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Blown Transformer heat pump

Heat pump unit will not operate on cool cycle, and I checked for 24 volts at the thermostat (no volts). Proceeded to blower unit and found that transformer primary side was shorted out and secondary side was ok. Replaced transformer and switched thermostat to fan only, and the blower operated. Next, switched to Auto and Cool and lowered temperature; but blower unit did not operate. Checked blower unit and found same problem--a blown transformer. I appreciate it if you can troubleshoot my problem.

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Blown transformers are usually from a low voltage short the first thing i would do is wire a automotive or resetable 3amp fuse in line with the transformer so you dont blow transformer after transformer the wire coming off the transformer that say 24v take that wire a couple of inches down and cut it and install the fuse in series there
24v----------------
24v----------x----------
24v--------{3ampfuse}----------

now you can go through your low voltage wires one by one and test them unhook all the wires to your outdoor condenser at your indoor unit(furnace or airhandler) and try turning it to cool now if you blow the fuse the short is between the tstat and the indoor unit if the fuse is still good leave it on cool and hook up one wire at a time to your outdoor unit starting with R a lot of times your contactor or your defrost board will short out on you also look for pinches in wires wires with cracks in the insulation and wires touching metal this situation can be a real pain sometimes i would recommend calling a hvac company if you start to get stumped
hope this will help you

Posted on Jul 26, 2009

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If the control voltage (24V) side is cooking, look at the thermostat/control voltage wiring shorted. Possible control board issue.

Posted on Jul 26, 2009

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1 Answer

Why won't the compressor run


This can be for a variety of reasons. It ranges from something as simple as no supply power (blown fuse, open breaker, faulty contactor, or run capacitor) or it could be more serious as a grounded or open winding in the compressor motor. My suggestion to any novice and or person without proper tools and knowledge; First check the low voltage (24 volt control voltage) by turning on the "Fan on" switch located on the thermostat to on, not "Auto" The blower fan should come on, indicating there's 120 volt and 24 volt available. Fan doesn't come on is an indication that there's no control power. The next step would be to check for power at the transformer and fuse located in the air handler. There should be 240 volts feeding the transformer, and 24 volts coming out. The control voltage is needed to operate the thermostat (which is the switch that sends the 24 volt signal to the compressor contactor to turn the compressor on/off. This 24 volt also powers other relays and switches in the system. knowing that 24 volt is available also tells you that the problem is most likely in the condensing unit (outside, where the compressor is located). At the condensing unit you should check for 240 volt supply power. Upon finding 240 volt supply power the question now becomes whether or not the thermostat is calling for anything (cool or heat if the unit is a heat pump). There should be 24-30 volt available at the small gauge wires feeding the contactor coil. While having the thermostat set at a temperature lower than the current room temperature (in the cooling mode) the thermostat should send a 24 volt signal to close the compressor contactor and turn it on. The non-metallic end of a screwdriver can be used to depress the moveable part of the contactor. After pushing in the contactor, should the compressor start then you may only need a new contactor. It may just hum because of a faulty run capacitor or grounded or shorted internal motor windings (grounded or shorted windings are usually indicated by tripped circuit breaker and/or blown fuse). It's a good idea to have a good multi-meter and knowledge of use before attempting any repairs or diagnosis on your own. I recommend some basic knowledge of electricity before even thinking about attempting any repairs or diagnosis.

May 08, 2014 | Goodman Manufacturing Goodman GSC130421...

