What do I replace this heating element with?
May 16, 2022 6:45 PM Subscribe
The heating element on my partner's beloved vintage electric teakettle died recently. The old element is a flexible sheet about .75" x 3" that fits inside a cylindrical housing in the bottom of the kettle. It looks like there's nichrome(?) wire wound around the flexible sheet, and it is broken in several places. Do I just get new nichrome wire and re-wind it, or is there something better these days?
The existing element is rated for 250W @ 120V. I think we need to maintain a similar power rating (any lower and I'm not sure it would boil water) but it would be kind of neat if there was a way to run it off a 36V battery instead or in addition, since we primarily use it when traveling by e-bike.
I am reasonably capable with electronics (ham radio operator and long-time hobbyist) but have never worked with heating elements much, so please excuse any ignorance of the subject.
The existing element is rated for 250W @ 120V. I think we need to maintain a similar power rating (any lower and I'm not sure it would boil water) but it would be kind of neat if there was a way to run it off a 36V battery instead or in addition, since we primarily use it when traveling by e-bike.
I am reasonably capable with electronics (ham radio operator and long-time hobbyist) but have never worked with heating elements much, so please excuse any ignorance of the subject.
I think the wattage of that kettle is much more likely to be 1250 rather than 250, because with heat loss due to evaporation and conduction, boiling a quart of cold water might take an hour or more at 250W.
I’ve taken a few such appliances apart, and all of them had nichrome ribbons on mica armatures in their bases, but I’ve never seen nichrome ribbon for sale, though it must be out there somewhere.
I also think your best bet would be to find an old, similar enough appliance at a thrift store and do a transplant, either of the wire or the whole element.
posted by jamjam at 1:05 AM on May 17, 2022 [1 favorite]
I’ve taken a few such appliances apart, and all of them had nichrome ribbons on mica armatures in their bases, but I’ve never seen nichrome ribbon for sale, though it must be out there somewhere.
I also think your best bet would be to find an old, similar enough appliance at a thrift store and do a transplant, either of the wire or the whole element.
posted by jamjam at 1:05 AM on May 17, 2022 [1 favorite]
How big is this kettle? Like jamjam says 250W is really low for a standard kettle, but travel immersion heaters are in that range and they boil a mug or two or water in a reasonable amount of time.
I would approach this by measuring the total length of nichrome wire, then get the thickness that would give a resistance of 60 Ohm with that length: 250W equals 2A at 120V, and as resistance equals voltage divided by current you get 60 Ohm. If the nichrome is held under the collar of a rivet or grommet at both ends it's quite feasible to redo this, but obviously you have to find the right size rivets/grommets.
For running the kettle off 36V the easiest way would be to get a boost converter that can handle the power; splitting the element into three sections that are fed in series for 120V, and in parallel for 36V is an option, but would require fitting a switch (which shouldn't ever be in the 36V position when you plug the kettle into the mains), or fitting a different (4-pole plus ground) power entrance with two differently-wired plugs on the respective 120V and 36V power cords.
posted by Stoneshop at 12:20 PM on May 17, 2022
I would approach this by measuring the total length of nichrome wire, then get the thickness that would give a resistance of 60 Ohm with that length: 250W equals 2A at 120V, and as resistance equals voltage divided by current you get 60 Ohm. If the nichrome is held under the collar of a rivet or grommet at both ends it's quite feasible to redo this, but obviously you have to find the right size rivets/grommets.
For running the kettle off 36V the easiest way would be to get a boost converter that can handle the power; splitting the element into three sections that are fed in series for 120V, and in parallel for 36V is an option, but would require fitting a switch (which shouldn't ever be in the 36V position when you plug the kettle into the mains), or fitting a different (4-pole plus ground) power entrance with two differently-wired plugs on the respective 120V and 36V power cords.
posted by Stoneshop at 12:20 PM on May 17, 2022
Response by poster: Thanks for the recommendations!
Pretty sure it isn't much over the marked 250W, though I haven't had a chance to put a power meter on it. It only boils about 1.5 cups of water, and takes ~15 minutes to do it. (-:
Looks like nichrome is available on ebay and McMaster-Carr, and probably other places. I did read that it isn't readily solderable; I think there are crimps involved in the original element; will have to pull it out again and check. Good to know that a regular squeeze with pliers may be insufficient!
Stoneshop, thanks for the tips on rivets/grommets and 36V conversion, that's really helpful! I will need to give it some thought, but the two-plug approach sounds very promising.
posted by sibilatorix at 12:28 PM on May 17, 2022
Pretty sure it isn't much over the marked 250W, though I haven't had a chance to put a power meter on it. It only boils about 1.5 cups of water, and takes ~15 minutes to do it. (-:
Looks like nichrome is available on ebay and McMaster-Carr, and probably other places. I did read that it isn't readily solderable; I think there are crimps involved in the original element; will have to pull it out again and check. Good to know that a regular squeeze with pliers may be insufficient!
Stoneshop, thanks for the tips on rivets/grommets and 36V conversion, that's really helpful! I will need to give it some thought, but the two-plug approach sounds very promising.
posted by sibilatorix at 12:28 PM on May 17, 2022
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Like, really, if the connections are crimped do NOT assume you can just wing it with some pliers, really good crimps are basically a cold weld so crimp-time plays a role.
I’m not an expert, just someone that’s investigated repairing an old toaster (and chose not to).
posted by aramaic at 9:18 PM on May 16, 2022