Installing generator transfer switch

[ericmark]

For emergancy light I have one of these,

I really need some more, but they light for 4 hours after a power cut, and can be used to find other touches etc.

I inherited this the inverter is only 300 watt, so of limited use, but the 15 Ah lead acid battery will power an up-lighter for quite some time, today we have these which do basic the same thing, it is called EPS rather than UPS (uninterruptible power supply) as its change over time is slightly longer, still less than a second.

Due to weight, in the main limited to around 3 kW in the portable form as shown, you can get a Tesla power wall etc, at 10 kWh, but they can't be put in the boot of your car, as to if 300 watt or 3 kW is required is down to what you want to run, the cheap freezers has a high start inrush, maybe 6 amps (1.4 kW) where the more expensive inverter control models may be around 200 watt, less than 1 amp when in defrost mode, rest of the time less than 100 watts.

I have solar panels, so my inverter is 5 kW and part of the solar install, with 6.4 kWh of battery, which will stop discharging at 10% so always 640 Wh how much more depends on time of day I get a power cut.

The old 12 volt to 230 inverter is only 150 watt, I made up a lead, so I can use old car batteries to power anything using a cig lighter plug, hope I will never need it, but I have two old 90 Ah batteries which would keep me going some time.

The inverter generator reasonable sound level, but needs to be outside, so first consideration is how to get power in the house, I have the same problem, even with an inverter, can't get the cables through the house internally, so done external. Under that window I have a box for mail, could put a generator or battery in a box like that, as it stands I can manage for around a day with no power in winter, and weeks in summer due to solar. I do have an open grate fire, which could be opened up, but having the central heating still working seems a better idea, which I have until battery goes flat.

But the main point is how far do you go just in case? Window cracked open with an extension lead into the house is likely good enough, with generator sitting outside. I have a gas camping stove, and one would hope any loss of power will not be for long.

 

[homesecurity]

@JasperW Please stop immediately and read this carefully before purchasing or plugging anything in. What you have described contains multiple critical life-safety hazards and misunderstandings of UK electrical regulations (BS 7671):
1. The 'Suicide Lead' (13A Plug to 13A Plug) Is Extremely Dangerous You mentioned seeing YouTube videos with a standard 13A plug on a lead coming from the transfer switch. In the electrical trade, that is literally called a 'widow-maker' or 'suicide lead', and it is strictly illegal and potentially lethal: - If that cable is unplugged while the generator is running, you have exposed, bare brass 230V live pins sitting in your hand. Touching them will kill you or anyone else nearby. - The ONLY safe and compliant method under BS 7671 and BS EN 60309 is an Appliance Inlet (a flanged male connector mounted permanently on the wall inside a weatherproof enclosure). - Power from the generator is delivered via an extension lead with a standard female socket coupler. The pins on the wall inlet are recessed, and they are only live when the generator lead is physically plugged into them.
2. Critical Earthing Hazard: The Gas Pipe Is NOT an Earth Electrode! You mentioned: 'the consumer unit is earthed to the gas pipe... so I am assuming if I earth the generator into ground close by they will share a common earth'. - Under BS 7671 Regulation 542.2.6, metallic gas pipework is STRICTLY PROHIBITED from being used as an earthing electrode! - What you are looking at on your gas meter is Main Equipotential Bonding (BS 7671 Regulation 411.3.1.2). That 10mm² green/yellow cable exists to ensure that if a fault occurs elsewhere in the house, the metal gas pipework doesn't rise to a hazardous touch voltage relative to true earth. It does NOT earth the electrical installation. - In a power outage, your house earthing system relies on your DNO supply (most likely TN-C-S / PME). If a power cut involves a broken neutral/PEN conductor on the street, attempting to earth through gas pipework can pass fault currents through gas meters and joints, causing sparking and severe fire/explosion risks. - For a generator supply, BS 7671 Section 551 mandates a dedicated copper earth electrode (earth rod) driven deep into the ground outside, connected directly to the generator frame and transfer switch.
3. The Floating Neutral & RCD Inaction Problem Small portable 3kW petrol generators have 'floating outputs' (IT system) where neither conductor is connected to the metal chassis: - If you plug a floating generator into your house wiring, your circuit breakers will NOT provide automatic disconnection of supply under earth fault conditions, because there is no return path to the generator winding. - Even if you upgrade to RCDs or RCBOs, an RCD CANNOT trip on an earth fault with a floating generator! An RCD requires a neutral-earth bond at the source to detect an imbalance between line and neutral. - To safely power a domestic installation, the generator output must be converted to a TN-S system: a Neutral-Earth bond link must be established at the generator or within the transfer switch, tied to your new external earth rod.
4. The Transfer Switch (Must Be 2-Pole Double-Break) Under BS 7671 Regulation 551.6.1 and 551.7: - The changeover switch MUST switch BOTH the Live and the Neutral (Double Pole, break-before-make). - You can NEVER leave the grid neutral connected while running on generator power, because circulating neutral currents can back-feed the substation and electrocute line technicians working to restore grid power. - Beware cheap unbranded changeover switches on Amazon. Use a certified, mechanically interlocked changeover switch from a reputable manufacturer (e.g. Hager, Lewden, or Craig & Derricott) rated for the prospective fault current.
Please have a qualified electrician install a proper 16A/32A BS EN 60309 appliance inlet, an external earth rod, and a certified double-pole changeover switch. And prioritize getting your consumer unit upgraded with modern Type A RCBOs before spending money on generator switchgear.

