12VDC: Can it drive a thermostat "rated for 24VAC usage"?

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In Son of a Fermentation =
Chiller(http://home.elp.rr.com/brewbeer/chiller/chiller.html)  there's =
some back and forth about whether or not you can use a 24V AC thermostat =
by powering it with a 12V DC wall adapter.

Any thoughts?  I'm electrically challenged.

Glen

Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?


Here's the thermostat I got:  =
http://www.hunterfan.com/prodSum.php?pid=3D2&pType=3Dthermo&sType=3DMecha= nical&type=3D2


  In Son of a Fermentation =
Chiller(http://home.elp.rr.com/brewbeer/chiller/chiller.html)  there's =
some back and forth about whether or not you can use a 24V AC thermostat =
by powering it with a 12V DC wall adapter.

  Any thoughts?  I'm electrically challenged.

  Glen

Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?
Glen Leslie wrote:

Quoted text here. Click to load it
http://www.hunterfan.com/prodSum.php?pid=2&pType=thermo&sType=Mechanical&type=2
Quoted text here. Click to load it
<http://www.hunterfan.com/prodSum.php?pid=2&pType=thermo&sType=Mechanical&type=2
Quoted text here. Click to load it

I'll say it will work. It's basically a set of contacts, no electronics
involved.


Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?


The thing of the matter is that the 24V AC is not somethingh that you =
would readely find. It would either be rectified from a wall outlet(120V =
AC 60Hz) or amplified and modulated from a lower voltage DC source such =
as a battery. Generaly a thermostat is a somewhat linear resistive =
device which would probably operate best on DC, but could be made to =
function on either source depending on the engineering done to create =
the display you would look at for deciding what the temperature of the =
sensor was. If you use DC to make a resistive sensor its pretty =
straightforward, but if AC is used all these different variables come =
out to play such as inductance and capacitance changing the equasion =
you're electronics are trying to run...

short answer: it might operate, but the calibration would probably be =
off, rendering it useless.
  In Son of a Fermentation =
Chiller(http://home.elp.rr.com/brewbeer/chiller/chiller.html)  there's =
some back and forth about whether or not you can use a 24V AC thermostat =
by powering it with a 12V DC wall adapter.

  Any thoughts?  I'm electrically challenged.

  Glen

Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?
 
Quoted text here. Click to load it
...

The "son of a fermentation chiller" uses a plain old analog, mercury
switch type thermostat in the design.  There's nothing 'powered' in that
type of thermostat so AC/DC doesn't matter.  That thermostat is only
a switch and the current flows thru the mercury/bimetal switch inside.
So......

Ratings wise, you are only worried about too much CURRENT (at ANY voltage)
going thru the switch (and other wiring inside) and melting something! :)
The design of the "SoaFC" uses the thermostat switch to control a small
DC computer fan which certainly doesn't pull too much current for the
thermostat.

NOTE - you have to match the fan you're using with the AC power adapter
you are talking about.  IE., you can't use a DC fan with an AC power
adapter that transforms to AC, nor can you use an AC fan with an AC
power adapter that transforms to DC.

Again, note, SoaFC is talking about a plain old mercury switch type
thermostat.  Do NOT try to switch DC/AC on a "smart" thermostat...  it
won't work because those thermostats need the DC to run their electronics.
((Mercury switch thermostats don't have electronics like that)).

That website discusses all this pretty well in the section "About
Thermostats."

Derric


Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?
On Thu, 7 Aug 2003 20:02:34 -0700, "Dr._Flouride"

Quoted text here. Click to load it
readely find. It would either be rectified from a wall outlet(120V AC 60Hz) or
amplified and modulated from a lower voltage DC source such as a battery.
Generaly a thermostat is a somewhat linear resistive device which would probably
operate best on DC, but could be made to function on either source depending on
the engineering done to create the display you would look at for deciding what
the temperature of the sensor was. If you use DC to make a resistive sensor its
pretty straightforward, but if AC is used all these different variables come out
to play such as inductance and capacitance changing the equasion you're
electronics are trying to run...
Quoted text here. Click to load it
Chiller(http://home.elp.rr.com/brewbeer/chiller/chiller.html)  there's some back
and forth about whether or not you can use a 24V AC thermostat by powering it
with a 12V DC wall adapter.
Quoted text here. Click to load it


24 VAC is readily available from a transformer available in most
electronic supply stores.  probably even from Radio Shaft!  110-125
VAC in = 24 VAC out,

AC is never rectified unless you are looking for DC.

