Generator transfer switch

[Dabop]

Australia is one of the more advanced countries re solar in many ways...
I got my gridtie licence back in 2004, and I have been doing offgrid installs since the early 1980's...
The UK is probably 10-15 years behind us in many ways, the Eu has some equal to us- to 50 years behind, and the US is struggling to get into the 1700's re solar...
:-(
Many people think that solar has only been a 'big thing' in the last decade- here we had widespread gridtie solar back in the 1990's- for the Sydney 2000 Olympic games, the 'Olympic Village' (Newington) built to house the athletes, every single house in the entire suburb was fitted with gridtie solar- and at that time it was already widespread...
That's 22 years ago...
:-O
My mums house had already had solar gridtie for nearly half a decade by that time- and it was the last in her street to get it...

 

[Spectric]

Plug in the double plug lead

You should never have exposed male pins on any interconnects, all connectors must comply as a minimum to IPxxb in order to comply with IEC 60529 and having a fully exposed live metal pin will not, it is a real no no. In most situations equipment has to comply with IP2x which introduces more than just your finger so with this live plug where you could grab it with your hand in good contact then this is a real potential killer. People really need to understand that a lot of people who thought what they were doing was safe and acceptable may never know that it was not because they are no more, poor old heart got a shock.

 

[HamsterJam]

Re solar not working when the grid is down- there are inverters that can run while the power is off- these are called 'hybrids' and they do cost more than simple gridtie inverters...

Depending on how much you want to spend, the cheapest hybrids (cost about twice as much as a standard gridtie one) simply run at reduced power from solar only- no batteries- so these will usually deliver about 1/5th of the panels rated output, and only during solar generating hours ie they can be handy when there is extended periods of outages such as cyclone damaged grids here in Australia, which could take a week or more to be repaired- a 'solar only' hybrid allows you to recharge 'camping lights' phones, tablets and laptops, or even a small battery to run a camping 12v inverter offand keep your fridge running during the day (turn it up to full, and fill the fridge and freezers unused areas with plastic bottles 3/4 filled with water- these will keep it cool at night even with no power) - these often only have a single socket on the front panel to plug stuff into...
(Outback makes inverters that can do this- a well known company that makes both gridties, hybrids and offgrid inverters, another is well known one is Growatt (note that not ALL their range does this, just selected ones, in both cases)

Next you have hybrids with a attached battery pack- often 24v or 48v- these require a sparky to isolate the circuits you want power to, these are then put on a separate sub-board- depending on the inverter, it may incorporate automatic switching, or have a manual 'changeover' switch needed (mine is such an inverter, although I use it purely as offgrid only) obviously more expensive than a straight gridtie only one (in my case about four times the price but as I am offgrid entirely, a straight gridtie would be pretty useless lol)

Mines a 230v, pure sinewave, 12kw continuous, 36kw for 20 seconds peak, dual MPPT solar inputs rated at 3kw each, circuits connected to the output have auto switching, and can be used as 'changeover' or in UPS mode, where they run continuously off the inverter, and it runs off the mains (good for places with 'dirty power') by Sigineer

View attachment 145036

Another option that is popular here in Australia is the 'powerwall' type system- may here have it to reduce electricity costs by storing power generated during the day from their solar in the powerwall first, then exporting any excess like a normal gridtie, during the night the powerwall supplies your household needs, only if the battery is close to depleted or the power required is more than its internal inverter can supply, will it go back to the mains grid- sorta like being 'offgrid' but using the grid as the 'emergency backup' instead of a petrol powered genny...- these run in the hundreds of volts range, Tesla is the one that 'everyone talks about', but there are many others Panasonic, BYD BBox etc that have been around just as long if not longer, and are far better value for money than the Tesla offerings...

https://www.savingwithsolar.com.au/byd-b-box-australia-review-price/(not affiliated in any way with any of them, I'm just a mostly retired sparky who has been doing solar for the last forty years lol)

Thanks for the info -
On-grid hybrid inverters need to automatically isolate themselves from the grid if the power fails (called islanding).
I don’t think these systems are common in the UK probably due to the higher cost and our (relatively) reliable power network although that may change of course.

