hacking MK dual gang shaver sockets!

[Fergus McMenemie]

Folks,

I recently replaced the shaver socket in the bathroom, and boy ... do I feel cheated. The old unit had two outputs one labeled 110v the other

220v with an external switch to select one or the other. I have both an electric toothbrush and an electric shaver and I was fed up having to keep track of which was being charged and for how long. So I replaced it with a 2 gang MK shaver socket from B&Q which had two outputs and no switch, one marked 110 and 220. Since both my devices will run on either 110 or 220 I intended to plug in both simultaneously and it would not matter about the different supply levels.

However it turns out the MK unit was switched, it had an hidden internal mechanism operated by insetting a plug. Only one of the sockets can be used at a time. A real pain. This was not marked on the packaging anywhere. I phoned MK and they gave all kinds of guff as to why things were the way they were. Interestingly the support guy did admit that these devices were designed decades ago and were not intended for continuous use, even if this continuous use only involved having to support trickle chargers. Some shaver sockets tended to overheat and would cut out, if say a shaver was left continuously plugged in! This has apparently been fixed.

However my question is has anybody hacked these units to allow both sockets to be used simultaneously? I am interested in any thoughts as to wiring the transformer's output to both sockets, and bypassing or disabling the switch. Assuming the transformer only has one secondary winding which is tapped to provide the 110v output. Should I use the 110 or 240 winding?

Thoughts?

[Scott M]

Not that I think two simultaneous charging devices will overload the thing, but how about removing the switch and making both sockets 110v by using the centre tap as a common to both sockets and each end of the xformer as the supply rails?

[Graham.]

I would have been surprised if the two sockets could have been used simultaneously and I would have assumed there would be a regularity requirement that they can't.

Cue someone who knows.

If they did work the way you wanted then it could be a (roughly) centre tapped secondary winding to give 110 and 240 or it could be two separate windings which with an in phase link in place would gibe you a 350volt supply in your bathroom. I know it's unlikely to happen by accident, but still. The same could happen with multiple isolated outlets near to each other, I wonder if there is a prohibition about this?

[Fergus McMenemie]

Duh... thanks!

[Graham.]

What happens if you drop the shaver in the bath while the toothbrush is in your mouth and you are holding the tap? Probably nothing, I know but safety is about unlikely sets of occurrences.

[Graham.]

OK bad example as a toothbrush is likely to be cordless, but consider two wired appliances.

[Andrew Gabriel]

That is why they are designed to allow connection of only one device.

[Andrew Gabriel]

The other problem is that, off-load, the 240V side is allowed to be up to 270V (due to poor transformer regulation). Chargers often look pretty much like no load, and can end up getting 270V. If the charger has a wide ranging 110-240V supply, it's often better to use the 120V side.

Socket has to cutout at loads over 25W, but this doesn't need to be quick, and often relies on the transformer overheating and a thermal trip.

[therustyone]

A bit OT, but I find trickle charging cordless devices heats the batteries and reduces their life a lot. Better let them discharge fully before charging and they should go for a decade. No doubt others will disagree.

rusty

[Dave Plowman (News)]

Running two devices off an isolating transformer negates the point of having one.

[Fergus McMenemie]

Well I would need to fit another shaver socket or move the existing one... however point taken. But both my shaver and toothbrush are cordless. But is your scenario any different from using the shavers single output and droping the charger into a sink full of water while holding the tap?

Given the above scenario above I do wonder if my houses built in current leakage protection is better than the decades old isolation transformer technology that is built into shaver sockets.

[Fergus McMenemie]

Why? Is this based on a worst case of it being able to touch any single wire safely? Touching two wires would still give a sock, isolating transformer or not?

[PeterC]

Probably not a toothbrush - mine doesn't get even luke warm even if it's on charge for 6 hours past full. I do tend to wait until the light starts flashing before recharging as it's not inconvenient and avoids the requirement for a full discharge every X months.

[Roger Mills]

These shaver sockets are current limited anyway but, assuming it can support both devices simultaneously, why not just use a two-way adapter?

That's how I power my toothbrush and radio off a single socket. Actually, mine is a 3-way adapter which I think I bought in Indonesia - but I assume they are available here.

Something like

perhaps - but I'm not sure of the significance of "earthing socket" in the description. Mine isn't!

[Graham.]

Yes, but my shaver is now half submerged in bath water in such a way as to create a low resistance path from one side of the tranny to deck.

Now what?

[Graham.]

Increases the likelihood of a hazardous situation arising.

But it does negate the point of having a transformer in one important sense, in my shaver in the bath scenario the transformer prevents the upstream RCD from tripping even though the victim is getting a shock to earth.

[Graham.]

Modern double insulated stuff is very safe, but I hope I have showed you that using two appliances must increase the risk, however slight, of getting the secondary of that transformer across your heart.

[Fergus McMenemie]

And another thing.... would I not need three hands! Very dangerous.

[Dave Plowman (News)]

It does assume you have two faulty devices, etc. However, the isolation transformer is only needed if a device is faulty.

[hugh]

In message , Graham. writes

The other side is 240v away. Get in the bath and stick your finger in that side and if you are still alive come back and tell us about your experience.