In automatic operation on a call for heat, the thermostat switch closes. This energizes the compressor contactor and the blower motor in the air handler. The compressor contactor closes and the compressor turns on along with the condenser fan motor.
Full Answer
What is the sequence of operation on a furnace?
We call it sequence of operation! Every technician that goes out to work on a furnace knows the operation steps and by that he can tell what is failing or what to replace. The thermostat calls for heat.
When the thermostat is satisfied the heating sequence of Operation?
When the thermostat is satisfied the main burners turn off 7. The blower continues to run to dissipate extra heat out of the heat exchanger. When the temperature reaches the cut-out setting on the fan limit control , the fan stops. Finally, the heating sequence of operation is complete
How does a thermostat heat relay work?
A thermostat heat call energizes the electric heat relay. 4. The electric heat relay contacts close, powering the heat elements and the indoor blower. 5. The heat call ends, and the thermostat de-energizes the electric heat relay. 6. The electric heat relay contacts open, de-energizing the electric elements and indoor blower. 7.
How do you know when the sequencer on a furnace is working?
Sequence Of Operation on an Electric Furnace The thermostat calls for heat. You should hear the furnace relay "Click". The Power now energizes the sequencer and the number one heating element has power (element starts getting warm) and the blower fan comes on,
What is the sequence of operation for heating?
Hot surface ignitor begins getting hot / direct spark ignitor begins to spark. Gas Valve opens. Furnace Lights. Flame Sensor senses flame.
What happens when a thermostat calls for heat?
When the thermostat calls for heat, a signal is sent to power up the furnace and the blower fan or the boiler, heating your home.
How a furnace works step by step?
0:445:46How a Furnace Works | Repair and Replace - YouTubeYouTubeStart of suggested clipEnd of suggested clipThe exhaust fumes are released through the flue gas vent. The blower fan then pushes air over theMoreThe exhaust fumes are released through the flue gas vent. The blower fan then pushes air over the heat exchanger. And circulates it around your home the furnace runs until the thermostat detects.
What turns on first in a gas furnace?
The venter motor will start and begin the pre-purge process ensuring that no combustible gasses are sitting in the combustion chamber. 5. The pressure switch will be proved closed. This will run the system through it's self safety test to ensure proper operation.
How do I know if my thermostat is calling for heat?
4:347:08Test the THERMOSTAT with Jumpers! - YouTubeYouTubeStart of suggested clipEnd of suggested clipAnd then we would go ahead and turn her power back on and see if our Heat turns on you may have yourMoreAnd then we would go ahead and turn her power back on and see if our Heat turns on you may have your blower motor turn on for about 30 seconds in order to cool off the heat exchanger.
Why is my thermostat working but no heat?
The most common reasons for such a problem are a dirty filter, thermostat malfunction, pilot ignitor, wrong settings, or low battery issue. In such a case, all you would have to do is clean the device, double-check the thermostat settings, or replace the batteries.
What is the first step in the operational sequence?
What is the first step in the operational sequence? The thermostat calls for heat. Hot Surface Ignition System (HSI) controls lockout after how many unsuccessful attempts? 3 or more attempts.
How should a furnace run?
While it should cycle throughout the day, clicking on too frequently may indicate a problem. Homeowners often find themselves wondering, "How often should my furnace cycle?" The answer lies in a gray area. On average, furnaces should kick on and turn off anywhere from three to eight times per hour.
What starts a furnace?
Your furnace starts when it receives a signal from the thermostat that tells it to turn on. Depending on the temperature you set, when the thermostat detects the air temperature dropping below that number, it activates the furnace.
How do you turn on a gas heater?
0:481:36How to Light Your Gas Heater - YouTubeYouTubeStart of suggested clipEnd of suggested clipWhat you want to do is turn it to pilot position press and hold how'd you do that get your igniter.MoreWhat you want to do is turn it to pilot position press and hold how'd you do that get your igniter. As soon as it lives keep holding your button down on pilot. For at least 20 seconds.
What does a thermostat do if it gets too cold?
If a thermostat gets too cool it will turn on the heat or turn off the cold air.
How do you know if the thermostat is bad?
7 Ways to Tell Your Thermostat Is BrokenThermostat Has No Power. ... AC or Furnace Won't Turn On. ... Heater or AC Won't Turn Off. ... Thermostat Doesn't Match Room Temperature. ... Thermostat Doesn't Respond. ... Short Cycling. ... Thermostat Forgets Programmed Settings.
How do I know if my thermostat is working properly?
6 Signs Your Thermostat Is BrokenYour HVAC System Won't Turn on. ... Your Air Conditioner or Heater Runs Non-Stop. ... Differing Temperature Readings Throughout the Home. ... Short-Cycling. ... Programmed Settings Keep Getting Deleted. ... There's No Response to Changes in Temperature Settings. ... Why Thermostats Break Down.More items...•
When should a thermostat kick on?
Getting the setback temperature right for your home can take a while and might require a bit of experimenting, but a good starting point is 60 degrees. The average home needs approximately 1 hour to warm up from 60 degrees to 70 degrees, so you should adjust your program accordingly.
