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]

"K Dog" <kd@dontspamme.com> wrote in message
news:HcZ3b.72773$bo1.66954@news-server.bigpond.net.au...

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?

** 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]

"K Dog" <kd@dontspamme.com> wrote in message
news:G_X3b.72664$bo1.3988@news-server.bigpond.net.au...

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]

"Defibrillator" <nospam@for.me> wrote in message
news:XZ14b.73162$bo1.40627@news-server.bigpond.net.au...

"K Dog" <kd@dontspamme.com> wrote in message
news:G_X3b.72664$bo1.3988@news-server.bigpond.net.au...
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


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]

On Sat, 30 Aug 2003 17:11:26 +1000, "Phil Allison"
<philallison@optusnet.com.au> wrote:

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]

"Phil Allison" <philallison@optusnet.com.au> wrote in message news:3f50af5e$0$6524$afc38c87@news.optusnet.com.au...

"Defibrillator" <nospam@for.me> wrote in message
news:XZ14b.73162$bo1.40627@news-server.bigpond.net.au...

"K Dog" <kd@dontspamme.com> wrote in message
news:G_X3b.72664$bo1.3988@news-server.bigpond.net.au...
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


Simple option.

But a **very nasty** one.

Nope.

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.

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]

"Defibrillator" <nospam@for.me> wrote in message news:yM24b.73226$bo1.1654@news-server.bigpond.net.au...

"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f50af5e$0$6524$afc38c87@news.optusnet.com.au...

"Defibrillator" <nospam@for.me> wrote in message
news:XZ14b.73162$bo1.40627@news-server.bigpond.net.au...

"K Dog" <kd@dontspamme.com> wrote in message
news:G_X3b.72664$bo1.3988@news-server.bigpond.net.au...
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


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

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]

"Rod Speed" <rod_speed@yahoo.com> wrote in message
news:biqrvq$c0jgp$1@ID-69072.news.uni-berlin.de...

Simple option.
But a **very nasty** one.

Nope.

** Robot nonsense.

Complete and utter drivel.

** Robot nonsense.

Very bloody unlikely indeed.

** Robot nonsense.





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

 

[Phil Allison]

"Defibrillator" <nospam@for.me> wrote in message
news:yM24b.73226$bo1.1654@news-server.bigpond.net.au...

"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f50af5e$0$6524$afc38c87@news.optusnet.com.au...

** 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
turation -
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


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 <philallison@optusnet.com.au> desperately attempted
to bullshit its way out of its predicament in message
news:3f514b69$0$15135$afc38c87@news.optusnet.com.au...
and fooled absolutely no one at all. As always.

No wonder its completely unemployable.

 

[Phil Allison]

"KLR" <kreed@bigpond.net.au> wrote in message
news:v9p2lvc03b0o7onpm7t0ua5amielasorp1@4ax.com...

On Sun, 31 Aug 2003 04:56:00 +1000, "Rod Speed" <rod_speed@yahoo.com
wrote:


"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f50af5e$0$6524$afc38c87@news.optusnet.com.au...

"Defibrillator" <nospam@for.me> wrote in message
news:XZ14b.73162$bo1.40627@news-server.bigpond.net.au...

"K Dog" <kd@dontspamme.com> wrote in message
news:G_X3b.72664$bo1.3988@news-server.bigpond.net.au...
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


Simple option.

But a **very nasty** one.

Nope.

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.

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.


These problems have been well documented for many many years.

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



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

 

[Rod Speed]

"KLR" <kreed@bigpond.net.au> wrote in message news:v9p2lvc03b0o7onpm7t0ua5amielasorp1@4ax.com...

On Sun, 31 Aug 2003 04:56:00 +1000, "Rod Speed" <rod_speed@yahoo.com
wrote:


"Phil Allison" <philallison@optusnet.com.au> wrote in message news:3f50af5e$0$6524$afc38c87@news.optusnet.com.au...

"Defibrillator" <nospam@for.me> wrote in message
news:XZ14b.73162$bo1.40627@news-server.bigpond.net.au...

