Our furnace stopped working so we called a repair person. He reset the flame rollout sensor and it worked - through 1 cycle then shut off at the end of the cycle. We replaced the flame rollout sensor. The furnace will work if we go under the house to reset it each time. While we're watching the unit, the sensor trips near the end of the cycle or is the sensor tripping and ending the cycle?
The flame rollout sensor is a rather important safety feature that ideally only trips when there's an overtemperture outside of the combustion chamber. I'd encourage you to get a better quality tech in ASAP to check for a cracked heat exchanger, gas overpressure, restricted airflow (changed the filter lately?), maybe a blocked condensate drain if this is a high efficiency furnace. If the sensor was replaced and it's still tripping, you've got a potentially dangerous overheating issue that you don't want to try to bypass.
Sounds like your burners need to be cleaned, you will need to pull them out and clean the rust out of them. the rust builds up on top of the burners and when you gas valve opens and fills the burners full of gas you will have a roll out of flames. hope that helps.
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1. Thermostat calls for heat.
2. Draft inducer motor starts.
3. Pressure switch attached by a small plastic or rubber tube senses the negative pressure produced by the draft inducer and closes.
4. Draft inducer runs for 30 seconds to a minute before you hear a gas hissing sound. The ignitor did not glow, the flame sensor (a small metal probe about 1/8" in diameter, with a white porcelain base) does not sense the flame, so after 8 to 10 seconds the hissing sounds stops with no ignition of gas to heat your home. Your furnace shuts down and goes into a lock out condition until you turn your power switch back off and on again. Then the sequence starts all over again with no ignition of the gas.
Solution:You probably need to purchase and install a new ignitor. I would suggest that you inspect your ignitor closely for cracks.Make sure you do not touch the ignitor with your bare hands. If you do not visually see a crack, then you could have a furnace control board problem or a limit, rollout switch problem. Please see "limits, rollout switches & furnace control boards" further down on this page. The furnace's control board might not be supplying the voltage to the ignitor. If your furnace lights and the gas stays on for 8 to 10 seconds, then shuts right back off, then you need to clean your flame sensor with light sand paper or steel wool. You might need a new flame sensor, but most of the time they can be cleaned an will work well after cleaning.
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If you have a cracked heat exchanger this will cause the flames to rollout and trip this switch. Its meant to stop the furnace from running and putting carbon monoxide in your home. Watch the furnace as it tries to light if when the gas valve opens and flame is established it should go into the tubes heat the heat exchanger and then your main blower motor will come on. When your main blower comes on is usually when you see the flames rollout and trip that switch. If this happens you can either buy a heat exchanger or new furnace if its a older unit Obama still has that awesome tax credit til 12-31-2010.
How do you test a
pressure switch and other limit controls? This is for people
who are experienced with electrical equipment and the use of a Volt Ohm meter.
*Please never by pass a pressure switch or limit control. The pressure switch
and limit switches are there for your safety. You would
test by setting your volt meter to "Volts AC" and test the rollout switch by
placing one meter probe on one terminal of the rollout switch and your other
meter probe to a good ground. Have the red probe touching the top
terminal of the rollout switch and the black probe touching a ground (body) of
the furnace. You should be getting 25.85 volts which means the rollout is
good on the top terminal. I would next test the bottom terminal of the rollout
by touching the red meter probe to the bottom terminal on the rollout switch and
the black terminal to ground. If I get 25.85 volts on the bottom terminal the
rollout is good. If I do not get any voltage on the bottom terminal then the
rollout has tripped and can be reset (if equipped) by pressing in on the little
button or replaced. If your rollout
switch is tripped you probably have a stopped up heat exchanger or a leaking
heat exchanger. I would recommend calling in a service technician to find out
why the rollout switch tripped. If you have an open limit control either
the furnace has over heated or the limit has gone bad. Problems that would make
a limit open up would be dirty filters, dirty evaporator coil causing a
restriction in the air flow or a slow blower motor (check the capacitor on the
blower motor to make sure it is good). A weak blower motor capacitor will cause
the blower to run slow and eventually fail. Pressure switches, and limit
switches can be tested with a meter in the same manner. With the furnace
calling for heat you can test each of the terminals on the pressure switch to
ground to make sure the pressure switch is closed. You should be getting between
24 to 28 volts from each terminal to ground if the pressure switch is closed. If
the pressure switch is open you either have a stopped up vent, drain line (if
you have a condensing furnace) or bad pressure switch.