 

[Lard]

Where is that woodieallen post quoted by Dabop? I can’t find it.

That‘s exactly what came into my mind.

Why cant we have something like a ‘throw switch’ that provides either/or connections to mains or whatever else?

In this way it wouldn’t allow any issues to anything outside of the dwelling.

 

[Spectric]

Why cant we have something like a ‘throw switch’ that provides either/or connections to mains or whatever else?

You can, they can be a manual changeover switch or where on loss of power a generator self starts then contactors are used, either way the system must be failsafe so you have either generator OR grid and pay careful attention to the earthing. With a PME system the earth is provided via the incoming neutral and therefore if disconnected by a changeover switch then you have a floating earth.

 

[Lard]

You lot have had me thinking about this all morning

We have solar and I’ve never considered the old power cut scenario and whether it could work without mains.

On the assumption that our ‘standard’ inverter does require mains, just how much current would it actually need? What I’m getting at is couldn’t I use a small genny (cos I have one) to power just the inverter which would then allow us to ‘run’ the house on whatever the sun provides?

Here’s hoping

Ps….I get the having to remember to switch the solar isolators on and off to stop mr lineman getting a belt.

 

[Sideways]

You lot have had me thinking about this all morning

We have solar and I’ve never considered the old power cut scenario and whether it could work without mains.

On the assumption that our ‘standard’ inverter does require mains, just how much current would it actually need? What I’m getting at is couldn’t I use a small genny (cos I have one) to power just the inverter which would then allow us to ‘run’ the house on whatever the sun provides?

Here’s hoping

Ps….I get the having to remember to switch the solar isolators on and off to stop mr lineman getting a belt.

It possibly would but the solar inverter may be quite strict about the voltage and frequency it needs to see to interpret as mains is on. Genny won't be too good at that. I bet the voltage and frequency are not very well controlled in a lot of them.

Second issue is that the solar is designed to push all its spare energy back into the grid, if your genny is now the grid then the PV will back feed into the genny - that isn't going to last long !

To answer the specific question, the inverter will draw very little power from the grid to do it's thing. They take just a few Watts to keep them alive overnight.

 

[Lard]

Well, well, you learn something new every day

….and damn it

 

[Dabop]

Thanks for the info -
On-grid hybrid inverters need to automatically isolate themselves from the grid if the power fails (called islanding).
I don’t think these systems are common in the UK probably due to the higher cost and our (relatively) reliable power network although that may change of course.

All gridtie inverters are legally required to have islanding- not having it is a 'bad' idea- killing a linesman type bad...
:-(
The 'solar only' hybrid ones are fairly common in cyclonic areas- simply because they give you a small amount of power if the grid is down for extended periods (a cyclone can knock down powerlines over extended areas, so you can be without power for a week or more until lines and poles are replaced etc...)

The 'powerwall' ones have become quite popular over the last few years, due to increasing power prices here- with these you are - to all intents and purposes- in most cases running pretty much offgrid, but with the grid still available as a 'backup'

Most inverters will not run off a genny, because they backfeed into it (some really advanced ones can, but these are the most expensive obviously)- most will simply not lock to a genny (as the basic ones are too unstable and the anti-islanding circuits won't lock- an 'inverter generator' has the required stability- BUT- their inverter isn't designed to handle external sources being fed to it- and usually the 'magic smoke' escapes....
Your normal'gridtie only' inverters can't be 'tricked' into working as a hybrid or standalone system- they are built down to a price and simply lack the required circuitry- and as these are the most common ones installed (because they are cheap) there really isn't a way around it- to get hybrid capabilities (including stand alone abilities)- you need to spend the extra $$$ to get an appropriate inverter...
Several posts were removed for some reason earlier (including one of mine) by MikeK

 

[quintain]

I have a very old generator, hardly used. I bought it for the supposed 'end of the world year of midnight 1999 into 2000'.
I occasionally run it ( ??every 2yrs about 30mins) and try to keep petrol out of it and sometimes change the oil for a new lot. Petrol for the lawn mower is always available.
I have set it up with a couple of extension leads that can go into our kitchen and our general living area.
I am hopeful if we need it in any prolonged elec outage the ext leads will supply some power to a heater, freezer, some table lamps and our router which may or not work. An old camping stove may get us some hot food.
I hope I never have to fully rely on my setup and I will (one day) test it out.