I switching power supply converts mains voltage to DC, then provided
square wave oscillation to drive a transformer to produce another AC
voltage which is then rectified to provide DC.

If you need 24 VAC, get the transformer.  DC cannot be used to drive
an AC item.  If you need help, ask one of the neighborhood techies who
will probably more than gladlyhelp you out for a couple of glasses of
suds...

RadioResearch


"Fuck 'em all but nine.
Six for pallbearers,
Two for roadguards,
And one to count cadence."
     old Army toast


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Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?
I'm more confused now.
Can someone just answer 'yes' or 'no'? Will the adapter work with a digital
thermostat?
I got a digital thermostat for free from my parents.
Should I get a more basic one?

Quoted text here. Click to load it
would readely find. It would either be rectified from a wall outlet(120V AC
60Hz) or amplified and modulated from a lower voltage DC source such as a
battery. Generaly a thermostat is a somewhat linear resistive device which
would probably operate best on DC, but could be made to function on either
source depending on the engineering done to create the display you would
look at for deciding what the temperature of the sensor was. If you use DC
to make a resistive sensor its pretty straightforward, but if AC is used all
these different variables come out to play such as inductance and
capacitance changing the equasion you're electronics are trying to run...
Quoted text here. Click to load it
off, rendering it useless.
Quoted text here. Click to load it
Chiller(http://home.elp.rr.com/brewbeer/chiller/chiller.html)  there's some
back and forth about whether or not you can use a 24V AC thermostat by
powering it with a 12V DC wall adapter.
Quoted text here. Click to load it
News==----
Quoted text here. Click to load it
Newsgroups
=---



Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?
Roger Dubet wrote:
Quoted text here. Click to load it
Just try it. It will either work or it won't. If it doesn't, reverse the
DC polarity and try again. If it still won't work get a 24 VAC adaptor.


Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?
Yes, it will work.  Period.  

I have a 12V computer supply fan (torn from an old pc) with a 12V
AC/DC power supply (the kind with the big square part that plugs in
the wall.)  It's wired to a $8 thermostat (cheap one from Home Depot)
and it works just fine.  One of the previous posters is right, what
matters is that you match your fan's required voltage with a proper
power supply.  The fan will have what it required printed on it
somewhere, just find a power supply to fit it.  I tore an old power
supply off a old print server, cut off the round end, attached the
wires according to my thermostat's instructions, and off I went.

Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?
The answer is a resounding NO!

If the adapter and the device do not match then DO NOT PLUG THEM IN. You
will very likely either destroy the adapter or the device. Not only should
you not use an adapter of the wrong voltage, but using a DC adapter in an AC
device is crazy.

Go to radio shack and ask them for an adapter that has the exact same output
as the device requires. If they don't have it look for on from a store on
the web or some other place that sells them in your area. 24VAC adapters are
actually quite common.

Larry

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digital
AC
all
some
Encryption




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Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?
I have to agree Larry, I tried my 12v adapter with my digital thermostat.
The fan spins but the thermostat didn't work.
I went to Radio Scrap and found a 24v adapter. It's $35.
I haven't bought it yet but I probably will.

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AC
output
are
a
which
either
DC
run...



Re: 12VDC: Can it drive a thermostat "rated for 24VAC usage"?
I use an analog thermostat for the very reason that it doesn't matter
if it's AC or DC.  Not to mention the fact that it cost $8 and saved
me quite a bit over a digital model.

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