Back up generator advice

[Bozza]

Currently approaching 3rd night without power due to storms.  Now looking at a back up generator system for my rural self build.  My understanding is that I’ll need to have a supply switch installed to switch from mains to genny, etc.  And only run essential circuits.

 

House & water heated via ASHP.  Looking ideally to run heating fridge, freezer, telly, just the basics.  Looking at this genny:  https://www.costco.co.uk/Home-Improvement/Power-Tools/Generators-Pumps/Draper-Petrol-Generator-with-Wheels-25KVA/p/329871

 

I’m certain someone here will have a back up generator system.  Any advice appreciated.

 

 

 

[markocosic]

Not worth it IMO.

 

15 litres for 11 hours at 1875 watts. Probably won't be much less at part load as efficiency falls off a cliff. Noisy as all heck. Would you actually use it?

 

 

Do you drive?

 

A modern car probably burns <0.5 litres per hour at idle, comes with a 50+ litre tank for 100+ hour runtime, has far cleaner exhaust emissions than any genset will, and is probably quieter.

 

Alternators will do about 100A at 14.5V. perhaps a little less at idle. Easily 500W. Maybe 1000W. More than enough for "the essentials" as it were.

 

Buy yourself an inverter:

https://www.beal.org.uk/inverters.html

(they lie about their true ratings - I'd go for 3 kW and assume that it can do 1 kW continuous...)

 

Buy yourself some Anderson connectors to hardwire onto your car battery:

https://www.beal.org.uk/anderson-connectors.html

 

Choose where to put the inverter (on top of something to keep it out of the water, under something to keep it out of the rain, and close to the 12V battery) and add the appropriate amount of cable. Cars with 12V batteries in the boot are handy. 

 

And buy yourself an earth rod and one of those "caravan hookups" that have an RCD and MCB etc in it to power the house.

 

 

This was my answer when looking at generators. Standalone kit is rubbish.

 

 

You're absolutely laughing if said car is a hybrid with a DC-DC converter between the main pack and the 12V pack that'll auto-start itself to recharge occasionally. If I were to do an off-grid build a smacked-up Toyota Prius costs pennies for what you're getting...

 

https://www.plugoutpower.com/

[SteamyTea]

8 hours ago, markocosic said:

Toyota Prius

And you get an Atkinson cycle engine, which I think is the most efference gasoline ICE currently available.

 

I like the idea of of just running an inverter off a car for emergencies.

Maybe a leisure battery in parallel with the car one, but 'in the shed with the inverter'.  Can be trickle charged as well.

There is a 130 Ah on on ebay for 77 quid.

Say you draw 50A for one hour, 600W, that would be the same as burning 1/4 of a litre of gasoline.  Or about 35p worth.  The equivalent grid electricity would be 15p.

I would hope a leisure battery would do 2500 discharge/recharge at that level.

The inverter is a bit more expensive.  A pure sine wave one (which is what you need) will be about £160 for a 2.5 kW, 5 kW peak one

So about £300 to sort something out that can be emergency charged from a car.

Pretty good considering that you can easily add an extra battery.

[TonyT]

Get a generator changeover switch and install next to consumer unit.

I have a TLC single phase unit rated at 125 amps so can switch the main house current

then wire it to a commando plug in the garage/outbuilding , mine is run in 4mm2 swa /t&e in the house and external.

 

when the power goes off, plug the generator in start and switch the changeover unit.

I have a 2kW inverter generator that runs the lights, fridge freezer, heating etc,  no loads like ovens, or immersions but thats fine for me.

 

 

 

[SteamyTea]

3 minutes ago, TonyT said:

no loads like ovens, or immersions but thats fine for me

Worth remembering that this are sometimes on timers.

I would have to split my supply as I am on E7, not hard, but worth remembering.

We were discussing the resent power cuts (BiL's parents had no power for 2 days).  I said I use my camping stove, BiL said that was what his parents do.

My Mother croaked up that there is a stove in the garage, there is, and a full gas bottle.

The 1960s have a lot to answer for.

[TonyT]

mine next to house consumer units.

 

25mm tails go in feeding switch, 25mm tails go out feeding consumer unit.

4mm cable from generator also provides the feed for the generator supply, only used when there is a power failure.

 

you could get this done as part of the house wiring and buy the generator later..

 

 

 

[Nickfromwales]

9 minutes ago, SteamyTea said:

Worth remembering that this are sometimes on timers.

I would have to split my supply as I am on E7, not hard, but worth remembering.

We were discussing the resent power cuts (BiL's parents had no power for 2 days).  I said I use my camping stove, BiL said that was what his parents do.

My Mother croaked up that there is a stove in the garage, there is, and a full gas bottle.

The 1960s have a lot to answer for.

We just forget how few trinkets we need to “survive” aka live perfectly well.

Fitted a few USB sockets in mine on the weekend, WiFi had to go off for about 30 mins. I was lucky to have escaped with my life  

Edited November 30, 2021 by Nickfromwales

[gc100]

I’ve done this. It was a no brainier though I did already have a 7kW generator that I was using for power on the build in the early days 

[Dave Jones]

spend your money on battery and inverter, no moving parts to go wrong and you can make it pay for itself by using a time of day electricity tariff (I use one for my powerwall). If you have solar pv as well this is a bonus.

 

If you work from home you can claim the cost back against tax as well.

