I've got a Honeywell MagicStat thermostat that has 2 jumpers marked as
"A" and "B" that are opened or closed by a screw head that you tighten
(to close the jumper) or turn out (to open the jumper).

There are 2 other jumpers (C and D) - C is to set Celcius or
Farenheight, but I don't know what "D" is for (there is no screw for
that one - so it's open). I can find no reference anywhere what D could
be for.

I'm not quite sure what exact model of MagicStat I have - there is
absolutely no number or name stamped or printed on this thing. Not even
the word "MagicStat". I've seen models like 28, 1000, 2800 and 3200
from web searches. I believe this one was purchased between 1996 and
1999.

This is the most similar picture I could find of the front panel:

http://img.ehowcdn.co.uk/article-pag...10-800x800.jpg

And this is the best picture for the entire unit:

http://www.honeywellcentral.com/medi...A1001-U_lg.jpg

The thermostat is controlling a 20+ year-old GE "Whisper-heat" natural
gas furnace. This is NOT a high-efficiency (or condensing) furnace, but
it does have an electronic control module, combustion damper gate and
electronic ignition.

The furnace is cycling too often to suit me, and so I'd like to know if
the thermostat can be modified to solve that.

The written documentation for the A and B jumpers are as follows:

Warm Air Furnace: Set at the Hot Water setting (A-out, B-in)
Electric furnace: Leave at the Warm Air Furnace setting (A-in, B-in)

(the way the second line reads is confusing)

It also says:

For high efficiency (90% AFUE): A-out, B-in

On the back of the unit these instructions are stamped into the plastic
case:

Warm Air Furnace: A-in, B-in, Fuel Switch F
Hot Water Boiler: A-out, B-in, Fuel Switch F
Electric Furnace: A-in, B-out, Fuel Switch E

On my thermostat, the current settings a

Warm Air Furnace: A-in, B-in, Fuel Switch F

I believe that the only thing the Fuel Switch does is turn on the fan
when heat is called for (in the E setting) otherwise the fan is turned
on by the furnace (in the F setting).

So if anyone knows, I'd like some clarification as to how exactly the A
and B settings work or how they modify the operation of the furnace.

It would be nice if there was a SPAN or hysteresis setting so I could
force a 1 or 2 degree swing so the cycles last longer, but I see no such
setting. I'm wondering if the A and B settings can accomplish this?

And - anyone know what the D jumper does?

On Dec 29, 8:52*am, HVAC Guy wrote:
I've got a Honeywell MagicStat thermostat that has 2 jumpers marked as
"A" and "B" that are opened or closed by a screw head that you tighten
(to close the jumper) or turn out (to open the jumper).

There are 2 other jumpers (C and D) - C is to set Celcius or
Farenheight, but I don't know what "D" is for (there is no screw for
that one - so it's open). *I can find no reference anywhere what D could
be for.

I'm not quite sure what exact model of MagicStat I have - there is
absolutely no number or name stamped or printed on this thing. *Not even
the word "MagicStat". *I've seen models like 28, 1000, 2800 and 3200
from web searches. *I believe this one was purchased between 1996 and
1999.

This is the most similar picture I could find of the front panel:

http://img.ehowcdn.co.uk/article-pag...a08/7r/3r/inst...

And this is the best picture for the entire unit:

http://www.honeywellcentral.com/medi...3200A1001-U_lg...

The thermostat is controlling a 20+ year-old GE "Whisper-heat" natural
gas furnace. *This is NOT a high-efficiency (or condensing) furnace, but
it does have an electronic control module, combustion damper gate and
electronic ignition.

The furnace is cycling too often to suit me, and so I'd like to know if
the thermostat can be modified to solve that.

The written documentation for the A and B jumpers are as follows:

* Warm Air Furnace: *Set at the Hot Water setting (A-out, B-in)
* Electric furnace: *Leave at the Warm Air Furnace setting (A-in, B-in)

(the way the second line reads is confusing)

It also says:

* For high efficiency (90% AFUE): *A-out, B-in

On the back of the unit these instructions are stamped into the plastic
case:

* Warm Air Furnace: *A-in, *B-in, *Fuel Switch F
* Hot Water Boiler: *A-out, B-in, *Fuel Switch F
* Electric Furnace: *A-in, *B-out, Fuel Switch E

On my thermostat, the current settings a

* Warm Air Furnace: *A-in, *B-in, *Fuel Switch F

I believe that the only thing the Fuel Switch does is turn on the fan
when heat is called for (in the E setting) otherwise the fan is turned
on by the furnace (in the F setting).

