Crossovers between burner 1 and 2 seemed show show some rollout after blower startup. But seeing that , I normally double check the 5/16s screws holding the clamshell to the front plate. When loose will allow blower air to hit the burners. Enjoy your vids.
Had a call last night on a gas package unit on the side of the house. The roofing company just replaced the roof and put a tarp over the package unit and blocked the exhaust vent which made the flame rollout and trip the rollout switch. After resetting the switch I watch the flames for 30 minutes and checked for carbon monoxide everything was good. Point being in my opinion a blocked exhaust will cause the flames to rollout and trip the rollout switch.
On Rheem condensing furnaces I've seen flame rollout due to one models Inducer tranistion tees had a restrictor inside to slow down the flue gas. Rheem did this to gain an extra 1% efficiency. In some conditions it causes the flames to rollout back out into the burner box and either trip the rollout or burn up the rollout wires.
Somehow I thought I'd commented on this video. I tried something similar on a 98% efficient Bryant furnace in the classroom, just to see if I could starve it of enough air to trip the pressure switches. At the time, the idea of a flame rollout possibly taking place never occurred to me. Although I didn't kick it up to the second stage, nothing I could do to the combustion air intake would get it to stop running.
Have has roofers cut thru the double walled Y style pvc pipe at the roof line. Obviously the exhaust and vent weren’t separated correctly afterward. Pressure switch killed it everytime unless I held it in correct place.
Yes, it does. My 4th burner (lowest) and eventually 3rd burner was choking and going off after 10-20 seconds and flame sensor was turning the furnace down. I detached the vent in the attic for a short test and it recovered back. Other furnace was fine so gas pressure was ok. I had my roof done recently and gas caps were replaced. Likely that they pushed it way too much, I called the guys and they will come/check.
Why not get a twist and lock cap? Recently, I have to replace furnace vent since the original builders of the house did a poor job and never really secured the very top 4 foot of the furnace vent. It was never twisted and locked and was secured by vent lead flashing for Spanish tile. So after about 14-15 years it rip away and blow off the 2nd level roof. When inspecting the furnace one day during the summer noticed that I can see light outside. Ended up replacing about 5 foot of the B-vent with home depot brand and ordered online a twist and lock b-vent cap that matches up with the same home depot b-vent brand. Also replaced the the rip up lead flashing.... I shortened the b-vent by a foot since current city regulations allowed it. It's just funny in this time and age that there are no industry standard for twist and lock for b-vent. You have to keep with the same brand or have some kind of adapter for different brand of b-vents.
Both.. This is still a rollout condition, towards the end you can see that the crossovers are lifting (most notably the far left). I assure you if you let this labor for 20-30 min that burner box would trip a rollout. However it may not run that long b4 it faults on flame rectification or pressure switch. Now for a real world scenario, throw a gust of wind at it and its likely to trip the PS especially being that closs to the balance point. A newer furnace with dual reference points, one before combustion blower housing (collector box) and one within blower housing, makes this an even less plausible condition. Usually a partially plugged secondary or large breach in primary is the only thing that will allow heavy rollout and not fault a pressure switch. Also worth noting, shouldnt any termination going threw structure be class B, pretty unlikely for a cap to be pushed too far down on interlocking fitting.
I will do a test of the longer operation. As for dual reference points, this is an 80% furnace. It does not use dual reference points. I may even try the wind gust. All 80% furnaces should be using B vent for the entire vent. But I would not guarantee that even with B vent, the termination could not be pushed down too far. GFM
@@grayfurnaceman I dont know that its really worth the effort for something so trivial, either way there is no harm or danger in either outcome as one of the 3 safeties would cause suspect. I think a better use of your time may be in testing the flame characteristics vs unmetered air like we spoke about in your other video. As far as wind caps, the ones I'm familiar with spin and lock into place, making it impossible to goof. And correct, which is why I said newer furnaces with dual ref design.
This rose a red flag with me as well, time to start working this out after making this a proper installation. Then and only then can you actually be confident in your diagnostics. Trying to fix a leaning building with a trash foundation.
I had this exact issue at my house. Except it took 15 years, one replaced heat exchanger, and two new furnaces to figure it out. The issue, it appears, is a partial blockage. The inducer fan spins up at a relatively fast rate, then settles to a more normal rate. That creates the vacuum needed, and the flame will start. But, after a while, back pressure builds, and you get enough heat backing up that the rollout switch detects a rollout. No actual flame rollout is evident.