 

[BS3036]

I was about to write a few lines explaining how to identify AI generated posts, but I recall that this apparently will 'tip off' the poster. To be fair all the points about are quite valid.

 

[Ragnar_AT]

Except I don’t think anyone has mentioned a lead with plugs on both ends. All I can remember is a plug wired to an appropriate transfer switch.

 

[JasperW]

@JasperW Please stop immediately and read this carefully before purchasing or plugging anything in. What you have described contains multiple critical life-safety hazards and misunderstandings of UK electrical regulations (BS 7671):...

Thanks, this is exactly the sort of information I was looking for!

1. What you are suggesting as a connector is what I was assuming I needed but didn't know what to ask for.

2. Yes, this makes complete sense and has taught me something (quite a lot actually)!

3. Point 2 now explains why the earthing rod is so important.

4. I would never try installing this myself! But I do want to understand why things need to be done in a certain way so when I do get an electrician to quote for the work I understand what I am paying for and can have a sensible conversation about the work.

In the mean time I'll just go with the original plan to run an extension lead into the house and power lamps and the fridge freezer off that.

 

[JasperW]

Except I don’t think anyone has mentioned a lead with plugs on both ends. All I can remember is a plug wired to an appropriate transfer switch.

Yes, that is correct, but it still looks incredibly "Wrong" to my eyes even if it is functionally behaving just like an Appliance Inlet

 

[ebee]

Ref post #17 by Homesecurity I had not considered that you meant the "Widow Maker" type of circuit.
Perhaps you did mean this.
I do not know.

Homesecurities caution is indeed correct.
Any lead with a plug each end is potentially fatal for mains voltages.
Any lead with an electrical potential (say on the output terminals of a generator or other source) of mains electricity is also potentially fatal if it has a plug on the end too.
I do hope you are not considering having any lead anywhere with a voltage approaching or exceeding 50 volts anywhere if it has a plug on it. In normal dry conditions - in other conditions such as bthrooms, swimming pools and outside then half that voltage to 25v max , better still do not do it anyway.
Anything with any voltage on it should not have a plug on the end.

 

[ericmark]

It seems it is OK if on a solar panel? I have seen the widow maker used a lot in Turkey, and the deaths don't seem to be that high, the problem is we are educated that if dangerous it would not be allowed, so we are not as careful with electric as those living in Turkey.

 

[BS3036]

It seems it is OK if on a solar panel?

The only reason that is allowed; is that the solar inverter must comply with the specification that it switches off in less time than you could touch the pins, if you pull the plug out. That won't happen with any generator you can buy at the moment.

 

[ericmark]

The solar inverter is classed as a generator, I personally don't think it is safe to allow reverse flow, not only due to live pins, but also damaging safety equipment like RCDs, but the government has allowed it.