Many boats use bog standard mains light switches for LEDs. When a switch is opened, there is a brief electrical arc between the two contacts that, over time, will erode those contacts and wreck the switch. Properly designed DC switches rapidly move the contacts a longer way apart to quickly quench the arc. This is expensive to manufacture. AC switches rely on the voltage dropping through zero a hundred times a second to quench the arc. The contacts only move a small distance apart. They are cheap to make and economies of scale in the huge household market make them even cheaper to buy. As a result, many boats have them for lighting circuits, where the current is low, especially for LED lights and the aesthetics are important. The question is, how long will a mains light switch last, switching low voltage DC, for which it is not designed?

 

I fitted out my boat eighteen yeara ago. It had LED lights and main switches from the start. One of those switches has just been replaced, after becoming unreliable. A second is on it's way out. Both were used at least once a day for those 18 years, so that gives, very very approximately,  6,500 break cycles. 

The replacement switch cost 99p from Screwfix and was fitted in a few minutes. 

 

Some long term, real world experience to contribute to this question. I would have no problems recommending using mains switches for LED lights. 

 

My boat was completed around 89-99 and fitted with incandescent bulbs and what appears to be mains switches. Annoyingly, both the light fittings and the switches are now intermittently failing, and I will have to replace the lot.

For my own satisfaction, I dismurgalified the switch and there is obvious erosion and pitting on the contacts visible at 10x mag. Unfortunately, my phone won't do macro photography, so this is about as good a pic as I can get. 

I’ve just changed my galley switches, not because they were faulty, but I put black LED’s in to replace chrome so matched the switches & 240v sockets to match. 
 I think most builders use the normal 240v switches, because there’s a far bigger variety in styles and colours, far more than 12v equivalents. So the switches can be easily matched to the other fixings/decor and also for most people the ease of which you can just pop down to B&Q, Srewfix to buy them, as you mentioned.

 I too have had them in for roughly 17 year(livaboard) with no issues or failures  and on/off many times a day like yourself. So they seem perfectly safe for the job.

 

Edited September 3Sep 3 by BoatingLifeUpNorth2

Just now, BoatingLifeUpNorth2 said:

I’ve just changed my galley switches, not because they were faulty, but I put black LED’s in to replace chrome so matched the switches & 240v sockets to match. 
 I think most builders use the normal 240v switches, because there’s a far bigger variety in styles and colours, far more than 12v equivalents. So the switches can be easily matched to the other fixings/decor.

 I too have had them in for roughly 17 year(livaboard) with no issues or failures  and on/off many times a day like yourself. So they seem perfectly safe for the job.

 

Electrical engineering types do the suck through the teeth thing at the very idea, but yes, for running LEDs, it is fine. 

Some of the light switches on Loddon that had had both tubes and LED in their life were the original ones fitted by the builder in 1993 so 30 years old and still working when I sold it.

I think I only have one mains switch for a DC appliance which is a 12v extractor fan above my hob in the galley. I fitted it nearly 20 years ago and it's still fine, but since the load of the fan is likely to be a lot higher than a led light should I replace the mains switch with a DC switch to be on the safe side? 

1 hour ago, Jen-in-Wellies said:

Electrical engineering types do the suck through the teeth thing at the very idea, but yes, for running LEDs, it is fine. 

Ahhhh😱, just hope the Electrical engineer on here doesn’t see any failings in this, as there’ll be guidelines out by the close of play tonight on the safe practices of fitting a switch, all because one failed, on one boat after 18 years of constant use.😂

Edited September 3Sep 3 by BoatingLifeUpNorth2

5 hours ago, BoatingLifeUpNorth2 said:

but I put black LED’s in

So when you turn the lights on it actually gets darker?  

34 minutes ago, Hudds Lad said:

So when you turn the lights on it actually gets darker?  

Like the Disaster Area spaceship in HHGTTG?

 

"'It's the wild colour scheme that freaks me out,' said Zaphod, whose love affair with the ship had lasted almost three minutes into the flight. 'Every time you try and operate these weird black controls that are labeled in black on a black background, a little black light lights up in black to let you know you've done it.'"

Edited September 3Sep 3 by IanD

4 hours ago, blackrose said:

I think I only have one mains switch for a DC appliance which is a 12v extractor fan above my hob in the galley. I fitted it nearly 20 years ago and it's still fine, but since the load of the fan is likely to be a lot higher than a led light should I replace the mains switch with a DC switch to be on the safe side? 

I think your in danger and should plan on swapping lt out sometime in the next 18 years....😂

 

I think I have one mainscswitch and its an architrave light switch working the gulper shower pump. Think it came with the boat so is probably 25 years old. About 10 years ago I thought I'll swap it out when it fails and move it somewhere more convenient.  ..haven't done it yet and  switching a pump motor would be a lot more demanding given the inductive load as well as probably 10x current of LED lights.

