The right inverter for battery storage and some other Qs

[Oldgreybeard]

Inverters that have an emergency power supply (EPS) option either do the changeover internally, or they need an external changeover contactor. Our Sofar is one that needs a changeover contactor. I have this contactor installed in the same small consumer unit that feeds our "essential circuits", which are the circuits I want to stay on if there is a power cut. In my case that small extra consumer unit has RCBOs to supply the lighting circuits, the water pump and sewage treatment plant plus a radial socket circuit that runs some other things we'd like to keep powered on.

The changeover is automatic. If the grid fails the inverter switches over to EPS mode, and in our case when it does that it energises the changeover contactor that then switches the power fed to our essential circuits from the grid to the inverter output. If the grid comes back on then the inverter just switches the contactor off and everything reverts to running from grid power.

Some inverters have this changeover contactor built-in, which makes things a bit simple, although the contactors aren't expensive (the Schneider one I bought was about £20 I think).

[Oldgreybeard]

I don't know about all. The RCD on my inverter cct is an old Crabtree 3-wide one repurposed, I have not found a lock to fit it, certainly the 2-pin one I bought for the purpose doesn't. A comprehensive kit like this https://www.cef.co.uk/catalogue/product ... ockout-kit would have cost more than the isolator. My interpretation of the standard is that it should be lockable with a padlock without any particular accessory kit.

I bet you anything you like that one of my cheapo lock-offs will fit it, not yet come across one they won't fit. The daft lock-offs with pins are far from universal, as are some of the crappy plastic ones, or any of the ones that try and crab the link pin holes, but these little alloy ones are as close to being completely universal as I've ever seen (three for under a fiver: https://www.ebay.co.uk/itm/363018223641):

Lock-off.jpg (59.39 KiB) Viewed 1732 times

There's nothing in the regs about the type of lock off, just says must be capable of being locked off. If there were more specific requirements then they would have to start specifying makes of acceptable padlock, as there are lots of locks off's that require padlocks with either a very long shank (to clear the housing) or a very slim shank (for those with stupidly small locking holes).

[ducabi]

What do I do if I need to bypass inverter when it stops working and I still want my fridge running?

I presume this is when it is on the UPS side of the inverter - cant you just plug it into the normal grid side sockets?

I mean what if inverter is broken. My understanding of previous posts is that electricity goes through inverter, so if inverter breaks then I won't have power from the grid.

You need to check how your planned inverter will be installed, RTM. A few other things...

I'm not getting much from the manual I'm afraid. I hope my electrician will do it properly but I want to have some brief understanding (e.g. he may not think SPD is required).

Your electrician will have his preferred sources for all this stuff. The RCD is Type AC, not sure this is current recommendation, OGB will know. The SPD needs to be fitted within ?0.5m of the intake so it may be better sited elsewhere

Good point. I think it has to be A. I want to make a list before i speak with electrician. Then happy to go with what he wants as long as we are on the same page.

[sharpener]

What do I do if I need to bypass inverter when it stops working and I still want my fridge running?

I presume this is when it is on the UPS side of the inverter - cant you just plug it into the normal grid side sockets?

I mean what if inverter is broken. My understanding of previous posts is that electricity goes through inverter, so if inverter breaks then I won't have power from the grid.

You need to check how your planned inverter will be installed, RTM. A few other things...

I'm not getting much from the manual I'm afraid.

Earlier posts talk of several different inverters. If you can say what you have bought or are now thinking of then someone will probably be familiar with it and better able to help.

[ducabi]

Earlier posts talk of several different inverters. If you can say what you have bought or are now thinking of then someone will probably be familiar with it and better able to help.

Sorry, it's Sofar HYD3600-es and arrived this morning.

[sharpener]

Earlier posts talk of several different inverters. If you can say what you have bought or are now thinking of then someone will probably be familiar with it and better able to help.

Sorry, it's Sofar HYD3600-es and arrived this morning.

From the manual here https://midsummer.ie/pdfs/sofar-hyd-user-manual.pdf it's pretty clear the normal loads are OK in case of inverter failure (unless it blows the company fuse), the critical loads connected to the UPS output not, you need a changeover switch as explained in section 4.6.

Fig 5 is for the Australian market and does not show the protective devices required in the UK but we have discussed those extensively in recent days.

[ducabi]

From the manual here https://midsummer.ie/pdfs/sofar-hyd-user-manual.pdf it's pretty clear the normal loads are OK in case of inverter failure (unless it blows the company fuse), the critical loads connected to the UPS output not, you need a changeover switch as explained in section 4.6.

Thanks! I worried that i would need bypass when inverter breaks. Is it clear to you because you can read the wiring diagram or because it's stated explicitly somewhere?

[sharpener]

From the manual here https://midsummer.ie/pdfs/sofar-hyd-user-manual.pdf it's pretty clear the normal loads are OK in case of inverter failure (unless it blows the company fuse), the critical loads connected to the UPS output not, you need a changeover switch as explained in section 4.6.

Thanks! I worried that i would need bypass when inverter breaks. Is it clear to you because you can read the wiring diagram or because it's stated explicitly somewhere?

It was clear once I had got as far as Fig 1 on p1.

The changeover switch in 4.6 is the same as your "bypass switch".

[marshman]

Page 18 of manual:

 If the HYD-ES inverter is faulty, manually change the switch to position 2. Grid will supply power to critical
load

and fig 18. (top of page 19)

Yes you need a changeover (bypass) switch to enable the critical loads if the inverter fails.

[ducabi]

Page 18 of manual:

 If the HYD-ES inverter is faulty, manually change the switch to position 2. Grid will supply power to critical
load

and fig 18. (top of page 19)

Yes you need a changeover (bypass) switch to enable the critical loads if the inverter fails.

I didn't pay much attention to that section as I thought it wasn't relevant given I'm not running it in UPS mode.
So, if it stops working and I want full power from the grid then only option is to fully disconnect it?