I see this quite a bit where the Roofer pushes down the Vent cap. Most of the time a water heater is "Y" into the vent. So the furnace exhaust pushes out the water heater hood. These roofers could kill someone with CO poisoning. Plus, the condensation at the venting seams is a dead giveaway
I think it would be interesting to see at what point the pressure switch WOULD drop the burner out. It got as high as -.45 which I would have though would drop out the burner.
If it got below .4, it shut down the burners. The point of this exercise was to determine if there was a point that the pressure switch would stay closed and the flame would rollout. GFM
All furnaces have pressure switches that are expressly there to stop the cycle if the vent is not clear. Does not mean they always work as they should. GFM
Sir I'm back, you helped me with my gas valve issue. Thanks you saved me 600 bucks. Now I'm back lol I'm getting 6 flashes on my Goodman and its says it's the flame rollout . My fans wont stop and the flame wont come on. How to fix?
This probably an open rollout switch. It is a manual reset switch probably located near the burners. However, resetting the switch is not a repair. It rolled out the flame for a reason. You could have a crack in the heat exchanger. Careful on this one. You may need a repairman. GFM
You are correct. A blocked secondary heat exchanger will cause a rollout, but will not shut off the pressure switch. However, a blocked CVA will cause the firebox pressure switch to open. GFM
If there is a water heater sharing the same vent, will a full blockage on the roof cause the furnace to malfunction? Or will the exhaust gases backfeed down the water heater exhaust and into the structure?
If there is a W/H on the vent, it will definitely backfeed. The result of this usually is the pilot light is extinguished. I look at this as a good result. The problem then is the tech that comes out for the water heater problem has to figure out it is not a problem with the water heater, but with the furnace venting. GFM
Grayfurnaceman, I just cleaned my burner tubes and orifices on my furnace. I switched it on to test it, and when I shut it off, there are small flames at all five orifices. It has spark ignition, no pilot light. It's been off for almost 10 minutes and the small orange flames are still burning? It's an older, Weather King outdoor combo unit, and has a Honeywell regulator? Flow valve? Not sure what it's called. Any suggestions would be appreciated.
@@grayfurnaceman It wasn't doing this prior to cleaning the unit. I'm assuming there's no way to clean the valve if I accidentally got some crud in it? Also, I'm running lpg, if I buy a new valve set for natural gas, can I use the lpg conversion out of the old valve to convert the new one? It only regulates flow pressure, and doesn't function as a valve, correct? Thank you for your speedy response to my initial question.
@@mattschamel6550 It is a combination valve which means it provides regulation, safety shut down and solenoid valve. Any replacement valve must be designed for LPG. GFM
Because it’s not completely blocked and that inducer motor pulling 1inch wc and the pressure switch closing at 0.5. It may or may not open the switch and error off on safety. If the exhaust pipe was completely blocked it would have error out and the pressure switch would not have closed. If u look at the manometer it’s running 0.4 wc which is still within tolerance, thus it’s still running.
The 1" wc is with a clear vent. I closed off the vent until the pressure would just barely close. The point of this exercise was to block the vent to the point that the pressure switch would barely close. If the flame then rolled out, there is a design problem with the furnace. The pressure switch is there to protect from this problem. GFM
Having a supplemental rollout switch is something that most furnsces have have down here in Oz for more than 20 years....AND perhaps pressure switch build qualitycould be tweeked somewhat?
At 4:27. Duh. It does roll out. But there isn't a roll out switch right there. That's your flame sensor on the left burner. Also.if the flue was partially plugged just enough for that pressure switch to stay closed for longer you would have seen that roll out again.
So what’s the conclusion? That the pressure switches and inducer are not working right? Or a blocked vent doesn’t matter? I bet on a wall furnace there would be rollout. I don’t know...
There is no exact conclusion. I will be doing this on more models of furnace to see if there is a difference with them. Actually a wall furnace with a draft hood will not rollout flame. The draft hood will spill. GFM
I know I have a issue with flame rolling over because I can see it, but it only does it when the fan kicks on? Can you point me in the right direction?