Tip

How to wire your new themostat


0a9962f0-eea8-41fa-881b-a1074d6aa966.pngThe heater has a transformer that steps down the line voltage supplied either 115v or 230v to 24 volts,a safe voltage to use for the thermostat's control voltage and a voltage which requires no license to install.
The most important thing to remember before you begin is that ,
Red or R is the "hot leg" of the 24 volts provided by the transformer and
Common or C is the "neutral leg" of the 24 volts provided by the transformer and
Common is the side of power which EVERY 24 volt circuit will terminate or return to in completing the circuit, thus the "Common " designation, note after each circuits device, be it AC or Heat or Fan,every 24 volt circuit returns to Common or it's circuit is not completed.
Every electric circuit ,regardless of voltage or polarity requires a device ,
without a device in a circuit, upon energizing that circuit it will be a direct short!
Red to Common, this will blow the fuse or worse the transformer if not protected by a fuse which some are not. If you have a device in the circuit you can energize a circuit, my point being do not let Red touch Common and as Common is grounded at the transformer, do not let Red touch any metal, as it is likely grounded too, so turn off power before doing anything.
Note the color of the wiring attached to your existing thermostat's terminals and make a diagram so you will not forget.
The new thermostat may have different terminals or more that you will not be using.
All thermostats have an R or Red terminal, it may be RC and an RH 2 separate terminals designating RC as red cool and RH as red heat.
There 2 terminals RC and RH are for 2 transformer systems which are obsolete old GE units so if you do have both RC and RH use a small jumper wire and connect the 2 terminals and wire the Red "hot leg" from the transformer to either RC or RH it will not matter if both are jumpered together, otherwise you will only have cooling or heating but not both available.
The Red hot leg of the 24 volts enters the thermostat on R and most modern thermostats are parasitically powered meaning they derive power from the heaters transformer, as a result the Common 24 volt neutral leg must be ran to the thermostat.
Note, the new NEST thermostats say they do not require Common to be wired, however 50% of the time the NEST will go dead in time and require a Common wire be used to power the thermostat satisfactorily.
Upon a call for heat the switch between the Red and White circuit closes making white electrically hot with the 24 volts which it sends out the white wire to the heater gas valve etc and return to common to complete the heat circuit.
Upon a call for AC the switch to Yellow closes and as you will notice the Fan switch on the thermostat has an AUTO and ON switch, in the AUTO position, upon a call for AC
the Yellow becomes hot with the 24 volts and as a result of the AUTO switch being closed, the indoor blower will automatically cycle as required.
The fan control for ON fan or AC is High speed, the fan control for heat is Low speed and controlled by a time or temperature delay at the initiation and termination of the heat cycle, this is to eliminate cold air from blowing until the heater warms up and upon termination it extracts the residual heat to not overheat the unit and be most efficient.
Green is the Fan circuit, it is the High speed fan and only used for heating with electric heaters as resistive heat strips or heat pumps and will be controlled in both heat and cool modes by the thermostat, this is designed in to the thermostat or part of the thermostats set up and programming if a universal type thermostat.
Common as explained is there to power the thermostat it being the other side of 24 volt power opposite from the red 24 volt hot leg.
Heat pumps will have an O and a B terminal, this gets the Orange wire on O if the reversing valve is energized in cool mode, if you get heat in the cool mode switch the Orange wire from O and put it on B, B is energized in the Heat mode.

This was not written for just heat pumps or any brand I had to pick a specific brand however this applies to all brands and types gas furnaces , heat pumps and electric heat.

on Oct 13, 2013 | Aube TH144HPN2H1C Thermostat: Heat-Pump...

1 Answer

Air conditioning thermostat not functioning


ab302475-b998-41c7-9c7c-4e106b68e0be.pngGo to your thermostat and look at the FAN switch, it will be in the AUTO position typically.
Set the FAN switch to the ON setting,
by doing this if the fan motor operates you know that the High voltage & the low voltage (24 volt control power) are present.
This saves you from having to go to the breaker panel and checking / resetting the breaker as well as checking the Transformer and automotive type 3 amp control circuit fuse (generally on the circuit board).

If you do not get any fan operation by switching the fan switch to the ON setting, you then will have to determine if the breaker, transformer and aforementioned 3 amp fuse are all good.

You will need a volt meter to test further.
At the thermostat remove the cover thus exposing the thermostats sub base and assorted circuits/wiring.

RED or R
Red is the 24 volt "hot leg" of 24 volt power which originates at the transformer. Red enters the thermostat on the Red or R terminal, some thermostats will have an RC and an RH terminal, these are jumpered together on single transformer systems as they are for Red Cool and Red Heat, without a jumper wire on RC and RH, the Red "hot leg" of the 24 volt control voltage will only energize the terminal its wired to, some stats are battery powered and do not use the transformers 24 volt power (parasitically) to power the thermostat.
If the thermostat is powered by the transformers 24 volt power, there will be a "COMMON" wire on the common terminal of the thermostat, this is the other side of the 24 volt power from the transformer, the side opposite from RED the 24 volt "hot leg"
Common is called common as its the side of power that EVERY
24 volt circuit terminates, or completes its circuit, thus the COMMON designation.
During a Heat call the 24 volt hot leg is sent out via the white/heat terminal to the gas valve etc.
So between terminals Common & White , it should read 24 volts during a call for heat.
Same for Fan which is the Green or G terminal,
Same for Cool which is the Yellow or Y terminal.
If you have no power to these terminals when calling for heat or cool or fan then yes the thermostat is defective and requires replacement.
DO NOT let the RED wire touch ground or the COMMON terminal, this is a direct short and blows the fuse or transformer
if not equipped with fuse protection.

Normally you should read 24 volts between RED and COMMON

Aug 01, 2013 | Goodman CKL36AR36 Air Conditioner

1 Answer

How to set a NOMA HTM311A thermostat


Go to the furnace, and see what the black is connected to. If it is not the Y terminal, disconnect it from the Y terminal at the thermostat. While you have the furnace open, check for a blown fuse inline to the transformer or on the control board. If the black was connected to the common or the transformer, and you connected it to the Y, and turned the thermostat to cool, you would have a direct short across the transformer output. You can use a black wire to control the A/C, but both ends need to be connected to a Y terminal.

