# Power cord routing



## tweeds (Jul 8, 2018)

hello, I'm in the process of building a double stacked enclosure out of MDF that I'm going to heat with heat cord under tiles. The question I have is what is the best way to run the power cord? I was thinking about drilling a hole just big enough to accommodate the cord, cut plug off then "have an electrition" reattach plug once I've fed it through the hole. Or is there a better way, or a reliable grommet of some sort?
Regards Alan


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## Bluetongue1 (Jul 10, 2018)

I am not quite sure what you are thinking here. There is no need to place a plug inside the enclosure. The length and wattage is given for a heat cord heating element. There is normally two metres of cold lead i.e. non-heating power cable, like all electric heaters have so plug them in and then position them where you want to. The end of a heat cord is slightly thicker than the rest of the heating element, and so all you need is a hole drilled in the back corner (where you intend to place the heat tile) large enough to fit that through. The heating tile can then be assembled inside the enclosure.

Here is some info I put together a while back on how to make a heat tile…

*Moveable Heat Tile*
A 30cm square slate or ceramic tile using all the heating element of a 15W heat cord will produce a stable temperature of close to 35 degrees C at room temps in the twenties. These tiles are sufficiently good conductors to spread the warmth evenly before it reaches their surface. They also have high specific heat, which means they need a lot of neat to raise their temperature. So while slow to warm up, a cold reptile lying on a warmed one can draw a significant amount heat for only a small drop in tile temperature.
To keep the heat cord evenly spaced under the tile, a grooved sheet of MDF about twice the thickness of the cord, and the same shape as the tile, can used. As wood is a good insulator, this helps direct the heat into the tile. For a wood base, starting 1cm in, cut parallel grooves at 2cm intervals right across the entire face. Repeat at right angles across the top and bottom end with 4 or 5 grooves. The grooves can be cut with a straight saw blade to the same depth as the cord is thick, and slightly wider to allow for bending around corners. The tile and base can be held in place, but still be easily separated, by using Blutack or a wooden edging on the base. Note that all wood must be sealed to make it water-proof for cleaning. The temperature can be reduced by routing less of the heating element under the tile and letting it hang out the back of the enclosure. Larger heat tiles can be made the same way, using larger or multiples tiles, an equivalent sized bas and a higher wattage heat cord.

*Additional Note*
It more energy efficient to use an insulating layer underneath, such as wood or firm Styrofoam, rather than another tile. Corflute, the stuff they use for light-weight outside ads, such as ‘house for sale’, can be used instead of cutting channels in wood. Just cut it a little bit smaller than the tile and for the heat cord mentioned here, simply weave it through every second core. If you have animals capable of chewing, then any electrical cable should not be left exposed. If necessary, it should be covered using conduit around it or metal tape to fasten it securely to the enclosure base &/or wall.


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## tweeds (Jul 17, 2018)

Bluetongue1 said:


> I am not quite sure what you are thinking here. There is no need to place a plug inside the enclosure. The length and wattage is given for a heat cord heating element. There is normally two metres of cold lead i.e. non-heating power cable, like all electric heaters have so plug them in and then position them where you want to. The end of a heat cord is slightly thicker than the rest of the heating element, and so all you need is a hole drilled in the back corner (where you intend to place the heat tile) large enough to fit that through. The heating tile can then be assembled inside the enclosure.
> 
> Here is some info I put together a while back on how to make a heat tile…
> 
> ...


 
Thanks for reply, I like your idea concerning the heat tile. I was going to do something similar, but was thinking of permanently attaching the tile to the routed piece of MDF. I understand what you're saying about running heat cord through small hole and building it in situ. Seems a good idea, but once it's in, it's in. I was just interested to see if there was a grommet of bulkhead of sorts that would facilitate the removal of an assembled heat tile.


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## Scutellatus (Jul 17, 2018)

tweeds said:


> Thanks for reply, I like your idea concerning the heat tile. I was going to do something similar, but was thinking of permanently attaching the tile to the routed piece of MDF. I understand what you're saying about running heat cord through small hole and building it in situ. Seems a good idea, but once it's in, it's in. I was just interested to see if there was a grommet of bulkhead of sorts that would facilitate the removal of an assembled heat tile.


You can get stretchable silicon grommets that have a solid plastic ring around them, they are used in plumbing and gas fitting. You may be able to find one the right size for your needs.


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## Bluetongue1 (Jul 19, 2018)

tweeds said:


> Thanks for reply, I like your idea concerning the heat tile. I was going to do something similar, but was thinking of permanently attaching the tile to the routed piece of MDF. I understand what you're saying about running heat cord through small hole and building it in situ. Seems a good idea, but once it's in, it's in...


The whole idea is to NOT permanently affix the tile to the base. Given the cord is simply pressed into the grooves in the base, it can easily be pulled out and re-routed or removed entirely from the enclosure for use elsewhere – hence the title “Moveable Heat Tile”.

The reason for having it non-permanently fixed is to allow it to be adjustable, in order to allow one to alter the temperature of the tile as and if required. This is done by changing the amount of heating element routed into the base under the tile. Any ‘excess’ heating element simply hangs outside the back of the enclosure, where the heat is dissipated harmlessly into the surrounding air.

I can see no reason for permanently affixing one to the other. If you use the thin wooden edging tacked around the outside edge of the wooden base, then the only way to separate the tile from the base will be to lift the whole thing, turn it upside down, and then shake the tile out. Why have a hole the size of a plug that an occupant could possibly escape through if not properly locked in place, when you can have a tiny aperture that there is no chance of it getting through? If loss of substrate is a potential problem through the small hole remaining around the cord, a standard rubber grommet of the appropriate size and thickness will easily fix that.

That’s the pro and cons that I have considered in the design given. I think it’s important to provide those so that you are fully informed prior to making a decision. At the end of the day the choice is yours and I respect that. Good luck with it, whatever you decide on.


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