kWp systems upwards, then wonder why they have loads of issues with inverters tripping out for over voltage (after installing multiple systems on the same street without obtaining prior permission as well).
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Leesparkykent
same as isis solar and home sun apart from a lot of these were fitted with fronius inverters.
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.
i thought some of the fronius inverters came with a 15 year guarantee?
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.
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Leesparkykent
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davesparks
If the ambient temperature is less then the cooling of the unit will be more efficient,
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.
The reasons in favour of it are based on sound scientific and engineering principles.
Think I'll stick to our methods and reasoning tbh.
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
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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
what are you talking about?
the panels themselfs are always generating electricity the inverter only checks for supply on ac and switches dc accordingly
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Leesparkykent
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
ah i didnt see a quote
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Leesparkykent
sorry mate should of quoted Gavins post #67
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.
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?
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
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
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.
Richo77
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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.
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