transformer lighting

[Guest]

Please excuse my ignorence, advice needed.
I am looking to replace the lighting on board, considered using lights from the diy stores the ones with a transformer. Can i connect the transformer direct to the 12v boat system? if so how This may seem a silly question or simple to you experts but my simple mind can't grasp the idea. Also Is there any way to switch them between 12v & 240v so when on a mooring i can use the same lights. I didn't want to fit lots of seperate lights if poss.
Any advise very much appriciated

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[chippie]

I think you are referring to the 12 volt halogen lights that have a transformer to operate them from the mains. There would be mains in to the transformer and 12 volts at the output. This is the side where the boat's power comes in. If you installed them direct to the boat's system the transformer wouldnt be needed. I would be possible to supply power to the mains side of the transformer from the shorepower but you would need to bypass the boat's electrics with some sort of two way switch on the output side. A friendly electrician should be able to sketch a circuit diagram for you. If you are unsure of this sort of thing take great care with the mains side of things in particular and even the 12V side could cause a fire in the worst case.

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[colvic]

We've used the flush mounted ones for five years now, living onboard, and they haven't let us down at all.

You don't need a transformer, just wire them into the 12v system and whenever you are moored in the marina just make sure the battery charger is switched on.

We use 10 watt bulbs in the small spotlights over the bunks and chart table and 20watt bulbs in the ones mounted in the roof lining. 50 watt bulbs were too hot.

Check out www.screwfix.com as they are about the cheapest supplier and the spare bulbs are a fraction of the cost from a chandlers.

Consumption is a little under 1 amp for the 10 watt bulbs and well under 2 amps for the 20 watts.

Phil

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[saturn]

refitting my boat at the moment and have used what they(lamp shops) call cabinet lights £6.99 each.use them without transformer, they come with 10 watt halogen bulb as standard but also you can get 5,15 and 20 watt. they can be surface or flush mounted.work a treat.

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[Alex_Blackwood]

My advice, on safety grounds, if nothing else would be to stay well clear of mixing the boats 12volt with 240volt shore supply. The 240 volt is ALTERNATING CURRENT and the 12volt boat battery is DIRECT CURRENT. Mixing these in any circumstances could be disasterous! The 12volt derived from the TRANSFORMER is also a.c. Remember you cannot transform D.C. If you apply the 12volt D.C. voltage to the output side of the transformer, even with nothing on the input side you would probably burn out the transformer, and possibly the boat.
If the lights you are talking about are the ones I think they are, you can buy them as seperates without the transformer. As someone has sugessted I would connect these to the boats 12volt system and run them from shore supply via a suitable Battery charger through the domestic or services battery.
Before installing the charger you need to determine the total wattage you will be drawing from the battery whilst alongside, everything, not just the lights.
If you divide watts by volts you will get the current (AMPS) being consumed you will need a charger that can supply that amount of current.
As it says on the label of all electrical equipment "IF IN DOUBT CONSULT A QUALIFIED ELECTRICIAN"
From what I can see the boating world is awash with "Enthusiastic Amatures" and "Non-Technical Terrorists" in the electrical field. Excuse the pun!


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[Stemar]

I've looked into this as well. I was assured by a potential supplier of these lights that the low voltage ones will be fine with 12v DC even though they are designed for 12v AC (From the mains via the transformer).

Some of them do get quite hot, so watch your watts - the 5, 10 & 20 w bulbs sugested by an earlier post sound like a good idea, and run one for several hours and check its temperature before you instal it too near anything that might melt or catch fire!

They're a lot more efficient than the normal car-type filament bulbs, so you'll need less power.

One final suggestion. Don't scrimp on the size of wire you use, or you'll find that the more lights you turn on the dimmer each one gets!

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[bedouin]

As others have said - the "transformer" will not be any use. You can connect the 12V lights directly to the boats electrical system - the one thing to note is that the system on the boat is actually never as low as 12V - and with the engine running it could be has high as 14.8V.

