The correct answer to this GURANTEED first question your
electrician is going to ask you, would depend on two factors: How many Watts, and whether 120 Volts or 240 Volts is used. Total Amperage
(current) can easily be calculated from the formula

E.g. The system is made of several mats. Each is
100W, voltage is 120V, so Amperage is:

100W/120V = 0.83 Amp. FOR EACH MAT!

The total Amperage of the system is the sum of the
individual components (mats). Two 100W mats = 1.66 Amp, Three 100W mats = 2.5
and so on…

SCENARIO: You have 3 of 480 Watts 120V
mats in the floor. The electrical receptacle in the bathroom is on the same
circuit as the floor heating. Then someone plugs in a 1600 Watts hair blower.
How much current would all of it draw? And don't forget about the 100 Watt
ceiling light!

What is wrong with this picture?

Answer: A dedicated line
was and is needed!

**Never allow for overloading of existing
lines!** ...and this is why your electrician is going
to ask you about Amps for this new floor heating idea of yours.

HINT: Installing
one couple hundred Watts mat is well within the abilities of a
handyman but it is often too much when large systems are planned. Seeking advice
of a licensed electrician before ordering heating mats may prove invaluable as
many installation scenarios require correct assessment of the existing circuits
and electrical panels.

Where all this science comes from? Ohm's Law, but Mr Ohm
wasn't a lawyer: |

Note that **P **from the formula above is being represented here
by **W **(Watts):

###
__OHM'S LAW EQUATIONS__

__OHMS__
VOLTS ÷ AMPERES
VOLTS ² ÷ WATTS
WATTS ÷ AMPERES ²

__VOLTS__
SQRT ( WATTS × OHMS )
WATTS ÷ AMPERES
AMPERES × OHMS

__AMPS__
VOLTS ÷ OHMS
WATTS ÷ VOLTS
SQRT ( WATTS ÷ OHMS )

__WATTS__
VOLTS ² ÷ OHMS
AMPS ² × OHMS
VOLTS × AMPS

__Few not so trick questions:__

*Ever wonder why your car jumpstart cables are so
***THICK **?

Because Volts are so low! The car has only 12 Volts
electrical installation! Because of low Voltage the Amps are quite high,
thus: a physical need for thick cables! By the same token that is why home
appliances using lots of Watts (wall AC's, kitchen range, electric boiler etc)
are using 230-240V Voltage! Look at the plug! It is different!

*Can you use the spare bulb from your car on the porch
light?*

Although it seems like a ridiculus question: *why not?*

It will not fit but even if it will unfortunatelly it will
only last fraction of the second. This said, you would not want to bother
or take the chances like this.

Your house electrical installation uses 10 times more Volts as
your car! The bulb would burn out right away!

By the same token **if the floor heating mat or cable is
meant for 110-120 Volts i cannot be used with 230-240 Volts!** It will
most likely last longer than seconds or even weeks, but not very long all.

Example #1, if you wish to find the watts ( W ) of a
circuit and you know the voltage ( E ) is 12 volts and the amperage ( I ) is 4
amps substitute the numbers into the equation:

W = E × I ..... W = 12 × 4
...... 48 watts

Example #2, if you wish to find the amperage ( I ) of a
circuit and you know the voltage ( E ) is 12 volts and the wattage ( W ) is 200
watts substitute the numbers into the equation:

I = W ÷ E ..... I = 200 ÷ 12
...... 16.66 amps