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Cheapest path to electric heat a surface?

 
gardener
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Lately I'm intrigued by kotatsu and creating a micro-heat bubble. (This PEP)

In the above link they recommend using a dog bed heater to heat the surface you are in contact with, but on Amazon, I'm seeing these run like $60-$70!
Like, seriously!??  That seems like a lot for a loop of wire and some padding.

I was wondering if people had other thoughts or experiences concerning heating a surface. What will/won't work? Which is the cheapest way to go?

Just brainstorming options, ...
* dog bed heater
* electric floor heater (like those intended to go under tile floors like in bathrooms)
* heated floor mat/bath mat
* roof heating cable
* pipe non-freeze tape
* diy+ carbon heat strips (an example diy project
)
* electric blanket
* seed starter warmer
* ... others?

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steward
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I have no experience. However i imagine the seed starting mats would be the cheapest. Maybe depending if they are under your feet, you can put a blanket above them to keep the heat from escaping.

The mats will probably have different heat settings. This mat uses 18 watts.
Vivosun Seedling heat mat for 25.99
 
pollinator
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I had to go look it up, I thought your prices sounded way too high.  Last time I bought a pet heater was almost exactly two years ago and the price has tripled.
 
master pollinator
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jordan barton wrote:Maybe depending if they are under your feet, you can put a blanket above them to keep the heat from escaping.



Personally, I would be cautious. I think there is a potential fire hazard in covering an electrical appliance with an insulating layer unless it is specifically designed for it. A mattress pad may be an option for some things, but it's not designed to be stepped on. Home improvement stores sell electrical grids designed to be installed under a protective layer like floor tile.
 
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I feel this has a lot to do with what you are wanting to heat.

The title suggests a surface though it is mentioned to use a dog bed heater.

What is it we are trying to heat?

Paul talks a lot about heating people and I feel that has something to do with the micro-bubble concept so is this what is being discussed?

I sit in my pantry almost all day.  It is not heated in the winter though it is in the center of the house with no windows.  It gets cold so I stay warm by "Heating people".  Warm house shoes, layered clothing, and if it is really cold I might use an inexpensive heating pad.  To me, I am using the "Micro=bubble concept".

I use incandescent lights as heaters.  They also happen to give off a lot of light.  Which, in the winter where the days are short, is good for you.  So rather than a light bulb plus a heater, I get a two-fer.



https://permies.com/t/160/4906/making-electric-heat#56730

this is a good time to talk about dressing smart.



https://permies.com/t/160/4906/making-electric-heat#56454

This is the thread about creating micro heater:

https://permies.com/wiki/110283/pep-electricity/Create-Micro-Heater-Bubble-PEP
 
K Eilander
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UPDATE:
I'm trying out the seed starter mat idea now.

Situation: mat on carpet with blanket over legs. Temperature of about 30F(52C) outside, no direct room heat.

Not hot by any means (like a warm cup of coffee, maybe less), but noticeable and pleasant warming effect when barefoot or socks.

Heat is very consistent and builds slowly over time when trapped under blanket.

Pros:
quiet
cost - $10 or less
waterproof/spillproof (good for under kitchen table)
low power - 21W continuous.
no thermostat to fail
can be repurposed back for its intended use of starting seeds
I feel like there's virtually no chance of fire with this thing, even under a blanket.  

Cons:
Not a whole lot of heat produced (only 21 watts, remember)
Probably good for only 1 person. (just one may not be enough for full-sized kotatsu)
I'm worried about how it will hold up to being walked on, especially on top of carpet.

 
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Re cost  - you aren't just paying for a wire. At that price point there should be some kind of temperature control built in, and some protection against overheating and short circuit. It get the attraction of looking for low cost, but I'd be much more comfortable cutting corners of electrical/thermal safety in the green house where only plants are at risk, than I would in the home.
 
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How about a fishtank heater in a sealed bucket of water, or a sealed square box under your feet of some sort. they come in all sorts of wattage and you wouldn't be walking on them so no chance of damage.
 
Anne Miller
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Cheapest method, not mentioned previously:

Sit with a dog or cat next to you or on your lap. Then wrap a blanket around your shoulders, including the pet.

I use my dog when I am asleep at night, I call her a heating pad.
 
Michael Cox
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Anne Miller wrote:Cheapest method, not mentioned previously:

Sit with a dog or cat next to you or on your lap. Then wrap a blanket around your shoulders, including the pet.