That is classic cracked heat exchanger. Either the heat exchanger or the furnace must be replaced. This is an unsafe condition. Possible CO poisoning. GFM
@@colonelradec5956 Thanks for the link. The furnace rollout did its job and shut down the burner when the temp got too high. I can't give a reason for the failure of the pressure switch. It should have shut down the sequence of operation before the burner came on. GFM
I was thinking more about a true residential set up with return air. As the space nears set point, warmer air and a blocked flue, to me would go off on high limit
@@grayfurnaceman , Just curious, why do you believe that? I get that there is limited air flow, but the heat of the flame is close to the limit switch, at least on my older furnace, which I believe both opened and closed within a predetermined heat range. Modern furnaces probably have a limit switch that cuts out only above a set temperature.
It's a Janitrol, cant use a GMP to test any theory. I'd put my career on that there are rings voided on that thing which would effect draw readings also. Love the vids tho.
@@grayfurnaceman I got her fired up today. . Ran it for a few Cycles. . Iran a manifold on the top and an air intake. I used the old stuff. Now I've just got to run some ductwork to the house. And we're in business. Thanks, brother. !
I question how blocked that furnace flue was. Where is the heated gas going if the flue is blocked? Back out anyway it can. As with the first test, you saw rollout on the left burner which made perfect sense... but not on the second test. What changed? CZcams is often untrustworthy.
I am not making a conclusion here. The 2 tests were done back to back. The only difference was the furnace during the first test was cold. The second test had a warm furnace. What I do think is that with an almost totally blocked vent, the pressure switch should have shut down the furnace. GFM
That is not a rollout. The intermittent flame failure is a failure to pull enough fuel air mix into the heat exchanger. If I had a rollout, the flames would be continuously rising above the entrance to the heat exchanger. GFM
@@grayfurnaceman I agree but at 4:27 the flame failure kind of has a roll out effect. And I've seen the newer units with more sensitive roll out switches trip on things like that. Also the switches on certain units are right above those burners and trip easily from.flame abnormalities. I love how you put a theory to a test. I would like to see and do more of this myself with a.c and heat.
Crossovers between burner 1 and 2 seemed show show some rollout after blower startup. But seeing that , I normally double check the 5/16s screws holding the clamshell to the front plate. When loose will allow blower air to hit the burners. Enjoy your vids.
i like the fact that you dive into the experimental/ scientific aspect of HVAC like what if cases, vs simple repair vids.
Thanks for the support.
GFM
Had a call last night on a gas package unit on the side of the house. The roofing company just replaced the roof and put a tarp over the package unit and blocked the exhaust vent which made the flame rollout and trip the rollout switch. After resetting the switch I watch the flames for 30 minutes and checked for carbon monoxide everything was good. Point being in my opinion a blocked exhaust will cause the flames to rollout and trip the rollout switch.
On Rheem condensing furnaces I've seen flame rollout due to one models Inducer tranistion tees had a restrictor inside to slow down the flue gas. Rheem did this to gain an extra 1% efficiency. In some conditions it causes the flames to rollout back out into the burner box and either trip the rollout or burn up the rollout wires.
Your like the new and improved Dr zarkloff. New subscriber here!
great video. very helpful.
Very helpful, thanks for this great video
Welcome
GFM
Just did a Reno and the ductwork needs to change but I was wondering if it could run for temporary heat. Maybe till the spring
Somehow I thought I'd commented on this video. I tried something similar on a 98% efficient Bryant furnace in the classroom, just to see if I could starve it of enough air to trip the pressure switches. At the time, the idea of a flame rollout possibly taking place never occurred to me. Although I didn't kick it up to the second stage, nothing I could do to the combustion air intake would get it to stop running.
What is being attempted here is not reducing combustion air but blocking vent gas from exiting the furnace.
GFM
@@grayfurnaceman Blocking the flue pipe on a high efficient furnace the board won't let it run if its blocked.
Have has roofers cut thru the double walled Y style pvc pipe at the roof line. Obviously the exhaust and vent weren’t separated correctly afterward. Pressure switch killed it everytime unless I held it in correct place.
Its hard to stop a trane. Unless theres a bird in the flue. Good video this is something i will keep an eye out from now on.
