Thread: If you see flame-what could this be?

Hello all,

I have an inspection on Friday March 26th. The buyer called me to line up the inspection. I asked if she had any concerns with the property and she said the furnace. She said they didn’t take any panels off but they were still able to see flame from the inside of the furnace.

I called the realtor to get more info on this and he said he never saw anything like this before. He said the furnace had one pvc pipe going to the exterior. He said he saw the flame too when the furnace was running. He thought it might be that the furnace doesn't have an outside air intake for combution air. So this would mean the furnace is using inside are like an older unit would. Is this acceptable (if that's what it is)??

Anyone have an idea what this is?

I know this isn’t very much info but maybe someone knows what this could be.

Thank you
mk

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MK: With the older strip burners you will definitely see flames through the openings in the cover. If you get at the right angle you will also see flames with jet burners. Not so in closed burner compartments.

Originally Posted by A.D. Miller

MK: With the older strip burners you will definitely see flames through the openings in the cover. If you get at the right angle you will also see flames with jet burners. Not so in closed burner compartments.

A.D. Miller
Would the strip burner or jet burner furnaces have a pvc pipe going to the outside?
Only the newer high efficiency furnaces have this right?
mk
Thnak you for your help

Originally Posted by Mike Krueger

A.D. Miller
Would the strip burner or jet burner furnaces have a pvc pipe going to the outside?
Only the newer high efficiency furnaces have this right?
mk
Thnak you for your help

MK: When info comes from laypersons, sans photos or professional eyes, I try to answer the question globally. I do believe I mentioned "closed burner compartments", which are present on high-efficiency units.

Maybe you should read my posts a bit more closely before commenting on them?

Originally Posted by A.D. Miller

MK: When info comes from laypersons, sans photos or professional eyes, I try to answer the question globally. I do believe I mentioned "closed burner compartments", which are present on high-efficiency units.

Maybe you should read my posts a bit more closely before commenting on them?

A.D. Miller

Thanks for your help.
mk

Some units have a plastic round sight glass to the combustion chamber (Trane).

If a furnace has provision for separate dedicated combustion air, it should be used-period. Even though a furnace may be listed for use drawing air from the CAZ, it is not good practice. If there is a draft hood equipped WH present, it can backdraft it.

HTH,
Bob

Originally Posted by Bob Harper

Some units have a plastic round sight glass to the combustion chamber (Trane).

If a furnace has provision for separate dedicated combustion air, it should be used-period. Even though a furnace may be listed for use drawing air from the CAZ, it is not good practice. If there is a draft hood equipped WH present, it can backdraft it.

HTH,
Bob

The situation Bob describes is exactly what I saw yesterday. An open draft hood gas water heater next to the high efficieny gas furnace that was drawing the combustion air from the basement. I can't understand why the installer wouldn't just run the intake pipe to the exterior considering they already had to run the exhaust to the exterior. Just laziness as far as I'm concerned. Also, the installer never reinstalled the duct for the humidifier that was connected to the return air trunk and that was also mechanically drawing in air around the water heater.

Originally Posted by Bob Harper

Some units have a plastic round sight glass to the combustion chamber (Trane).

If a furnace has provision for separate dedicated combustion air, it should be used-period. Even though a furnace may be listed for use drawing air from the CAZ, it is not good practice. If there is a draft hood equipped WH present, it can backdraft it.

HTH,
Bob

Good info Bob thank you!

Originally Posted by Nick Ostrowski

The situation Bob describes is exactly what I saw yesterday. An open draft hood gas water heater next to the high efficieny gas furnace that was drawing the combustion air from the basement. I can't understand why the installer wouldn't just run the intake pipe to the exterior considering they already had to run the exhaust to the exterior. Just laziness as far as I'm concerned. Also, the installer never reinstalled the duct for the humidifier that was connected to the return air trunk and that was also mechanically drawing in air around the water heater.

Nick,

Are/were you able to see the flame if you looked into the fresh air intake that wasn't hooked up?

mk

Mike, I was able to see the flames. It's very normal. Like Bob described, high efficiency units with sealed combustion chambers typically have a small plastic viewing window that allows you to see a very small portion of the combustion chamber and flames while the unit is in operation. Some units may have the view port on the top removable access panel. Other units have the view port window behind the access panel.

