powering home with generator

[awemawson]

Isolator / changeover switches MUST be 'break before make' or things will die !

I would be very dubious using relays with a home brew unless you introduce a delay between dropping the mains contactor and pulling in the generator one. Contactors take a finite time to switch they are not instant. Remember also that relay contacts can weld together when switching heavy loads, especially inductive ones.

When I built my 'DC Injection Braking' circuits on my big Dominion woodworking machine (three 3 phase motors @ 7.5 hp each) I introduced an electronic delay circuit fired by loss of AC to the motor, and when and only when that timed out did I fire the 'DC Injection contactor. So this set up is very similar to that you'd need for auto change over.

 

[gt6s]

Supply off?

Double pole or single switch?

Single pole. Secondary board (no meter on this board) in main shed beside genny, the neutral is grounded. Common with generator installs

 

[Robotstar5]

Isolator / changeover switches MUST be 'break before make' or things will die !

I would be very dubious using relays with a home brew unless you introduce a delay between dropping the mains contactor and pulling in the generator one. Contactors take a finite time to switch they are not instant. Remember also that relay contacts can weld together when switching heavy loads, especially inductive ones.

You can get mechanically interlocked contactors so while one is in the other cannot pull in. Another option is to electrically interlock them using auxilliary contacts on one relay to feed the coil on the other. If you want to get into the safe interlocking world look at positive guided contact relays

 

[bricol]

I Dominion woodworking machine (three 3 phase motors @ 7.5 hp each)

Slight hi-jack - there's a name I didn't expect to hear on here - used to be built from their works just up the road from my childhood home in Hipperholme. Now a discount carpet shop and various other little units.

 

[awemawson]

Here you go then, have a look !

Dominion Supreme Elliot Universal Woodworker

Dominion Supreme Elliot Universal Woodworker

www.madmodder.net

 

[GRW]

Isolator / changeover switches MUST be 'break before make' or things will die !

I would be very dubious using relays with a home brew unless you introduce a delay between dropping the mains contactor and pulling in the generator one. Contactors take a finite time to switch they are not instant. Remember also that relay contacts can weld together when switching heavy loads, especially inductive ones.

When I built my 'DC Injection Braking' circuits on my big Dominion woodworking machine (three 3 phase motors @ 7.5 hp each) I introduced an electronic delay circuit fired by loss of AC to the motor, and when and only when that timed out did I fire the 'DC Injection contactor. So this set up is very similar to that you'd need for auto change over.

Good auto changeover controllers give a a dead-band timer (adj) so you can delay the transition between "break" and "make" to look after your contacts and interlocks etc

 

[Justme]

Single pole. Secondary board (no meter on this board) in main shed beside genny, the neutral is grounded. Common with generator installs

My understanding is that:-
Needs a double as your ground might not be at the same potential as the grid supply ground.
Your N might or might not be bonded to the ground ( i know yours is)
Either of those can create potential across the N & E.

Remember L & N are both lives.

 

[Matrixx]

You can get mechanically interlocked contactors so while one is in the other cannot pull in. Another option is to electrically interlock them using auxilliary contacts on one relay to feed the coil on the other. If you want to get into the safe interlocking world look at positive guided contact relays

The contactors must be mechanically and electrically interlocked, the electrical interlock also prevents them jamming up (via the mechanical interlock), if the mains has gone it should drop out, but you can get brown outs ( Low Voltage) which might just keep the mains contactor in.

Positive guided contacts are used in safety circuits i.e. E stops, usually Pilz relays.

BS7671 states that neutral must be treated as a live conductor, so now you should use two pole isolation.

 

[cocker]

We often get power cuts - normally when it's been raining hard .
Now with all this talk of possibly more to come , We've got a chap coming to give a quote .
I'll have to find some lube now !

£13,000 for a 20kva genny , 30 yards from the house , with a automatic switch .