Yes, it does. My 4th burner (lowest) and eventually 3rd burner was choking and going off after 10-20 seconds and flame sensor was turning the furnace down. I detached the vent in the attic for a short test and it recovered back. Other furnace was fine so gas pressure was ok. I had my roof done recently and gas caps were replaced. Likely that they pushed it way too much, I called the guys and they will come/check.
They do sometimes push them down far enough to block it off.
GFM
Why not get a twist and lock cap? Recently, I have to replace furnace vent since the original builders of the house did a poor job and never really secured the very top 4 foot of the furnace vent. It was never twisted and locked and was secured by vent lead flashing for Spanish tile. So after about 14-15 years it rip away and blow off the 2nd level roof. When inspecting the furnace one day during the summer noticed that I can see light outside. Ended up replacing about 5 foot of the B-vent with home depot brand and ordered online a twist and lock b-vent cap that matches up with the same home depot b-vent brand. Also replaced the the rip up lead flashing.... I shortened the b-vent by a foot since current city regulations allowed it. It's just funny in this time and age that there are no industry standard for twist and lock for b-vent. You have to keep with the same brand or have some kind of adapter for different brand of b-vents.
very good, thank you ...
Both.. This is still a rollout condition, towards the end you can see that the crossovers are lifting (most notably the far left). I assure you if you let this labor for 20-30 min that burner box would trip a rollout. However it may not run that long b4 it faults on flame rectification or pressure switch. Now for a real world scenario, throw a gust of wind at it and its likely to trip the PS especially being that closs to the balance point.
A newer furnace with dual reference points, one before combustion blower housing (collector box) and one within blower housing, makes this an even less plausible condition. Usually a partially plugged secondary or large breach in primary is the only thing that will allow heavy rollout and not fault a pressure switch. Also worth noting, shouldnt any termination going threw structure be class B, pretty unlikely for a cap to be pushed too far down on interlocking fitting.
I will do a test of the longer operation. As for dual reference points, this is an 80% furnace. It does not use dual reference points. I may even try the wind gust.
All 80% furnaces should be using B vent for the entire vent. But I would not guarantee that even with B vent, the termination could not be pushed down too far.
GFM
@@grayfurnaceman I dont know that its really worth the effort for something so trivial, either way there is no harm or danger in either outcome as one of the 3 safeties would cause suspect. I think a better use of your time may be in testing the flame characteristics vs unmetered air like we spoke about in your other video. As far as wind caps, the ones I'm familiar with spin and lock into place, making it impossible to goof. And correct, which is why I said newer furnaces with dual ref design.
This rose a red flag with me as well, time to start working this out after making this a proper installation. Then and only then can you actually be confident in your diagnostics. Trying to fix a leaning building with a trash foundation.
I had this exact issue at my house. Except it took 15 years, one replaced heat exchanger, and two new furnaces to figure it out. The issue, it appears, is a partial blockage. The inducer fan spins up at a relatively fast rate, then settles to a more normal rate. That creates the vacuum needed, and the flame will start. But, after a while, back pressure builds, and you get enough heat backing up that the rollout switch detects a rollout. No actual flame rollout is evident.
I just came across that exact problem on a new construction and sure enough I checked the vent on the roof and it was blocked by the cap
I see this quite a bit where the Roofer pushes down the Vent cap. Most of the time a water heater is "Y" into the vent. So the furnace exhaust pushes out the water heater hood. These roofers could kill someone with CO poisoning. Plus, the condensation at the venting seams is a dead giveaway
I have seen that too. I think they just don't understand how that cap works.
GFM
What's the Carbon monoxide reading at the burners?
I think it would be interesting to see at what point the pressure switch WOULD drop the burner out. It got as high as -.45 which I would have though would drop out the burner.
If it got below .4, it shut down the burners. The point of this exercise was to determine if there was a point that the pressure switch would stay closed and the flame would rollout.
GFM
Please do a co/combustion test on a furnace with this condition!
That will be a good idea see the Ppm s. With a combustion test.
I had a bird block a vent and it was a concentric termination and had someone at the furnace and the flames did roll out it was a Bryant furnace.
@Marco A yes they do but somehow it wasn't working.
All furnaces have pressure switches that are expressly there to stop the cycle if the vent is not clear. Does not mean they always work as they should.
GFM
@@grayfurnaceman this is true.
Good one.
