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Author Topic: 24V CFLs for the house  (Read 4998 times)
Outtasight
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« on: January 29, 2011, 11:49:48 AM »

I'm toying with the idea of converting my house lighting to DC.  I run the inverter up to power the mains CFL lighting but this is pretty inefficient.  I found a site that sells 5, 11 and 15W 24V CFLs for about 6 each.  Not as bad a price as I thought they'd be, but still 10x what you can get the same bulbs for in mains Voltage.

I could replace the mains bulbs with these ones and just run the lighting ring at 24V DC.  I'd not get the generation credits for my solar power (as that's dependent on the power going through the AC OFGEM kWh meter) but given that I have so little battery power to spare in the winter months, it's better than switching the house lights back to grid power and not using solar at all...

We mostly run 9 and 11W bulbs so the wiring won't stress.  We only have about 67W of mains CFLs on the two house circuits (excludes table lamps and so on that are on the ring mains) and at 24V that's only 2.8A for the whole house.  The bulbs will work down to 21V, so can take a bit of a line Voltage drop.

They are available in 2700K and 6400K white, but only E27 screw base (although they sell an adaptor for BC bayonet)...  I might just convert all the pendant lights to be E27.  All of Ikea's gear is E27 anyway so it's easy to get the fittings. 

Won't link to them but google EDC 24V CFL.

Navitron sell some Lumina DC fluorescent fittings, but these are whole fittings with dedicated tubes.  The ones above are just like the CFLs you get in mains fittings but 12V and 24V DC.
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Billy
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« Reply #1 on: January 29, 2011, 12:12:59 PM »

Outta,

I run a few 24vdc 2D cfls.  I have had one go in three years but that was probably a fault as the glass cracked in the fitting.  I am never sure if it is worth it as they do cost more and I do run the inverter most of the time anyway.  At least I can cool, heat, light and cook it the inverter packs up but it might have been cheaper to have bought a standby inverter.  I have spent a small fortune trying things out over the years.

The rest of the lights are leds and I am happy with the colour and longevity so far.

billy

 Grin
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Justme
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« Reply #2 on: January 29, 2011, 02:19:20 PM »

Why?

For a small inefficiency in the inverter or what 90+% if its sized correctly?

Use a smaller inverter, should be cheaper than the cost of the bulbs.

Just because you can does not mean you should.

I think I would consider leaving the lights as is & have them switchable back to the mains. Then you can give the bats a dam good charge from the minimal solar & only use them when you have enough spare power.


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eabadger
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« Reply #3 on: January 29, 2011, 03:37:56 PM »

i have 12v cfl in our off grid house, 6 off ebay, very good so far.
word of caution as a profesional, running dc in a normal house is fraught with issues, not least insurance, remeber current in dc low volatge is so much higher, with greater loss's in normal household cable crossection,
if you do do it, make sure all joints and connections are tight, at the very least.
i have used standard ac fittings, but do check for loose wires.
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Outtasight
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« Reply #4 on: January 29, 2011, 06:29:05 PM »

The house is divided into two lighting circuits, upstairs and downstairs.  Upstairs we use no more than 29W in the evening (two dens and the landing light).  If we're downstairs then it's something like 17-29W.  So the typical load on each circuit would be 1.2A at 24V.  Each lighting circuit is rated for 6A AC.  Hardly seems likely there would be much issue with the wiring.  Although, I did find a melted chocblock in the top of one light fitting I replaced a while back... Doubt it melted from the current, just from being directly above a 100W tungsten bulb jammed into a fitting that says "60W max." on it by the previous owners of the house Roll Eyes. The funny thing is, I replaced it with a new light fitting that says "11W max. CFL ONLY" on it and has an OEM plastic chocblock right next to the bulb holder Grin.  What was a bit of a cowboy job has become fully legit just by changing the safety label on the product.

Running the 3kW inverter costs 35W DC plus the load at 92% conversion efficiency, so running the 29W AC load upstairs actually costs 66W in DC power (only 44% efficiency).  Doubling the DC load on the battery means a halving of the number of days autonomy without decent charge or doubling the battery size for the same level of autonomy.

