if you have a single heat source under the middle, the edges may still freeze over,

This is where convection gets involved. Heated water moves away from the heat source. If it isn't moving enough, you need more heat.
The shape of the convection currents will depend on things like whether you use a point source, a ring around the perimeter, or an air cavity with a mostly uniform temperature of air. None of these things rely on heat sink grease. If the bucket doesn't absorb the applied heat fast enough, the temperature in a confined space will simply increase until it does. Simply put, equilibrium must happen eventually, and it doesn't take all day to do that.

I'm working with 30 years of experience as a State Certified thermodynamic designer and 10 years as a show dog breeder, but I don't feel compelled to micro-manage a dog water bucket. Just shove a heater under it and see if it's frozen in the morning. If fail, increase the energy input or the insulation on the bucket. If you want to listen to Doktor Jones, put some heat sink compound on the heater(s) and paint the bottom of the bucket. It won't hurt anything.

Where is your DOG kept outside when it is freezing cold?

I don't know about this guy, but the Eskimos leave their dogs outside in the most horrid blizzards, so it's probably OK in the lower 48. IIRC, this is about a Labrador. They come equipped with fur coats and are large enough to have an energy surplus, most of the time. They are also smart enough to hide from the wind chill effect. I expect the dog will go in his dog house, hide under a mobile home or a car, or find a corner somewhere to curl up with his tail over his nose. If all else fails, they are smart enough to scratch at the door.

 

OK, time for the peanut gallery to make comment. And it's OK to laugh at what I say - but:

I was thinking about grabbing an old microwave oven and stripping the high voltage transformer of its high voltage windings. Wind in a couple turns of somewhat large gauge wire to form a very low voltage source with rather high amperage. Take that wire and wrap it around the metal water bucket and create a dead short. I'm somewhat dubious of whether the transformer might overheat and self destruct, but in concept it might work. Given enough turns of heavy gauge wire around the water can may resist enough of the current to prevent overheating.

Now, regarding the metal bucket and the dog's propensity to chew things, and given that styrofoam is VERY chewable, I would probably opt for a metal can, larger than the metal bucket. Get some of that expandable foam that comes in a can and begin by making the cavity that will reside under the water bucket. If you go with a light bulb heater then mount that in the metal can beneath the metal water bucket. Set the water bucket on some sort of support so that it can be held up and not compress onto the light bulb. A trap door built into the outer metal can will allow access to the light bulb should you need to replace it.

Now, there should be space between the inner bucket and the outer metal container. Using the canned expandable foam, fill up the air spaces to the full point. Leave some space at the top so you can fashion a cover to prevent the dog from gaining access to the foam and install the cover.

You should now have a double steel wall, insulated water system with a light bulb in the bottom for heat. If you go with the microwave transformer and the heavy gauge wire you may find water temperatures getting a little too high. Using PWM to modulate the amount of power going into the transformer you might be able to reduce the amount of energy being used and bring your water to a manageable temperature. Using a thermocouple to provide feedback on the water temperature you might be able to modulate the PWM and control water temperature that way. Even using a simple stack of diodes can work as a temperature sensor of sorts. That diode stack would be series diodes, probably 3 to 6 diodes - I don't know the ideal number.

But all that sounds like a whole lot of work. Wouldn't it be easier to buy a heating pad and set the water bowl on top of it? Or like someone else said 'a chicken water heater'.

Everybody - remember that the dog likes to chew things up. My neighbor has two dogs that I felt very sorry for. Their dog houses consisted of holie sides, a large opening and the back was missing the bottom board. Air flow through the house was guaranteed. So we built an insulated dog house. Wood, foam, wood. One dog chewed through the wood and got to the foam. Then chewed through the back to the outside. How the heck a dog managed to chew a flat piece of wood is beyond me, but he managed. It was a Chow. Passed away now from other causes, old age and disease, my neighbor now has a hound/shepherd mix. Big and dumb as a dog can come but he's stronger than a country Ox. Tears EVERYTHING to pieces. Even the chain link pen, buried 12 inches into the earth, standing seven feet high, he still gets out. Had to put another chain link over the top like a roof. Even then he manages to pull that down fairly often and gets out. And I mean this dog is as sharp as a fuzzy tennis ball.