I use my dog when I am asleep at night, I call her a heating pad.



 
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Fun thread here. One more idea for riffing: microwaveable flannel rice bags. I've sewn long snakes filled with rice, buckwheat hulls, lentils or mung beans for wrapping around my neck like a boa. Microwave until warm. Or heat the flannel rice bags in a crockpot or Dutch oven.
If you want to make a foot warmer, try putting those small lava gravel pieces in a pan in the oven or on the wood stove. When warm, pour the lava-gravel into a flannel pillow case and tie. Snuggle your feet into the fabric cover.
 
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Amy Gardener wrote:Fun thread here. One more idea for riffing: microwaveable flannel rice bags. I've sewn long snakes filled with rice, buckwheat hulls, lentils or mung beans for wrapping around my neck like a boa. Microwave until warm. Or heat the flannel rice bags in a crockpot or Dutch oven.
If you want to make a foot warmer, try putting those small lava gravel pieces in a pan in the oven or on the wood stove. When warm, pour the lava-gravel into a flannel pillow case and tie. Snuggle your feet into the fabric cover.



I just took my favorite(aka biggest) one to my neighbor's daughter to use. I made it more than a decade ago, and the whole family has used it. I think it's time to make up a bunch of them, to give as gifts!
 
Amy Gardener
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And I’m thinking about how to heat dry rice in a flannel bag with something electric. And while sitting here at this hammered copper kitchen table, I’m getting super cold! Encouraged by this thread to get creative with electric objects, I walk over to the pantry and grab my little $15 Oster single burner electric hotplate and flip it burner side down onto the copper table top. Low is okay (heat radiates out about 18” from the burner. Medium is amazing! In 5 minutes, the entire 4’ diameter table top is warm (well above 98.6 F) and so am I. On the negative side, the hot plate uses 900 W. Fortunately, I only used it for 5 minutes. The wooden 1.5 inch wooden surface under the thin layer of copper must be insulating because the top is still warm after an hour.
 
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I've brought up the idea before about using a loop of nickel chromium wire or the like, embedding it into whatever it is that needs heating, and applying just enough electric current to get it to warm without burning anything up.  I'm not an electrical engineer, so I'll leave that up to the guys with the know-how to chime in on that.
 
jordan barton
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After mr.barton finished taking his apple pie out of his electric oven. He put the pie over near the window to cool down. Next he turns around and grabs something out of the oven.

Well what do you know it is his fashionable brick shoes. straight from the oven! He turns to me and says.
"Martha, there is nothing like a freshly baked apple pie, however the ways me feets feels after wearing my brick shoes makes me warm and fuzzy all over!"

Next thing he dons the brick shoes!



Ooooh Mr. barton what will he think of next.

Hahah!
 
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Another possibility is, conductivity and infrared heat from a light.  That way, you can walk on the heat conductive surface all day and not worry about problems mentioned above.

Granite fabrication places have, literally, tons of granite they have to dispose of, so it is free for the taking, upon request, from many.

If a person wanted, they could cut the granite down just using a circular saw and a diamond blade.  All it takes is a dribble of water to keep the blade cool. I've gone this route for pieces too big to cut on my tile saw many times. Of course, you have to apply common sense rules when using electric tools around water.

If need be, you could layer something like diatomaceous earth on top the stone, to act as insulation against heat loss in areas not used for the actual heating process and just to get the heat from the lamp to point B.


Somewhere on the Net, it may have been on the Instructables web site, I saw plans for making your own heater for dog dishes. Large 10 watt resistors were laminated to the bottom of a galvanized trough.

If I were going that route, I'd opt to toss in ground fault protection and a way of monitoring how much voltage I was pumping into the resistors (e.g., a volt meter) and a means of checking the heat (e.g., a laser thermometer).

The latter would require an investment, but would have all sorts of uses.  You could start with a Variac and feed it to outlets AND a rectifier module, for DC outputs [along with a DC meter].  Power lights for clear indication of power in and out could be handy too.  

Circuit-Drawing-2.jpg
[Thumbnail for Circuit-Drawing-2.jpg]
Power-Supply-2.jpg
[Thumbnail for Power-Supply-2.jpg]
 
K Eilander
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Another interesting option... what about using a homemade "sand battery" as a foot warmer?