If you still remember the where the 4 wires were connected to the White Roger thermostat, take note of the name of the terminals the 4 wires are connected to. That may help as sometime the colour of the wires are not always correct.

Or you really want to test it out:
connect RED wire to GREEN wire should turn on the fan
connect RED wire to WHITE wire should turn on the heat


Did you disconnect the power at the furnace first? Maybe you blew a low voltage fuse.

Make sure you increase the heat setting to go above the room temperature.
Thermostat wire color codes explained.
Please note. Not all installers use the proper color codes when they install or replace equipment. It may be necessary go go to the furnace or outdoor unit to verify what wires are for what purpose. Also be sure there are no splices in the wire that could change the wire colors between components.

R (red) or Rh (Red heat) 24 volts from equipment.
Rc (Red cooling) 24 volts from transformer in cooling equipment.
Note: If only furnace has a transformer and cooling equipment does not jumper Rc and Rh.
W (White) sends 24 volts to furnace control to start the heating cycle.
W2 (no standardized wire color, usually whatever wire color is available) controls second stage heat.
Note: W2 is most often used for heat pumps to control what is called emegency heat or Auxillary heat, and most often will use the white wire.
Y (yellow) often (blue) is used, controls cooling unit (outdoor condensing unit) also is used for heat pump heat.
Y2 (no standardized wire color, usually whatever wire color is available) controls second stage cooling.
G (Green) controls the fan "on" operation of the furnace/air handler. Also often is used to start the blower for many electric furnaces.
C (common) most often brown but can also be black or other color available to installer.
O (orange) Energizes heat pump reversing valve for cooling (Trane and most other brands).
B (Blue) Energizes heat pump reversing valve for heating (Rheem, Ruud and Weatherking).


Hope it helps.


Thanks for using fixya.....

Nov 29, 2010 | Heating & Cooling

1 Answer

I tring to change thermosat I can not remeber what color go where


Typical Thermostat Wiring for 4 or 5 wire Heat/Cool Thermostat (not heat pumps)
4 Wire Termostat
R = Red One Side of 24 volt Transformer
G = Green Blower
Y = Yellow Cool
W = White Heat
5 Wire Thermostat
with one transformer for both units
Rc One Side of 24 volt Transformer
Rh Jumper Rc to Rh
G = Green Blower
Y = Yellow Cool
W = White Heat
5 Wire Thermostat
With 2 transformers one for indoor unit
And one for outdoor unit
Rc = Red One Side of (outside) 24 volt (outside transformer)
G = Green Blower (outside transformer)
Y = Yellow Cool (outside transformer)
Rh = Blue One side of (inside) 24 volt (inside transformer)
W = White Heat (inside transformer)
COOLING ONLY Thermostat
R = Red One Side of 24 volt Transformer
G = Green Blower
Y = Yellow Cool
HEATING ONLY
R or Rh One Side of 24 volt Transformer
W = White Heat

Feb 09, 2010 | Heating & Cooling

1 Answer

How do you wire a honeywell round mechanical thermostat


What are you trying to wire up?
Typical Thermostat Wiring for 4 or 5 wire Heat/Cool Thermostat (not heat pumps)
4 Wire Termostat
R = Red One Side of 24 volt Transformer
G = Green Blower
Y = Yellow Cool
W = White Heat
5 Wire Thermostat
with one transformer for both units
Rc One Side of 24 volt Transformer
Rh Jumper Rc to Rh
G = Green Blower
Y = Yellow Cool
W = White Heat
5 Wire Thermostat
With 2 transformers one for indoor unit
And one for outdoor unit
Rc = Red One Side of (outside) 24 volt (outside transformer)
G = Green Blower (outside transformer)
Y = Yellow Cool (outside transformer)
Rh = Blue One side of (inside) 24 volt (inside transformer)
W = White Heat (inside transformer)
COOLING ONLY Thermostat
R = Red One Side of 24 volt Transformer
G = Green Blower
Y = Yellow Cool
HEATING ONLY
R or Rh One Side of 24 volt Transformer
W = White Heat

Feb 09, 2010 | Honeywell CT87B ROUND HEATING&COOLING...

