240V Water Heater Fed 120v

[jap]

50 gal Water Heater temped it in with a 16 guage extension cord for roughly 6 months. 4500w upper and lower 4500w connected. It was an A.O Smith ENL-40 100.

Heated the water, didn't burn the cord and didn't trip the breaker.

It did have a sticker on it that said heater equipped for non simultaneous operation on standard 2 wire circuit + white for 120v and 277v.
Not sure what all that meant.

I rewired it to a 30 amp 240v feed.

Just wondering how it even worked as good as it did for as long as it did.

You all ever come across one?


JAP>

 

[jap]

P.s it was plugged into a standard 120v receptacle along with the furnace with no issues.

JAP>

 

[ActionDave]

It worked because it was only drawing about five amps. There must not have been much demand for hot water.

 

[jap]

How's that with a 4500w element?

Jap>

 

[jap]

Yes.
There was very little demand for hot water.

JAP>

 

[petersonra]

50 gal Water Heater temped it in with a 16 guage extension cord for roughly 6 months. 4500w upper and lower 4500w connected. It was an A.O Smith ENL-40 100.

Heated the water, didn't burn the cord and didn't trip the breaker.

It did have a sticker on it that said heater equipped for non simultaneous operation on standard 2 wire circuit + white for 120v and 277v.
Not sure what all that meant.

I rewired it to a 30 amp 240v feed.

Just wondering how it even worked as good as it did for as long as it did.

You all ever come across one?


JAP>

30 Amp at 240V is is only 7200 W. How are you connecting two 4500 W elements to it without it tripping on overload eventually?

If you only hooked up one of the 4500 W elements to the 120 V line it would produce just 1125 W, or about 10 Amps.

 

[texie]

50 gal Water Heater temped it in with a 16 guage extension cord for roughly 6 months. 4500w upper and lower 4500w connected. It was an A.O Smith ENL-40 100.

Heated the water, didn't burn the cord and didn't trip the breaker.

It did have a sticker on it that said heater equipped for non simultaneous operation on standard 2 wire circuit + white for 120v and 277v.
Not sure what all that meant.

I rewired it to a 30 amp 240v feed.

Just wondering how it even worked as good as it did for as long as it did.

You all ever come across one?


JAP>

You need to learn the math as this is very basic stuff. I'll tell you that a 4500 watt resistance heating element designed for 240 volt will be 1125 watts at 120 volt. That's why it was fine on the #16 cord. Can you tell us what the amps would be?

 

[jap]

I was using W=VxA or A=Watts/Volts or 4500/240= 18.75 x 1.25= 23.44 or a 30a 240v circuits.

What do you all run to this type of Water Heater?

JAP>

 

[jap]

30 Amp at 240V is is only 7200 W. How are you connecting two 4500 W elements to it without it tripping on overload eventually?

If you only hooked up one of the 4500 W elements to the 120 V line it would produce just 1125 W, or about 10 Amps.

4500w connected, both elements are never on at the same time.

JAP>

 

[jap]

You need to learn the math as this is very basic stuff. I'll tell you that a 4500 watt resistance heating element designed for 240 volt will be 1125 watts at 120 volt. That's why it was fine on the #16 cord. Can you tell us what the amps would be?

9.38 amps.

JAP>

 

[infinity]

9.38 amps.

JAP>

Yup, with a resistive load the lower voltage causes a proportional lower current draw. Dropping from 240 volts to 120 volts cuts the current in half and reduces the output to 1/4 of the original 4500 watts.

 

[texie]

I was using W=VxA or A=Watts/Volts or 4500/240= 18.75 x 1.25= 23.44 or a 30a 240v circuits.

What do you all run to this type of Water Heater?

JAP>

OK, you have the math correct. This is the most common water heater known to man and will not have a marking for the max OCPD. 422.12 requires this to be considered continuous load as you noted. Also as you noted,that is 23.44 amps which means you would use the next size up standard OCPD value which is 25 amp. However, this application would be allowed to have a 30 amp OCPD per 422.11(E).
But back to your original question. Do you see why the #16 cord did not over heat? Can you tell us the amps and watts?

Edit-I see you got the answer before I posted.

 

[jap]

OK, you have the math correct. This is the most common water heater known to man and will not have a marking for the max OCPD. 422.12 requires this to be considered continuous load as you noted. Also as you noted,that is 23.44 amps which means you would use the next size up standard OCPD value which is 25 amp. However, this application would be allowed to have a 30 amp OCPD per 422.11(E).
But back to your original question. Do you see why the #16 cord did not over heat? Can you tell us the amps and watts?

I'm looking for the formula that cuts the wattage to 1125 watts for 120v.

I would think that heating 5 gallons per hour as opposed to 21 gallons per hour at roughly 10 amps on a 16ga cord would have some ill effects other than simply taking much longer to heat the water.

I may be all wet on this one.

JAP>

 

[david luchini]

I'm looking for the formula that cuts the wattage to 1125 watts for 120v.

I would think that heating 5 gallons per hour as opposed to 21 gallons per hour at roughly 10 amps on a 16ga cord would have some ill effects other than simply taking much longer to heat the water.

I may be all wet on this one.

JAP>

4500W x (120V/240V)² = 1125W. What ill effects would you expect to see?

 

[texie]

I'm looking for the formula that cuts the wattage to 1125 watts for 120v.

I would think that heating 5 gallons per hour as opposed to 21 gallons per hour at roughly 10 amps on a 16ga cord would have some ill effects other than simply taking much longer to heat the water.

I may be all wet on this one.

JAP>

Look carefully at the ohms law wheel chart. You will see how we got the 1125 watts @120 volt.
Not sure where you are getting the gallons figures. Just know that at 120 volt you had 1/4 of the heating capacity.

 

[LarryFine]

How's that with a 4500w element?

Jap>

Because, with a restive load, the current varies with the applied voltage. When you halve the voltage, you also halve the resulting current, which quarters the power.

I = P / E = 4500 / 240 = 18.75 amps

R = E / I = 240 / 18.75 = 12.8 ohms

I = E / R = 120 / 12.8 = 9.375 amps

P = E x I = 120 x 9.375 = 1125 watts


4500 / 4 = 1125 watts at 120 volts

 

[LarryFine]

30 Amp at 240V is is only 7200 W. How are you connecting two 4500 W elements to it without it tripping on overload eventually?

That's what non-simultaneous operation provides, which is why they're rated "4500w upper, 4500w lower, 4500w total."

The upper thermostat is a SPDT switch, so the lower element doesn't energize until the upper 'stat is satisfied.

 

[jap]

My mind was working opposite of the math.

I was thinking since the voltage was half the amperage would double like in a motor application.

Why is it different? I have to say, calculations are my weakness. I completely had this wrong in my mind.

JAP>

 

[electrofelon]

My mind was working opposite of the math.

I was thinking since the voltage was half the amperage would double like in a motor application.

Why is it different? I have to say, calculations are my weakness. I completely had this wrong in my mind.

JAP>

Because there isnt really such thing as a 4500 watt element - it is a "4500 watt when 240V applied" element. Look at the resistance of the element and note that that does not change. Inductive loads are more complicated and tend to draw approximately constant power within a certain range.

 

[LarryFine]

My mind was working opposite of the math.

I was thinking since the voltage was half the amperage would double like in a motor application.

Why is it different? I have to say, calculations are my weakness. I completely had this wrong in my mind.

JAP>

The difference is designing a load for a specific voltage (or range) as opposed to merely supplying a different voltage to a given load.

Yes, a motor attempts to be a constant-power load, so a 208/240v motor uses more current at 208v, but it won't run very well on 120v.