Me? I'm wondering about the transformer thing.

 

But all that sounds like a whole lot of work. Wouldn't it be easier to buy a heating pad and set the water bowl on top of it? Or like someone else said 'a chicken water heater'.

Why would anyone who owns a pet ask for something easy. Isn't that the whole reason to own a pet? It's like, "hey, honey, the kids are out of the house and our life is too easy, I need a pet to suck the life out of us." Or, I need a pet to have an excuse to leave work early. I need a pet so I can tell my relatives I can't travel to meet them for event x, y or z. I need a pet so my wife and I have a mutual enemy and, because 'the enemy of my enemy is my friend' theory, my wife and I have a reason to stay together. I need a pet, otherwise I have trouble getting my lazy ass out of bed - this way I am motivated to get up otherwise, I'll have to clean dog crap off of the carpeting. Or, I need something to spend $2700 on this month, I think my dog need surgery or some other expensive vet procedure. That is my view of dog owners.

If you think dog owners want something that is easy, they would pay for a lethal injection.

 

Have you seen the anti freezing pipe tape ?

http://www.ebay.com/bhp/pipe-heat-tape

self regulating,

wrap it around 'bowl' probably wrap that in something to keep heat in and protect from attack, wire under bowl out way .

 

anti freezing pipe tape

There you go. Even easier. Or that stuff you put on the roof to melt snow. Wrap it around your metal bucket and then insulate it from the outside. At temperatures below 40 degrees (I believe) they come on and melt snow off of the roof. Incorporate the controller into your thermal insulation and you have a system that will heat until 40˚ F. That's all Heat Tape is - a very long resistor.

 

There you go. Even easier. Or that stuff you put on the roof to melt snow. Wrap it around your metal bucket and then insulate it from the outside. At temperatures below 40 degrees (I believe) they come on and melt snow off of the roof. Incorporate the controller into your thermal insulation and you have a system that will heat until 40˚ F. That's all Heat Tape is - a very long resistor.

There you go again, still rambling on about "easier".

 

There you go again, still rambling on

HEY! I'm all about the "easier". If there's an easier way I'm all for that. At home I use the "Add Minute" button on the microwave instead of entering a 1, a 0 and another 0 and then pressing the START button. And I'll set it for 90 seconds as opposed to 1:30 because it's one less button to be pushed.

So why do I ramble on when I post? Paradox I guess.

 

HEY! I'm all about the "easier". If there's an easier way I'm all for that. At home I use the "Add Minute" button on the microwave instead of entering a 1, a 0 and another 0 and then pressing the START button. And I'll set it for 90 seconds as opposed to 1:30 because it's one less button to be pushed.

So why do I ramble on when I post? Paradox I guess.

OK, Mr. Easy, if that is how you run your life, I bet you don't own a dog.

 

Nope. Two cats. And we spend the bucks on them. Also own two gold fish. Spent 50¢ on them and spent $600 on their pond.

 

Hi, sorry first post.

I am trying to keep my dogs water bowl outside from freezing up. I know there are commercial products that can do this, but most of these are either very expensive, or they only hold a small amount of water.

I use this,

https://www.lowes.com/pd/Behrens-5-5-Gallon-Residential-Bucket/3452176

as his water bowl, its a 5 gallon, metal water bowl. I was under the impression, that i could use this

https://www.amazon.com/NTE-Electron...UTF8&qid=1481215322&sr=1-1&keywords=nte+dto60

inline to open or close a circuit that contained just a resistor and I could use thermal paste to attach the thermostat and the resistor to the bottom of the water bowl.

Then when temp falls, the circuit closes, the resistor gets hot, and heats the water bowl, then when water heats up, circuit opens. Rinse and repeat.....

Question is, what resistor should I use, or should I use multiple resistors.


Sorry for the very basic and laymans terms, but trying to get this solved before the really cold temps get here.

Do you have an old Mr. Coffee type (2 or 3 cup) coffee maker? You might consider taking the heater out of that.

 

Do you have an old Mr. Coffee type (2 or 3 cup) coffee maker? You might consider taking the heater out of that.

I think this guy's poodle froze to a fire hydrant so he gave up on the water dish.