Question about Heating & Cooling

1 Answer

My ac unit does not have power to the thermostat. There is 200 volts going into the transformer and 24 volts going out. There is 24 volts on the back side of a terminal with thermostat wire running to the thermostat and the outside AC unit. However, no power on the front side of this terminal and therefor no power to the thermostat.

Posted by on

  • Bill Long May 11, 2010

    What brand and model thermostat and is it a heat pump stat?

×

Ad

1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

    Vice President:

    An expert whose answer got voted for 100 times.

  • Master
  • 585 Answers

Please exercise due caution in checking voltages in live circuits!

24 volts sourced by the transformer, through the thermostat, then through the contactor (turns on power to compressor/fan) and returns to the transformer, If the thermostat is closed (calling for cool) you will see no voltage across it, but instead the contactor should be energized. Please note, 200 volts seems odd, you should have between 215 and 235. It sounds more like the contactor relay coil may be open. Is the contactor/transformer one piece?

Posted on May 15, 2009

Ad

1 Suggested Answer

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi,
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
goodluck!

Posted on Jan 02, 2017

Ad

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

Compressor want come on


Here is what to do . Pull out or turn off Electrical disconnect behind unit . Carefully remove panel covering controls in unit . Note most units have a flat panel with a few screws, but some GE units have a welded metal box on top of unit which needs to be removed. After exposing controls. replace or turn on disconnect. Then take a plastic handled screwdriver and push in on center of contactor (boxlike part with a lot of wires hooked ) If the compressor now comes on release contactor , and check for 24 Volts AC at base of contactor where thermostat (small wires that run on outside of black refrigerant line ) with thermostat on and calling for cool you should measure 24 to 28 volts . If voltage is present replace contactor after disconnecting from power. If no voltage go inside , remove cover from thermostat, and check for 24 volts between red ( R) and yellow (Y ) terminals on thermostat , If voltage is present , replace thermostat , no voltage check voltage in heater / air handler if you have voltage at air handler , replace thermostat wire from heater to thermostat / if no voltage check for blown fuse in heater , this should be either an inline fuse or an automotive type fuse plugged into circuit board (with power to heater disconnected check broken wire or black mark in fuse when held up to light. If fuse good turn on power to heater and check for 230v to one side of transformer, if you get voltage to Primary (incoming side ) of transformer, check output side of transformer for 24 - 28 volts. If transformer shows input but no output replace transformer after turning power off. If you heard a buzzing or grinding noise , when pushing in contactor , but compressor didn't start look at run capacitor (this is round or oval shaped object with wires going to contactor and compressor ) Looking at area where wires plug this should be a flat surface , if it looks domed shaped or bulging out , it is blown and needs replaced , use same mfd rating and 440 Volts to be on safe side. / If there was no noise from compressor when contactor was pushed in , put your hand on top of compressor (black object in center of unit ) If hot , allow to cool for at least three hours with power to unit turned off and retest . If compressor comes on after cooling , check for bad fan motor in outside unit (it may make a squealing or wining noise and stop runing for a while , also check for / clean outdoor coils
Hope this helps .
Thanks,
Alex


Oct 04, 2014 | Carrier Comfort 3.0 Ton 13 Seer Ac Only...

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

Wiring diagram for Thermoking V700MAX


Red or R is the "Hot leg" of the Transformers 24volt supply,
Common or C is the "Neutral leg" of the Transformers 24 volt supply;
and the side of power to which ALL the 24 volt control circuits
terminate to complete the circuit, example; Heat=W, Cool=Y, Fan=G.
Upon a call for heat a switch closes betwen the Red and White Thermostat terminals.
The stat sends the 24 volts to White or W for the heat circuit on W on the
furnaces LVTB low voltage terminal board.
Yellow or Y goes from Thermostat to furnace Y on LVTB, which is simply
a connecting point on its way to the AC units 24v contactor coil located outdoors.
It actually isnt even attached to the furnace many times as it serves no purpose there and simply
continues to the AC unit with the copper lineset that the AC unit feeds.
The remaing 24 volt Thermostat wire goes back to common on transformer to complete the Yellow
24 volt control circuit.
Green or G exits the Thermostat and connects to G on LVTB for the fan relays 24volt coil
and returns to Common to complete the Green 24 volt control circuit.
O is for a Heat pump reversing valves 24 volt solenoid, and return to Common as all 24v circuits must to terminate or complete the circuit.
Some parasitic type Termostats need the 24v power to run, some are battery, some are both.

Nov 01, 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

Have a Ruud AC unit the problem I have after installing a new condenser fan motor when I throw the circuit breaker the unit will not turn on but when I push the contacts on the contactor in manualy the fan...


The contactor engages from low voltage power from the thermostat as does the outside condensing unit. You may have blown the low voltage transformer or have a loose thermostat wire. Check line voltage(220 volts) to the transformer. Check load voltage(24 volts) from the transformer. If no voltage out,replace the transformer. If you have voltage out(24) check the thermostat wires and the thermostat. If you have a digital thermostat there is a 5 minute delay in the thermostat after power is restored before it activates.

Oct 08, 2009 | Ruud Central System Air Conditioner

1 Answer

Carrier (outside) Coleman Evcon (inside) Air Conditioning question


transformer has just 4 leads. 2 for primary which is your 110 volts and 2 for secondary which is supposed to be 24 volts ac. if you splice the two secondary wires coming out of your transformer, you should be able to get a 24 v ac there.

the box that you are referring to could be a fire controller that in case of fire, it would shut off the fan and the compressor outside.


tnx 4 using fixya,

drcool

Oct 01, 2008 | Heating & Cooling

1 Answer

I have a Carrier 38tra048340 ac 4 ton unit outside, heater in attic. Thermostat is Totaline P374-1100. Power went out than back on after a few hours due to vehicle crashing into power pole. AC was running...


Blank screen sounds like a fried thermosat. Abrupt outages can affect certain types of thermostats. Make a jumper wire and jump across R and G. See if you get any action from anywhere. If a fan or compressor kicks in you know you have a burned out thermosat...

Jun 23, 2008 | Carrier Heating & Cooling

Not finding what you are looking for?
Heating & Cooling Logo

Related Topics:

158 people viewed this question

Ask a Question

Usually answered in minutes!

Top Heating & Cooling Experts

paulcarew

Level 3 Expert

2519 Answers

Dan Webster
Dan Webster

Level 3 Expert

8220 Answers

Donni Steen

Level 3 Expert

659 Answers

Are you a Heating and Cooling Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...