Electrical question

RESLLS

Well-known Member
Looking at electric baseboard heater. Question is. Two heaters have same output wattage. #1 is 120v, #2 is 240v. #1 uses 8.3 watts, #2 uses 4.1.
Is the 4.1 per leg/line so would equal 8.2 or is it only 4.1 together? Can't see how it would use half the power to produce same BTU. If indeed 4.1 for both lines together it would cost half as much to run, right? Thanks for the help. Bob
 
P (watts) power equal E voltage times I current. Watts is what you are paying for. Current draw is 1/2 for 240 volt but you draw from both legs. What wiring 240 volts allows you to do sometimes is run smaller wire plus get a better load balance.
 
In theory using 240 volts will save you $$ in the long run due to the fact at 240 volts things tend to work a bit better so also saves $$ over the long haul.
 
Hello reslls,

They are both about the same capacity, just different voltages. 120v x 8.3amps = 996 watts

The 240 volts draws 4.1amp total. So 240v x 4.1 amps = 984 watts,

Guido.
 
1 kw-hr us = to 3412 BTUs. The voltage and amps doesn't really matter, it's the watts and time, ENERGY.

If you think about it, solar collectors use a very large bank of batteries, so you could make heat with light bulbs and batteries if you want. Better have a lot of batteries.

240v doesn't make it cheaper. 110v heaters are for people who don't want to hard wire 220v heaters or don't know how.
geo
 
Looks like you have confused Amps with Watts. Electric resistance strip heaters produce around 3.41 BTU/Watt.

Power in Watts = Volt x Amps

The 120 Volt unit at 8.3 amps = 996 Watts = 3396 BTU of heat DRAWS TWICE THE AMPS AS THE 240 VOLT UNIT

The 240 Volt unit at 4.1 amps = 984 Watts = 3355 BTU of heat DRAWS HALF THE AMPS AS THE 120 VOLT UNIT

LOOKS LIKE THEY BOTH MAKE ABOUT THE SAME AMOUNT OF HEAT AND EITHER COSTS ABOUT THE SAME TO OPERATE AS YOURE CHARGED FOR WATTS X HOURS OF ELECTRIC ENERGY

A typical small 120 volt electric heater is around 5000 BTU so what youre looking at isnt very big you know???

Which would I choose as a former electrical power distribution design engineer???

I would use the 240 volt unit which only draws half the amperage so as to reduce I Squared R energy loss in the wiring. SUBJECT TO the ease and availability and existence of a 240 volt circuit or panel nearby.

NOTE if you run a branch circuit to feed a single 240 Volt 4.1 amp unit, even though only 6 amps of ampacity is necessary, I would stull run 12/3 wire (NOT 14 Gauge or less) which has two hots (240 volts between Red & Black) plus a ground WHICH IS RATED FOR 20 AMPS OR A 16 AMP MAX CONTINUOUS CURRENT LOAD.

There are old wives tales among some lay persons or those electrically challenged that any 240 volt circuits must be 30 amps and use 10 gauge wire NOTTTTTTTTTTTTTT If the heater draws 4.1 amps and that's all on the branch circuit you dont need 10 gauge wire !!!!!!!!! The wire must have an amapacity of no less then 125% of max continuous load

John T Electrical questions draw a lot of responses as typical
 
#1 uses 8.3 amps, #2 uses 4.1 amps on each leg, adds up to 8.2 amps. The electric company doesn't give anything away.
 
not true in this case old. A baseboard heater is a pure resistive load so the power factor issues that you are referring to don't apply. Old would be correct if this were a motor.
 
Even in a heater 240 volts does save because it is more effect use of power which save all be it a very small amount but saves any how
 
John T,

Wouldn't the I squared r loss be energy in the form of heat? If the wiring is in the walls of the area you want to heat, then the "loss" is not really actualized?

D.
 
sorry Old but you are wrong. If you want more information about it go here: http://www.allaboutcircuits.com/textbook/alternating-current/chpt-11/true-reactive-and-apparent-power/
 
You are indeed CORRECT if all the wires and resultant I Squared R heat are in the area that needs heated NO PROBLEM but often the wires are in the garage or crawl space or attic or no tellin where lol and its NOT heating the room the heater is in

VERY GOOD POINT YOU RAISE

John T
 
dr is correct: In a closed circuit, 240 VAC Source to Load and return, there's NOT different amps in each leg WELL DUH

John T
 
ma is correct. A pure resistive load (electric resistance heater) has a unity ONE Power Factor unlike an inductive (such as a motor) load with maybe an 80%to 90 +% Power Factor

John T Retired Electrical Engineer
 
John T. little ot, but still electrical.
What size of conductor is necessary to handle a 50 amp draw ?
thanks
 
Cannot agree just the fact it uses as little as 0.001 amp less due to being 240 instead of 120 is enough to save $$ over time. Ya maybe not enough to notice as such but it does save. I was an E.T. at one time so electronics is something I have studied over the years and have forgotten more them then most people have ever learned
 
I put in baseboard heaters about 2 years ago. The 4foot 120 volt, 1000 watt, 8.3 amp puts out 3412 BTU. The 4 foot 240 volt, 1000 watt, 4.1 amp and puts out 3413 BTU. There's a big difference in BTU out put when you go to a 6 foot heater. The 120 volt, 1500 watt,12.5 amp puts out 5,118 BTU and the 240 volt,1500 watt, 6.3 amp, puts out 6,826 BTU. The heater I have used are made by Marley and so far so good.
 
The general answer if 6 Gauge Copper but all those ampacity charts are subject to enclosures and how many conductors and if copper or aluminum and the type of insulation and whether in an enclosure and/or if in free air or jacketed or conduit etc etc etc.

John T
 
masalser wins this discussion and is CORRECT

A pure resistive electric heater having a unity one Power Factor

RUNS THE SAME AND HAS THE EXACT SAME EFFICIENCY (3.41 BTU per Watt) REGARDLESS IF OPERATED AT 120 OR 240 VOLTS PERIOD

While some loads such as an inductive motor and where non unity Power Factors are concerned it can be better if ran at the higher voltages, THATS JUST NOT TRUE FOR A PURE RESISIVE HEATER LOAD

HOWEVER lower current in the wire from the panelboard to the heater (if ran at higher voltage) means less I Squared R energy (in form of heat) losses in the wire but the fact remains the heater itself runs the same AND HAS SAME EFFICIENCY AT 120 OR 240...............

Hope this helps yall understand the topic and efficiency versus voltage discussion in electric resistive heaters

Best wishes n God Bless

John T Retired Electrical Engineer with over 40 years in the practice albeit still rusty grrrrrrrrr lol
 

Watts is watts no matter if it the voltage is 120 or 240.
My maternal grandfather would connect every 240V electric water heater to 120v and proudly tell everyone he was heating the water with only half the power that 240V used.
 
(quoted from post at 10:49:48 11/20/16)
Watts is watts no matter if it the voltage is 120 or 240.
My maternal grandfather would connect every 240V electric water heater to 120v and proudly tell everyone he was heating the water with only half the power that 240V used.

A 100 watt 240 volt light bulb wired for only 120 volt will only put out 25 watts.

Dusty
 
(quoted from post at 19:22:06 11/20/16)
(quoted from post at 10:49:48 11/20/16)
Watts is watts no matter if it the voltage is 120 or 240.
My maternal grandfather would connect every 240V electric water heater to 120v and proudly tell everyone he was heating the water with only half the power that 240V used.

A 100 watt 240 volt light bulb wired for only 120 volt will only put out 25 watts.

Dusty

talking about heating a tank of water, not a dim bulb.
 

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