How to Assemble an Electric Heating Element from Scratch | Hacker News Reader

How to Assemble an Electric Heating Element from Scratch

solar.lowtechmagazine.com

110 pointssurprisetalk70 comments

True story (even though as the years go by I find it hard to comprehend myself)

I was in a boarding school in Ghana in the late 80's and pretty much every day there would be someone boiling water with a fork directly wired to a 240 volt socket. All the beds were metal bunk beds and there was plenty of combustible material in each dormitory.

I am pretty sure this was replicated in the dozens of other boarding schools across the country. Somehow I never heard of any deaths or serious injuries from it.

Not in the slightest bit advocating for it. It was a desperate solution in desperate times but it has massively skewed my comprehension of risk compared to pretty much anyone I meet in Europe.

Not uncommon in Brazil to have an electric water heater installed on a shower head, sometimes with lightly covered wiring. Was gobsmacked when I first saw them. One even gave me a tingle when touching the faucet and I told the owner. :sweat-smile:

I remember some showers I took in Rio that, to my surprise/dismay, required bringing a match along to light the water heater within the shower. That now seems tame by comparison.

My flat in Czechia had a gas burning tankless water heater in the shower. Standard tub with a shower head and water heater directly on the wall.

The floor of the tub was also at least 10" above the bathroom floor. I literally broke a rib trying to get out of the damn thing

Those things were everywhere in the Netherlands when I was a child - 70's. I had one above the sink in the kitchen in my student apartment (half of a pigsty converted to human habitation, pigs in the other half, a thin wall in between - that's what you get when studying at an agricultural university and living on a farm) running off a propane tank in the garden. We had one in the kitchen and a bigger one in the bathroom, running off natural gas which the country had plenty of after the discovery of a large gas deposit in the northern Netherlands. There were no vents to the outside, the things just vented into the room. They're called 'geisers' (geysers) in Dutch.

Those would output absolutely blisteringly hot water as well. Almost boiling. As I recall they'd often also have the tap directly attached to them. We kept the pilot light on ours always lit, though I can totally see people turning them off fully when not in use for a bit. The fancy ones had a button to light them. The less fancy ones involved a match and a startle as the gas caught fire.

Thanks for the trip down memory lane. I had forgotten all about those!

Extremely common in the UK too - you just have a 7.2kW feed going into your shower cabin, while regulations prohibit you from having any electrical sockets anywhere in the bathroom lol.

Which leads to an idiotic situation where in Europe it's extremely common to have your washing machine in the bathroom, but in the UK everyone goes "oh no we can't have that it's extremely unsafe" while standing next to an electric shower fused at 32amps.

Tbf the building regulations are meant to make it somewhat safe, but I've personally seen dodgy work done by electricians where they wired a shower using a 16amp wire which obviously subsequently melted after some use.

Sounds like a instantaneous electric hot water heater. Quite common, in places like Philippines, that do not have cool/cold air temperatures, and less developed electricity supply.

The UK doesn’t allow any receptacle circuits in a bathroom? Not even if they’re protected with an RCD? That’s a GFCI for Americans.

I am well acquainted with throwing water on resistive heating elements from taking a lot of electric saunas, so electric instant hot water heaters don’t really scare me. The proximity of the current is irrelevant to me when just 30 mA will kill you.

Electric tank water heaters work on the same principle, a high resistance conductor encased in a ceramic insulator which is encased in metal.

>>The UK doesn’t allow any receptacle circuits in a bathroom? Not even if they’re protected with an RCD? That’s a GFCI for Americans.

So to be fair - until last year(or 2023?) you couldn't have them at all, then they changed the rules to say you can, but they have to be at least 3 metres away from the nearest bath or shower. For reference, my entire bathroom is 2.5m by 2m - and I suspect 99% of British bathrooms aren't much bigger than this. So in theory - you can. In practice....not so much.

Splashes and wet hands are much riskier for receptacles than for a permanent and/or hidden connection. Not to mention hairdriers, space heaters, TVs etc falling into the bath. Pretty much everything smaller than a washing machine is bound to end up in there if the flex is long enough

Sure, but it's not like continental Europe has a higher rate of electrical accidents in bathrooms just because you can dry your hair in the bathroom - RCDs are a thing everywhere.

UK regs don't disallow hairdriers in the bathroom though. On the other hand, if EU regs do nothing to prevent plugging a socket from the bath, what are they even for?

Yeah, got one of those in a hotel in Florence. Definitely weirded me out conceptually, but I assume they're not electrocuting people on the daily so whatever.

As so someone living in the US, I'm often amazed by most the rest of the world relying on outlets and plugs for safety, instead of safer voltages.

The US uses 120 V because it evolved that way historically, not because it’s safer. Europe’s 230 V systems have better plugs, grounding, and breakers, and they end up being just as safe in practice, if not safer.