So if anyone knows, I'd like some clarification as to how exactly the A
and B settings work or how they modify the operation of the furnace.

It would be nice if there was a SPAN or hysteresis setting so I could
force a 1 or 2 degree swing so the cycles last longer, but I see no such
setting. *I'm wondering if the A and B settings can accomplish this?

And - anyone know what the D jumper does?

I remember that Thermostat . The A and B screws act as a heat
anticipator does ; the more you back out the A screw with the B
screw turned all the way in....the greater the differential will be
and the greater the room temperature swing will be . It is all done
by trial and error using the screws , so, you have to set the screws
then cycle the system thru a couple times to see what kind of room
temperature drop youre getting before the next heating cycle starts.
Since the furnace has electronic ignition, youll want to set it up as
if it were a high efficiency gas furnace which ordinarily would
correspond to a .8 amp anticipator setting ; thats what you have to
shoot for by trial and error by adjusting the Magic Stat screws.
(They dont call it an 'inexpensive' thermostat for no reason !) .
If , after youve done that and you still get a rapid cycling
response...then you could install a simply spst start relay at the
furnace which would effectively reduce the heat anticipator (amp)
demand of the Magic Stat and possibly bring you within the operating
range of the A / B screws for more consise adjusting . ... the Magic
Stat would operate the added relays coil directly , with the relay
contacts making and breaking R to W at the furnace control board
strip . Good luck. ALso, theres a Honneywell Thermostat Tech 800
number for Contractors ; if you need it i can try and find it for
you.

" wrote:

I remember that Thermostat . The A and B screws act as a heat
anticipator does ; the more you back out the A screw with the B
screw turned all the way in....the greater the differential will be
and the greater the room temperature swing will be.

Your explanation indicates that the amount of turns of the screw is
somehow sensed by the thermostat's circuitry.

This assumption is incorrect.

On this thermostat, the screw is not functioning as the core of an
inductor or coil (as per your explanation). The only function the screw
has is to bridge the wire contacts on the upper surface of a machined
plastic block. The wires connect to the PC board.

If variable operating was desired, then Honeywell would have used a
potentiometer instead of a significantly more complicated reactance
circuit.

All the printed manuals for these thermostats indicate that the screw
has basically only 2 settings: Fully turned in (tightened down) or
unscrewed (turned out) by one turn. The one turn is sufficient to raise
the underside of the screw head enough so that it is not contacting
(bridging) the wires.

On Dec 29, 8:44*pm, HVAC Guy wrote:
" wrote:
I remember that Thermostat . *The *A and B screws act as a heat
anticipator does ; *the more you back out the A *screw with the B
screw turned all the way in....the greater the differential will be
and the greater the room temperature swing will be.

Your explanation indicates that the amount of turns of the screw is
somehow sensed by the thermostat's circuitry.

This assumption is incorrect.

On this thermostat, the screw is not functioning as the core of an
inductor or coil (as per your explanation). *The only function the screw
has is to bridge the wire contacts on the upper surface of a machined
plastic block. *The wires connect to the PC board.

If variable operating was desired, then Honeywell would have used a
potentiometer instead of a significantly more complicated reactance
circuit.

All the printed manuals for these thermostats indicate that the screw
has basically only 2 settings: *Fully turned in (tightened down) or
unscrewed (turned out) by one turn. *The one turn is sufficient to raise
the underside of the screw head enough so that it is not contacting
(bridging) the wires.

Whenever i adjusted the 'A' screw in or out partially...it DID make a
difference on the cycle time (differential) . I wouldnt give
Honneywell too many accolaides as far as engineering goes because this
thermostat of theirs is a poor example of quality..certainly one
Engineers wet dream to flood the market with a most inexpensive
thermostat without much consideration to accuracy. A proper
electronic thermostat that is designed well, is one where the Person
can make a definitive selection between 1,2,or 3 degrees F.
differential for heating AND for cooling....and not a psuedo-
thermostat like a Honneywell Magic Stat. Sadly, these are things the
typical homeowner isnt up to par on.

" wrote:

Whenever i adjusted the 'A' screw in or out partially...it DID
make a difference on the cycle time (differential) .

My gut feeling, based on turning out the A screw, is that the furnace
cycle time has been lengthened to a more satisfactory condition, with no
discernable change in overall ambient air temperature.

A-out / B-in Hot water boiler (radiant heat?)

So this is, in effect, telling the thermostat that instead of
controlling a conventional mid-efficiency forced-air natural gas
furnace, that it's controlling a hot water boiler.

