Thoughts on shed solar system

[DavidCB]

Hello,

Looking for advice on my system, I’m looking at a 48v GTIL (grid tied inverter that is limited zero export). I have 280ah mason battery with heat pads plus extra PIR insulation in the sheaf and can put around the battery in Colder months (UK) this is on a shed in my garden on an NW / SSE roof. Looking online one mppt sharing both East and West roof panels may lose 2% efficiency to this but is more cost-efficient than an MPPT on each.

The Sun GTIL inverter will be onto the mains though a dedicated steal armorer cables and consumer boxes in the house and shed (still need to put in with an electrician).

I have most of these components already although need further cabling and switch.
I would appreciate any thoughts you may have esp if I’ve missed anything important.

Thanks

David

 

[DIYrich]

Any reason not to buy an off-grid inverter? You can put the grid into the generator input. It will not feed back power to the generator port.

never mind. I see you are putting the CT all the way back at the meter.

 

[SeaGal]

Welcome!

I'm not familiar with that Victron unit but are you sure:-

a) you only lose 2% with having one MPPT on panels that are pointing NW and SE at 36.5 degrees - doesn't sound right to me? If that was the case, why would any inverter have more than one MPPT circuit.

b) with only 2 panels you have about 76V (as you mentiong), but the diagram shows "Max PV open circuit current 150v (145v startup and operating max)". Again, that doesn't sound right - assume by current you meant voltage? And if it has 145V startup, you're not going to achieve that with just 2 panels in series. And both startup and operating max voltages being the same as each other doesn't makes sense to me.

 

[DavidCB]

The SUN GTIL allows me to use solar / battery to towards reducing the house loads and the clamp will prevent export, it won’t cover all / bigger loads but should reduce my grid use by supplementing anything I’m using.

However if there’s an issue with that an off grid inverter may be the way to go. Esp when more money allows.

 

[DavidCB]

Welcome!

I'm not familiar with that Victron unit but are you sure:-

a) you only lose 2% with having one MPPT on panels that are pointing NW and SE at 36.5 degrees - doesn't sound right to me? If that was the case, why would any inverter have more than one MPPT circuit.

b) with only 2 panels you have about 76V (as you mentiong), but the diagram shows "Max PV open circuit current 150v (145v startup and operating max)". Again, that doesn't sound right - assume by current you meant voltage? And if it has 145V startup, you're not going to achieve that with just 2 panels in series. And both startup and operating max voltages being the same as each other doesn't makes sense to me.

Hello,

Those specs are on the panel specs :
www.solartradesales.co.uk/phono-solar-twin-plus-black-mono-perc-ps405m4-22/wh-166mm-x-83mm?gclid=Cj0KCQjwl8anBhCFARIsAKbbpyTyHc9QCMHLEI13dkG7EfwYG0pn9BtjVLCsTzAqD1UPG230Ai0slPcaAqSFEALw_wcB

I've 8 panels - 4 on each side ( 4 pairs on series and then all in parallel). I used an online calculator to get those figures for output. 405w x8 panels = 3,240w

The 2% reduction on a east west mounts I was reading from on the forum somewhere that had been testing that again the same setup but split to two mppts. I’m sure there is more losses with tilt and so on but that’s purely on the est west split. Will see when it’s up.

 

[SeaGal]

Ah.. just spotted the grid-tied bit. Is that inverter G98 approved? I couldn't see it on the ENA database

ENA Type Test Register

ENA Type Test Register

www.ena-eng.org

If not, you mustn't connect it to the grid in the UK.

 

[DavidCB]

Solar panel spec sheet

 

[DavidCB]

Ah.. just spotted the grid-tied bit. Is that inverter G98 approved? I couldn't see it on the ENA database

ENA Type Test Register

ENA Type Test Register

www.ena-eng.org

If not, you mustn't connect it to the grid in the UK.

If the inverter turns off when no grid and can't island itself / house etc; If the grids down the. The house is still off - does it need it? If the house can use the power the inverter doesn’t send power.

 

[SeaGal]

Yes it is required.

It is illegal to connect grid-tied equipment to the UK electricity network without using a G98 (for < 3.6kW) or G99 (for > 3.6kW) approved device.

With G98 you must inform your DNO within 28 days of commissioning, for more than 3.6kW, you need approval from your DNO before installation.

These requirements are to protect both the safety of engineers working on the line and to ensure the quality of supply to your neighbours.

 

[SeaGal]

So, my 2p worth would be to not use the Victron and GTIL inverter, but instead use something like a hybrid Solis / Growatt / SunSync grid-tied inverter. That will then give you 2 MPPT circuits for putting in 2 strings of 4 panels each.