Construction Heater Thermostat

[Daryl]

I have a 4800 watt construction Heater in my Workshop and would like to hook this up to a wall mounted Thermostat. 2 supply stores have told me I can use a 20amp baseboard heater Thermostat. Is this correct? The Heater is presently hooked up to a 30amp/220.

[mdshunk]

That heater draws exactly 20 amps at 240 volts. If you have anything less than 240, it will draw less current.

Most line voltage thermostats, such as the White-Roders 1A65W-641 or the Honeywell T498B1512 (top picks) are both rated at 22 amps resistive. You should be fine with one of those, unless you have excessively high voltage at your location.

[dznewz]

That heater draws exactly 20 amps at 240 volts. If you have anything less than 240, it will draw more amperage. If your actual voltage is 230, the heater will draw 21 amps.

Can you explain, please?

Why will the heater current increase with a voltage reduction?

[mdshunk]

It's just electricity math....

This heater is rated 4800 watts at 240 volts.

Using Ohm's law we can solve for the ohmic resistance of this heating element:

240 volts squared devided by 4800 watts equals 12 ohms.

This is a 12 ohm load. Now, using Ohm's law again we can solve for the current draw for this load at another voltage:

230 volts devided by 12 ohms equals 19.16 amps
220 volts devided by 12 ohms equals 18.33 amps

At these lower voltages, the effective watt output of the heater is reduced:

230 volts squared devided by 12 ohms equals 4408 watts
220 volts squared devided by 12 ohms equals 4033 watts

[Daryl]

Thank you very much I appretiate it, now if I could only spell. :D :D

[dznewz]

At these lower voltages, the effective watt output of the heater is reduced:

230 volts squared devided by 12 ohms equals 4408 watts
220 volts squared devided by 12 ohms equals 4033 watts

Thanks for the clarification.
Your earlier post said the current would increase at a lower voltage.