This seems to have the effect of not turning on the furnace as often.

Sorry guys but some how you guys getting on my nerves
you being discussing this Fxxxxxx Magic Thermostat for past month
and I don't see positive explain what type heat does it has
is it hot water or is it hot air electrical/gas or does this thermostat controls home/buld. temp.
Or you are trying to use VW motor to drive Cad.

"HVAC Guy" wrote in message ...
" wrote:

Whenever i adjusted the 'A' screw in or out partially...it DID
make a difference on the cycle time (differential) .

My gut feeling, based on turning out the A screw, is that the furnace
cycle time has been lengthened to a more satisfactory condition, with no
discernable change in overall ambient air temperature.

A-out / B-in Hot water boiler (radiant heat?)

So this is, in effect, telling the thermostat that instead of
controlling a conventional mid-efficiency forced-air natural gas
furnace, that it's controlling a hot water boiler.

This seems to have the effect of not turning on the furnace as often.

"HVAC Guy" wrote in message ...
I've got a Honeywell MagicStat thermostat that has 2 jumpers marked as
"A" and "B" that are opened or closed by a screw head that you tighten
(to close the jumper) or turn out (to open the jumper).

There are 2 other jumpers (C and D) - C is to set Celcius or
Farenheight, but I don't know what "D" is for (there is no screw for
that one - so it's open). I can find no reference anywhere what D could
be for.

I'm not quite sure what exact model of MagicStat I have - there is
absolutely no number or name stamped or printed on this thing. Not even
the word "MagicStat". I've seen models like 28, 1000, 2800 and 3200
from web searches. I believe this one was purchased between 1996 and
1999.

This is the most similar picture I could find of the front panel:

http://img.ehowcdn.co.uk/article-pag...10-800x800.jpg

And this is the best picture for the entire unit:

http://www.honeywellcentral.com/medi...A1001-U_lg.jpg

The thermostat is controlling a 20+ year-old GE "Whisper-heat" natural
gas furnace. This is NOT a high-efficiency (or condensing) furnace, but
it does have an electronic control module, combustion damper gate and
electronic ignition.

The furnace is cycling too often to suit me, and so I'd like to know if
the thermostat can be modified to solve that.

The written documentation for the A and B jumpers are as follows:

Warm Air Furnace: Set at the Hot Water setting (A-out, B-in)
Electric furnace: Leave at the Warm Air Furnace setting (A-in, B-in)

(the way the second line reads is confusing)

It also says:

For high efficiency (90% AFUE): A-out, B-in

On the back of the unit these instructions are stamped into the plastic
case:

Warm Air Furnace: A-in, B-in, Fuel Switch F
Hot Water Boiler: A-out, B-in, Fuel Switch F
Electric Furnace: A-in, B-out, Fuel Switch E

On my thermostat, the current settings a

Warm Air Furnace: A-in, B-in, Fuel Switch F

I believe that the only thing the Fuel Switch does is turn on the fan
when heat is called for (in the E setting) otherwise the fan is turned
on by the furnace (in the F setting).

So if anyone knows, I'd like some clarification as to how exactly the A
and B settings work or how they modify the operation of the furnace.

It would be nice if there was a SPAN or hysteresis setting so I could
force a 1 or 2 degree swing so the cycles last longer, but I see no such
setting. I'm wondering if the A and B settings can accomplish this?

And - anyone know what the D jumper does?

Sounds like your trying to use the thermostat to mask the primary
problems.... and that would be having a furnace that is a whole lot bigger
than you need, and not enough insulation.
20 years is a normal *high* life span for a gas furnace. It would be time to
look into replacing the furnace before it becomes a problem and craps out
when its really cold.

The contractor that installs the new furnace should do a complete
room-by-room Manual J heat load/loss analysis to correctly size the new
furnace for your home. You might be surprised at the results.

On 12/29/2011 01:16 PM, Steve wrote:
"HVAC wrote in message ...
I've got a Honeywell MagicStat thermostat that has 2 jumpers marked as
"A" and "B" that are opened or closed by a screw head that you tighten
(to close the jumper) or turn out (to open the jumper).

There are 2 other jumpers (C and D) - C is to set Celcius or
Farenheight, but I don't know what "D" is for (there is no screw for
that one - so it's open). I can find no reference anywhere what D could
be for.

I'm not quite sure what exact model of MagicStat I have - there is
absolutely no number or name stamped or printed on this thing. Not even
the word "MagicStat". I've seen models like 28, 1000, 2800 and 3200
from web searches. I believe this one was purchased between 1996 and
1999.