Sir I'm back, you helped me with my gas valve issue. Thanks you saved me 600 bucks. Now I'm back lol I'm getting 6 flashes on my Goodman and its says it's the flame rollout . My fans wont stop and the flame wont come on. How to fix?
This probably an open rollout switch. It is a manual reset switch probably located near the burners.
However, resetting the switch is not a repair. It rolled out the flame for a reason. You could have a crack in the heat exchanger.
Careful on this one. You may need a repairman.
GFM
Also.happens all the time on a plugged secondary heat exchanger or plugged cva on high efficient unit.
You are correct. A blocked secondary heat exchanger will cause a rollout, but will not shut off the pressure switch. However, a blocked CVA will cause the firebox pressure switch to open.
GFM
@@grayfurnaceman What is a CVA ?
@@uski Combustion and ventilation air.
GFM
@@grayfurnaceman Thanks !
@@uski Welcome
GFM
It look like a rollout flame,to me
If there is a water heater sharing the same vent, will a full blockage on the roof cause the furnace to malfunction? Or will the exhaust gases backfeed down the water heater exhaust and into the structure?
If there is a W/H on the vent, it will definitely backfeed. The result of this usually is the pilot light is extinguished. I look at this as a good result. The problem then is the tech that comes out for the water heater problem has to figure out it is not a problem with the water heater, but with the furnace venting.
GFM
Yes it will come out the draft hood on the water heater.
Grayfurnaceman, I just cleaned my burner tubes and orifices on my furnace. I switched it on to test it, and when I shut it off, there are small flames at all five orifices. It has spark ignition, no pilot light. It's been off for almost 10 minutes and the small orange flames are still burning? It's an older, Weather King outdoor combo unit, and has a Honeywell regulator? Flow valve? Not sure what it's called. Any suggestions would be appreciated.
@@grayfurnaceman It wasn't doing this prior to cleaning the unit. I'm assuming there's no way to clean the valve if I accidentally got some crud in it? Also, I'm running lpg, if I buy a new valve set for natural gas, can I use the lpg conversion out of the old valve to convert the new one? It only regulates flow pressure, and doesn't function as a valve, correct?
Thank you for your speedy response to my initial question.
@@mattschamel6550 It is a combination valve which means it provides regulation, safety shut down and solenoid valve. Any replacement valve must be designed for LPG.
GFM
@@grayfurnaceman thank you, I appreciate your help.
Because it’s not completely blocked and that inducer motor pulling 1inch wc and the pressure switch closing at 0.5. It may or may not open the switch and error off on safety. If the exhaust pipe was completely blocked it would have error out and the pressure switch would not have closed. If u look at the manometer it’s running 0.4 wc which is still within tolerance, thus it’s still running.
The 1" wc is with a clear vent. I closed off the vent until the pressure would just barely close. The point of this exercise was to block the vent to the point that the pressure switch would barely close. If the flame then rolled out, there is a design problem with the furnace. The pressure switch is there to protect from this problem.
GFM
Having a supplemental rollout switch is something that most furnsces have have down here in Oz for more than 20 years....AND perhaps pressure switch build qualitycould be tweeked somewhat?
The rollout switch became standard when induced furnaces were developed. The pressure switch on this unit operates within specs.
GFM
At 4:27. Duh. It does roll out. But there isn't a roll out switch right there. That's your flame sensor on the left burner. Also.if the flue was partially plugged just enough for that pressure switch to stay closed for longer you would have seen that roll out again.
The unit was set so that there was just enough vacuum to keep the pressure switch closed. And again, that is not a rollout. It is a flame failure.
GFM
So what’s the conclusion? That the pressure switches and inducer are not working right? Or a blocked vent doesn’t matter? I bet on a wall furnace there would be rollout.
I don’t know...
There is no exact conclusion. I will be doing this on more models of furnace to see if there is a difference with them. Actually a wall furnace with a draft hood will not rollout flame. The draft hood will spill.
GFM
I know I have a issue with flame rolling over because I can see it, but it only does it when the fan kicks on? Can you point me in the right direction?
That is classic cracked heat exchanger. Either the heat exchanger or the furnace must be replaced. This is an unsafe condition. Possible CO poisoning.
GFM
it's dancing and flickering enough on the cross overs it may eventually cause the roll-out switch to trip. but no guarantees.