 

[knighty]

personally I'd just get a big contactor, with 2x no and 2x nc contacts and use that

have the incoming mains power the coil


then just start and stop the generator manually..... unless there were a lot of regular power cuts

as above, only really need to power a few lights and the boiler

 

[addjunkie]

£13,000 for a 20kva genny , 30 yards from the house , with a automatic switch .

To the untrained eye, that doesnt actually sound too bad.

 

[not done it yet]

To the untrained eye, that doesnt actually sound too bad.

You are right there - to the untrained eye. It depends on a lot of circumstance to pay out that much for a back-up supply. 20kVA, for a domestic property must mean it’s a mansion?

I can get by with my 3kW - enough to operate anything (except starting a large motor or welding with the stick welder) - but not everything, all at the same time.

Unless using 13kW (or more) continuously, the installation may not fare too well and be very uneconomical.

 

[addjunkie]

You are right there - to the untrained eye. It depends on a lot of circumstance to pay out that much for a back-up supply. 20kVA, for a domestic property must mean it’s a mansion?

I can get by with my 3kW - enough to operate anything (except starting a large motor or welding with the stick welder) - but not everything, all at the same time.

Unless using 13kW (or more) continuously, the installation may not fare too well and be very uneconomical.

Yes my standy by is 6kva, runs everything in the house except the washer/dryer and electric cooker, so long as we load it up carefully. And was far less than 13 grand. Really must get round-to ordering a new start solenoid for it, to save messing about with a screwdriver by torch light.

As for economical…..In the occasional emergency does it really matter I have a 2500 ltr red diesel tank. But the small petrol ones are a tad thirsty.

 

[GRW]

(Small) Petrol sets actually don't use much more fuel than diesels - the advantage was the cheaper fuel which lowered running cost.
But.... the vast cost difference between a diesel and a petrol genny.... buys a LOT of fuel (more than you'll ever use if its a backup for mains).

Petrol storage is more of an issue - so if that is a concern, buy a dual fuel genny (petrol/lpg) I.e. a petrol set with a Propane Conversion kit fitted. The cost of the lpg kit on top of a petrol set still works out maybe 1/3 - 1/2 the cost of a diesel setup.

My work is with gennys - the only reason to go for a big industrial set with auto mains etc on a domestic home - is if you have loads of money and simply want all the bells and whistles (or if there was someone there who is disabled and power is essential for life support etc).

 

[nikos]

Such a lead is referred to as a 'suicide lead'. I've recently bought a smaller (2.8 kva) used genny off FB market place and it came with such a lethal lead, wrong colour (yellow = 110 v should be blue = 240v) - amazing what people do

We call them "Jesus plugs"...

 

[nikos]

You could go really ghetto like this...

 

[GRW]

You could go really ghetto like this...
View attachment 339720

Unless those breakers are both electrically & mechanically interlocked... then (if you have an incident and/or Utility Co see it) you're going to be in bother.
There has to a single switching operation that breaks the utility supply and closes the Gen supply (& vice-versa) - this needs 2 operations and therefore a mistake by the user allows power to back-feed (Gen onto Mains & vice-versa).
People blow stuff up and (worst case) electrocute someone with stuff like this.
Given its not much more to buy a proper Manual Changeover Switch over something like you've put up - it's a no-brainer to use one.

 

[nikos]

Ok, but I'm not following... There can only be one breaker on at any one time.
But yes, a manual changeover is cheap enough...

 

[Farside]

Here's what I've got.

The box on the left plugs into a small petrol genset via flylead (with attention paid to correct way around - no suicide plugs here). The box on the right supplies three main loads labelled 1, 2 and 3. Each of those plugs will plug into the box on the left when the power goes down. I make sure the immersions, etc are off.
At a push, the black box is a nominal 1500W inverter, which can be coupled up to a car drawn up at the workshop door.
All totally manual, and fool proof.
Underneath that lot will be a shelf where the genset can sit, with its exhaust pipe out through the wall, but that's a roundtoit.