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NorthSidePK 10-29-2012 06:05 PM

Heat won't stop running, just installed new thermostat
So this is prolly my bad...But here's the situation.

I just installed a new programable thermostat (model 3M-25)

I followed the instructions pretty well but the provided wiring diagrams did not match my wires exactly.

I had a wire labeled R2, but no Rc or Rh.

Anyhow after poking around 3M's website I saw that R is a hot wire for the heat so I hooked it up to the Rh on the thermostat and the a/c has worked just fine.

But now its getting cold, so I turn on the heat.

I have the heat programmed at 70F.

So it gets cold and the heat cuts on at the correct temp.....

But it just stays on...until I manually turn it off...

I mean it was 79F when I got home today.....

Anyhow I could use some help..

HVACTECH96 10-29-2012 06:22 PM

What are the other wires hooked to, and what type of equipment.Usually W=white G=green Y=yellow/blue R or RH & RC =red

NorthSidePK 10-29-2012 06:34 PM

I have C,B,O,W2,Y,RH & G connected on the new thermostat

The old thermostat had C,B,O,W2,R,& G connected

I hooked the wired labeled R on the old to the RH on the new

The new has W,Y2, & RC empty and unconnected

The heater is electric and has Goodman model A24-08 marked on it

Thanks for the help BTW

NorthSidePK 10-29-2012 06:37 PM

O is orange
G is green
C is white
W2 is White
R is red
Y is yellow
B is black

hvactech126 10-29-2012 06:40 PM

Sounds like you have a heat pump. Did you setup the stat for that? Did you use the HP terminal designations?

HVACTECH96 10-29-2012 06:42 PM

is this air to air heat pump

NorthSidePK 10-29-2012 06:43 PM

I have the jumpers set for elec heat.....I guess I could change it to the heat pump setting to see if it helps...

Whats the difference between a heat pump and an elec heater? if you dont mind me asking??

HVACTECH96 10-29-2012 06:46 PM

heat pump uses freon ran in reverse direction and electric is usually strip heaters in an air handler.

NorthSidePK 10-29-2012 06:51 PM

So my jumpers go like this:

1-on=24hr clock <-----I have no jumper on 1
1-off=12hr clock

2-on=Celsius disp. <----I have no jumper on 2
2-off=Fahrenheit Disp.

3-on=Gas/oil Heat <----I have no jumper on 3
3-off=no fan

4-on=elec heat <----I have no jumper on 4 ( i just took it off)
4-off=no fan

5-on=heat pump <----I have a jumper on 5 (I just put it on)

6-on=HP-AUX Only <-----I have no jumper on 6
6-off= normal

7-on=RC-RH connected <-----I have a jumper on 7 (should I??)
7-off=RC-RH separate

8-on=gas/oil HP AUX <--------I have no jumper on 8
8-off= elect HP-AUX

Does this sound correct?

hvactech126 10-29-2012 06:54 PM

need the jumper on 4.........

NorthSidePK 10-29-2012 06:55 PM

ok, so I have a jumper on 4,5 and 7 now.....

hvactech126 10-29-2012 06:58 PM

not sure if 6 should have one or not I would have to look up your stat install instructions.

NorthSidePK 10-29-2012 07:08 PM

The wiring diagram that is closest to mine in the stat install manual is a 5-wire heat pump with aux heat.

the diagram shows C,W2,Y,RH,G and B or O for a total of 6 wires...

I have 7 wires, cause I have a B and an O....

Either way it sounds like I should jumper 6...right?

digitalplumber 10-29-2012 07:08 PM

post model number of units so folks can tell you what you have

NorthSidePK 10-29-2012 07:13 PM


Originally Posted by digitalplumber (Post 1040586)
post model number of units so folks can tell you what you have

Model numbers ar 3M-25 on the thermostat


goodman a24-08 on what I thought was an elec heater...but is actually a heat pump..

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