# Heater info please



## evnz (Jul 24, 2010)

Its dropping in temp here and i need a heater the cab is small inside so i was looking at taking apart a hair dryer and mounting it in a box between the fan and ducting 
My question is if the hair dryer is 1000 watts at 240 v ac what will it be at 140 volts dc thanks
Owen


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## Ivansgarage (Sep 3, 2011)

evnz said:


> Its dropping in temp here and i need a heater the cab is small inside so i was looking at taking apart a hair dryer and mounting it in a box between the fan and ducting
> My question is if the hair dryer is 1000 watts at 240 v ac what will it be at 140 volts dc thanks
> Owen


Half the watts. Why not look for a ceramic heater 110v plugged into the pack.

Heaters like these.
http://www.amazon.com/s/ref=nb_sb_s...ywords=ceramic heater&sprefix=ceramic,aps,190

Ivan


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## dougingraham (Jul 26, 2011)

I would look at a ceramic space heater you can get inexpensively. The ones I am using have four elements and you could rewire it to operate at different voltages.

Best Wishes!


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## davidmillin (Dec 14, 2013)

Hi Owen



> Its dropping in temp here and i need a heater the cab is small inside so i was looking at taking apart a hair dryer and mounting it in a box between the fan and ducting
> My question is if the hair dryer is 1000 watts at 240 v ac what will it be at 140 volts dc thanks


Someone with better electrical Knowledge can correct me but my understanding of resistive circuits is if you halve the voltage the power is in fact quartered 

Power = volts x amps or 1000w = 240v x 4.17 amps
resistance = volts/amps or 240/4.17 =57.55ohms
amperage at 140v =V/R =140/57.55=2.43A
power at 140v= V x A= 140 x 2.43= 340watts

This is simplified by assuming no inductive/capacitive loads in the hair dryer and is just substituting AC voltages for DC voltages whereas I think DC values are in fact divided by 1.41 (RMS value) making power output smaller still and furthermore the 1000w rating on the hairdryer has a sizable chunk of that power going to it's fan.

Despite the cab size of your Hilux I think less than 300watts will struggle to clear mist off the windscreen let alone provide any meaningful heat. I think it makes sense to use heater elements or hairdryers using US power supplies (110v) as power output is quadrupled from NZ ones. Also you could look at putting an oil column heater or similar running off the mains being switched on by a timer switch overnight so your ute is warm and toasty when you go to use it in the morning in the meantime.

Cheers 
David


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## evnz (Jul 24, 2010)

Thanks for that I think 340 w is small as for the ceramic heaters they are a 240 v 1800 w so on that it should drop to 620 ish yes?


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## davidmillin (Dec 14, 2013)

Yeah that sounds about right but with a ceramic heater element all the power is going into heating. here's what I have been considering using
www.ebay.com/itm/261374709815?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649.
If you want to wire up more than one you can connect them in parallel

Hope this helps
David


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## evnz (Jul 24, 2010)

thanks
do you think it will handle 155 v dc and is it under 10amp (my ssr is rated at 10 amps)


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## davidmillin (Dec 14, 2013)

I think it should handle 155 volts just fine and draw around 10 amps continuously. If the SSR should fail you could upgrade to a 25 or 40 amp one


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## evnz (Jul 24, 2010)

Thanks david odered one and a second ssr to switch between 50% and 100% so I will not get to warm just need to wait for it to get here by the way the ssr is 25 amps got it wrong heater done! $60 sweet


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## dougingraham (Jul 26, 2011)

The ceramic heater elements I am using are actually 4 resistors in series with wires to the switches at each connection. Each resistor starts out cold with a resistance of a couple of hundred ohms. This limits the inrush current when cold to about 2.4 amps. The resistance of this type of element drops to about 54 ohms as the temp rises to 320 degrees F. (This is about 9 amps at 120 volts.) At that point the resistance starts to go back up as the temp continues to rise. At some point equilibrium is reached as both the current and temp stabilizes.

Here is how they are wired on the 110-120VAC US version.