1 Answer

I have a coleman Evcon model AH16-0 . I am


Typical Thermostat Wiring for 4 or 5 wire Heat/Cool Thermostat (not heat pumps)
4 Wire Termostat
R = Red One Side of 24 volt Transformer
G = Green Blower
Y = Yellow Cool
W = White Heat
5 Wire Thermostat
with one transformer for both units
Rc One Side of 24 volt Transformer
Rh Jumper Rc to Rh
G = Green Blower
Y = Yellow Cool
W = White Heat
5 Wire Thermostat
With 2 transformers one for indoor unit
And one for outdoor unit
Rc = Red One Side of (outside) 24 volt (outside transformer)
G = Green Blower (outside transformer)
Y = Yellow Cool (outside transformer)
Rh = Blue One side of (inside) 24 volt (inside transformer)
W = White Heat (inside transformer)
COOLING ONLY Thermostat
R = Red One Side of 24 volt Transformer
G = Green Blower
Y = Yellow Cool
HEATING ONLY
R or Rh One Side of 24 volt Transformer
W = White Heat

Jan 06, 2010 | Heating & Cooling

1 Answer

Trying to figure out thermostat wiring diagham on a split system


Typical Thermostat Wiring for 4 or 5 wire Heat/Cool Thermostat (not heat pumps)
4 Wire Termostat
R = Red One Side of 24 volt Transformer
G = Green Blower
Y = Yellow Cool
W = White Heat
5 Wire Thermostat
with one transformer for both units
Rc One Side of 24 volt Transformer
Rh Jumper Rc to Rh
G = Green Blower
Y = Yellow Cool
W = White Heat
5 Wire Thermostat
With 2 transformers one for indoor unit
And one for outdoor unit
Rc = Red One Side of (outside) 24 volt (outside transformer)
G = Green Blower (outside transformer)
Y = Yellow Cool (outside transformer)
Rh = Blue One side of (inside) 24 volt (inside transformer)
W = White Heat (inside transformer)
COOLING ONLY Thermostat
R = Red One Side of 24 volt Transformer
G = Green Blower
Y = Yellow Cool
HEATING ONLY
R or Rh One Side of 24 volt Transformer
W = White Heat

Jan 05, 2010 | Heating & Cooling

1 Answer

Thermostat wiring


Normal 0 MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman";} Thermostat wire color codes explained.
Please note. Not all installers use the proper color codes when they install or replace equipment. It may be necessary go go to the furnace or outdoor unit to verify what wires are for what purpose. Also be sure there are no splices in the wire that could change the wire colors between components.
  • R (red) or Rh (Red heat) 24 volts from equipment.
  • Rc (Red cooling) 24 volts from transformer in cooling equipment.
Note: If only furnace has a transformer and cooling equipment does not jumper Rc and Rh.
  • W (White) sends 24 volts to furnace control to start the heating cycle.
  • W2 (no standardized wire color, usually whatever wire color is available) controls second stage heat.
Note: W2 is most often used for heat pumps to control what is called emegency heat or Auxillary heat, and most often will use the white wire.
  • Y (yellow) often (blue) is used, controls cooling unit (outdoor condensing unit) also is used for heat pump heat.
  • Y2 (no standardized wire color, usually whatever wire color is available) controls second stage cooling.
  • G (Green) controls the fan "on" operation of the furnace/air handler. Also often is used to start the blower for many electric furnaces.
  • C (common) most often brown but can also be black or other color available to installer.
  • O (orange) Energizes heat pump reversing valve for cooling (Trane and most other brands).
  • B (Blue) Energizes heat pump reversing valve for heating (Rheem, Ruud and Weatherking).

Jun 02, 2009 | Carrier Heating & Cooling

1 Answer

I need help with my central heat and air unit, it has a heat pump. the model number is GQ3RA-036K. I am changing the theromstat out and the wires are connected to it. there are eight wire colors that are...


Normal 0 MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman";} Thermostat wire color codes explained.
Please note. Not all installers use the proper color codes when they install or replace equipment. It may be necessary go go to the furnace or outdoor unit to verify what wires are for what purpose. Also be sure there are no splices in the wire that could change the wire colors between components.
  • R (red) or Rh (Red heat) 24 volts from equipment.
  • Rc (Red cooling) 24 volts from transformer in cooling equipment.
Note: If only furnace has a transformer and cooling equipment does not jumper Rc and Rh.
  • W (White) sends 24 volts to furnace control to start the heating cycle.
  • W2 (no standardized wire color, usually whatever wire color is available) controls second stage heat.
Note: W2 is most often used for heat pumps to control what is called emegency heat or Auxillary heat, and most often will use the white wire.
  • Y (yellow) often (blue) is used, controls cooling unit (outdoor condensing unit) also is used for heat pump heat.
  • Y2 (no standardized wire color, usually whatever wire color is available) controls second stage cooling.
  • G (Green) controls the fan "on" operation of the furnace/air handler. Also often is used to start the blower for many electric furnaces.
  • C (common) most often brown but can also be black or other color available to installer.
  • O (orange) Energizes heat pump reversing valve for cooling (Trane and most other brands).
  • B (Blue) Energizes heat pump reversing valve for heating (Rheem, Ruud and Weatherking).

May 07, 2009 | Heating & Cooling

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