with just the information you have provided, i would guess you have a rollout sensor somewhere that has been tripped. there are usually a push button reset on the goodman models. this usually happens when you have flame outside the heat exchanger and is not a good thing. i have seen some goodmans where the wiring for the safety sensors is melted from the flame rolling out due to a crack in the heat exchanger. it this is the case, you need to replace the heat exchanger or consider getting a new furnace. the safety wiring on most goodmans is usually purple. trace all the purlple wiring and see if some of it is melted or if any of the push button switches has tripped. on a high efficiency model, there will be several wires and rollout switches located along the top of the burner box above the burners. good luck. by the way, anytime a safety has been tripped, the fan will default to the on postion as a precaution in case the furnace has got too hot. that may explain the fan running all the time.
You need to find the rollout switch and see if it has a manual reset button on it or not. There are 3 styles of rollout controls. One is a disc type that mounts behind the burner ends, there may be more that one,possibly one on each side of the burner tray. This style rollout is usually manual resetting. It most likely will be black or silver in color and usually is about the size of a penny in diameter and about 1/2" in thickness with 2 wires going into it and a red push type button in the middle. The next style is similar two the first as it is manual resetting also, but this rollout uses a small copper capillary tube that runs just behind the burner ends and is mounted to the burner tray. If you follow this tube it will lead you to the manual reset button which is most likely mounted below the burner tray. The last style rollout is what they call a fuseable link, this is mounted behind a burner end and looks like a resister used in electronics, it is about 3/4" long and about 3/16" in length and is silver in color. It is mounted in a porcelain mount. This style is not resettable it has to be replaced with one of the same temperature rating. You would need to go to a Carrier/Bryant dealer to get the right one. Either take it with you or bring the model and serial number of your furnace. The most important thing about rollouts is that there is a reason it opened up(went faulty). The reason they trip or open up is due to the burner flames are rolling back out of the burner box and getting the rollouts hot enough to trip or open up. This is telling you there is a serious issue with your furnace that needs to be found and repaired. There are a couple of things that is causing this. They are that your exhaust is not venting properly. Your exhaust venting could be restricted with whatever. You need to pull your venting off and look for restrictions all the way from your heater to the end of the chimney. The next thing it could be is that your heat exchanger is cracked enough to allow positve air pressure on the exhaust system when the indoor blower fan is running. You can check this out yourself by watching the burner flames when the indoor fan comes on. If the heat exchanger is cracked enough the burner flames will flutter or move back toward you when the indoor fan comes on causing the rollout to trip or open up. Most manufacturers have a 20 year warranty on the heat exchanger(parts only,you pay the labor cost). Depending on the age and condition of your furnace it may not pay to have the heat exchanger replaced. I hope I was able to steer you in the right direction!! Good luck!!
Roll out flames are a safety device on a furnace. On the furnace back up under where your burners are located, you will see a switch with a manual reset button on it. What is happening is the flames have rolled out further than they should have at one point during its cycle, and tripped this switch to keep the flames from burning the wiring and what ever it might reach.It is one of many safety's on you're furnace.Reset this switch, like I said, it would be where the flames would come out a little to far. Sometimes they will trip if you get a gust of wind down the flue pipe from the roof. Or, if the burners are getting plugged up with black soot.Check this also.Until the switch is reset, the burners will not come on. You should have no problem finding it, mounted just at the end and above the burners. Walk out side and make sure your flew cap is in place. I have found birds nesting in flew pipes that will cause this.Reset it and watch it for awhile to see how it burns.Don't worry, as that is why the switch is there, for you're safety. I am sorry for such a long solution, but it is called for on this problem. Please let me know how it turns out. Sincerely, Shastalaker7
Heat sensor....Or a flame sensor. Flame sensor is connected to a "single" wire under the buners usually found on the left side. Heat sensors (or flame rollout switches) are found surrounding the burner box. The most common bad one will be located just above the burners. it "should" have a small reset button in the middle just between the two wires. If the furnace does light even for a short time the rollout switch is not bad.
you have a flame rollout switch tripped or a limit switch open. in either case you should call a hvac service company. how old is your unit? the carrier unit is designed to run the fan contin. in the event of either of these failures.