The dancing and flickering is pretty normal for this furnace. Janitrol GMP model.
GFM
fair point
Would you happen to know what model that furnace is. I have one just like it but I cannot find anywhere where it says the brand or model number.
Its a Goodman GMP080 from the middle 1990s.
GFM
grayfurnaceman thank you so much!
How to wire a furnace and therostat?
The power wiring is straightforward. Black to black, white to white green to ground. Thermostat, R to R and W to W.
GFM
theres a video on youtube of a blocked vent causing rollout. he went on roof moved it and it ran fine after.
Send me the link.
GFM
@@grayfurnaceman czcams.com/video/fWC2smK9hvg/video.html thats the youtube vid link.
@@colonelradec5956 Thanks for the link. The furnace rollout did its job and shut down the burner when the temp got too high. I can't give a reason for the failure of the pressure switch. It should have shut down the sequence of operation before the burner came on.
GFM
@@grayfurnaceman yea im no pro but i thought the same. seems like they don't always work? which is kinda sketchy lol.
Would instead trip on high limit? I've seen roll out do to cracked heat exchanger, pressure switch issues with blocked flue.
The limit should not open.
GFM
I was thinking it may have tripped on the high limit switch, but his second test eliminated that thought as it ran much longer.
I was thinking more about a true residential set up with return air. As the space nears set point, warmer air and a blocked flue, to me would go off on high limit
A blocked flue will not open the high limit.
GFM
@@grayfurnaceman , Just curious, why do you believe that? I get that there is limited air flow, but the heat of the flame is close to the limit switch, at least on my older furnace, which I believe both opened and closed within a predetermined heat range. Modern furnaces probably have a limit switch that cuts out only above a set temperature.
It's a Janitrol, cant use a GMP to test any theory. I'd put my career on that there are rings voided on that thing which would effect draw readings also. Love the vids tho.
The ht exchanger is intact on this one. No rings off.
GFM
I'll quit tomorrow, good day.
Can a natural gas furnace be utilized without duct work.
It can be, however, the circulating fan may overdraw power without ductwork.
GFM
@@grayfurnaceman Thank you so much for the reply. Any chance you could slap a video together? ?
I will see what I can do.
GFM
@@grayfurnaceman I got her fired up today. . Ran it for a few Cycles. . Iran a manifold on the top and an air intake. I used the old stuff. Now I've just got to run some ductwork to the house. And we're in business. Thanks, brother. !
A low powered Inducer motor or failing inducer motor will cause flame rollout.
not really if the pressure switch is working
My kid put a rock into the exhaust. Is that bad? I can't get it out.
If the furnace still works ok, its fine. If it stops and give a pressure switch fail, you will have to get it out.
GFM
I question how blocked that furnace flue was. Where is the heated gas going if the flue is blocked? Back out anyway it can.
As with the first test, you saw rollout on the left burner which made perfect sense... but not on the second test. What changed?
CZcams is often untrustworthy.
I am not making a conclusion here. The 2 tests were done back to back. The only difference was the furnace during the first test was cold. The second test had a warm furnace.
What I do think is that with an almost totally blocked vent, the pressure switch should have shut down the furnace.
GFM
You still have a draft. Try blocking the vent completely. The flames can’t get drawn in unless there is air moving out of the flue.
If you block the vent completely, (and this vent was very close to that) the pressure switch will shut it down.
GFM
interesting,nice post GFM
side note the c.o. would be high and rising. danger danger
right i have seen this before on a furnace with a partially blocked chimney
You tripping? The left burner was rolling out sporadically the first time you fired it up.
That is not a rollout. The intermittent flame failure is a failure to pull enough fuel air mix into the heat exchanger. If I had a rollout, the flames would be continuously rising above the entrance to the heat exchanger.
GFM
@@grayfurnaceman I agree but at 4:27 the flame failure kind of has a roll out effect. And I've seen the newer units with more sensitive roll out switches trip on things like that. Also the switches on certain units are right above those burners and trip easily from.flame abnormalities. I love how you put a theory to a test. I would like to see and do more of this myself with a.c and heat.
What causes intermittent flame failure?
@@JuanRivera-ff6fd intermittent would look at flame sensor. Gas valve. Depends if millivolt system etc
@@CommonSenseFishing209 my system has a standing pilot light ?