Cement Block Heater for Feet

[iFred]

what is it, what is it???

I sit by my computer pretty much a lot and do programming mostly.

In any case, I remember an old friend of mine about 3 years ago came up

with a neat way to keep feet warm, I thought at the time he was smart for

thinking it up. Lately as I get older, I noticed that my feet also are constantly

cold, so what to do. I could buy a small foot warmer, but the problem with them is that they run all the time, and really waste the energy, and I would have to buy it...

What your looking at is a cement block about 2 to 2.5 inches thick and about 1 x 1 ft wide. embedded in the cement is a 500 watt stove element. I made up some cement, found a cardboard box, laid a little bit of styro down for support, then poured about 1 inch of cement in, next I cut up some coat hanger wire and layer them across for more support, and laid the heater on top of that. Then filled the rest up with more cement about an inch or so. let dry for one week. Solder wires to a cord and heat it up, then let cool, do this a couple times to get the mosture out.

Does it work well... OHHHH YEA!! Nice and warm in a blanket for about one hour before another preheat, which takes about 3-4 mins of heat. Done..

So very efficient I think, so do my feet.

[skravlinge]

Very nice device. I sometimes heat a flat slate  by the stove, you get warm twice, once when you move it and once when it release the acumulated heat.

[wooferhound]

Too Cool ,  Now it's time to do the whole bathroom floor.

You need a temperature sensor in the cement too, so you can have automatic heat control.

I'm thinking that cement is conductive to electricity, so you should insulate your connections real good.

[iFred]

The connections for the stove element come right out of the cement, when I was building it I poked them out and pushed them through the cardboard box, just the two connection points. Cement when dry is not conductive. Only water would be if the block was wet. Maybe just a reostat or lamp dimmer might do....ummmmm

[picmacmillan]

hi fred......you are right on......everything you touch turns to paracticality...you should be on monster garage.....you could make some pretty cool stuff....you're house is like the bat cave....nobody ever knows what goes on in there until POOOOWWWWW! out comes something cool....happy new year...pickster

[chux0r]

Dude... I just put my feet on the COMPUTER!  Those things have heat sinks for a reason.  It's because they generate heat!

You could even argue that this counts as cogeneration, since the heat would otherwise be wasted... (or wasted more!)

Of course mine's a Pentium 4, which is basically the same as a stove heater element.  Your computer might not be so generous.

[iFred]

HE HE... Thats a good one, but I got yea beat! LOL

I have p4 2.8 ghz. I am a tech after all.

But I still would love to see a picture of how you warm your feet on your little tiny heatsink! LOL

[Ungrounded Lightning Rod]

A couple decades back I got my first Unix box.  (The whole net's email site list fit on 3 pages in those days.)  It was an Altos 68000.  The thing made all too good a space heater.

The venting consisted of a 4" muffin fan exhausting the box.  So I got a couple dryer vents, some hose, and some wood.  Cut up one dryer vent to make a fitting that I mounted over the 4" fan to hook the hose to it, made a replacement for the window screen with the other vent mounted in it and hooked the hose between the two.  Venting the heat outside dropped the room temp about 20 degrees without adding an air conditiner.

I also added a diverter valve to switch to a floor vent in the winter.  Never had to heat that room.  B-)

[tecker]

 

  My electric socks pale in comparison the bats can't keep all night . I look like a fool with a car batt in tow.

[bob golding]

hi fred. my answer is to  put the bed next to the stove and  get under the covers with the laptop on my, err lap. stove keeps  my arms warm, bed keeps my  feet warm ,cat does that as well when she is in the mood, plus i also keeps a gallon pot of water on the stove top for when the fire dies. luckely this part of south west england doesnt really get that cold for long. watch the chillblanes.

bob golding

[Jeff7]

I'm not so sure about cement being nonconductive.

Our house had lousy wiring - there were a few outlets with hot and neutral reversed, and a few others without grounding.

While standing barefoot on a concrete floor, working on a computer, I noticed I'd get a mild shock from the case if I touched it. As soon as I got off of the floor, which is always quite dry, then there was no shock. A voltmeter to the case, and with the other contact firmly pressed into the floor, I registered about 5VAC. Once the outlet was grounded, the shocks of course went away.

But it appears that the concrete, at least here, is a little bit conductive. I found that rather odd too.

[nothing to lose]

That is a cool idea!

I think I will build a few of those for here! We get cold feet all the time at the computers too. Mine are cold now actually!

Seems that's one place the air does not circulate well, under the desks, and of course they are all on an outside wall also. 3 peoples and 3 systems.

Since you have made one like this, what would you think about using a heat element and probe from like a deep fryer, crock pot, or similar kitchen device. You can often get them almost free at yardsales and thrift stores. They have the temp dial and probe so you can set them from about 200F to 450F. Maybe either take one apart or just cut the bottom around the element part and cast that in the cement. Plug the control in when needed to warm and take it off when not needed. Could also be heated on a wood burner when available. With removeable cord no need to worry about melting it.

Hmm, would you mind if I market these next year

NTL leather clad thermal foot pad,

Variable adjustable removeable temp control

Removeable concrete insert for stove top or woodburner emergency heating.

If I can find it I do have one of those crockpots that still works, it got bent or something, I no  longer use it for food anyway. Maybe I was melting wax in it for casting before or something. I'll try that.

[jimjjnn]

You will get shocked standing on cement floors as they always have a small amount of moisture and rebar in them. Dry cement is non-conductive the way iFred is doing. It has no direct contact with earth ground and is dry and without rebar. I think in iFred's case, I would still run a grond wire in the power cord fastened to a small piece of copper pipe imbedded in the concrete to ground any stray currents that may exist

[iFred]

Go for it, do whatever you like, but make it cheap! use whatever you have laying around or can salvage for free. Check out some junk yards or salvage yards and hunt for good stuff! Enjoy and let me know how it works for you.

P.S. make sure that you use lots of breaded or chicken type wire or fence, the cement when it gets hot tends to fracture into ruble. Support is critical. I will also be making another one and that will be thicker. I estimate around 3-4 inchs or so. And the cement I have to figure out a way of making it even stronger. So, make it really strong if your going to do it.

[nothing to lose]

One thing they use at the cement companies is fiberglass. I think it was about $5 a yard more to have it added to my mix for a slab I had poured. I think this was just shredded stands like loose hairs. Didn't pay alot of attention. Supposed to make it alot stronger, I was pouring a slab on a graded drive with nothing in it for support so I had the fiberglass added then So far only about a year or less but all weather and lots of heavy cars on it and it has not got one crack yet. About 5" thick, 10'X20'.

Had fairly heavy truck on it a few times also. I really expected cracks by now, but glad I don't have any yet