US residential power distribution transformers are 240 V, with a center tap. There are sometimes 240 V plugs, when high-current appliances aren't hard wired. Usually that's clothes driers and ovens/ranges. Water heaters and central HVAC systems are usually hard wired to 240 VAC.

For everything else, where more than a KW or two is overkill, the plugs connect between the center tap and one output of the transformer, for 120 V. It gives the advantage of high power where it's needed, up to 12 KW peak or 9.6 continuous, without dangerous voltages where the power isn't needed.

Modern outlets do have all of the modern safety features, like shutters and arc or ground fault detection, but the more appropriate voltage means that when they aren't available, it's still safe. There's kind of a running joke for DIYers that everyone claims to turn the power off before rewiring outlets, but no one really does, unless it's a 240 V outlet.

The concept of not cutting the power before rewiring seems hogwild to me. I touched a 120v line I thought I had turned off and am really grateful my ass fell backwards because no one else was home

I blew a chunk out of my electrician's pliers with 120.

A near-retirement electrician died wiring up his wife's new mall store by himself with 120.

120 is usually safe-ish, but it has dangerous power still.

What brand of pliers were they, and did they seem to be made from recycled gum wrappers?

A trick I learned when you want to flip the breaker but don't want to go all the way back to the panel is to just stick a screwdriver into a light socket.

Heh. Or shaving blades [0]. Just don't touch the water!

[0] https://www.youtube.com/watch?v=MjJ1N4uJyV8

I remember reading (or watching) about these shower heads and IIRC, there is very little current making it's way into the water (or at least it wasn't traveling very far down the streaming water to reach the bather, I don't remember the details).

  I reckon if the mineral content were just right, it might not end so well though.

People in prison in the US use the same method to boil water for ramen/drinks on 120V household current.

One thing to be aware of: nichrome wire heats up. Solder melts with heat. So if you solder them together, and your nichrome wire gets hot enough, they will not stay attached. Hence commercial devices use a mechanical, crimp connection.

Probably not an issue for oven or cooking temperatures, but it is if you're working on hotter things like heaters or hairdryers and such.

Good luck soldering nichrome in the first place, though, at least without using some kind of crazy acid-core solder. You'll need to crimp it.

The article seems to recommend wrapping several coils of nichrome around the wire supplying electricity, and just globbing a load of tin solder on. Not ideal, I'd say.

Your standard electronics solder is not going to stick to nichrome anyway. You have to seek out special brazing materials and difficult fluxes to even get that far.

This article tries to use large solder blobs to mechanically trap the nichrome wire, which I don't recommend for the reasons above. You really should use a crimp connection.

The appliances I've opened up used spot welding.

So, not soldered.

Correct. Typical electrical solder won't stick to nichrome, and encapsulating the wire in a blob of solder sounds short term at best. If it's not a good connection, it will heat up and eventually melt the joint.

Crimps are also far more vibration resistant than solder joints, which is especially necessary with wire-to-board connections.

Just a nit pick... but

Don't all metals melt with heat...?

What I think you mean to say is that (some) solders melt at the temperatures that this heating device operates at?

Plenty of non-metal materials melt with heat, too. Solder is the only one relevant to the comment, which is presumably why it was the only one mentioned.

The description in the comment Im replying to - reminded me of the replaceable element in electric jugs, which where common during 1970s. The nichrome wire was meant to be replaceable , so had a mechanical connection , not soldered.

  Here is a good picture of what I have attempted to describe ....    https://www.lighting-gallery.net/gallery/displayimage.php?pos=-130368

That's not why they weren't soldered, as others have mentioned.

Or spot weld it.

> Probably not an issue for oven or cooking temperatures

Just looked it up and it appears that most soft solder(what we commonly think of as solder) melts around 400F (200C). so I would worry about a soldered joint in the hot part of an oven as well.

No short-circuit protection?

[Also, I don't like the quality of the images. How can I take their advice seriously if the images are barely viewable. It looks like someone actually made an effort to reduce the quality of the images. For artistic effect, probably. Don't do that.]

About the quality of the images, it's on purpose:

> By dithering, we can make images ten times less resource-intensive, even though they are displayed much larger than on the old website.

This is needed because the website is solar-powered and self-hosted on low-tech hardware, read more here:

https://solar.lowtechmagazine.com/about/the-solar-website/

I just took the original first image from the article and compressed it to a 37k JPEG, the same size as the dithered image, and it looks a lot better. They must be considering resources to display the image, not just file size and network bandwidth.

Images aren't like that for artistic effect, but for lower energy consumption.

> We further apply default typefaces, dithered images, off-line reading options, and other tricks to lower energy use far below that of the average website.

https://solar.lowtechmagazine.com/about/the-solar-website/

Ok, I didn't read that. But I still think it's _not_ a good idea to do that for a topic where personal safety is at stake. And besides, the quality is really too low anyway. I can barely recognize the thermocouples in those images.

How can I take your comment seriously if you didn't read the article? It looks like someone didn't actually make an effort to understand the context of the images.

