Power supply isn't my area of expertise but I've done a bit of online research and wondering if I can get away with using resistors to reduce the voltage for my purpose.
I have acquired an electric kettle from circa the 1930s, the voltage is rated 200-220V. UK mains voltage is nominally 230 but I just measured and I'm getting about 248 at the moment. I'd probably be happy to give it a go if it was about 10V above the rating but I feel 30V is pushing it a bit. I don't want to destroy a kettle that has somehow survived for about 85 years. Can I use resistors to reduce the voltage or is this not advisable? If I were to get a transformer, what is the simplest one I can use and where can I get one (I live in the UK)

Before anyone gets too alarmed, I have already tested the kettle and it isn't as deathy as it first appears, there is no leakage from the circuit to the body of the kettle. The kettle didn't come with a flex, so I have made one from a cheap extension cord and some bullet connectors that I found in a car parts store. I have added an earth which I'm pretty sure was never an original feature. Oh and I put a 5 amp fuse in the plug as it draws 3.1 amps.
Images attached!

(oh and the resistance across the heating elements is 62 Ohms combined in case you're interested)

 

Keep it polished and on a shelf.

 

Keep it polished and on a shelf.

Oh wow, I was actually expecting a helpful reply, maybe I'll join another forum.

 

I agree, use it as decorative item, before you get yourself into real 'hot water'.

 

I would say don't use it as kettle for boiling water is a helpful reply,
Any 1930's mains electrical equipment could be a serious risk, if in doubt take it into your local electrical safety centre, ask their advice.
E

 

Guys, I've tested it and I'm not going to lick it when its plugged in, I'm at risk of flipping the RCD at most.
I completely regret sharing my interesting project here and not just putting a vague post for info on how to step down mains voltage supply to 200- 220V for a heating element.

 

You want to drop say 25V at 3 Amps , that requires at least a 75 Watt resistor, say 100W.
A transformer with a 240V primary to a 210V secondary at 3A is approx 650W, with isolation.
You maybe able to get an Auto transformer 240V tapped at 210V at 3A rating, BUT no mains isolation.

We are not trying to put down your project, don't do it, is our professional advice.

 

We are not trying to put down your project, don't do it, is our professional advice.

Especially not with the safety earth via a crocodile clip.

 

Presumably, the resistance measurement of 62Ω of the heater element was determined when the kettle was cold. The resistance will increase as the element heats up.

With a nominal resistance of 62Ω, the element would demand 780W @ 220V and 929W @ 240V.

If you want to reduce the power to the kettle, a 1000W variac or light dimmer would work.

 

Keep it polished and on a shelf.

I wouldn't even polish it. Removing the patina reduces its collector value.

 

Especially not with the safety earth via a crocodile clip.

When I used to help my grandad fix CRT TVs, we used to earth the high voltage capacitors with a crocodile clip onto a screwdriver, it worked fine, imho its better than no earth at all.

 

Presumably, the resistance measurement of 62Ω of the heater element was determined when the kettle was cold. The resistance will increase as the element heats up.

With a nominal resistance of 62Ω, the element would demand 780W @ 220V and 929W @ 240V.

If you want to reduce the power to the kettle, a 1000W variac or light dimmer would work.

I've read similar advice in other threads, I'm mostly concerned that if I plug it straight in at 240 the heater element will be damaged and I don't want to spend lots of money on a step down transformer, I'll give the dimmer switch a go, thanks!

 

Power supply isn't my area of expertise but I've done a bit of online research and wondering if I can get away with using resistors to reduce the voltage for my purpose.
I have acquired an electric kettle from circa the 1930s, the voltage is rated 200-220V. UK mains voltage is nominally 230 but I just measured and I'm getting about 248 at the moment. I'd probably be happy to give it a go if it was about 10V above the rating but I feel 30V is pushing it a bit. I don't want to destroy a kettle that has somehow survived for about 85 years. Can I use resistors to reduce the voltage or is this not advisable? If I were to get a transformer, what is the simplest one I can use and where can I get one (I live in the UK)

Before anyone gets too alarmed, I have already tested the kettle and it isn't as deathy as it first appears, there is no leakage from the circuit to the body of the kettle. The kettle didn't come with a flex, so I have made one from a cheap extension cord and some bullet connectors that I found in a car parts store. I have added an earth which I'm pretty sure was never an original feature. Oh and I put a 5 amp fuse in the plug as it draws 3.1 amps.
Images attached!

(oh and the resistance across the heating elements is 62 Ohms combined in case you're interested)

Don't worry about the mains voltage , UK is 230V +/- 6% , thats anywhere from 217 to 243V.

Lovely copper kettle too nice to use,,
personally i would use it as an ornament with dry flowers in it.

 

Don't worry about the mains voltage , UK is 230V +/- 6% , thats anywhere from 217 to 243V.

Lovely copper kettle too nice to use,,
personally i would use it as an ornament with dry flowers in it.

Hi Dodgydave, I tested the mains voltage with my multimeter and it read 248 so we are deffo at the higher end of the +/-6% (It's not a very high spec multimeter but should be +/-1.5%)
I have been pretty tempted just to plug it in and see, though I'm waiting to hear back on another forum I found which is primarily for vintage radios but they have forum space for other vintage electrical items and they have a few threads about this sort of kettle but none with the 210-220 voltage rating, so its more likely that the guys there will have more knowledge about this sort of heating element.
I don't really do ornaments, but each to their own

 

I vote for the lamp dimmer.

ak

 

A dimmer rated at 1 kW or more

 

doesnt make any difference as the heater never exceed temp of boiling water

It will heat up a little faster

Creepy reasoning people believe appliances run just on the margin of damage, high precision would be required or any beneficiary.

You should however test it dry, it should turn off, the coil will look a bit burnt but thats normal.

 

doesnt make any difference as the heater never exceed temp of boiling water

It will heat up a little faster

Creepy reasoning people believe appliances run just on the margin of damage, high precision would be required or any beneficiary.

You should however test it dry, it should turn off, the coil will look a bit burnt but thats normal.

Do not test this dry. We don't know how old is the kettle and what over-temperature protection was installed or if it is even functional.

 

You should however test it dry, it should turn off,

I wouldn't trust it to turn itself off. Health and Safety was in its infancy back in the 30's, so the kettle may not have any safety turn-off mechanism.

 

Do not test this dry. We don't know how old is the kettle and what over-temperature protection was installed or if it is even functional.

+1
I would not run such a test unless there is clearly a mechanism to do the turn-off, and then only with extreme caution and careful attention until I could confirm the mechanism is working.