# Heating Element in series vs in parallel pros and cons

#### mfizz

Joined Mar 11, 2019
4
Hi,

Newcomer to electronics trying to understand some basic principles. I see most underfloor heating or any heating for that matter that is powered directly by the power outlet is a long piece of insulated resistance wire (heat wire) placed in a snake like shape on the floor.

My question is what determent would it be if i were to wire it up in parallel. If one of the wires (resistor) breaks it would mean the rest of the wires can still have power and continue producing heat.

Assuming an AC supply of 110v 60Hz

Thanks
work.

#### AlbertHall

Joined Jun 4, 2014
9,047
In the series connection, each element will get 1/5 of the supply voltage. In the parallel arrangement each element sees the full supply voltage.
That will result in a 25 times increase in the power dissipation in each element. That is likely to cause damage quite quickly.
[EDIT] Unless of course they were designed for parallel connection.

#### mfizz

Joined Mar 11, 2019
4
Thanks for your response. From a design point of view then it would be quite dangerous to have AC supply of 110v in parallel however a dc12V might not be so bad?

#### Yaakov

Joined Jan 27, 2019
1,612
Thanks for your response. From a design point of view then it would be quite dangerous to have AC supply of 110v in parallel however a dc12V might not be so bad?
Since there is a proportional relationship between voltage and current you will be increasing the current requirement be about an order of magnitude. The power supply to provide 12VDC at sufficient current will be large and expensive.

If you have 120V and need, say, 1200W, you'll end up with 10A. If you have 12V and need 1200W, that's 100A. See the problems?

#### mfizz

Joined Mar 11, 2019
4
Thank you for your response. So, if we bring it down a level and perhaps convection heater is not the best example, but rather if the goal is a uniform heat supply, lets say a hot plate, or a heated blanket. Modern heated blankets run on DC supply, i am assuming the wattage required there would be about 32w meaning but they too would be probably be wired in series and not parallel correct?

Out of curiosity how does one model AC supply from mains 110v 60hz in LTSPICE? Are there other parameters that need to be considered?

#### Alec_t

Joined Sep 17, 2013
10,746
Out of curiosity how does one model AC supply from mains 110v 60hz in LTSPICE?
Use a voltage source with the parameters amplitude = 110 x √2 = 155, frequency = 60, and series resistance = a fraction of an Ohm, e.g. 0.2Ω.

#### Sensacell

Joined Jun 19, 2012
2,544