Hey everyone got a question. I’m trying to build a small heating pad for my front porch but I’m having a hard time figuring out what I could use as a heating element. Any ideas?

 

What is the function of the pad, de-icing?
What Temp range?

 

Hey everyone got a question. I’m trying to build a small heating pad for my front porch but I’m having a hard time figuring out what I could use as a heating element. Any ideas?

For safety reasons and to save time and money, I recommend NOT reinventing the wheel and building your own.

An off-the-shelf heating pad would save you a lot of hassle if that's the sort of thing you're looking for. You might consider de-icing cable if you want just a mild warming.

 

Certainly creating a safe and long lasting heater pad would be a very involved process. I do not recommend it either.
First we need to understand the purpose, and also the anticipated temperatures, which vary a lot among the different localities of participants in this forum.

 

What is the function of the pad, de-icing?
What Temp range?

Trying to make a rollout cover that will cover my patio so I don't have to shovel snow.

 

...a small heating pad[.../QUOTE]

What does 'small' mean ?

 

Trying to make a rollout cover that will cover my patio so I don't have to shovel snow.

There is Raychem Chemelex heat trace cable.
What do you consider "Small"?
May be a hard task to solve efficiently.

 

There is Raychem Chemelex heat trace cable.
What do you consider "Small"?
May be a hard task to solve efficiently.

Probably 5’X10’

 

For 5' x 10', a couple of these :

 

Here's the snow melting cable I use on my roof.
https://www.amazon.com/gp/product/B0041TPRG8

It would work fine on a patio but would be laying there in plain sight. Not sure if that's acceptable.

 

For surface heating a radiant heat source is another option. It would avoid having anything electrical that would be subject to damage and become a hazard. Really, an an IR absorbing roll-out cover would not require any electrical connections and thus could be simpler and cost a lot less. And IR radiant heating is a mature technology with quite a few U.L Registered products available.

 

For surface heating a radiant heat source is another option. It would avoid having anything electrical that would be subject to damage and become a hazard. Really, an an IR absorbing roll-out cover would not require any electrical connections and thus could be simpler and cost a lot less. And IR radiant heating is a mature technology with quite a few U.L Registered products available.

How would it work if snow covered it though? Wouldn't it need light to reflect in order to be heated?

 

How would it work if snow covered it though? Wouldn't it need light to reflect in order to be heated?

The Chemelex cable is also used to prevent eave troughs from freezing up.

 

A radiant heater would be located above the area to be heated, so as to radiate the heat toward the snow to be melted. One additional consideration is that electric heating of cement walkways is terribly inefficient, and is seldom used by those folks aware of how expensive it is.

 

I installed a few of these systems, that were popular in the UK at the time, (they may still be!?)
They are Electric Thermal Storage unit, ETS for short, is a home heating storage device that contains several ceramic bricks.
A heating element runs between these ceramic bricks heats them up over night to a point that they’ve stored enough heat to keep the area of your home where the ETS is located comfortable all the next day.
A built in, thermostat-controlled, forced convection heater blows the heat stored in the bricks into the surrounding room. This keeps the temperature comfortable all day long.
They also employed the same method for in-floor heating.
The power was applied during the night (Off-peak), at a lower rate per unit of power.

 

One advantage with the Chemelex heat trace cable method, it is self regulating along its length, i.e. automatically controls along its length according to temperature at that point.

 

The TS was asking about a heating pad fora front porch, and as "covered with snow" was a possible condition, it would be exposed to the weather. quite different from one of those stored heat systems. A heated pad on top of a cement slab would lose a lot of heat by conduction, unless there were some insulation between pad and cement.
While it should be possible to calculate the heat loss through some insulating barrier, the total wattage required to hold some unknown surface temperature with some unknown ambient temperature with some unknown passing air temperature is beyond my scope of experience.
In addition, my concern for safety with a mains powered electric heating pad in a wet traffic area leads me to suggest a commercially made and UL accepted heating mat rather than building one..

 

Raychem has just about all eventualities covered, they have been around for eons!
https://www.nvent.com/en-us/raychem