 

[Spectric]

One of the issues with most solar panel installations is that not only do you want to power the house but also make money by selling the excess which requires a more complex system where you need to convert your Dc power from 0 to +Ve from the panels into a higher voltage Dc that has a positive and negative rail that can then be switched to deliver an Ac waveform. This voltage will not be 230 because that is the RMS value, it will be 0 to around 330 volts alternating and it has to be phase syncronised before connecting it to the grid.

We are still in the early days of properly ultilising our energy supplies in a more efficient manor, we are really all over the place because with solar we go from Dc to get Ac then in many cases we use equipment with plug in power supplies and chargers to deliver low voltage Dc to the load, even LED light bulbs have a power supply built in. It would be more efficient to have electrical distribution systems in our houses where all the lights were on an extra low voltage Dc circuit that could easily be powered by a solar panel and battery system where only at a given level would the grid be used to charge the battery, all the LED lights would be Dc and not require the built in psu.

Then you could have other Dc circuits where other electronic equipment would plug straight into without the need for that Ac to Dc wall charger, so only heavier loads would be on the grid at 230 Ac.

 

[quintain]

One of the issues with most solar panel installations is that not only do you want to power the house but also make money by selling the excess which requires a more complex system where you need to convert your Dc power from 0 to +Ve from the panels into a higher voltage Dc that has a positive and negative rail that can then be switched to deliver an Ac waveform. This voltage will not be 230 because that is the RMS value, it will be 0 to around 330 volts alternating and it has to be phase syncronised before connecting it to the grid.

We are still in the early days of properly ultilising our energy supplies in a more efficient manor, we are really all over the place because with solar we go from Dc to get Ac then in many cases we use equipment with plug in power supplies and chargers to deliver low voltage Dc to the load, even LED light bulbs have a power supply built in. It would be more efficient to have electrical distribution systems in our houses where all the lights were on an extra low voltage Dc circuit that could easily be powered by a solar panel and battery system where only at a given level would the grid be used to charge the battery, all the LED lights would be Dc and not require the built in psu.

Then you could have other Dc circuits where other electronic equipment would plug straight into without the need for that Ac to Dc wall charger, so only heavier loads would be on the grid at 230 Ac.

This forum is second to none; the amount of excellent information to me and many others is world class.
Some of the information which even I (albeit partially) understand. Please - Please put yourselves forward to run the country, you will have my vote.
Spectric of North Cumbria, if you are ever in mid Cumbria, to be correctly renamed Cumberland in April 2023, there will always be a cup of tea and a discussion on my 47 self build housing development.

 

[Spectric]

I will admit that the subject of electromagnetics has always been something of a fascinating subject for me, you cannot see electricity but you can certainly feel it but you can neither see or feel a magnetic field yet it can transfer huge amounts of power. The historical progression has also been incredable, from basic analogue psu's based around simple components to high frequency switching supplies that now incorporate digital signal processors to provide the waveform and control.

The big problem is that our government is not addressing the building regs so they are fit for purpose for the future, yes they do talk about retrofitting insulation to our homes but they are still building high density housing that is aimed at making a large turnover for the shareholders rather than accepting that housing needs much thicker insulated walls and you will have to accept less houses for a given area to accomodate them. Maybe they need to look at a shared heating system for a housing estate rather than trying to push each one down the heat pump route, that way they could look at a more industrial system on a larger scale than just smaller domestic systems.

