Shaver Socket in Bathroom on Lighting Socket

JohnW2 · 11 Jan 2020

Taylortwocities said:
Yes, I know.…

I must say that, particularly given that I am almost at the end of the DNO's run from their transformer, I'm quite surprised by how constant my supply voltage is (at the origin of my installation). Whenever I've looked, it's very rarely been far from 244V, and I'm not sure that I've ever seen it below 240V.

Kind Regards, John

winston1 · 11 Jan 2020

At this point in time my supply voltage is 245.4v.

DetlefSchmitz · 12 Jan 2020

Sad to say I have to agree with Winston's findings. I have the same shaver socket, and measured the voltage using an up market multi-meter which I trust. Off load I got 279.6V. Interestingly, with either a razor charger, or a toothbrush attached it went up to about 280.2V. Maybe something to do with the EMC components. Neither charger would have been taking much as both items were pretty much charged. For information our actual supply voltage is pretty consistent at 250V (transformer across the road). (Though of course the nominal voltage is 230V here.) Having said this we have used this toothbrush charger for many years and it still functions perfectly, so I am doubting that the higher voltage actually causes any damage. This is the most popular electric toothbrush charger available too, so the use case is probably fairly typical.

JohnW2 · 12 Jan 2020

DetlefSchmitz said:
Sad to say I have to agree with Winston's findings. I have the same shaver socket, and measured the voltage using an up market multi-meter which I trust. Off load I got 279.6V. Interestingly, with either a razor charger, or a toothbrush attached it went up to about 280.2V.

Interesting. Do you happen to know what the voltage was/is when a mains-powered razor is plugged in? As I wrote recently, given that mains-powered razors are what they were initially designed for, and given the probable fairly high 'internal resistance', to be able to satisfactorily supply 230/240V to such a load might well require quite a high off-load voltage.

Of course, whether or not ~280V would do any harm to a charger is a much less certain question. I would have thought that the nature of SMTPSs is that there would not necessarily be much/any more heat generated when the supply voltage was high - and if that's so, the main question would be whether the 'input components' could stand the voltage (and I would have hoped that things wouldn't be so marginal if they wouldn't be able to stand it). Does that make sense?

Kind Regards, John

DetlefSchmitz · 12 Jan 2020

I don't think I've ever had a non-rechargable shaver so I can't test that. Your comments about SMPSs make sense in that it's just absolute maximum voltage of certain components that matters.

JohnW2 · 12 Jan 2020

DetlefSchmitz said:
I don't think I've ever had a non-rechargable shaver so I can't test that.

I must have a few very dusty ones in drawers somewhere, but I doubt I've used any of them for better part of 50 years, so am not at all sure that they would still work!

DetlefSchmitz said:
Your comments about SMPSs make sense in that it's just absolute maximum voltage of certain components that matters.

That's what I thought and was suggesting, but winston was saying that they 'overheat' with an excessive supply voltage - which, as I said, I would not really have expected to happen with an SMPS.

Kind Regards, John

winston1 · 12 Jan 2020

What I actually said was in post 22:
"but I did have an overheated rechargeable shaver that I had to throw away due to this."

I never said this always happens, just one instance. Having happened once I see no point in chancing it again.

This one instance was a long time ago with an early rechargeable shaver. On a post mortem before I chucked it I found the chargeable part was a small transformer feeding a bridge rectifier to nicads rather than a SMPS. The part which overheated was the transformer. it didn't actually fail but it smelt horrible and the plastic case cracked, bent, and split.

JohnW2 · 12 Jan 2020

winston1 said:
What I actually said was in post 22: ... "but I did have an overheated rechargeable shaver that I had to throw away due to this."

That was actually in post #20, not #22. However, what you did say in post #22 (and what surprised me) was:

winston1 said:
Because it ran very hot in the shaver socket, but was normal connected directly to the mains.

As I said, that's what surprised me, since (as I wrote previously) I would not have expected that to happen with an SMPSU. I could have understood if you had said that 'it work fine when connected to the mains, but blew up when plugged into the shaver socket', since that could have been due to over-volt rage failure of a component, but I'm not sure I understand the mechanism that would cause an SMPSU to get significantly hotter when supplied with a higher voltage. What am I missing?

Kind Regards, John

winston1 · 12 Jan 2020

JohnW2 said:
That was actually in post #20, not #22. However, what you did say in post #22 (and what surprised me) was:
As I said, that's what surprised me, since (as I wrote previously) I would not have expected that to happen with an SMPSU. I could have understood if you had said that 'it work fine when connected to the mains, but blew up when plugged into the shaver socket', since that could have been due to over-volt rage failure of a component, but I'm not sure I understand the mechanism that would cause an SMPSU to get significantly hotter when supplied with a higher voltage. What am I missing?

Kind Regards, John

Post 37 (right this time), it was not a SMPS but a transformer/rectifier.

JohnW2 · 13 Jan 2020

winston1 said:
Post 37 (right this time), it was not a SMPS but a transformer/rectifier.

Ah, I missed that - apologies.

In that case, what you described was 'as expected', but probably irrelevant to the present day - since I doubt whether you'll find any rechargeable razors or toothbrushes which don't use an SMTP. As I've been saying, unless the (slightly) high voltage causes an SMPSU to 'blow up', I doubt that it would cause any harm (and, as I said, I can't see how it could cause significant overheating).

So, whilst the warning you are given might have been valid in days of old, it very probably isn't particularly relevant any more. Indeed, I strongly suspect that those SMPSUs specified as "100-240V" say that because that range covers almost all supply voltages found globally, rather than because they are likely to 'blow up' at, say, 245V - it's very possible that most would be OK at 300V, perhaps even higher.

winston1 · 13 Jan 2020

Although I've not opened up a SMPS for a shaver or toothbrush I have opened failed CF lights and the main reservoir capacitor is usually rated at 400v, occasionally 375v. An RMS of 282v or 265v for the latter would reach these DC voltages. They should be OK but I would expect a shorter life when used at max values.

JohnW2 · 13 Jan 2020

winston1 said:
Although I've not opened up a SMPS for a shaver or toothbrush I have opened failed CF lights and the main reservoir capacitor is usually rated at 400v, occasionally 375v. An RMS of 282v or 265v for the latter would reach these DC voltages. They should be OK but I would expect a shorter life when used at max values.

Fair enough, but as I wrote ...

JohnW2 said:
.... I could have understood if you had said that 'it work fine when connected to the mains, but blew up when plugged into the shaver socket', since that could have been due to over-volt rage failure of a component, but I'm not sure I understand the mechanism that would cause an SMPSU to get significantly hotter when supplied with a higher voltage. What am I missing?

securespark · 13 Jan 2020

When I plug my electric toothbrush into the 115V side, the charging LED's don't illuminate.

JohnW2 · 13 Jan 2020

securespark said:
When I plug my electric toothbrush into the 115V side, the charging LED's don't illuminate.

What voltage range does the toothbrush claim to accept? Does it actually charge, even though the charging LEDs don't illuminate?

Kind Regards, John

securespark · 13 Jan 2020

220-240.
No.

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Shaver Socket in Bathroom on Lighting Socket

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