How to go from 1200w to 600w???

[K Dog]

Hi,

I have a small fan heater which I am going to use to design my own fruit
dehydrator (on of those food dehydrators that people use dry fruit and beef
jerky etc). I have the fan and heating mechanism (the fan heater has
everything I need for that) and a 0 to 70.C thermostat which I will use the
control the temperature.

I have only one small problem. The wattage is just too high, at 1200w, I'd
cook the fruit instead of drying it. I only need 600w. How would I adjust it
to reduce it to 600w? I will note that there are three settings on this fan
heater, one is 2400w, one is 1200w and the other setting just uses the fan.

Thank you,

Regards
Ben

 

[K Dog]

1. A triac dimmer set to 50% duty cycle - pretty cheap.

I didn't think dimmers could take a load of 1200 watts and that they'd just
burn out and melt if they took too big a load...am I wrong?

5. Two such fan heaters wired in series and set to full power - very
cheap.

Sounds interesting.

Regards
Ben

 

[Phil Allison]

I didn't think dimmers could take a load of 1200 watts and that they'd just
burn out and melt if they took too big a load...am I wrong?

** Huh ? I did not say or mean a $10 wall plate job from K-mart.

Something just a bit bigger will do you - I built a heat / fan control
for a fan heater for myself with a simple 15 amp triac / diac dimmer cct -
no problems.




............. Phil

 

[Defibrillator]

Hi,

I have a small fan heater which I am going to use to design my own fruit
dehydrator (on of those food dehydrators that people use dry fruit and beef
jerky etc). I have the fan and heating mechanism (the fan heater has
everything I need for that) and a 0 to 70.C thermostat which I will use the
control the temperature.

I have only one small problem. The wattage is just too high, at 1200w, I'd
cook the fruit instead of drying it. I only need 600w. How would I adjust it
to reduce it to 600w? I will note that there are three settings on this fan
heater, one is 2400w, one is 1200w and the other setting just uses the fan.

Thank you,

Regards
Ben

Simple option. Put a diode in series with the heating element. It'd only
conduct on half the cycle so would halve the power output giving 600 on low
/ 1200w on high. You'd need a diode with at least a 400V 5A rating.

Leave the fan wired up to the full 240v (i.e. before the diode).

 

[Phil Allison]

adjust

Simple option.

** But a **very nasty** one.


Put a diode in series with the heating element. It'd only

conduct on half the cycle so would halve the power output giving 600 on low
/ 1200w on high. You'd need a diode with at least a 400V 5A rating.

** Doing that draws DC current from the AC supply and is *not legal* for an
appliance that is used continuously.

One side effect is creating a DC offset on the supply of several volts
forcing larger power transformers on the same cct into core saturation -
particularly any toroidal ones - with consequent high losses and loud
humming noise.

Another side effect is anodic ( or cathodic ? ) corrosion to AC system
ground stakes and earthed conductors that connect to the neutral.

This crude idea was in fact the first I thought of but **deliberately**
did not include in my list of 5.





............ Phil

 

[Spajky]

5. Two such fan heaters wired in series and set to full power - very
cheap.

rewire those 2x1200W heaters to serial connected inside: even cheaper!

BTW Be careful the fan speed is still adequate - it will fall off
with lower voltages too.

-- Regards, SPAJKY
& visit - http://www.spajky.iscyber.com
Celly-III OC-ed,"Tualatin on BX-Slot1-MoBo!"
E-mail AntiSpam: remove ##

 

[Rod Speed]

But a **very nasty** one.
Nope.

Doing that draws DC current from the AC supply and
is *not legal* for an appliance that is used continuously.

Complete and utter drivel.

One side effect is creating a DC offset on the supply of
several volts forcing larger power transformers on the same
cct into core saturation - particularly any toroidal ones

Very bloody unlikely indeed.

- with consequent high losses and loud humming noise.

Another side effect is anodic ( or cathodic ? ) corrosion to AC system
ground stakes and earthed conductors that connect to the neutral.

This crude idea was in fact the first I thought of
but **deliberately** did not include in my list of 5.

Your problem. And I bet you're lying.

 

[Rod Speed]

Good point. I guess with these sort of currents, there could be these
problems.

I wasn't aware that it was illegal though.

It aint.

I've used this method temporarily in the past for a hastily needed
power reduction but we were only talking 20W there. And aren't
half wave rectified PSU's effectively presenting the same sort of load
Yep.

(although no respectable PSU would be half wave rectified anyway!)?

Its not that uncommon if the power required isnt that high.

 

[Phil Allison]

Nope.

** Robot nonsense.

Complete and utter drivel.

** Robot nonsense.

Very bloody unlikely indeed.

** Robot nonsense.





............ Phil

 

[Phil Allison]

for
an appliance that is used continuously.

Good point. I guess with these sort of currents, there could be these
problems.

I wasn't aware that it was illegal though.