 

https://www.solarguide.co.uk/solar-batteries/tesla-powerwall-2-0-vs-powervault-g200-which-is-the-best-solar-battery#/

 

[SteamyTea]

39 minutes ago, Nickfromwales said:

WiFi had to go off for about 30 mins.

Use the hotspot built into most phones.

All by 'communications' come via my phone wifi.

[Nickfromwales]

On 30/11/2021 at 08:53, SteamyTea said:

Use the hotspot built into most phones.

All by 'communications' come via my phone wifi.

Yup. Then see the inclusive data disappear at eye-watering cost to replace.

You’re gotten by the bollaux either way ?

[joe90]

1 minute ago, Nickfromwales said:

Yup. Then see the inclusive data disappear at eye-watering cost to replace.

You’re gotten by the bollaux either way ?

Well I have just changed to hot spot data (mainly fir being on this forum on my iPad) and the cost is cheaper than a landline with broadband !

[Nickfromwales]

2 hours ago, joe90 said:

Well I have just changed to hot spot data (mainly fir being on this forum on my iPad) and the cost is cheaper than a landline with broadband !

Mine is 6 devices with 100gb shared. Topping up if you run out is not done at a sympathetic rate…..

[joe90]

10 minutes ago, Nickfromwales said:

Mine is 6 devices with 100gb shared.

Yikes,, ?

[SteamyTea]

I think mine is unlimited data.

[gc100]

On 30/11/2021 at 08:29, Dave Jones said:

f you work from home you can claim the cost back against tax as well

where can I get more information about this?

 

[Nickfromwales]

55 minutes ago, gc100 said:

where can I get more information about this?

 

Your accountant ? 

[gc100]

On 03/12/2021 at 09:10, Nickfromwales said:

Your accountant ? 

I don’t have one 

[Iceverge]

@markocosic

 

I'm intrigued by this idea as I've destroyed two cheap Chinese generators already on the build  They certainly don't match what they say on the tin. 

 

However I don't want to destroy the 180A alternator in the car. What will prevent the big ball of smoke if someone flicks on the 6kw immersion? 

 

We already have a generator change over switch and a 32A input socket in the garage so your plan would work perfectly. 

 

 

 

 

[TonyT]

The inverter would trip out if you turned a 6kW immersion on.

 

You need to manage high power loads, ie turn them off!

[Nickfromwales]

53 minutes ago, TonyT said:

You need to manage high power loads

Deffo. Switching off the breakers in the CU which feed any 'danger' loads is necessary diligence to prevent inadvertent switch-ons, by a 3rd party for eg.

[markocosic]

Do go overboard on his thick three inverter cables to battery are (your main risk is due from sustained high currents and cheap cable/connector).

 

If you draw to much you'll soon flatten the battery. I wouldn't go above 1 kW sustained draw / 3 kW peak on a 12V system. The alternator is unlikely to give full rated output at idle speed. (usually above 2000 rpm engine speed is full output)

 

Fit say a 10A Type B MCB to the inverter output of you're paranoid. Most inverters will trip long before the MCB does. Melting cables between inverter and battery is main risk.

[Iceverge]

Right in anticipation of powercuts today I went and picked up a cheap 3000w continuous/6000w max inverter this morning. 

 

It came with nice thick 8mm core copper cables. 

 

I bolted it directly on to the battery of my car and backed my car into the garage beside the 32A generator input plug and changeover switch. 

 

I connected a normal 13a 3-pin plug to a 32A socket with a 2.5mm2 cable and plugged it in. 

 

Then I turned off everything at the CU which wasn't necessary. Immersion, Oven, biocycle unit and isolated the washing machine and dryer.  

 

I began experimenting in the house. Two LED bulbs were flickering, others were ok and the few Incandescent ones were all good too. The TV, the MVHR, laptops and fridge freezer were all good as was the water pump in our borehole.  

 

I tried the induction hob. It turned on and appeared to be working OK but was buzzing so I abandoned that. 

 

Then being an optimist I tried the kettle. To my amazement it began to boil as normal. However the 2 LED's that were previously flickering dimmed almost to nothing and in short order started to smell like burning. I abandoned my endeavours and shortly afterwards the smoke alarm sounded. Que running around the house pressing the silent button on each alarm until I found the offending room, I think it was another LED bulb in a desk light making the smell in there but not certain. I've been monitoring it but the smell hasn't returned. 

 

Anyway, I turned the mains back on and even thought there's a storm passing our power has stayed on so I can't add any more for now. 

 

What I can't figure is that only 2 pendant light LED's and one plug in LED lamp were misbehaving. The others were fine. Any insights? 

 

 

Edited December 7, 2021 by Iceverge

[SteamyTea]

37 minutes ago, Iceverge said:

Any insights

Is this inverter you bought a pure sine wave one.

Just taking  stab in the dark, if it is not, and the lights/induction hob also 'chop' the power, rather than do it properly then there may be times when all the peaks line up and a higher voltages is achieved.

Then there will be times when one is on the way up, and another is on the wat down, which may draw more current than designed.

I only have basic understanding of power electronics, not as simple as text books make out.

[Iceverge]

I very much doubt it. 

 

That makes sense. Maybe I'll return it and invest in a better unit now that the concept has been proven.  Either that or offload it on my parents with their ancient electronics.