What does "call for heat" mean?
A call for heat energizes the heating relay in the indoor air handler. This brings on the electric heating elements. In some cases, selecting emergency heat also powers an emergency heat relay. This relay's contacts electrically bypass any outdoor thermostats used to stage the electric heat elements.
What is emergency heat setting?
Mechanical:The emergency heat setting on the heat pump thermostat is manually selected by the equipment owner. This is usually in response to a malfunction in the outdoor unit. Doing so locks out the outdoor unit. The indoor auxiliary heating system must provide the heat required. Setting the thermostat to the heat position allows the outdoor unit to operate. Due to the expense of electric resistance heating compared to the efficiency of the heat pump, repairs should be made as soon as possible.
How does a refrigerant vapor travel?
8. The cold refrigerant vapor travels through the larger, outdoor vapor line to the reversing valve. The reversing valve directs the refrigerant into the accumulator.
What happens when you move the thermostat selector to the emergency heat position?
1. Moving the thermostat selector to the emergency heat position breaks the electrical circuit to the compressor contactor and the indoor blower relay.
How does refrigerant flow?
Refrigerant flows through the insulated, indoor vapor line to the finned indoor coil. Air from the indoor blower removes heat from the refrigerant vapor warming the indoor air and heating the house. When enough heat is removed, the vapor condenses into a high-pressure liquid.
How does a heat pump work?
Mechanical:Heat pump cooling operation is similar to the operation of a standard cooling system. 1. The compressor pumps out high-pressure, superheated refrigerant vapor. 2. The vapor leaves the compressor and passes through the reversing valve. 3. It flows through the outdoor vapor line to the finned outdoor coil.
What controls liquid refrigerant and refrigerant oil flow back to the compressor?
8. The accumulator controls liquid refrigerant and refrigerant oil flow back to the compressor.
When is the sequence of operation on a furnace?
Sequence Of Operation On Your Furnace. Posted by Darin DeVries on January 16, 2019. When your furnace isn't running properly or you start hearing the furnace make different noises how can you determine what is the problem is or narrow down the part that is failing, I get call after call from customers that have problems ...
What happens at the end of a heat call?
At the end of the heat call the thermostat in the house is satisfied it will send a signal to the furnace for shut down it closes the gas valve and the flame goes out.
What does the thermostat call for?
The thermostat calls for a heat call.
How long does it take for a furnace to turn on a 4th element?
This takes place in the sequencer (Low voltage turns on High Voltage) After about 15 to 30 Seconds the third element will come on (If you have a 15KW furnace. After about 15 to 30 seconds the fourth element will come on (If you have a 20KW Furnace.
What happens when the power comes on in a sequencer?
The Power now energizes the sequencer and the number one heating element has power (element starts getting warm) and the blower fan comes on,
When does a furnace turn off the blower?
Once the furnace is cool the fan thermostat in the furnace will turn off the blower until the next heat call.
What is the discharge air setting on a RTOM?
Units controlling modulating heat with thermostat inputs will use the Discharge Air Setpoint (DASP) from the RTOM (50-150 degrees F) to control the temperature of the units discharge air within +/- 2.0 degrees F (measured by the discharge air sensor). The discharge air will be used to satisfy the thermostat call from the space.
How long does it take for a modulating heat to go to 100%?
If the modulating heat output reaches 80% fire and remains there for 15 consecutive minutes without a call for 2 nd stage heat, the modulating heat output will go to 100% until all heat calls are cleared.
What happens when a modulating heat unit is lit?
On a modulating heat unit, when a call for heat is received, the burner will light at full fire (100%). After burner is lit, the unit controls will calculate a Discharge Air Setpoint and modulate the input rate down to match the load.
How long is the inter stage timer?
The 15 minute inter-stage timer is then reset.
What is a standing pilot gas furnace?
The standing pilot gas furnace is the most basic of all modern gas furnaces. They are being replaced with newer electronic ignition gas furnaces. The standing pilot gas furnace remains in use. So it is necessary to troubleshoot a standing pilot gas furnace from time to time. With most standing pilot gas furnaces, you will have two major components in the gas furnace that will need to be checked for problems.
What is Trane gas furnace?
Additionally, Trane gas furnaces are an example of a company that makes their own electronic ignition gas controls for their furnaces.
How does a gas valve work?
2. The main valve in the gas valve energizes provided none of the safeties are tripped. 3. Provided the pilot light is lit the main burners fire and begin heating the combustion chamber. 4. As the combustion chamber heats up the fan limit control slowly heats up.
What to do if you have a doubt about your furnace?
Additionally, you need to understand the basics of furnaces. If there is any doubt whatsoever, it is best to call a professional and let them troubleshoot the furnace. After all, we are talking about fire and gas that can explode. When in doubt, leave it to the professionals to troubleshoot your furnace.
Can a technician walk up to an electric furnace?
A good technician can walk up to an electronic ignition gas furnace and figure out basic problems in a few minutes. Furthermore, for the sequence of operation for an electronic ignition gas furnace see this article. Of the different types of electronic ignition gas furnaces, there are direct-fired gas furnaces and indirect-fired gas furnaces.