At the bottom of the page:

Battery status 63%, not charging Power used 2.69W Uptime 5 weeks, 11 hours, 36 minutes

Traffic from HN may be a problem today...

>Uptime 5 weeks, 1 day, 3 hours, 46 minutes

Seems to have had no issue whatsoever! Even through the whole night period. Shows the depth of inefficiency of our 'advanced' systems.

> Battery status 44%

down from 63% yesterday but yeah, really good!

> It looks like someome actually made an effort to reduce the quality of the images. For artistic effect, probably.

They did, and it’s part of the footprint-reduction techniques used to host the site off solar full-time. https://github.com/lowtechmag/solar/wiki/Solar-Web-Design#im...

I don't know, they are making electric heaters.

Might as well use your server to generate some of that heat ...

That's fine for the main article but I think there should be a way to get higher quality images should the reader request them. If power is a concern those can be hosted elsewhere.

I think it's acceptable for the drawings to be compressed this way but the photographs are very unclear.

There is. Click the small pixely looking X at the end of the photo's caption.

I see. They should make it more obvious.

> No short-circuit protection?

That’s the first thing I noticed too. You can buy a 277VAC/60VDC 7A DIN rail miniature circuit breaker that can handle 7,500 amps of fault current for $20 [0] there’s no excuse other than ignorance for the lack of overcurrent protection. I only know how to use a calculator to figure out AC fault current but that should be enough to handle a solar panel.

It does mention an optional thermal switch and optional thermal fuse, my sauna stove definitely has a thermal switch and I’d include one if I was building this thing too.

[0] https://www.digikey.com/en/products/detail/phoenix-contact/1...

So glad someone responded to the main part of my comment.

I’m an electrical PM so the lack of overcurrent protection jumped out at me, I have to consider overcurrent protection for every single circuit I reason about, it’s mandatory and should be included in this installation.

The image part of your comment was nerd bait so everyone replied to that :P

I've always been curious how modern electric heating elements are assembled in a safe manner. I mean ones that use nichrome heating wire , inside a metal tube. The metal tube is packed with insulating material. Like how is the heating wire maintained in a position so it touches the smallish diameter metal pipe.

From Google - about how manufactured ....An electric heating element inside a metal pipe is a common design for tubular heaters, which consists of a resistance wire (often Nichrome) coiled in the center of a metal tube. The space between the wire and the tube is packed with an electrical insulator, such as magnesium oxide powder, which conducts heat efficiently while preventing the wire from shorting against the pipe. This design allows for durable, efficient heating as the heat is conducted from the element to the pipe's outer surface....

> I've always been curious how modern electric heating elements are assembled in a safe manner. I mean ones that use nichrome heating wire , inside a metal tube. The metal tube is packed with insulating material. Like how is the heating wire maintained in a position so it touches the smallish diameter metal pipe.

Probably in a very similar way to mineral insulated cables, if not the exact same process: https://en.wikipedia.org/wiki/Mineral-insulated_copper-clad_...

Lowtechmagazine is building a solar powered electric oven [0]. This is why they want to build an electric heating element that works on a relatively low voltage.

[0]: https://solar.lowtechmagazine.com/2025/10/how-to-build-a-sol...

This pairs well with their other articles on heating like one about using hot water bottles to heat people instead of rooms. https://solar.lowtechmagazine.com/2022/01/the-revenge-of-the...

Nichrome increases in resistance with temperature = choose the right wire gage and coil length and you can achieve a steady state at a particular voltage which will mean it will approach a temperature = not burn food, although this design does not look like it will have that problem - unless the insulation allows it?

Next article, how to mine your own nickel from scratch? "It's a lot cheaper"

Here's a similar approach for converting a trackball or mouse into a heated input device: https://rz01.org/heated-trackball/

Anything’s an electric heating element if you can jam enough current through it.

Heat-resistant electric cable. These electric wires are encapuslated in silicone mesh rather than plastic.

Silicone is not commonly used for this purpose. More common these days is fiberglass, and long ago it was asbestos.

It's a filter checkbox on McMaster-Carr when searching for High Temperature Cable. It also is the largest sub group in that category.

Why not use cast or wrought iron and fire bricks for a higher temperature rating? What you’d have then is basically a wood stove except with the wood replaced with electricity.

Some solution with a maximum power point tracking inverter would probably be a whole lot more efficient. But probably depends a lot on the exact resistances and panels involved.

But I guess that would go against the "low tech" spirit. And if panels aren't the limiting factor why not

I only half-humorously thought the article would include how to make the wire from ore, or at least a functional equivalent.

ElectroBOOM had the idea first and did it better.

https://www.youtube.com/watch?v=MrnCDKB1hE0

Reminds me of The Toaster Project

So many complaints about dithered images when they're effectively thumbnail equivalents, click on the pixelated X for the original, ffs people.

All in one subthread, which you didn't reply to.

Reply on news.ycombinator.com