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240v block heater plugged into 120v

4116 Views 18 Replies 10 Participants Last post by  9812ver
So my oem blck heater is shorted out so I ordered what I thought was an upgraded heater. Once I received it I realized it is a 240v heater. :shock: I plugged it into a 120 plug and it got good and hot.
Is this a no no? I know normally plugging 120 into 240 unit is def a NO but being that this is a simple heater I figured I'd ask before I return it.
P.s. the 120v plug plugs right into the 240v heater.
Tx for ur help!
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I can't fathom why a 240 volt block heater would be produced. Where would one find a 240 volt source to use it? I guess my question is, how did you determine it to be 240 volt?
I can't see 240 volt on a 120 plug in
It takes three wires for 120 and four for 220 by UL listing

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Wrong. You can get 220 from two lines (two wires plus a ground) I just don't see why they would put a 120v plug end on it.
Yes you can if you do it but you can't buy it that way

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I probably wouldn't continue to use it being wired up for 240 it could cause problems or at the very least unnecessary amperage draw on your circuit you have it plugged into
It says 240v 1000w on the face of the heater. Being a simple item such as a block heater, i didn't think it would really matter.
return and get right part
I spent some time doing an internet search. I found block heaters from 600 watts to over 1000, but they were all 120 volt. It won't hurt anything to use yours, a heating element will only draw the power that is supplied to it. I am puzzled by the 240 volt, yet only having the two prong connector. It is the L-shaped element that goes into a freeze plug hole like this one isn't it?
Cummins Engine Block Heater - 5.9L 12V-Geno's Garage
a heating element will only draw the power that is supplied to it.
That was exactly what I was thinking. Yup, it looks exactly like the oem one from the freeze plug.
google search result

ebay has listings for them as well.
I would send it back because it is way over priced.
That isn't the one i ordered. That is just another one I found online. I ordered mine off ebay for $60.
I still think it was too expensive. The heating element draws amperage when it produces heat. The more amps, the more heat. 240 volts, 750 watts=only 3.125 amps. Using 120 volts the amperage doubles to 6.25. The 1000 watt, 120 volt Cummins heater draws 8.33 amps.
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well, i do thinkn i'm going to retrun it anyways. I heard back from the seller and hey is going to send me a return label. I'll just make sure to find a 120v!
Some countries don't use 110 and you need a transformer when you visit if you want to use their grid to power your stuff. They usually have a weird looking prong set up on their cords, nothing like we have here. Cummins is global, I'll bet that part has Hecho en China all over it.
The element will only get half as hot as it should because it is only getting half the voltage. The element is a simple 'resistor', the resistance hasn't changed, and with half the voltage you are going to get half the heat.

In real America, a 120V plug has the 'vertical' prongs, the 240 single phase has the 'horizontal' prongs (as one style).

It won't do any damage, it wont work as well either.
If the heater's rated output is 1000W @ 240V it will only produce 1/4 the heat output or 250W @ 120V.


Resistance of the heater is the constant R=240^2/1000 or 57.6 Ohms

Therefore @ 120V P=120^2/57.6 or 250W

Should be enough to keep it from freezing but wont warm up the whole block and start as easy as with the full 1 kW
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