I've got a smaller inverter that would reduce the idle loss to 15W but it means running two inverters and the small one still won't count towards the FIT payment as the output of the big one goes through the kWh meter.  Worse, if I wanted to run the lights and the TV, my DC idle losses would increase to 50W. 

My other thought was to swap the inverters for the Winter.  There's never enough power in the Winter to run the bigger stuff that I got the 3kW one for (water heating, using the kettle, running the fridge-freezer, an induction hob, running the video projector are do-able in Summer).  The little 1kW one can do any of the above in isolation (except for the fridge-freezer and hob) but accidentally doing two at the same time caused an overload.  All it took was for the missus to put the kettle on at the same time as the water heater was running...

From May to August, it's a non-issue.  There's so much solar power, that last year I left the 3kW inverter on 24x7 and plugged all the 24x7 leeches into it (LAN switches, DECT phones, CCTV) as well.

Just ideas at the moment...  Until this week, I didn't even know you could get 24V E27 CFLs.  I also noticed today that you can even get 6V ones, although I'm not sure why you'd want to.

For now, I've just got one room on DC lighting because it just happens to be the battery room!  I got some 12V LED lights that fit into two E27 spot lamp holders wired in series on the wall and connected to the lighting output of the small PV charge controller. 
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guydewdney
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« Reply #5 on: January 29, 2011, 08:11:32 PM »

chuck in these
http://cgi.ebay.co.uk/E27-MR16-Adapter-lamp-light-fitting-bulb-LED-/200567201605?pt=UK_Light_Fittings&hash=item2eb2bc9f45

then use

http://cgi.ebay.co.uk/10x-12V-24V-SMD-LED-Light-Bulb-Lamp-MR16-24-Volt-Solar-/250599522679?pt=UK_Light_Fittings&hash=item3a58e54177


?
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Outtasight
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« Reply #6 on: January 30, 2011, 06:29:33 PM »

Thanks,

Looks good for an anglepoise/gooseneck type table lamp (and would be better than the 1W very tight beam E27 LED lamp I have for the one in my computer room). 

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rogerhoward
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« Reply #7 on: January 17, 2013, 08:24:26 AM »

How have you got on, Outtasight?
I wish I'd thought of this before my 4kW Solar PV installation - it sounds like an excellent idea. Unfortunately my inverter is up in the loft of my 1920s cottage, so I guess I'd have to recharge from the mains though.

Still sounds interesting, although personally I'm attracted to the LEDs idea. Call me ignorant of LEDs, but does anyone know of any 12v DC LEDs & fittings suitable to to replace my 8 CFLs (between 12-20w each)? The ones I've seen all seem to have nowhere near enough wattage.
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derekmt
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« Reply #8 on: January 17, 2013, 10:01:53 AM »

i have 12v cfl in our off grid house, 6 off ebay, very good so far.
word of caution as a profesional, running dc in a normal house is fraught with issues, not least insurance, remeber current in dc low volatge is so much higher, with greater loss's in normal household cable crossection,
if you do do it, make sure all joints and connections are tight, at the very least.
i have used standard ac fittings, but do check for loose wires.
current for a 240V  60 w incandescent = 0.25AMPS
Current for a 12v 6w led = 0.5 amps
(double but not signifcant on commonly used Lighting circuit conductor sizes)

The excuse for schedule P including low voltage lighting was all about 12v dicroics with 4 Amps per light.
So the world went back to 240v and so we increased the chances electric shock for reduced chances of fire.
« Last Edit: January 17, 2013, 10:03:43 AM by derekmt » Logged
Outtasight
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« Reply #9 on: January 18, 2013, 03:47:02 PM »

Yep.

CFLs are the work of the devil and should be banned.

I went for 230V replacement LED lighting around the house.  A good 6W LED GLS lamp is about the same brightness as a 40W tungsten or a 9W CFL.

The trick is in finding "good" LEDs... Not all are created equal and there's a lot of cheap rubbish floating about.
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jonesy
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« Reply #10 on: January 18, 2013, 10:16:47 PM »

I ran standard 230 cfl off 200v dc.  16 or so 12v sla 7 ah last a long time. No inverters, no volt drop issues.
Charged them using a rectifier and variable transformer once a week.
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