Posted by stu on July 19, 2008, 12:42 am
I want to use the element in a hot water heater as a dump load. If the
element is 240VAC 2400W and I am dumping 30V 3 phase DC, am I limited to
the current of the element at 240V? 2400/240A?
Thanks
*by 3 phase DC I of course me rectified 3 phase
Posted by M Q on July 19, 2008, 1:03 am
stu wrote:
> I want to use the element in a hot water heater as a dump load. If the
> element is 240VAC 2400W and I am dumping 30V 3 phase DC, am I limited to
> the current of the element at 240V? 2400/240A?
> Thanks
>
> *by 3 phase DC I of course me rectified 3 phase
>
>
240 V / 10 A = 24 ohms.
At 30 V and 24 ohms you get 30/24 = 1.25 Amps
30 V * 1.25 A = 37.5 watts
Probably not what you had in mind.
Posted by Charles Foot on July 19, 2008, 7:42 am
M Q wrote:
> stu wrote:
>
>> I want to use the element in a hot water heater as a dump load. If the
>> element is 240VAC 2400W and I am dumping 30V 3 phase DC, am I limited to
>> the current of the element at 240V? 2400/240A?
>> Thanks
>>
>> *by 3 phase DC I of course me rectified 3 phase
>>
>>
>
>
> 240 V / 10 A = 24 ohms.
> At 30 V and 24 ohms you get 30/24 = 1.25 Amps
>
> 30 V * 1.25 A = 37.5 watts
>
> Probably not what you had in mind.
>
On the right track though... you just need more of them, i.e. 2 in
parallel = 75 watts, 4 in parallel = 150 watts, etc...
Posted by Jim Wilkins on July 19, 2008, 12:43 pm
> M Q wrote:
> > stu wrote:
> >> I want to use the element in a hot water heater as a dump load. If the
> >> element is 240VAC 2400W and I am dumping 30V 3 phase DC, am I limited to
> >> the current of the element at 240V? 2400/240=10A?
> >> Thanks
> >> *by 3 phase DC I of course me rectified 3 phase
> > 240 V / 10 A = 24 ohms.
> > At 30 V and 24 ohms you get 30/24 = 1.25 Amps
> > 30 V * 1.25 A = 37.5 watts
> > Probably not what you had in mind.
> On the right track though... you just need more of them, i.e. 2 in
> parallel = 75 watts, 4 in parallel = 150 watts, etc...- Hide quoted text -
> - Show quoted text -
How much power do you have to put into the water? A string of power
resistors around the tank under the insulation might do it.
Posted by stu on July 19, 2008, 9:23 pm
> M Q wrote:
> > stu wrote:
> >> I want to use the element in a hot water heater as a dump load. If the
> >> element is 240VAC 2400W and I am dumping 30V 3 phase DC, am I limited
to
> >> the current of the element at 240V? 2400/240A?
> >> Thanks
> >> *by 3 phase DC I of course me rectified 3 phase
> > 240 V / 10 A = 24 ohms.
> > At 30 V and 24 ohms you get 30/24 = 1.25 Amps
> > 30 V * 1.25 A = 37.5 watts
> > Probably not what you had in mind.
No it isn't. But thanks. (still shaking my head as to why I didn't use ohms
law myself... must be getting old)
> On the right track though... you just need more of them, i.e. 2 in
> parallel = 75 watts, 4 in parallel = 150 watts, etc...- Hide quoted text -
If the elements on the new water heaters are like the one on my old water
heater, it would be pretty easy to tap into it in 6+ places. I'll look into
it.
How much power do you have to put into the water? A string of power
resistors around the tank under the insulation might do it.
Well I have tested it to 200W, around 500W should be possible.
Thanks again guys, I'll look into modifying the element.
> element is 240VAC 2400W and I am dumping 30V 3 phase DC, am I limited to
> the current of the element at 240V? 2400/240A?
> Thanks
>
> *by 3 phase DC I of course me rectified 3 phase
>
>