Solar for Beginners [ask your questions here]

ELM327 · 10-10-2022 12:29pm

https://www.boards.ie/discussion/comment/119725335#Comment_119725335

I went through a similar consideration and (over)paid for a professional to do it. TBH most of it is easily done yourself (idiotic mistakes excepted like my overvoltage) but the one bit I would not attempt myself is the roof mounting. Leave it to the professionals IMO.

Maybe subcontract a roofer?

unkel · 10-10-2022 12:33pm

The roof mounting is actually very straight forward on a standard pantile roof. It was the one thing I was not looking forward too as I'm not the handiest when it comes to these sort of things. Lots of YT watching later, I did it myself.

I did pay a roofer to install panels on my high roof though, I'd really rather not go up there myself unless it was an emergency

bullit_dodger · 10-10-2022 12:38pm

https://www.boards.ie/discussion/comment/119725273#Comment_119725273

Real life example of how they might "shade each other".

https://www.dropbox.com/s/kerqir7f6ywffi7/2022-10-10%2012.33.32.jpg?dl=0

Note the panels on the right (the more south ones) are casting a shadow which currently is under the ones of the left. In another month or so, that shadow with the lower sun could well be hitting the actual cells on the left panels. This is why I had to have the panels on the right with a lower angle (10deg verses 30 degrees)

AckwelFoley · 10-10-2022 12:44pm

https://www.boards.ie/discussion/comment/119725424#Comment_119725424

I see.

Would it not have be a consideration to mount them on the one frame to mimick a pitch roof. No possible shading off each other and only 4 points of contact with the road to worry about

Something like this

Granted, you look like you might not have to room for landscape and portrait might have you too high?

WestWicklow1 · 10-10-2022 12:54pm

https://www.boards.ie/discussion/comment/119725253#Comment_119725253

He's learning, just as you are.

bullit_dodger · 10-10-2022 12:55pm

https://www.boards.ie/discussion/comment/119725462#Comment_119725462

The honest answer is.....I simply didn't think of it until you mentioned it now. If I had....I would have given it some serious thought. I wanted a pretty high angle though for the panels. Originally i put the ones on the left at 40deg (from the horizontal)....but reduced this to 30 degree after I saw it in place. I was worried about wind loading on the panels. Really I should put some vertical slats to break up the lifting effect of the wind underneath the ones on the left.

Had I done this all as one frame I may have gotten an extra 2 panels up there. Pity.

On the bright side, you may have given me next summers project to expand the shed by 2x panels. LOL

Paul Kiernan · 10-10-2022 12:58pm

https://www.boards.ie/discussion/comment/119725403#Comment_119725403

I have a choice between a single storey flat roof or a low single storey pitched roof (SE 45deg). I'd prefer to use the pitched but it's got 100 year old stone slates that fall apart if you touch them. Now maybe if I could slide a hook under the slate and fix it from the inside that might just work but I don't think any standard fittings are designed for this. The weight of the panels would also be pressing down on the slates but it would be directly over the rafter. The worry with the flat roof is I'd be relying totally on ballast to hold everything in place as I daren't penetrate the membrane.

Paul Kiernan · 10-10-2022 1:26pm

https://www.boards.ie/discussion/comment/119725462#Comment_119725462

That's a nice setup. Are those concrete pads sold as part of the mounting kit? Something like that would be ideal for me!

AckwelFoley · 10-10-2022 1:36pm

https://www.boards.ie/discussion/comment/119725524#Comment_119725524

Yea, I definitely think there is room for another kw/h up there. I'd probably make up a demountable frame, but also something that would allow for a change of panel if something with a higher output takes your fancy down the line or you're replacing panels. Fairly doable for sure

Richard tea · 10-10-2022 1:44pm

I switched from bord gas to electric Ireland 2 months ago. Im trying to work out my annual consumption of electricity but I cannot log into my old account to find out. Any work around? My first bill with electric Ireland was an estimate and was Aug - Sept

AckwelFoley · 10-10-2022 1:44pm

https://www.boards.ie/discussion/comment/119725655#Comment_119725655

That was just a screen shot off the net that I took to show what was in my head when explaining the layout

Those concrete base mounts would be easily made up BUT I personally wouldn't like to use them in most circumstances. The load bearing capacity of a flat roof would never be calculated with consideration of putting that type of weight up on them. If I knew they were going up there, sure the roof could be built with that in mind, but not after the fact

The weight of the panels wouldn't be a consideration, they're very light

ELM327 · 10-10-2022 1:55pm

https://www.boards.ie/discussion/comment/119725522#Comment_119725522

Absolutely. But there's a difference between putting a few panels on a pump house roof that's about 6 foot off the ground, and installing lots of panels on an actual roof. We're all learning here. I meant no offense by my question or my initial post - where I clearly mentioned mistakes I've made too!

graememk · 10-10-2022 2:04pm

https://www.boards.ie/discussion/comment/119725335#Comment_119725335

The amount of panels you can put on an inverter is usually governed by what voltage it can handle..

For solis its 600v open circuit. per string

Although you do have to take in account that voltage will rise the colder the panel gets and there is also a margin of error on each panel too.