This is the most similar picture I could find of the front panel:

http://img.ehowcdn.co.uk/article-pag...10-800x800.jpg

And this is the best picture for the entire unit:

http://www.honeywellcentral.com/medi...A1001-U_lg.jpg

The thermostat is controlling a 20+ year-old GE "Whisper-heat" natural
gas furnace. This is NOT a high-efficiency (or condensing) furnace, but
it does have an electronic control module, combustion damper gate and
electronic ignition.

The furnace is cycling too often to suit me, and so I'd like to know if
the thermostat can be modified to solve that.

The written documentation for the A and B jumpers are as follows:

Warm Air Furnace: Set at the Hot Water setting (A-out, B-in)
Electric furnace: Leave at the Warm Air Furnace setting (A-in, B-in)

(the way the second line reads is confusing)

It also says:

For high efficiency (90% AFUE): A-out, B-in

On the back of the unit these instructions are stamped into the plastic
case:

Warm Air Furnace: A-in, B-in, Fuel Switch F
Hot Water Boiler: A-out, B-in, Fuel Switch F
Electric Furnace: A-in, B-out, Fuel Switch E

On my thermostat, the current settings a

Warm Air Furnace: A-in, B-in, Fuel Switch F

I believe that the only thing the Fuel Switch does is turn on the fan
when heat is called for (in the E setting) otherwise the fan is turned
on by the furnace (in the F setting).

So if anyone knows, I'd like some clarification as to how exactly the A
and B settings work or how they modify the operation of the furnace.

It would be nice if there was a SPAN or hysteresis setting so I could
force a 1 or 2 degree swing so the cycles last longer, but I see no such
setting. I'm wondering if the A and B settings can accomplish this?

And - anyone know what the D jumper does?

Sounds like your trying to use the thermostat to mask the primary
problems.... and that would be having a furnace that is a whole lot bigger
than you need, and not enough insulation.
20 years is a normal *high* life span for a gas furnace.

I think you're assuming a LOT (like where the O.P. resides).

It would be time to
look into replacing the furnace before it becomes a problem and craps out
when its really cold.

The contractor that installs the new furnace should do a complete
room-by-room Manual J heat load/loss analysis to correctly size the new
furnace for your home. You might be surprised at the results.

"cjt" wrote in message
...
On 12/29/2011 01:16 PM, Steve wrote:
"HVAC wrote in message
...
I've got a Honeywell MagicStat thermostat that has 2 jumpers marked as
"A" and "B" that are opened or closed by a screw head that you tighten
(to close the jumper) or turn out (to open the jumper).

There are 2 other jumpers (C and D) - C is to set Celcius or
Farenheight, but I don't know what "D" is for (there is no screw for
that one - so it's open). I can find no reference anywhere what D could
be for.

I'm not quite sure what exact model of MagicStat I have - there is
absolutely no number or name stamped or printed on this thing. Not even
the word "MagicStat". I've seen models like 28, 1000, 2800 and 3200
from web searches. I believe this one was purchased between 1996 and
1999.

This is the most similar picture I could find of the front panel:

http://img.ehowcdn.co.uk/article-pag...10-800x800.jpg

And this is the best picture for the entire unit:

http://www.honeywellcentral.com/medi...A1001-U_lg.jpg

The thermostat is controlling a 20+ year-old GE "Whisper-heat" natural
gas furnace. This is NOT a high-efficiency (or condensing) furnace, but
it does have an electronic control module, combustion damper gate and
electronic ignition.

The furnace is cycling too often to suit me, and so I'd like to know if
the thermostat can be modified to solve that.

The written documentation for the A and B jumpers are as follows:

Warm Air Furnace: Set at the Hot Water setting (A-out, B-in)
Electric furnace: Leave at the Warm Air Furnace setting (A-in, B-in)

(the way the second line reads is confusing)

It also says:

For high efficiency (90% AFUE): A-out, B-in

On the back of the unit these instructions are stamped into the plastic
case:

Warm Air Furnace: A-in, B-in, Fuel Switch F
Hot Water Boiler: A-out, B-in, Fuel Switch F
Electric Furnace: A-in, B-out, Fuel Switch E

On my thermostat, the current settings a

Warm Air Furnace: A-in, B-in, Fuel Switch F

I believe that the only thing the Fuel Switch does is turn on the fan
when heat is called for (in the E setting) otherwise the fan is turned
on by the furnace (in the F setting).