What is the sequence of operation of a heat pump?
Heat Pump Sequence of Operation - Every electrical-mechanical piece of equipment has a sequence of operation. While some manufacturers of heat pumps vary slightly with their heat pump sequence of operation the overall sequence of operation for a heat pump is the same for most manufacturers. So unless you have a special type of heat pump (they are out there – the Acadia heat pump is designed for extreme cold weather temperatures up North like Canada) the sequence of operation for your heating equipment should be very similar to what is described here. This is the basic operation of a heat pump like you will find in conventional heat pumps.
Where is the thermostat located on a condensing unit?
The thermostat is located near the return. When the thermostat senses the temperature is at the set point it breaks the switch inside the thermostat to turn off the heat. The compressor contactor inside the condensing unit de-energizes and the compressor shut down along with the condenser fan motor. The blower continues to run on a time delay and when the time expires the blower shuts down. That is the operation without including the defrost cycle.
How does a refrigerant blower work?
The refrigerant passes through the evaporator coil while the blower is blowing air across the coil where the heat is transferred from the refrigerant and coil and into the air. The air flows through the ductwork and is delivered into the spaces via the diffusers.
What happens when a heat pump defrosts?
When the defrost cycle energizes, the reversing valve switches mode to the air-conditioning mode. This switches the whole heat pump system into an air conditioner in the cooling mode. This is necessary to defrost the condenser coils. It is counteracted through heating strips by the defrost control.
How does a compressor work?
The compressor contactor closes and the compressor turns on along with the condenser fan motor. The refrigerant inside the refrigeration circuit begins to flow. The refrigerant in the condenser absorbs heat from the outside air. The refrigerant is transferred indoors to the evaporator coil where the blower is energized.
Why does my heat pump collect frost?
On colder nights when the heat pump runs for an extended period of time the heat pump will collect frost simply because it typically operates below the dew point and so the humidity will accumulate in the form of frost or ice on the condenser coils. This ice needs to be defrosted.
Why do manufacturers energize the reversing valve in the cooling mode?
The reason most manufacturers energize the reversing valve in the cooling mode is that if the valve fails they want the valve to fail to the heating cycle as heating is more important than cooling from the air conditioner.
What are the Typical Air Temperatures Supplied by Warm Air Heating Furnaces?
A conventional gas fired warm air furnace will provide heated air at 140 to 170 °F at the supply plenum. Naturally the temperature of this air drops as it moves through the ductwork system and will be cooler exiting the air supply registers.
Where does the air flow from a furnace?
inside the furnace blower compartment draws returning cool air from the living area and blows it across the outside of a steel "box" called the heat exchanger , sending the now-warmed air onwards into the furnace's output side or "supply air" plenum where it is sent into the building warm air duct system for delivery to the occupied space.
What happens when the thermostat is turned off?
When the thermostat has been satisfied and turns off the oil or gas burner at the furnace, the fan limit switch will cause the blower or fan unit to continue to operate until the temperature at the supply plenum has reached or dropped below the "cut-in" or "fan-on" lower limit on the switch.
Why does my furnace oil burner cycle on and off?
If the furnace oil or gas burner is very high capacity, or if the furnace fan/limit controls have been set to cause this effect, the burner may on some systems cycle on and off periodically while the warm air blower continues to run.
Why does my furnace blower blow so fast?
A dirty or blocked air filter or a dirty or blocked blower fan can cause this symptom because it is reducing the rate of air flow across the heat exchanger.
How does a furnace get hot?
Hot combustion gases produced by the oil or gas burner circulate inside of the furnace's metal heat exchanger causing it to get hot . Combustion gases leave the inside of the heat exchanger and flow through a flue vent connector to a building chimney where they are vented safely outside.
What does AFUE mean in furnaces?
Each furnace model is assigned an AFUE number. AFUE is an abbreviation for Annual Fuel Utilization Efficiency. In short, the AFUE tells you, for each dollar you spend on energy for heating by gas, oil, or another fuel, just how much of your dollar shows up inside the occupied space of your building as heat.
What is the first stage thermostat call?
12. The first stage thermostat call satisfies and ends the call for heat.
What controls liquid refrigerant and refrigerant oil flow back to the compressor?
8. The accumulator controls liquid refrigerant and refrigerant oil flow back to the compressor.
How does a refrigerant vapor travel?
8. The cold refrigerant vapor travels through the larger, outdoor vapor line to the reversing valve. The reversing valve directs the refrigerant into the accumulator.
How does refrigerant flow?
4. Refrigerant flows through the insulated, indoor vapor line to the finned indoor coil. Air from the indoor blower removes heat from the refrigerant vapor warming the indoor air and heating the house. When enough heat is removed, the vapor condenses into a high-pressure liquid. The liquid temperature is slightly warmer than indoor air temperature.
Is a heat pump a mechanical system?
Mechanical: Heat pump cooling operation is similar to the operation of a standard cooling system.
Is the heating cycle the same as the cooling cycle?
Electrical: The heating electrical cycle is similar to the cooling cycle.