Got this equation a while back :

Worst scenario at -20 degrees is 40.8 (Panel Open circuit voltage) x 12 panel x 1.1215 temp coeff x 1.03 tolerance = 565.55V

So its usually about 12 panels per string, looking at the new longi (405w ones) the panel voltage is only 37v. where you could get 13... maybe 14.. but at that stage the string is about 50% over sized. (5.6kwp on a 3.6kw string!)

DC999 · 10-10-2022 2:23pm

https://www.boards.ie/discussion/comment/119725717#Comment_119725717

Hey, phone or email your last supplier. They can tell you the yearly usage. And they can go back further if you were with them for longer than that. They should provide it.

Failing that, see do you have the reading from when you moved. Might be in an email, or letter from them. Or from Bonkers if used a service like that. The you can see the average per month. Bear in mind it was summer so factor in any changes for immersion, heating…. And if you were on hols during that time.

Or check if the old bill emails from them had any meter readings. Even ones from years ago will tell you the average (assuming nothing major changes like an EV, moving to electric cooking, heating…). Will give you some sense.

It’s deffo worth recording that somewhere once a month so then you can start to see how much you use. What we measure we can (maybe) improve 😊

Paul Kiernan · 10-10-2022 2:53pm

https://www.boards.ie/discussion/comment/119725888#Comment_119725888

"but at that stage the string is about 50% over sized. (5.6kwp on a 3.6kw string!)"

Does that mean my panels are producing more power than I can get through the inverter so it's going to waste? But this is rare? So if the panels are producing anything from about 65% up (of their peak potential) I'll get a full 6kw?

I was thinking of 8 or 10 per string (Longi 405w). Is it worth paying the extra grand for 10 instead of 8?

Manion · 10-10-2022 4:26pm

https://www.boards.ie/discussion/comment/119724620#Comment_119724620

Deductable expenses for income taxes are listed on the revenue website. It's a case of something having to be listed. Your average person isn't going to be able to claim solar installation as a business expense. That said, I suppose if I got it installed on the rental property I could claim back at 12.5% yearly. Have you managed this for your own principal private residence?

graememk · 10-10-2022 5:00pm

https://www.boards.ie/discussion/comment/119726226#Comment_119726226

In short yes, but wasted isnt the right term.. but i was chatting about a 14 panel system. The power just isnt produced when the inverter reaches its limit.

1k for 2 more panels. thats a bit steep, seeing as they are up on the roof already, putting up rails and such.

An oversized string is more for the "less than perfect days" and on the good days the inverter will "clip"

Heres an example of mine, I have 8.6 on a 6kw inverter. My panels are NE/SW on a low slope too (12 degrees)

Something else to note, Panels generate more when they are cold. So intermittent cloud can cause it to be very spikey(as you can see around 11 am)

you can see the "flat top" of the curve only at this point the panels are over producing what the inverter can handle

Only the tip of the peak is cut off and all other times what the panels produce is under the inverters capacity,

AckwelFoley · 10-10-2022 5:31pm

That's a good point @graememk makes. And it's the reason I've looked at more panels already. The real great days you will be limited, but I think the reality is, you want to try increase return.

My panels are 6.5kw.. this tome of year, if they're producing 3kw an hour I'm pretty happy, even 1.5 kw an hour is not bad in a poor ish day. But more panels means that figure 1.5 or 3.5 will be greater per hour. And these poor days coming into winter are often when you often need it most

The more days I can get 12 to 16kw are the days I don't need Grid electricity

During the summer when your inverter will clip your amount over 6kw you'll have a longer peak at the max output theoretically

con747 · 10-10-2022 5:57pm

https://www.boards.ie/discussion/comment/119725655#Comment_119725655

You could look into these https://www.renusol.com/en/solar-panel-mounting/flat-roof/cs/

Punchin A Keyboard · 10-10-2022 8:15pm

Panels generate more when they are cold.

As Andy's smoking solar multimeter will testify in one of his recent vids.

cobham · 12-10-2022 11:09am

What does SOC stand for in the App stats?

unkel · 12-10-2022 11:35am

State of charge. Basically the percentage of capacity the battery still has at any point. To be taken with a grain of salt as most home built and commercial batteries use the LiFePO4 chemistry which is very flat, batteries are typically about 3.2-3.3V per cell, whether mostly empty or mostly full

Paul Kiernan · 13-10-2022 11:54am

Quick question someone might be able to answer -

Does the solar inverter have to be wired to the meter or to the distribution box or does it matter? Thanks, Paul

micks_address · 13-10-2022 11:56am

Wired to distribution board is my understanding

HugosDad · 13-10-2022 12:46pm

New install here: 14 panels, 5kw Solis inverter and 10kw Puredrive batts.

I have the solis connected via modbus to smarthome controller and the stats prompted me to check the settings for a couple of reasons.

I'm still seeing (small) amounts of electricity imported when the battery has loads of charge left.

The battery takes just longer than my off-peak window to charge.

The charge and discharge limitation are both at 100A, but I was wondering what the 'Backup Supply' was and why it might be disabled?

con747 · 13-10-2022 2:16pm

https://www.boards.ie/discussion/comment/119738752#Comment_119738752

The back up supply is to use the battery power available during a power cut, did your installer fit a double socket beside the inverter? If so that should be live to use when the power goes. It is turned on at the moment on that screen, if you change that to enable you will be turning it off. The small amounts you see are probably normal but just keep an eye on the levels.