Pv solar install the inverter in loft or garage

don0301

Dave_Fowler wrote: »

Sorry Don, I have missed your point, and looking back to your previous post I now don't understand what point you were raising - if it wasn't the one I answered.

my point was, you agreed an inverter internal temperature would not be > 150C

therefore, i agree with your point

Dave_Fowler wrote: »

At temperatures up to 150C, failures due to temperature in semiconductors are mainly due temperature cycling where fractures in bonding wires and substrates can occur. One should note however that the temperature of the silicon in a device under load is not that of the ambient, but is higher depending on the power dissipated.

Dave_Fowler

don0301 wrote: »

my point was, you agreed an inverter internal temperature would not be > 150C

The manufacturer of an inverter should ensure that the internal temperature of the inverter is kept at a point where the semiconductor junction temperatures are kept below 150C.

This probably means derating the inverter at ambient temperatures above 50C where the internal temperature of the inverter is likely to be 70C and the heatsink temperatures 95C

Dave F

zeupater

Dave_Fowler wrote: »

I'm not certain what the length of my cables has to do with this argument.

The losses in a cable are proportional to the square of the current through it. It does not matter if the cable carries AC or DC. If you need to run 20 meters of cable between your loft and the connection to the mains grid the losses will be lower if the cable carries a lower current. If the DC cables carry a lower current than the AC cables it obvious to anyone with any electrical knowledge that the DC cables can be of a smaller diameter for the same electrical power loss.

I'm sure GrahamC will agree that the national grid carries high voltage / low current to minimize losses. If your DC voltages are higher than 240V then it is advantageous to have the longer runs at DC.

I of course am neglecting losses due to the RF radiation from wires carrying AC before someone jumps on that band wagon.

Dave F

Hi Dave

Cable lengths are obviously aimed at me for some reason which eludes me, but the problem is that whatever the losses are on our system make no difference to any other system with different length cable runs.

My calculator gives the same answer as anyone else's so having a cable run which is less than 50% longer provides us with a very marginal gain from using heavier gauge runs .... as mentioned previously, the AC and DC cable losses can be modelled in the SMA SunnyDesign software if anyone reading needs clarification of what the differences would be in their own circumstances (http://www.sma.de/en/products/software/sunny-design.html).

HTH
Z

don0301

zeupater wrote: »

Cable lengths are obviously aimed at me for some reason which eludes me, but the problem is that whatever the losses are on our system make no difference to any other system with different length cable runs.
Z

let me remind you...

zeupater wrote: »

ps - For anyone who hasn't had time to follow all of the threads on inverter location over the past couple of years - my inverter is in the garage, this being for good reasons.

why so shy with your measurements, when you like to tell people how clever you are with what you decided?

you have been arguing for some hours now, that your garage installation is better than in your loft?

some measurements to test that?

don0301

zeupater wrote: »

As one so unworthy to stand in the light cast by the mere presence of greatness, I humbly bow & scrape at the feet of my master in homage ... :think:, alternatively, ignore Troll-like comments and commentary and attempt to help those who ask .....

zeupater wrote: »

Whether you agree or not doesn't really make any difference to me, perhaps, as this isn't really a technical forum, you would consider expending a little time airing your views on one of the fora which are mainly frequented by installers to gauge what the consensus is amongst the 'experts', and provide us all with a little insight from inside the industry ....
Z

pathetic attempts to infer I am a Troll (cos I challenged your "logic") or an "Installer" (Lol) really don't do your argument any justice....

don0301

Dave_Fowler wrote: »

The manufacturer of an inverter should ensure that the internal temperature of the inverter is kept at a point where the semiconductor junction temperatures are kept below 150C.

This probably means derating the inverter at ambient temperatures above 50C where the internal temperature of the inverter is likely to be 70C and the heatsink temperatures 95C

Dave F

do lofts with solar panels absorbing/reflecting light and insulation (anyone not have an insulated loft these days?) regularly go above 50C?

yes, any decent installation will derate the inverter (how many people have an install that doesn't?)

grahamc2003

Don, I'm not sure whether, in your own eyes, your are being funny, amusing, or (god forbid) intelligent or informed, but don't you ever tire of this peurile confrontational absurd idiotic behaviour - always aimed at those who are informed and trying to give valuable information to others in spite of the enormous challenges you place in their way? Give it a rest for a day or two, for your own benefit as well as everybody else's.

don0301

grahamc2003 wrote: »

Don, I'm not sure whether, in your own eyes, your are being funny, amusing, or (god forbid) intelligent or informed, but don't you ever tire of this peurile confrontational absurd idiotic behaviour - always aimed at those who are informed and trying to give valuable information to others in spite of the enormous challenges you place in their way? Give it a rest for a day or two, for your own benefit as well as everybody else's.

you keep calling me names (who's the child?)

is it internet bravery?

informed? rofl like you that I've corrected several times?

If I don't agree with something I will challenge it...problem?

*pat*

Dave_Fowler

don0301 wrote: »

do lofts with solar panels absorbing/reflecting light and insulation (anyone not have an insulated loft these days?) regularly go above 50C?

yes, any decent installation will derate the inverter (how many people have an install that doesn't?)

Last summer here in Bedfordshire was appalling. Apart from one day in July all the other peak outputs were in April - May. The loft did get up to 35C during late summer (I think you'll remember the unseasonally hot weather we had in October). I wouldn't like to say what temperature I might get during a 'real' summer like we had when I was a lad. (Probably not as high as sunny Essex:)).

My inverter (Mastervolt XS3200) is rated to operate at ambient temperatures up to 60C with a derating when the internal temperature is above 75C - the manual does not state what difference between ambient temperature and internal temperature can be expected. I see the Fronius inverters will operate up to an ambient of 50C and start to derate at ambients between 40 and 45C.

edit - just found in the text (not specifications) section of my manual that it will derate at ambients above 45C

Dave F

don0301

Dave_Fowler wrote: »

Last summer here in Bedfordshire was appalling. Apart from one day in July all the other peak outputs were in April - May. The loft did get up to 35C during late summer (I think you'll remember the unseasonally hot weather we had in October). I wouldn't like to say what temperature I might get during a 'real' summer like we had when I was a lad. (Probably not as high as sunny Essex:)).

My inverter (Mastervolt XS3200) is rated to operate at ambient temperatures up to 60C with a derating when the internal temperature is above 75C - the manual does not state what difference between ambient temperature and internal temperature can be expected. I see the Fronius inverters will operate up to an ambient of 50C and start to derate at ambients between 40 and 45C.

Dave F

as a bit of fun, I'm gonna start measuring my loft temperature

wrong end of winter but I have to help zeupater right?

I'll also measure at midday, he really needs help right?

of course zeupater could measure his garage at same time

time will tell.................