 

[Dabop]

One of the issues with most solar panel installations is that not only do you want to power the house but also make money by selling the excess which requires a more complex system where you need to convert your Dc power from 0 to +Ve from the panels into a higher voltage Dc that has a positive and negative rail that can then be switched to deliver an Ac waveform. This voltage will not be 230 because that is the RMS value, it will be 0 to around 330 volts alternating and it has to be phase syncronised before connecting it to the grid.

We are still in the early days of properly ultilising our energy supplies in a more efficient manor, we are really all over the place because with solar we go from Dc to get Ac then in many cases we use equipment with plug in power supplies and chargers to deliver low voltage Dc to the load, even LED light bulbs have a power supply built in. It would be more efficient to have electrical distribution systems in our houses where all the lights were on an extra low voltage Dc circuit that could easily be powered by a solar panel and battery system where only at a given level would the grid be used to charge the battery, all the LED lights would be Dc and not require the built in psu.

Then you could have other Dc circuits where other electronic equipment would plug straight into without the need for that Ac to Dc wall charger, so only heavier loads would be on the grid at 230 Ac.

You would be surprised lol
I have been in the offgrid solar game for forty years (now semi retired ) and doing solar gridtie since 2004 (although its been around almost a decade prior to that in Australia) our current mppt inverters are running up to 95%, with most (even the cheapest) running over 90% efficient

One thing that most don't know (but is common knowledge in the offgrid world) is that anything with a switchmode power-supply in is can happily run off high voltage DC, and with battery banks in the offgrid world usually 96v or higher, in most cases you can run those switchmode PSU's directly from the battery bank...
So if it has that '100v-240v, 50/60hz' label on it and you have a modern 96v battery bank (indeed most switchmode PSU's will even run on the older 72v banks) then you can run them directly connected to the battery bank, no inverter needed at all!!!
Phone 'chargers' TV sets, LED 'non dimmable' bulbs and lamps- literally anything with this label...

will run happily from straight DC...

As for using the 'central PSU/ house wide low voltage' (which one- 5vdc, 12vdc, both, more???) that has often been put forward, but in reality- it actually ends up costing more to install (thicker cables to compensate for voltage drop) the big PSU has a higher idling current and has to be left running 24/7, rather than having smaller supplies that can be turned off at the outlet switch instead when not needed, and limits your locations for things like phone charging- unless you duplicate a 5vdc 'socket' at every mains location, fed from the central PSU...

 

[Spectric]

In the Uk we are to used to the easy life, flick a switch and light but in other places like Oz and Alaska where you can be too far from the grid it must drive invention and ingenuity to get by and to learn by experiment, something we have lost here.

 

[Dabop]

In my case, the mains (in the form of a rural SWER system- doubt they even have them in the UK) runs right in front of my property- but the cost of installing a transformer and poles back 1/2km back to where the shed is (and house will be eventually) was going to cost $42k Australian and is limited to a 8kw max draw- plus you get ever increasing bills at the end of it- where my offgrid solar is 18kw of solar panels, and an inverter rated at 12kw continuously, 36kw peak for 20 seconds...(well it will be once I finish building the house lol- currently only 1.5kw of solar is up and running to power the caravan)), with a 20kwh 48v battery bank- total cost was $17500Au- I could have literally doubled its size and still cost less than getting the grid installed...
:-O
My battery bank was most of that ($11.5k) and because it is LiFePO4, rather than L/A, it will last well in excess of 20 years before needing replacement, rather than the 5-7 years that lead-acids do before they start showing signs of deterioration...

 

[HamsterJam]

All gridtie inverters are legally required to have islanding- not having it is a 'bad' idea- killing a linesman type bad...

