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HVAC Guy posted on December 29, 2011, 9:52 am
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-page-main/ehow/images/a08/7r/3r/installation-instructions-honeywell-t8000c-1010-800x800.jpg
And this is the best picture for the entire unit:
http://www.honeywellcentral.com/media/product_images/CT3200A1001-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 are:
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?
"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-page-main/ehow/images/a08/7r/3r/installation-instructions-honeywell-t8000c-1010-800x800.jpg
And this is the best picture for the entire unit:
http://www.honeywellcentral.com/media/product_images/CT3200A1001-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 are:
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?
IlBeBauck@gmail.com posted on
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
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.
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
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.
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
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.
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
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.
Grumpy posted on
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
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.
Steve posted on
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
instructions for this antique big box store POS stat.
Either the OP is an idiot (this is a given), and/or he's just too freakin
lazy to actually look for it, and/or hes nothing but another troll.
A simple yahoo search gets over 19,000 hits. How hard is this??
http://customer.honeywell.com/TechLit/pdf/69-0000s/69-0653.pdf
You can also go to the Honeywell site and get it from there....
Daniel who wants to know posted on
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
Because not every Honeywell manual is perfect, especially for a cheap HwHwST
The manual for mine, a Honeywell RTH221B1000 that I got 3 of for $5 each
from the Orscheln Farm and Home bargain bin makes no mention of cycles per
hour. If you Google the model RTH221B, you get this manual:
http://www.honeywellcentral.com/ssi/pdf/honeywell/RTH221-Owners-Manual.pdf
However if you Google RTH221B cycles per hour you get this manual:
http://customer.honeywell.com/techlit/pdf/PackedLit/69-2060EFS.pdf
Or Google RTH221B1000 cycles per hour and get this manual:
http://customer.honeywell.com/techlit/pdf/PackedLit/69-2448ES.pdf
The latter 2 manuals both explain how to press both temp arrows together for
3 seconds to enter the hidden settings menu.
If you want a real Honeywell manual you have to step up out of the HwHwST
class and into the professional class, Google Honeywell t8600d t8601d and
get:
http://www.thermostatshop.com/manuals/T8602D%20users%20manual.pdf
Now That's what I call a manual.
HwHwST=Honeywell hardware store thermostat.
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
Of course not.
Because the number of cycles per hour will depend on
- the temperature span or hysteresis around the desired set point
- the heat loss of the space being controlled
- the BTU capacity of the furnace
If the stat has a setting for cycles per hour, then you're going to have
a variable hysteresis, and the stat is going to take some time to learn
what that's going to be for a given set of conditions.
To make it more complicated, the heat loss of the space is going to be
affected by ambient outside weather (wind and temperature) and how well
the space is insulated. As that changes, the thermostat will have to
re-learn how to control the furnace to keep the desired set-point while
maintaining the desired cycles per hour.
It's far simpler to set the hysteresis (2 or 3 degrees instead of 1
degree) and live with what-ever cycles per hour you end up getting,
rather then aim for a set or fixed cycles-per-hour.
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
Did you read any of the PDFs?
Anyway the problem here isn't Honeywell's choice of CPH over hysteresis
degrees, it is how this stat (RTH221) seems to function, when set to 5 CPH
it calls for heat every 12 minutes as expected, but when set to 3 or 1 CPH
in my house it only drops to calling for heat every 13 minutes, and this is
after several hours to adapt. I have a 90+ condensing gas furnace and this
style is only supposed to be cycled about 3 times per hour.
Also interesting with this model is that when set to 62° F as it cycled its
reading would swing from 58° to 65° with each cycle while 3 other
thermometers, a non-connected Lux digital thermostat, a digital meat
thermometer, and an indoor/outdoor thermometer and hygrometer weather
station all placed right beside the RTH221 would all show the swing as being
from 61-63°. When the temp setting on the RTH221 was first set down to 62°
from 68° its reading quickly dropped to 61° and stayed as the 3 others
showed the normal gradual drop. When the others started to show 61° as well
the RTH221 dropped to showing 60° and shortly thereafter called for heat.
It is an odd model for sure.
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
Yup... big box store junk..... There is a sucker born every minute that will
buy one.
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
degrees, it is how this stat (RTH221) seems
expected, but when set to 3 or 1 CPH in my house
hours to adapt. I have a 90+
times per hour.
reading would swing from 58° to 65°
********************************************************************
Ok enough of this crap apparently your cheepy Tst is much more sensitive
Than the others, to make it more stable you can cover Tst with something
To see how much of effect will have, or/and if you have forced air heating
Make sure that your duct discharge is not blowing on to Tst.
**********************************************************************
with each cycle while 3 other
thermometer, and an indoor/outdoor thermometer
show the swing as being from 61-63°.
reading quickly dropped to 61° and stayed
show 61° as well the RTH221 dropped to
buy one.
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
That's what I thought at first so I wedged some plumber's putty in the
corner where the thermistor is located (it sits epoxied into a small recess
in the bottom left corner of the plastic housing) to add thermal mass, this
showed no change. Besides have you seen how fast a meat thermometer reacts
to temp changes? In air it only takes a few seconds per degree for a small
change, in meat they don't call them "instant read" for nothing.
I thought about also putting a clear storage bowl or one of those
anti-tamper plastic boxes over it.
Nope, the supplies are on the other side of the room.
The Daring Dufas posted on
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
I'm afraid I didn't follow this thread that closely but did anyone
mention making sure any holes in the wall behind the T-stat were sealed?
That would be the first thing I always look for. I've found that even
the tiniest holes can let in enough air to screw with an electronic
sensor. Even air getting past/through the little plastic anchors for
the mounting screws. o_O
TDD
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
In my case that is covered too, the thermostat is mounted to a paneling wall
of the closet that the furnace is in, the walls are bare studs inside the
closet, and the furnace is direct return instead of ducted with 2 20x25
filters in an A frame shape on top (it is a downflow), IE the area behind
the thermostat is conditioned space.
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
Cool! No pun intended. ^_^
TDD
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
http://img.ehowcdn.co.uk/article-page-main/ehow/images/a08/7r/3r/installation-instructions-honeywell-t8000c-1010-800x800.jpg
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.
cjt posted on
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
http://img.ehowcdn.co.uk/article-page-main/ehow/images/a08/7r/3r/installation-instructions-honeywell-t8000c-1010-800x800.jpg
I think you're assuming a LOT (like where the O.P. resides).
It would be time to
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
http://img.ehowcdn.co.uk/article-page-main/ehow/images/a08/7r/3r/installation-instructions-honeywell-t8000c-1010-800x800.jpg
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.
Re: Honeywell MagicStat thermostat -> questions about jumper settings on the back
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.
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