240 volt heater

[domnic]

If use 110 v for a 220 v heater i will get 1/4 the heat ?

 

[GoldDigger]

If use 110 v for a 220 v heater i will get 1/4 the heat ?

If you connect 120 volts across the same terminals as you would have connected 240, then P=V²/R tells us that the power going into the resistance heat element will be 1/4 the design amount. If there is a fan in the heater, it may not work well at all.

The wire typically used for resistance heating (unlike a tungsten light bulb filament) does not have a large enough temperature coefficient of resistance to affect the calculation much.

 

[Dennis Alwon]

How do you measure heat? Are you talking wattage?

 

[Dennis Alwon]

Given a 4800 watt heater at 240V then we can calculate the resistance-

240*240/4800 = 12 ohms

P = V*V/ R
P= 120*120/12 = 1200 watts

so yes the wattage is 1/4 the 4800 watt element

 

[Besoeker]

How do you measure heat? Are you talking wattage?

Heat is energy. Energy is expressed/measured in Joules. At least it is with SI units.
Simple. One volt times one amp for one second is a joule.
I'm working on getting you guys converted!!

 

[GoldDigger]

Heat is energy. Energy is expressed/measured in Joules. At least it is with SI units.
Simple. One volt times one amp for one second is a joule.
I'm working on getting you guys converted!!

Speaking of conversion, this website http://www.unitconversion.org/power/watts-to-joules-per-second-conversion.html gives you a convenient watt-seconds to Joules converter as well as the advertised watts to Joules/second converter. You type in a number in either box and it shows up in both boxes.
Accepted that conventionally heat is energy. But the output rating of a heat producing appliance is usually specified as the power of that appliance, whether in watts or in BTU/Hour. (The BTU is of course a unit of energy and not power.)

Given four times as long to work, the 120 volt connection will eventually have produced just as much heat as the 240 volt connection.

 

[Jraef]

You will get 1/4 the wattage out of the heater element. It's a resistive circuit. Power (W) = E²/R

So R (the heater element resistance) remains the same, and the voltage is 1/2, then 1/2 x 1/2 = 1/4

Example: 500W 240V heater, the resistance (R = E² / P) = 240² / 500 = 115.2 ohms

New voltage = 120V, so 120² / 115.2 = 125W.

New wattage: 500 / 4 = 125

 

[iwire]

I'm working on getting you guys converted!!

Good luck with that.

They tried forcing it on us in the 1970s and that pretty much failed.

 

[Besoeker]

Speaking of conversion, this website http://www.unitconversion.org/power/watts-to-joules-per-second-conversion.html gives you a convenient watt-seconds to Joules converter as well as the advertised watts to Joules/second converter. You type in a number in either box and it shows up in both boxes.

Interesting results, eh?

Accepted that conventionally heat is energy.

Not conventional. It just is.

But the output rating of a heat producing appliance is usually specified as the power of that appliance, whether in watts or in BTU/Hour. (The BTU is of course a unit of energy and not power.)

We Brits gave up on the BTU, British Thermal Unit, decades ago. The amount of energy required to heat a pound of water by one degF....
I'm old enough to have been educated in both Imperial and SI and I can convert from one to the other and often have to - my good lady likes to cook and bake. Recopies in Imperial, ingredients in metric. Stuff in fluid ounces just stated as ounces sometimes gets a bit difficult explain.....four ounces of breadcrumbs doesn't weigh the same as four ounces of butter.

 

[Besoeker]

Good luck with that.
They tried forcing it on us in the 1970s and that pretty much failed.

I had some experience with that.
We were trying to market some fairly big SCRs manufactured by a company in west coast USA.
I had the task of converting the catalogues to European format. Forty some years ago.
Page sizes were wrong, data on physical sizes needed converting.
But the biggest pain was redrawing the characteristics. By hand.
Now I have a variety of tools at my disposal that hadn't even been a blot on the horizon then.

 

[GoldDigger]

"Accepted that conventionally heat is energy."
Not conventional. It just is.

Well, if you want to get all thermodynamic about it (which I sometimes do), heat is not energy per se but rather one form in which energy can be transferred. Without transfer of energy from one body to another by thermal mechanisms, there is no heat present even though both bodies may have all sorts of energy including thermal. The dimensional units are exactly the same though.