** AS3100: 3.12 DC Component from AC normal use.

" Equipment shall be designed so that in normal use the value of any direct
current in the equipment neutral will not contribute uduly to the failure of
the installation earth electrode by corrosion. "

"The permissable direct current in the equipment neutral shall not
xceed -

(i) for equipment considered as operating continuously 5mA or

(ii) for other than continuously operated equipment ( 5 x 24 ) / t
mA where t = daily average time in hours."

" The maximum value of direct current permited in the neutral is 1.4 amps
which could be applicable to equipment with assesed daily average operating
time of 5 minutes or less. "

I've used this method temporarily in the past for a hastily needed power

reduction but we were only talking

20W there. And aren't half wave rectified PSU's effectively presenting the
same sort of load (although no respectable PSU would be half wave rectified
anyway!)?

** I have a 1600 watt hot air gun ( Black and Decker made in UK) which
uses a diode for half power - when in use the AC supply develops a 1.5 volt
DC offset. Toroidals of 225 VA or greater go into near full saturation and
other transformers on the same AC circuit growl audibly.

If an appliance has a mains tranny then no DC current in the AC
supply is possible.



................ Phil

 

[Rod Speed]

Some completely unemployable pathetic
excuse for a bullshit artist claiming to be
Phil Allison <[email protected]> desperately attempted
to bullshit its way out of its predicament in message
and fooled absolutely no one at all. As always.

No wonder its completely unemployable.

 

[Phil Allison]

These problems have been well documented for many many years.

** Yes, but robots are such narcissists they only read science fiction.



........... Phil

 

[Rod Speed]

These problems have been well documented for many many years.

And its an approach thats been used for many years too.

 

[Phil Allison]

And its an approach thats been used for many years too.

** Ahhhh, so the Robot charges his battery banks directly with half
wave AC mains.

Typical of the rusty cheapskate





.......... Phil

 

[Rob Judd]

Hi,

I have a small fan heater which I am going to use to design my own fruit
dehydrator (on of those food dehydrators that people use dry fruit and beef
jerky etc). I have the fan and heating mechanism (the fan heater has
everything I need for that) and a 0 to 70.C thermostat which I will use the
control the temperature.

I have only one small problem. The wattage is just too high, at 1200w, I'd
cook the fruit instead of drying it. I only need 600w. How would I adjust it
to reduce it to 600w? I will note that there are three settings on this fan
heater, one is 2400w, one is 1200w and the other setting just uses the fan.

You could use an autotransformer to supply the fan heater. But a better
solution is to use refrigerated drying, which is a lot cheaper to run.

I'll leave the research to you.

Rob

 

[Bristan]

** But a **very nasty** one.

Put a diode in series with the heating element. It'd only

** Doing that draws DC current from the AC supply and is *not legal* for an
appliance that is used continuously.

One side effect is creating a DC offset on the supply of several volts
forcing larger power transformers on the same cct into core saturation -
particularly any toroidal ones - with consequent high losses and loud
humming noise.

Another side effect is anodic ( or cathodic ? ) corrosion to AC system
ground stakes and earthed conductors that connect to the neutral.

This crude idea was in fact the first I thought of but **deliberately**
did not include in my list of 5.

........Interestingly, two commercial appliances I recently pulled apart both
used this method of power reduction.
A small hair dryer for the low heat setting and one of those room
deoderisers which contain a small heating element to evaporate the
deodorant.

 

[Phil Allison]

Put a diode in series with the heating element. It'd only for


.......Interestingly, two commercial appliances I recently pulled apart both
used this method of power reduction.
A small hair dryer for the low heat setting

** Did you see the word "continuously" in my post above ????

Did you read the sections I quoted verbatim from AS3100 in this
thread ?????



and one of those room

deoderisers which contain a small heating element to evaporate the
deodorant.

** See above info - learn something.





.............. Phil

 

[Bristan]

** Did you see the word "continuously" in my post above ????

well I don't think the original posters requirement was for "continuous"
operation either which makes your rule quoting not applicable.

Did you read the sections I quoted verbatim from AS3100 in this
thread ?????

Yes ,see above

and one of those room


** See above info - learn something.

Sounding defensive there....
What am I supposed to learn ???,

I merely made the observation that these commercially available items, which
one would assume had approval , used a method which you claim to be illegal
for an application similar to that required by the original poster.
Either they are wrong or you are.

 

[Phil Allison]

well I don't think the original posters requirement was for "continuous"
operation either which makes your rule quoting not applicable.

** Bullshit - the app was a continuous one.

Yes ,see above

** See above.

Sounding defensive there....
What am I supposed to learn ???,

** What a goose you are.

I merely made the observation that these commercially available items, which
one would assume had approval , used a method which you claim to be illegal
for an application similar to that required by the original poster.

** Wrong.

See the 1.4 amp DC 5 minute limit ?

The OPs app would exceed it if done by a diode.

Either they are wrong or you are.

** A third possibility exists - that you are a fool.




........... Phil

 

[Bristan]

"Bristan" <daed> wrote in message

(snip all the crap)>
** A third possibility exists - that you are a fool.

so your one of those............
Bullshit and abuse when defeated.

Ta Ta !!!