So if anyone knows, I'd like some clarification as to how exactly the A
and B settings work or how they modify the operation of the furnace.

It would be nice if there was a SPAN or hysteresis setting so I could
force a 1 or 2 degree swing so the cycles last longer, but I see no such
setting. I'm wondering if the A and B settings can accomplish this?

And - anyone know what the D jumper does?

Sounds like your trying to use the thermostat to mask the primary
problems.... and that would be having a furnace that is a whole lot
bigger
than you need, and not enough insulation.
20 years is a normal *high* life span for a gas furnace.

I think you're assuming a LOT (like where the O.P. resides).

He still has a 20+ year old furnace.... doesn't matter where he lives... and
short cycling still indicates a grossly oversized furnace no matter where
you live.


It would be time to
look into replacing the furnace before it becomes a problem and craps out
when its really cold.

The contractor that installs the new furnace should do a complete
room-by-room Manual J heat load/loss analysis to correctly size the new
furnace for your home. You might be surprised at the results.

Steve wrote:

He still has a 20+ year old furnace.... doesn't matter where he lives.
.. and short cycling still indicates a grossly oversized furnace no
matter where you live.

Why are you such a trollish Klown?

Or are you naturally stupid when it comes to furnaces and thermostats?

Any boob knows that it's the thermostat that controls the cycling of the
furnace.

You can make ANY furnace short-cycle given a tight temperature span.

"HVAC Guy" wrote in message ...
Steve wrote:

He still has a 20+ year old furnace.... doesn't matter where he lives.
.. and short cycling still indicates a grossly oversized furnace no
matter where you live.

Why are you such a trollish Klown?

Or are you naturally stupid when it comes to furnaces and thermostats?

Any boob knows that it's the thermostat that controls the cycling of the
furnace.

You can make ANY furnace short-cycle given a tight temperature span.


Sure... go ahead on... you know what your doing, so you don't need to worry
with posting questions about ancient POS big box stats.... when you can get
a good one for $50 or so.

Just cause your "HVAC Guy" doesn't mean squat.... you should have a decent
stat on your truck that you can use instead of screwing with a POS.

I've got the Honeywell CT3200, which matches your pictures but not your
description. My unit has 3 dip switches and a larger fuel switch.
The manual offers no suggestions about altering the duty cycle. The
furnace is expected to cycle about 5 times per hour and is meant to hold
within 1 deg F of the setpoint.

Dave M.

"Dave M." wrote:

I've got the Honeywell CT3200, which matches your pictures but not
your description. My unit has 3 dip switches and a larger fuel
switch.

I obtained the documentation for a MagicStat CT3300 and it shows a
diagram of the back of the unit that is identical to what I have. I
copied that diagram and it can be seen he

http://www.fileden.com/files/2008/7/.../Magicstat.gif

The PDF file itself can be downloaded from he

http://www.fileden.com/files/2008/7/...StatCT3300.PDF

The manual offers no suggestions about altering the duty cycle.

That appears to be the case from what I read as well.

The furnace is expected to cycle about 5 times per hour and
is meant to hold within 1 deg F of the setpoint.

That's a pretty tight temperature range and to be able to hold it within
1 degree F and keep to only 5 cycles per hour really depends on a lot of
factors (how the premesis is constructed, how drafty it is, how cold /
windy is it outside, how many BTU's the furnace puts out, etc).

This thermostat basically has 4 binary-selectable settings:

A-in / B-in Conventional warm-air (nat-gas?) furnace
A-in / B-out Electric furnace (or electric base-board?)
A-out / B-in Hot water boiler (radiant heat?)
A-out / B-out not defined (hmm...)

Just guessing here, but why would a thermostat need to know between
which of the above 3 systems is it controlling?

The speed of response of the system? Nat-gas forced-air can respond
faster than a boiler, for example. To anticpate the call for heat
(reduce the control span?)

The thermostat doesn't want the ambient temp to drop too far below the
setpoint, and it doesn't want to over-shoot the setpoint. It's not
clear which of the above options would give me a wider span (and hence
fewer cycles per unit time). I guess I'll just have to experiment - or
buy a new thermostat with a user-settable span or hysteresis setting.

Guy,

I agree with your conjecture that the screws (in your case) or DIP
switches (in mine) change the anticipator circuit and thus adjust the
cycling.
I suspect that experimenting with them will be harmless but unrewarding.
The settings recommended in the manual are those that will work best.
Let me know if you find better settings.

Dave M.

replying to HVAC Guy, Dorothy wrote:
Can you still purchase this thermostat

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