1--/\/\/\--2--/\/\/\--3--/\/\/\--4--/\/\/\--5


1,3,5 are tied to the power switch and 2 and 4 are tied to a bimetal switch that opens if the temp is too high and the other side of that switch is tied to the neutral.

For 230 volt operation you could tie 3 to the bimetal temp switch and 1 and 5 would be tied to the hot through the power switch. 2 and 4 would be left open.


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## EVfun (Mar 14, 2010)

I think that every ceramic heater I've seen is built that way. I've taken a couple apart where the element was divided into 2 separate units with 3 electrical connections each, but they where still wired the same. 

For a low/high function in a VW Pickup I wired 2 and 4 together to pack negative and use 2 relays to operate the heater. 1 relay would power tab 3 and the other tabs 1 and 5.


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## evnz (Jul 24, 2010)

davidmillin said:


> Yeah that sounds about right but with a ceramic heater element all the power is going into heating. here's what I have been considering using
> www.ebay.com/itm/261374709815?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649.
> If you want to wire up more than one you can connect them in parallel
> 
> ...


Thanks david its on the way i will let you know how it goes


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## johnsiddle (Jun 22, 2011)

davidmillin said:


> Hi Owen
> 
> 
> 
> ...


Correct....


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## johnsiddle (Jun 22, 2011)

I have used a heater from a US sourced 110v Dishwasher and plumbed it into the original heater pipes, I use the expansion tank as a reservoir and a small (cheap) 12v Chinese water pump.
You need a heavy duty contactor or relay (I use a secondhand Kilovac also from China) to switch it unless you want a small mig welder under the bonnet (sorry, hood) when you switch off. 
DC doesn't like breaking a resistive load. 
Also don't forget some spark suppression across the contacts as a precaution.
John


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## evnz (Jul 24, 2010)

johnsiddle said:


> I have used a heater from a US sourced 110v Dishwasher and plumbed it into the original heater pipes, I use the expansion tank as a reservoir and a small (cheap) 12v Chinese water pump.
> You need a heavy duty contactor or relay (I use a secondhand Kilovac also from China) to switch it unless you want a small mig welder under the bonnet (sorry, hood) when you switch off.
> DC doesn't like breaking a resistive load.
> Also don't forget some spark suppression across the contacts as a precaution.
> John


Using two soild state relays (500watts each) 25 amps 220vdc my pack is only 170 fully charged so they should work


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## evnz (Jul 24, 2010)

Its here I was thinking a few weeks but no so tomorrow its going in 
Smaller than I thought it was going to be


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## evnz (Jul 24, 2010)

davidmillin said:


> Yeah that sounds about right but with a ceramic heater element all the power is going into heating. here's what I have been considering using
> www.ebay.com/itm/261374709815?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649.
> If you want to wire up more than one you can connect them in parallel
> 
> ...


hi all put this in today its ok for the small space in the ute but will be to small for a car ,it takes the chill off in the ute nicely and just for your info 1.6kw ([email protected] 155v)on start but dropped to 1kw ([email protected]) 
owen


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## davidmillin (Dec 14, 2013)

Thanks for letting me know Owen. When I get up to that stage I might use 2 in parallel.

Cheers David


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## johnsiddle (Jun 22, 2011)

evnz said:


> Using two soild state relays (500watts each) 25 amps 220vdc my pack is only 170 fully charged so they should work


The sparking (arc drawn out) has little to do with the power/current drawn.
Whe the arc has struck the current drops fairly low BUT the heat generated is metal melting.

If you go this way do a bench test first or at least put the relays where you can easily change them or at least pull the wires off quickly.


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## johnsiddle (Jun 22, 2011)

evnz said:


> hi all put this in today its ok for the small space in the ute but will be to small for a car ,it takes the chill off in the ute nicely and just for your info 1.6kw ([email protected] 155v)on start but dropped to 1kw ([email protected])
> owen


Thats because the resistance of the heating wire increase's with temperature therefore the current drops.
The same thing happens with filament type lamps, that's also why they usually blow when you switch them on, they have weakend with age or shock and the high switchon blows the weak spot.


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