Solar for Beginners [ask your questions here]

Just to clarify that for you Old Jim (incase you misinterpret it) .... no problem having different panels on different strings, but all panels on the same string have to be the same, or you'll drop to the lowest panel.

e.g. if you have 8x450w on one string and 6x390 on another string, that's totally fine, but you can't mix and match different panels on the same string. So 4x450 + 2x390 on the same string would result in the 450watt panels behaving like 390's.

If a future expansion is unlikely, set up now to leave it alone. So split the panels over 2 strings.

But get the installer to put less on the string that could take a future expansion. So you have space.

I have that setup of panels on 2 angles on the same string. Same orientation but different angle.

Works fine with optimisers on one group at a different angle. My optimisers are on a flat roof so easy to replace if ever they die (which I'm not worried about). Optimisers are needed for me as they get different light levels so flat roof would drag the main roof down at times without optimisers. You don't need optimisers until you expand and only on the new panels on a different angle on the same string.

I'd suggest get as many panels as you afford can now. Cost will be less than getting them out again for a small expansion in the future.

I checked the Voc of the panels (44.67V) and tried to take into account the temp coefficient based on my nearest weather station data to come up max 12 panels per string (600V/47.5 = 12.6 panels)

If I should have used the Max MPPT voltage, then the max number of panels per string is 10. (520V/47.5 = 10.9)

The angles are different alright - 15deg and 45deg approx. So is the best action to put 10 panels on one string, 5 on the other, then add the future panels to the string of 5. Match panel wattage for future panels and use optimizers when adding additional? Do I need to match panel wattage if using optimizers?

In the future, I don't think you'll need to use optimizers when adding new panels on the same string with the same orientation. If you have currently installed 400W panels and you come along later and add 420w panels, the new 420w panels will behave as 400w panels. And you shouldn't need optimizers on those ones.

I would however try to maximise the panels now. I know.....it's hard to do that cost up front, but really if there is one regret that people have with solar is that they didn't max their panels at initial install time.

True - as long as your aware that those 450w (or whatever) you buy next year will behave as 390w because that's what you are going for today. There'll be no advantage in buying those 450w next year over getting more 390w's .... assuming of course that the 390w are still available and cheaper than the 450w.

I did my own DIY installation (with micro-inverters). It's not hard, but I would advise a bit of caution. For me with micro-inverters I was dealing with single panel voltages of ~40vdc. Working on a string of 10-12 panels though, you could be dealing with 450-500vdc. Not crazy dangerous, but you'd want to make sure that your careful and properly cable up things. Only mentioning so you're aware.

Apologies, somewhat off topic here but is the zero VAT on panels being removed at some stage this year?

hi folks, i have an electrician wiring up a socket to my givenergy inverter eps at the weekend. The instructions from givenergy are to add a 10 amp breaker between the inverter and the socket to avoid overload and to make sure the socket is earthed. The instructions are sort of uk specific but mentioned adding a new earth rod etc.. we have that already for the house.. is it ok for the electrician to 'tap' into the earth running back to my main consumer board which then goes to the earth rod? He says should be fine.

cheers,

mick

Can someone confirm for me that if I have two strings coming off the panels I need four 4sq dc cables to the inverter and I’ll need a 3 or 4 core 1.5mm flex and a 6sq Earth cable to the inverter. Is a fireman’s switch required at the panels in the attic space ??

and two DC isolators one for each string and an AC isolator between the inverter and the CU

consumer unit and inverter will be side by side but the DC cables to the panels will be 18m away.

EPs socket wired today..happy out. Inverter running in ups mode so I'm running the virgin media modem and my router through the socket. Kinda finishes the setup for me now I think. I'll be looking forward to power cuts to try it out 😁 after 5 in the last winter we probably won't have any again for years! Was a long run of cables to where I wanted the socket but the electrician did a tidy job with conduit..10 amp breaker fitted between the socket and inverter.

Thanks as Jonathan says just curious if the internet will work with a powercut in the area. No guarantees. Still be useful to able to run a few lights and the TV and boil a low powered kettle if want to make a cup of tea, charge a mobile phone etc

For work stuff you can hotspot of a mobile to get internet on that. So if / when the house internet drops in a power cut, then switch to the mobile hotspot.

That's pretty brutal. I presume you're not in the Dublin area? In my experience in Dublin, a power cut of more than an hour is rare. Less than once a year.

Do you have to have a fireman’s switch installed for solar