Emergency Power option - Automatic Switch

[cojmh]

Hi all,

After advice again please

Now that I have batteries and they are working - I have been thinking about implementing the EPS (Emergency Power) option on my hybrid inverter.

(I am sure you know this but just for the completeness of information) - basically if the grid power goes out the inverter can still supply the house from the batteries - but naturally this has to be isolated from the grid for several reasons not the least of which is for safety.

My intention is to wire one of my consumer units (two lighting circuits, two ring mains, loft and pantry) to this EPS consumer unit. Everything with a heavy load is on a separate consumer unit (showers, cookers, washing machine, dishwasher, kitchen etc.) so there is nothing I really need to think about with respect to ensuring I do not overload the inverter as I know everything is below my 2.5 KW limit.

So I have been looking at automatic switch over switches - so the consumer unit lives on the grid most of the time but if the power goes off then it will switch over to the EPS side of the inverter when that starts up and isolate from the grid.

I have found some automatic switches like this one:

Automatic switch

So my question are:

1. Is it safe to use an automatic switch like the one above? I have also found other ones but primarily for generators which are potentially smarter but not sure if this might cause me issues.
2. I am wary of safety related stuff from Chinese makers - does anyone have something like this already and can recommend a product?
3. Do I need to inform anyone of this install (such as DNO)?

Thoughts welcome.

Thanks

[ClockmanFRA]

Its very important to Use a good make/manufacturer.

And make sure the switch over can cope with the amps and plus, especially applainces that have surge loads.

I fit these Kruass & Naimer, they do automatic switching as well .

[Fintray]

It's a bit worrying that the one you show doesn't seem to have any covers for the live terminals and as clockman says it's best to use a good make/manufacturer.
Bigclive does an assessment of a Chinese one that you may like to watch.

[cojmh]

Its very important to Use a good make/manufacturer.

And make sure the switch over can cope with the amps and plus, especially applainces that have surge loads.

I fit these Kruass & Naimer, they do automatic switching as well .

Thank you,

I will have a look at these, I agree a better make is definitely worth paying extra for but not sure who to go with

[cojmh]

It's a bit worrying that the one you show doesn't seem to have any covers for the live terminals and as clockman says it's best to use a good make/manufacturer.
Bigclive does an assessment of a Chinese one that you may like to watch.

Thank you, I will have a watch - I had seen these too.

The other issue with the one I pictured, was that I don't like how close power input 2 and the load output terminals are ..... especially as nothing is covered!

[openspaceman]

My intention is to wire one of my consumer units (two lighting circuits, two ring mains, loft and pantry) to this EPS consumer unit. Everything with a heavy load is on a separate consumer unit (showers, cookers, washing machine, dishwasher, kitchen etc.) so there is nothing I really need to think about with respect to ensuring I do not overload the inverter as I know everything is below my 2.5 KW limit.

So I have been looking at automatic switch over switches - so the consumer unit lives on the grid most of the time but if the power goes off then it will switch over to the EPS side of the inverter when that starts up and isolate from the grid.

How long do you expect the battery to supply you with power for these smaller loads? How frequently do you find the grid goes down? Here in the last 40 years I don't think we have lost power for more than 8 hours.

Why would your solution be any better than isolating the bigger loads and having a sine wave generator as the alternative supply with the changeover switch? This would island the house and keep the solar PV and battery online wouldn't it?

3. Do I need to inform anyone of this install (such as DNO)?

That's an interesting one, no replies yet?

[cojmh]

How long do you expect the battery to supply you with power for these smaller loads? How frequently do you find the grid goes down? Here in the last 40 years I don't think we have lost power for more than 8 hours.

Honestly, I don't know exactly how long the batteries would last - but at the moment the PV and batteries seem to be coping with the house load (apart from the showers and the electric oven) without needing the grid power - so I would hope that it can cope. I would expect any issues to be in the winter though with the weather so that is a totally different ball game. So I don't know is my honest answer.

In the last few years we have not experienced power cuts for longer than a couple of hours. But my grandmother's house had fluctuating supply for a couple of days earlier this year from the storms. So it is possible.

Further more, we are not living in such stable times anymore aside from weather there are other ways we can loose power.

Just trying to cover all the bases given the hardware can do it .... just need to do the smart bit to make sure it is done safely now the batteries are in place to "buffer" the supply.

Why would your solution be any better than isolating the bigger loads and having a sine wave generator as the alternative supply with the changeover switch? This would island the house and keep the solar PV and battery online wouldn't it?

In either scenario I would need to isolate the heavier loads and as I am having the rewiring done anyway I am just trying to find the approach that gives me the most options in the future.

Adding the sinewave generator would not add any extra abilities (as far as I am aware) because my understanding is that the PV and batteries would still stay functioning but would just be limited to 2.5KW as this is the maximum the inverter can supply from the batteries if there is no more solar power to be had. However if it is during the day then I guess I could still generate more than the 2.5KW if some of it was going into the batteries.

Not sure I have explained that very well .... hopefully it makes sense?

Thanks for your thoughts ....

I know people with generators have done this for a long time ... but I just cannot find out if they were legally obliged to inform someone - as this scenario is pretty much exactly the same with the generator substituted for the PV/batteries.

[marshman]

__

[cojmh]

Do you need it to be automatic?

Thank you for your really detailed response - it is very helpful. In terms of do I need it to be automatic .... the short answer is no I don't need it to be automatic.

However I try to plan for me not being there and explaining how to do things (even as simple as switching a switch) to someone who doesn't really want to know about it means for me it would be easier. Certainly less exasperating than the phone call trying to explain it.

As far as I can tell, some of the automatic switch over devices are not too expensive - so I figured if it can do both (manual and automatic) then it covers all bases.

If your inverter has the "back up" option and you are going to run a separate consumer unit anyway doesn't the inverter automatically switch over - effectively performing a UPS function? I know this is what my Solis Hybrid inverter does if the function is enabled. If so the change over switch is redundant anyway. I decided against the hassle of splitting the consumer unit and switch over manually and just monitor the loads - my inverter can provide 5kW so we can get away with heavier loads.

From reading the manuals it would seem that the EPS only works when the grid goes off (and all of the wiring diagrams show some for of switch over). I guess this is so that both systems are completely isolated from each other and there is no chance of a failure leading to a cross over from grid to EPS or vice versa. As I need to the consumer unit to be powered by the grid most of the time it would seem that the switch over is what is needed.

There is no need to inform the DNO, they are not interested as long as it properly isolates your property from the grid whilst you are using a "back up" supply. I do however think that the work to fit one is covered by Part P of the building regs, therefore is notifiable and should be signed off by a registered electrician.

One other word of caution - you need to pay attention to your earthing. If you are on PME (TN-C-S or TN-S) you rely on the incoming grid connection for your earth, if there is a power cut there is a fault somewhere, possibly on the neutral and you may lose your earth. That's OK if there is no power but when you then switch to your back up system - where is your earth connected to??? There is no one simple answer as every property is potentially different.

Thank you for this - I have to admit that is beyond my knowledge so I will speak to an electrician - especially about the earthing as it has to be done correctly and I want it to be belts and braces so to speak.

Thank you for your help.

Jon

[marshman]

__