1 hour ago, jonathanA said:

I think your in danger and should plan on swapping lt out sometime in the next 18 years....😂

 

I think I have one mainscswitch and its an architrave light switch working the gulper shower pump. Think it came with the boat so is probably 25 years old. About 10 years ago I thought I'll swap it out when it fails and move it somewhere more convenient.  ..haven't done it yet and  switching a pump motor would be a lot more demanding given the inductive load as well as probably 10x current of LED lights.

Ditto, except for domestic water pumps on the hirefleet. Gave virtually no troubl, but that was  pover 50 years ago so maybe better quality switches..

Most switches that are rated for ac, also have a current rating for dc which is usually quite a bit less. But with a house light switch probably rated at at least 6A ac, when running a led or 2 at 12v dc, it will be operating at much lower current and thus last adequately. Of course the whole concept of moving bits of brass around to turn things on and off is pretty archaic, all our boat lighting (and everything else) is switched using MOSFETS.

55 minutes ago, nicknorman said:

Most switches that are rated for ac, also have a current rating for dc which is usually quite a bit less. But with a house light switch probably rated at at least 6A ac, when running a led or 2 at 12v dc, it will be operating at much lower current and thus last adequately. Of course the whole concept of moving bits of brass around to turn things on and off is pretty archaic, all our boat lighting (and everything else) is switched using MOSFETS.

You can also get the opposite problem using switches for low-voltage/low-current DC which were intended for HV AC -- the contact materials are optimised for current capacity and can oxidise, without the HV to break though this you get poor contacts at LV DC... 😞 

 

My LED lighting also uses a Hafele centralised controller so the actual (24V) light switching/dimming is done by MOSFETs, the on/off wall switches just tell this what to do but AFAIK they switch logic-level DC signals to the controller.

Edited September 3Sep 3 by IanD

9 hours ago, Jen-in-Wellies said:

Electrical engineering types do the suck through the teeth thing at the very idea, but yes, for running LEDs, it is fine. 

Teeth sucking is a pre requisite in the latest wiring regulations for electricians. They have to do a short training course for it now. It also includes rolling your eyes skyward whilst simultaneously saying “we’re not really allowed to do it that way anymore mate, you’re looking at a full rewire.” I think RADA were consulted over the course content. 

Edited September 3Sep 3 by Llamedos

Not forgetting the hand to forehead followed by "who installed this death trap"....

2 hours ago, IanD said:

You can also get the opposite problem using switches for low-voltage/low-current DC which were intended for HV AC -- the contact materials are optimised for current capacity and can oxidise, without the HV to break though this you get poor contacts at LV DC... 😞 

 

My LED lighting also uses a Hafele centralised controller so the actual (24V) light switching/dimming is done by MOSFETs, the on/off wall switches just tell this what to do but AFAIK they switch logic-level DC signals to the controller.

For logic level switching you really want gold plated contacts because otherwise as you say, a tiny oxide layer can prevent the voltage getting through. I originally had some quite expensive boat lighting momentary action switches - but they turned out to be fairly crap for the above reason (just switching logic level virtually zero current) and I replaced them with keyboard "tactile buttons" on my own design pcb (because there is a group of 6) with 3d printed facia. Now works flawlessly.

Edited September 3Sep 3 by nicknorman

15 minutes ago, nicknorman said:

For logic level switching you really want gold plated contacts because otherwise as you say, a tiny oxide layer can prevent the voltage getting through. I originally had some quite expensive boat lighting momentary action switches - but they turned out to be fairly crap for the above reason (just switching logic level virtually zero current) and I replaced them with keyboard "tactile buttons" on my own design pcb (because there is a group of 6) with 3d printed facia. Now works flawlessly.

Same issue as audio signal switching in the good old days of relays, always go for gold-plated contacts (or reed relays) -- not an issue nowadays, everything is done electronically... 🙂 

Edited September 3Sep 3 by IanD

The on/off switches on the lights in my last boat were needle valves.

 

 

 

 

2 hours ago, MtB said:

The on/off switches on the lights in my last boat were needle valves.

 

 

 

 

Lucky you mine was a taper and a snuffer 😁 

Edited September 4Sep 4 by Jon57
Lights went out

2 hours ago, MtB said:

The on/off switches on the lights in my last boat were needle valves.

 

 

4 minutes ago, Jon57 said:

Lucky you mine was a taper and a snuffer 😁 

You had lights? Luxury!

15 minutes ago, Jen-in-Wellies said:

 

You had lights? Luxury!

Yep. No boat or house. But we were happy 😁 

You had it easy, there were 36 of us living int cardboard int middle of the road. 

10 hours ago, plato said:

You had it easy, there were 36 of us living int cardboard int middle of the road. 

You had cardboard? You were lucky, we 'ad ter live in t'hole where a cats eye 'ad bin...

On 03/09/2026 at 18:08, Llamedos said:

I think RADA were consulted over the course content. 

 

Are they not the 'special keys' you get to give access to disabled toilets ?