This is likely to reduce the life of the bulbs themselves significantly if they are regularly used with the engine running (or with a shorepower battery charger connected)

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[Heckler]

in what camp pray do you put yourself? armature or the other?
stu

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[tcm]

Re: 12v ac hm?

i think the the transformer turns the 240 ac into 12v dc. The light bulbs for 12v can be inserted either way round. DC, surely?

Anyway for the wiring ...this is the whole thing about 12v lights for which the main advantage in a house is that they look sexy. In a boat, they of course are the only option.

240 volts isn't put in houses to kill people on purpose. It's put in to allow more power, and less power loss, avoiding the massive wiring thickness needed for 12v throughout.

A 12watt light bulb on a 12 volts ystem draws 1 amp. (Watts =Volts x Amps) whereas a 60 watt bulb on a 240V system (like in a house) draws only 0.25 amps. If you had ten 12v lights in a boat each with a 20w bulb , then the whole system is drawing 8 amps. Have a look at the amphour rating of the batteries and you'll see that the battery on it's own will not last long powering the lights. Don't fit 50 w 12 volt bulbs as these will draw that much more current.

So, the answer for our friend with the 12v light reuqirements is

1. fit as few 12 lights as you can get away with, cos each one draws loads of current. Use 20 watt bulbs.

2 The wires to each light need to be short, and thick, and in parallel so each one gets the 12 volts. The 12 volt lights from a diy shop are fine - but you do not need the transformer to step down from 240 volts, cos it already 12 volts.

3. Fit 240 completley separate 240 volt wiring, and lights, and switches. You can't havem autoswitching with the same bulbs. If you want these 240 lights to be sexy or "atmsopheric", makem as side lights as overhead lights tend to be harsher. You can fix (with screws) little sidelights or table lights. 40V lights are fine in a a saloon, and note that these draw only 1/6 of an amp from a 240 volt system - so don't need the thick wires.

4. Get a mate to help out a bit, and you do the donkey work going to the shops, making the teas and so on.



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[philip_stevens]

Re: 12v ac hm?

I believe the 240vac transformers push out 12vAC as they are not transformer-rectifiers.

Most resistive loads (lamps, heaters, etc) can be connected any way around - there are exceptions.

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Philip

 

[bedouin]

Re: 12v ac hm?

I agree that 12V halogen bulbs will run equally well on AC or DC.

I believe that a 12V system may be either. I have two 12V set-ups in my house. One cheap one from Ikea that seems to have a wound transformer, so probably uses 12V Ac and one more expensive set up which I suspect has a switched mode PS or something similar - probably putting out DC.

One day I might attach the 'scope to them and find our

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[Alex_Blackwood]

Re: transformer lighting (re sonsy_lass)

Purely professional! Sorry if I upset any one with the Enthusiastic AMATURE (An ARMATURE is a moving device within an electric field) N.T.T comment. It was meant in a light hearted way. Although things don't always appear as you mean them to!
I really enjoy reading about all your electrical problems and I know that a lot of you are doing it on a budget so am quite pleased to be able to offer advice if possible.
Happy sailing!

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[DeeGee]

Re: transformer lighting (re sonsy_lass)

Well if we are being fussily professional, it is AMATEUR.

Anyway, the only thing that matters about these, or any other, lights, is whether they are more EFFICIENT. If we compare two bulbs, and one gives out most of its energy as light, and a little as heat (eg flourescent devices), then it will be far preferable to one which puts out more heat with its light, for the SAME consumption of energy. As well as pure efficiency, we need to consider the spectrum of wavelengths of the light. If this spectrum is more closely matched to the characteristic of the eye, then it will APPEAR brighter than another which is pumping out a less well matched spectrum, including, for example the radiant heat referred to above. A narrow bandwidth (ie a narrow spectrum) is detrimental to apparently effective illumination as well - even if well matched.

What does all this b**x amount to? If we can use a lower-energy bulb, which manages to put out the same apparent, or effective, light as a higher-energy brother, then we are going to save that energy and our battery juice.

I think a halogen bulb is a) more efficient b) better matched to our visual response, so we should replace more powerful conventional bulbs with halogen less powerful bulbs - THAT would make real sense.

<hr width=100% size=1>Black Sugar - the sweetest of all