I think most UK grid-tie inverters have anti-islanding rather than islanding.
As I understand it, the difference is a grid-tie anti-islanding inverter will closedown when the grid goes off to prevent back feeding onto the grid, avoiding a ‘power island’. This is because that island is likely to include some of the grid, potentially harming a linesman who thought it was isolated.
Whereas a grid-tie inverter with islanding can generate power when the grid is down but it must automatically disconnect the incoming feed so it can’t back-feed onto the grid. I.e. the ‘island’ is allowed but restricted to your installation, keeping the linesmen working on the grid safe.

 

[Spectric]

The SWER system is certainly a distribution system done on the cheap, supply live and return via the ground which must cause many issues. Just thinking of earthing rod's and mesh systems in the UK which can be problematic and depend upon ground conditions to get low resistivity.

Then when you hear that the Western australian dessert covers 150,000 square miles you start to see the bigger picture and the massive problems they might have with distribution systems over such huge expanses and so hard to visualise when you live on a little island like the uk where getting anywhere is possible within hours.

potentially harming a linesman who thought it was isolated.

When these guys work on the overheads they attach grounding cables to them to ensure they are at zero potential, if they get it wrong then things like this can happen.

https://www.brisbanetimes.com.au/na...was-his-employer-s-fault-20180220-p4z11j.html

 

[Dabop]

I think most UK grid-tie inverters have anti-islanding rather than islanding.
As I understand it, the difference is a grid-tie anti-islanding inverter will closedown when the grid goes off to prevent back feeding onto the grid, avoiding a ‘power island’. This is because that island is likely to include some of the grid, potentially harming a linesman who thought it was isolated.
Whereas a grid-tie inverter with islanding can generate power when the grid is down but it must automatically disconnect the incoming feed so it can’t back-feed onto the grid. I.e. the ‘island’ is allowed but restricted to your installation, keeping the linesmen working on the grid safe.

Correct- it should have been anti-islanding (indeed even hybrids capable of running in island mode are stiill required to have antiislanding capabilities on their grid facing side- ie if they are running in their hybrid mode- the power produced MUST NOT- under any circumstances- feed back to the grid...

They can (and usually do) run in gridtie under normal circumstances- but the instant the grid connection is lost, they must self isolate

 

[nickds1]

One thing that most don't know (but is common knowledge in the offgrid world) is that anything with a switchmode power-supply in is can happily run off high voltage DC, and with battery banks in the offgrid world usually 96v or higher, in most cases you can run those switchmode PSU's directly from the battery bank...
So if it has that '100v-240v, 50/60hz' label on it and you have a modern 96v battery bank (indeed most switchmode PSU's will even run on the older 72v banks) then you can run them directly connected to the battery bank, no inverter needed at all!!!
Phone 'chargers' TV sets, LED 'non dimmable' bulbs and lamps- literally anything with this label...

View attachment 145199

will run happily from straight DC...

This is indeed true.

Most SMPS work by converting the incoming mains to DC, then using that DC source to drive the rest of the converter - if the voltage is being stepped down, this is called a "buck" converter - almost every SMPS in your property is of this type. The principle reasons for doing this are: independence from incoming mains voltage and frequency (so a given bit of equipment works anywhere in the world), small size & weight (no transformer so no heavy & bulky iron & copper), and efficiency (less energy lost to heat). Oh, and because of all that they're cheap & easy to make and ship around the place.

One significant downside is they generate a load of electrical interference which is bad for analogue radio, hifi etc. Another slight downside is that as they have no transformer at the mains input, there's no galvanic isolation for most of the circuitry so repairing an SMPS is very much a specialist job as the risks are substantial - most of the circuitry is at a high voltage (230VAC gives around 325VDC peak) - one slip of a probe or touching something you shouldn't could be very nasty indeed.

However, there are things in your property that are designed to run off AC only and can/will be damaged by seeing DC at their input, e.g. motors used in fridges, central heating pumps, dish/clothes washers etc. Traditional transformer power supplies (e.g. most hi-fi, older "wall warts" etc.) will also just cook and be a possible fire hazard if supplied with DC.

So, if going down the DC route, keep AC-only equipment on a separate circuit as the consequences of failing to do so are not good!