Don't take what the client or realtor tells you over the phone as gospel. Reserve judgement on the situation until you get to the inspection and see it for yourself. And take some pics as well to post up here afterwards.

The basic problem with a CAT IV furnace is that the combustion chamber must be sealed to operate. If you somehow open the combustion chamber in an attempt to visualize the flames, you will trip the pressure switch. The window allows visualization while firing.
HTH,
Bob

And, Mike, I guess it goes w/o saying...please accept our most humble apologies, and you know to what I'm referring

Originally Posted by Eric Russell

And, Mike, I guess it goes w/o saying...please accept our most humble apologies, and you know to what I'm referring

Thank you sir!

Amen to your foot note. I pray He comes back soon!

A true direct vent is sealed combustion. What you described is not. The system you described is power vented but the combustion air is de-coupled from the vent. This means it is susceptible to backdrafting and pulling room air instead of outdoor air. We know passive makeup air doesn't work, which is what this is. There is no suction pulling air in unless the entire room is put into a negative state with this intake becoming the path of least resistance. Otherwise, it will supply very little air for combustion but can be a source of cold air infiltration at standby, which will cause the t-stat to cycle more. True direct vents do not suffer these effects.

Because the burners are open to the room, you do not need an inspection port. Because the flames are exposed to the room, you can get combustion malfunctions related to house pressure regimes and backdrafting. If the vent discharge becomes blocked with ice, theoretically, it is possible this unit could vent into the room without tripping the pressure switch or primary high limit. You would have a spill switch to protect you but depending upon where that is positioned, the backdraft could miss it. Also, this furnace would tend to depressurize the CAZ and could backdraft a WH if in a confined space.

Bob

A.D. Miller
Would the strip burner or jet burner furnaces have a pvc pipe going to the outside?
Only the newer high efficiency furnaces have this right?
mk
Thnak you for your help



MK: When info comes from laypersons, sans photos or professional eyes, I try to answer the question globally. I do believe I mentioned "closed burner compartments", which are present on high-efficiency units.

Maybe you should read my posts a bit more closely before commenting on them?A.D. Miller



A.D. Maybe you should read replies to your posts a bit more closely before commenting on them? MK didn't 'comment' on your post. He was not 'doubting' you, just asking a legitimate question- does pvc vent = sealed combustion chamber? He even thanked you for the info. You sure seem defensive for some reason.

If the unit is a high efficiency furnace and you see "flame roll-out" then you have a cracked heat exchanger or a clogged flue. A high efficiency furnace will have an "inducer motor" either above or below the combustion chamber/heat exchanger. It will also have a PVC pipe instead of a "B-Class Vent (metal). The 'flame roll-out switch" will detect this and shut the unit down. If the 'flame roll-out switch is bad, the unit will not even come on. If the unit still runs and does not shut down then you have an older gas furnace, probably an 80% or less efficiency. You should only see the flame on the burner, not coming out of the combustion chamber. That would indicate a clogged flue or cracked heat exchanger on the older model. It will need t be replaced.

Thank you Randy West I appreciate that! Your interpretation of my question (my intentions) are correct.

I don’t want to create any animosity between anyone. This site is priceless with all of the pros willing to help. In this business you’re kind of out there on your own. The only guys that can really help you are your competition.

Thanks again
mk

I did the inspection this afternoon. The furnace is an Armstrong manufacture date is 1993. The unit has a blower below the combustion chamber. You can see the flame through the sight glass on the front of the unit when the front panel is off. Everything looks normal and it seems to function well (nice blue flame-natural gas…). On the top of the unit there is one pvc pipe going to the outside. Right next to that is an opening in the outer shell of the unit. When looking into the unit about an inch or two down you can see a small grate that has 3 or 4 nuts holding it in place. Just below the grate you can see the flame in the combustion chamber through the rusted/deteriorating sheet metal at the top of the combustion chamber. I do have a pic of this through the grate but was not able to attach it because of its size. It needs to be 600 x 800. I’m not sure how to do this. I will mess with it some more when I have a little more time (maybe Sunday night).

Thank you all for your help with this.