"K Dog" <kd@dontspamme.com> wrote in message
news:G_X3b.72664$bo1.3988@news-server.bigpond.net.au...
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


Simple option.

But a **very nasty** one.

Nope.

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.

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.


These problems have been well documented for many many years.

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

 

[Phil Allison]

"Rod Speed" <rod_speed@yahoo.com> wrote in message
news:bis2ce$c7l41$1@ID-69072.news.uni-berlin.de...

"KLR" <kreed@bigpond.net.au> wrote in message
news:v9p2lvc03b0o7onpm7t0ua5amielasorp1@4ax.com...

These problems have been well documented for many many years.

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]

K Dog wrote:

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]

"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f50af5e$0$6524$afc38c87@news.optusnet.com.au...

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.

........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]

"Bristan" <daed> wrote in message
news:3f567416$0$28118$afc38c87@news.optusnet.com.au...

"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f50af5e$0$6524$afc38c87@news.optusnet.com.au...

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
turation -
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

** 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

 

[Clifford Heath]

K Dog wrote:

I have a small fan heater which I am going to use to design my own fruit
dehydrator

I understand you've bought a dehydrator now, but depite being too late,
thought I'd comment for anyone else who was interested.

I built a very effective dehydrator many years ago using a small fan
heater - the flattish rectangular type with a drum fan inside, Vulcan
brand. It had a switch plate with about six buttons, which reconnected
two elements to get different power levels - I rotated the switch plate
to the front of the dehydrator. I just leave it on the lowest power and
fan-speed setting, but it's not that important...

The heater has an overheat cutout which disconnects the element and
leaves the fan on. I replaced that with an adjustable one, since the
existing one triggered at 60 degrees and you need to be able to adjust
from about 50 up to 65 degrees, depending on what you're drying. 60 is
too much for most fruit, browning it a little, but about right for
jerky I'm told (I don't make the stuff).

With this setup it doesn't matter what power level you use, as long as
the switch gear can handle the power and number of on-off cycles, and
nothing else in your house minds that load being constantly switched
in and out of circuit.

My design used MDF to create an inner box. The side walls of the box
are attached to vertical rails on the outside at the front and back.
Then a circular saw was used to make two horizontal cuts in each wall
for each shelf. One cut runs right through the wall, and serves as an
air vent. The other cut is 10mm lower and runs only halfway through
the MDF. By breaking away the MDF above this cut (between it and the
through-cut), you get a small ledge on which the (recycled fly-screen)
trays slide.

The inner box is surrounded by an outer box, such that you get an air
channel down one side (into the heater intake), across the bottom,
and up the other side. An 80mm hole in the front of one of the side
channels allows for air exchange (everything else is closed so no air
actually blows in or out of this hole), and a hinged door on the front
completes the dehydrator.

Sometimes I use all 13 trays, but more normally I use every 2nd one,
and if I need fewer than 6 trays I place a fixed piece of Masonite
across the exit vents for the lower trays, to force the airflow through
the necessary slots.

The design is original, easy and cheap to make from recycled parts, and
works a treat. You could easily make one with whatever tray area you
want, up to many square metres. Mine has about 2 square metres with all
trays in, so I can easily dry an entire fruit-case of almost anything
in one go.

Clifford Heath, http://homes.managesoft.com.au/~cjh/

 

[Bristan]

"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f567cf5$0$14560$afc38c87@news.optusnet.com.au...

"Bristan" <daed> wrote in message
news:3f567416$0$28118$afc38c87@news.optusnet.com.au...

"Phil Allison" <philallison@optusnet.com.au> wrote in message
news:3f50af5e$0$6524$afc38c87@news.optusnet.com.au...

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
turation -
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


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


** 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]

"Bristan" <daed> wrote in message

.......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 ????

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.

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


Yes ,see above

** See above.

and one of those room
deoderisers which contain a small heating element to evaporate the
deodorant.


** See above info - learn something.

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