Sand would be super comfy on the toes.  Your own personal tropical beach!

Like this, only lower voltage...

 
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A lot of folks here use old school incandescent Christmas light strings to put out enough heat to prevent things like citrus trees and bananas from freezing in our occasional freezes.

Possible adaptation for heating humans and other things?

You could regulate it ghetto style via screwing in/unscrewing bulbs for more or less heat or, if we're going fancy,   a dimmer would work, this is a link to an inexpensive one but it's not able to handle the wattage of an entire string of lights...which is to say figure out your wattage and buy a dimmer accordingly.:

https://www.amazon.com/Lutron-Credenza-Halogen-Incandescent-TT-300H-WH/dp/B0000BYEF6/ref=sr_1_1?

You'll want the C 9 larger bulbs, like this:

https://www.amazon.com/Clear-Christmas-String-Light-Set/dp/B009CZVM2Y/ref=sr_1_4_sspa?

Amazon has them in colors too if you like things a bit more lively:

https://www.amazon.com/Multicolor-Christmas-Incandescent-Roofline-Decorations/dp/B08CZR44SF/ref=sr_1_29?
 
Kelly Craig
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Another possible alternative to using nichrome wire (heating elements) MIGHT be, a parabolic lens.  

I have a large screen television parabolic lens, which has to be stored carefully, because a bit of sunlight shown through it can be enough to melt a brass padlock. In other words, it concentrates enough energy from the sun to do some major heating and could, easily, take out a shop, garage or house, if not stored right.

I long wondered about burying a culvert vertically in the ground, filling it with basalt rock and focusing the beam of the parabolic lens on it.  

Mindful of that heat rises, piping could be ran through the basalt to allow the heat focused on them and the liquid in them to transfer to radiators inside a green house or other structure.



K Eilander wrote:Another interesting option... what about using a homemade "sand battery" as a foot warmer?

Sand would be super comfy on the toes.  Your own personal tropical beach!

Like this, only lower voltage...


 
Carla Burke
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Thomas Tipton wrote:I've brought up the idea before about using a loop of nickel chromium wire or the like, embedding it into whatever it is that needs heating, and applying just enough electric current to get it to warm without burning anything up.  I'm not an electrical engineer, so I'll leave that up to the guys with the know-how to chime in on that.



Many people couldn't use it at all, if the nickel or chromium (or, in my hubby's case, both) were even the slightest bit exposed, due to allergies. Nickel, in particular, is notoriously hyper-allergenic.
 
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K Eilander wrote:Lately I'm intrigued by kotatsu and creating a micro-heat bubble. (This PEP)

In the above link they recommend using a dog bed heater to heat the surface you are in contact with, but on Amazon, I'm seeing these run like $60-$70!
Like, seriously!??  That seems like a lot for a loop of wire and some padding.

I was wondering if people had other thoughts or experiences concerning heating a surface. What will/won't work? Which is the cheapest way to go?

Just brainstorming options, ...
* dog bed heater
* electric floor heater (like those intended to go under tile floors like in bathrooms)
* heated floor mat/bath mat
* roof heating cable
* pipe non-freeze tape
* diy+ carbon heat strips (an example diy project)
* electric blanket
* seed starter warmer
* ... others?

IMG_20221120_173401.jpg
More energy efficient than baseboard
More energy efficient than baseboard
 
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Lately I'm intrigued by kotatsu and creating a micro-heat bubble. (This PEP)

In the above link they recommend using a dog bed heater to heat the surface you are in contact with, but on Amazon, I'm seeing these run like $60-$70!
Like, seriously!??  That seems like a lot for a loop of wire and some padding.

I was wondering if people had other thoughts or experiences concerning heating a surface. What will/won't work? Which is the cheapest way to go?


The

 micro-heat bubble.

Idea was pre RMH days so obviously the current appropriate technology is a miniture RMH if you do not have the space for a full sized one.
Another posible need is needing a small warm work space in a large workspace that should not be heated or is open on the sides.
 
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I just bought a meat defrosting tray for my wife for Christmas - an aluminum tray that I believe is reinforced to hold the weight of the meat as well.  I like the concept of adding the piping hot water into the tray under the aluminum plate to quickly spread out the heat to another surface.

With water heated from a RMH or rocket stove, I feel like this would be a very efficient way to heat a surface, especially if you've ever had the experience of pouring hot water into an aluminum can before!
 
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