Connecting backup power to your house Featured

It turns out there's a variety of cheap-ish automatic transfer switches now available, eg:

I was puzzled how the first two designs are wired - at first glance it appears the deal is the standby input is always connected to the load, which means it becomes live in the presence of mains. That could be awkward, eg if you have a male Commando plug to hook up the generator, the pins would be live while mains is present. Although it may be that standby and output terminals are adjacent but not connected.

The third (blue) and fourth kinds appear to have contactors for both mains and standby inputs, so I suppose there is not feed back into the standby input.

Of course, you may not trust the grade of Chinesium they're made of. Although it doesn't look terrible:

Theo

We have got a gennie on a remote site and this is the switch that we used to use it MUST be a break before make type like these ones that have an ON 1-OFF-ON 2 format.

A later arrangement saw a couple of mains contactors that not only were electrically interlocked but had a mechanical lock as well in order to ensure that the local generated power wasn't folded back down the line!.

The one in the video above is basically two normal circuit breakers with a motor operating their handles. When mains power fails, a motor is engaged that rotates a cam that physically turns off the mains breaker and turns on the backup breaker. Because it's a rotating cam there's a definite period when they are both off, and it's mechanically not possible to have them both energised at once (although maybe if the breaker handle were to snap off?)

On the first video I linked it's an arrangement with two solenoids. Changeover time is about 20ms which is quite good. I'm not sure if there's a purely mechanical interlock, but there is a relay interlock.

I like how basic they are: feel more confident with mechanical and relay interlocks than something electronic.

Any of those automatic, or all manual changeover?

Theo

You've given me an excellent solution Andrew. I didn't get around to adding a fused spur for the thermal store so just stuck a plug on it, and it powers all 3 pumps on the sustem. Unfortunately the central heating UFH manifolds etc are on their own feed but I could at least run the wood burner circulation pump rather than have it dumping hot water to waste via it's internal quench coil.

And by chance I also have a 300w Belking "A/C Anywhere" inverter" never been used, and an old leisure battery in the garage I randomly top up.

Might just have to give it a trial run in as soon as it's cold enough to light the burner again.

Cheers - Pete

Well it all moved on to using these units which are very similar. One of them senses the incoming mains and if that goes missing then it starts the gennie warm up i.e. glow plugs are warmed up then it has a number of start attempts and if successful with that then lets the gen warm up for a short while whilst checking the mains is still missing and if so fires of the changeover module.

Its got a crafty feature it can tell when Gen is running by sensing the Oil pressure switch! If thats OK then gennie must be running if not then it knows gen is not going.

Anyway can fire off a alarm signal and when mains comes back will wait for a short time to see if its a genuine return once it seems it is will fire the changeover unit and then check all's well then it lets the gennie run off load to cool down then it switches off gennie.

Has worked on a number of occasions and very well each time, the times for various functions an actions are programmable inc the number of gennie engine start attempts etc. It all works off a 12 volt supply thats battery backed..

changeover unit.

The pricing on that kit is significantly more reasonable than I would have expected :-)

Yes and it hasn't gone up that much since we bough the units concerned! And they were built well too!

They are doing some other useful bits and that and I think there a few other suppliers in that market now..

Interesting. I hadn't thought about all the necessary sequencing requirements for cold-starting a generator.

It's not bad, but I note that box is only the timer/sequencer. You still need to supply external contactors and an electrical interlock, and it needs an external DC supply. So it's only doing half the job.

Theo

Shouldn't that be a sharpening mask ?, since that is what you want to do ?.

PS Pixel 7 has redefined this now, it has an UnBLUR feature :-)

Crikey. You will have WW3 in the cage if you keep them together for longer than a bit of nookie. Hamsters generally don't like company.

I think the name of the process comes from a traditional darkroom technique where you use the out of focus negative to make a contact copy of the film to another bit of film - but from the "wrong" (i.e. the emulsion) side of the film - that creates a "softer" copy of the original.

That copy is then used as a mask - ganged up with original - which gives a reduced dynamic range combined image. Printed onto high contrast paper, you get a low pass filtering effect - making the fine detail more pronounced.

Yup, that is a much more difficult process!

Almost exactly what I have provided my parents with.

Just enough to power the central heating, the PC and a couple of lights and for a short burst a 700W travel kettle.

It is called an unsharp mask for historical reasons. You make a slightly blurred copy of a negative and then sandwich them together to allow you to enhance the high frequencies in a wet chemistry analogue process.

Digitally it is blur it a bit, subtract off the original and rescale.

Some of the modern unblur functions are way more sophisticated than unsharp masking. It used to be the territory of super computers and array processors but today some mobile phones have enough grunt.

its served them well having a bright spark of a son!

True, but the external switchgear can be for a few kW to lots of kW and possibly three phase etc. But those units fitted into a box that was set in the wall of this place and for the money looked very neat and a has form some years worked very well surviving the odd lightning strike on the way;!.

The main switchgear is on another box a little distance away..