Gas and Oil Home Heating Furnaces - Cleaning a Split System HVAC in attic..
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11-10-01, 09:05 AM
Howdy! :)
I recently started having a problem with my pilot light cutting off every couple of days, so I figured it was time for a cleaning - The system had never been cleaned since my wife and I bought the home about 4 years ago, and I have no idea how long it has been before that since it's been cleaned -- anyway, took the vacuum up into the attic and started taking stuff apart.
I took off the louver and pulled out the heating assembly (which consists of about 5 rows of burners), and boy DID it need cleaning; there was enough dirt and rust flakes on the bottom of that assembly that it was almost up TO the burners; I'd say that it was around 2-3" deep. (Is this normal??)
Sheesh! Went through 2 vacuum bags cleaning all that junk out. :) I then replaced the assembly and started looking for a way to get into the blower area, so clean the fan and the coils -- I found the access panel to the blower (which was relatively clean, surprisingly), but I wasn't able to find any type of access panel to the A-Frame coils; will I have to dismantle the entire unit pretty much to get to these?
Your assistance greatly appreciated!
Southern
I recently started having a problem with my pilot light cutting off every couple of days, so I figured it was time for a cleaning - The system had never been cleaned since my wife and I bought the home about 4 years ago, and I have no idea how long it has been before that since it's been cleaned -- anyway, took the vacuum up into the attic and started taking stuff apart.
I took off the louver and pulled out the heating assembly (which consists of about 5 rows of burners), and boy DID it need cleaning; there was enough dirt and rust flakes on the bottom of that assembly that it was almost up TO the burners; I'd say that it was around 2-3" deep. (Is this normal??)
Sheesh! Went through 2 vacuum bags cleaning all that junk out. :) I then replaced the assembly and started looking for a way to get into the blower area, so clean the fan and the coils -- I found the access panel to the blower (which was relatively clean, surprisingly), but I wasn't able to find any type of access panel to the A-Frame coils; will I have to dismantle the entire unit pretty much to get to these?
Your assistance greatly appreciated!
Southern
PHnd
11-10-01, 12:41 PM
Cooling coils have no access panel for cleaning. When the time comes they have to be removed or an access is cut into the duct. If the blower is clean, the coil is clean. If there is gunk build-up on the blower wheel, there will be more built up on the cooling coil. Since its clean, Don't worry about it unless you have an air flow problem.
The real problem is your furnace. If you have that much rust in and around the burner assembly, contact a heating contractor and have the heat exchanger checked for cracks. This is not something for the untrained eye nor is it something to take lightly, have it checked. If the chamber is cracked, replace the furnace. If not, have him complete the chamber cleaning then check and adjust the gas pressure. At the same time they need to find out why you have so much rust. My first guess would be your flue pipe is not installed properly. You might see rust and corrosion around the draft hood. Thats the box on the furnace the flue pipe is attached to. If so, thats a sure sign of poor draft through the flue. Normal dirt in a furnace amounts to a fine rusty powder, maybe a small amount of the same dirt found through out the attic. Anything more, you have a problem that needs to be taken care of.
The real problem is your furnace. If you have that much rust in and around the burner assembly, contact a heating contractor and have the heat exchanger checked for cracks. This is not something for the untrained eye nor is it something to take lightly, have it checked. If the chamber is cracked, replace the furnace. If not, have him complete the chamber cleaning then check and adjust the gas pressure. At the same time they need to find out why you have so much rust. My first guess would be your flue pipe is not installed properly. You might see rust and corrosion around the draft hood. Thats the box on the furnace the flue pipe is attached to. If so, thats a sure sign of poor draft through the flue. Normal dirt in a furnace amounts to a fine rusty powder, maybe a small amount of the same dirt found through out the attic. Anything more, you have a problem that needs to be taken care of.
resercon
11-10-01, 12:56 PM
The reason why the blower wasn't dirty is because of your filter and because it was, it is safe to say the heat exchanger and the cooling "A" coil are probably clean too. But it would be prudent to inspect them. There are no panels for access to that side of the exchanger or the "A" coil. Usually the plenum is slipped over the "A" coil and attached, unless the coil was installed after the heating unit was.
The dirt and flakes probably came from the dust in the attic which is considerably more dusty than your home and/or basement. In order to have combustion you require oxygen and the oxygen is coming from the air in the attic. When the unit comes on, it acts like a vacuum cleaner and draws the air with dust to the burners for combustion. The dust deposited itself on and/or near the burners. The flakes are probably from dust clinging to the exchanger and then being burnt off by the burners and then dropping back onto the burners. You should check this side of the exchanger and this is usually done with a flash light and a mirror. The new high energy efficienct furnaces use increase surface area and heat exchanger design that will amke it difficult for you to see the entire exchanger. That is why it is prudent to have a carbon monoxide detector, especially with a gas hot air furnace. If there was a breach in the heat exchanger the detector would alert you.
The dirt and flakes probably came from the dust in the attic which is considerably more dusty than your home and/or basement. In order to have combustion you require oxygen and the oxygen is coming from the air in the attic. When the unit comes on, it acts like a vacuum cleaner and draws the air with dust to the burners for combustion. The dust deposited itself on and/or near the burners. The flakes are probably from dust clinging to the exchanger and then being burnt off by the burners and then dropping back onto the burners. You should check this side of the exchanger and this is usually done with a flash light and a mirror. The new high energy efficienct furnaces use increase surface area and heat exchanger design that will amke it difficult for you to see the entire exchanger. That is why it is prudent to have a carbon monoxide detector, especially with a gas hot air furnace. If there was a breach in the heat exchanger the detector would alert you.
11-10-01, 01:26 PM
Thank you PHnd & Resercon; great information!
When I stated that the blower assembly was "surprisingly" clean, I won't say that it looked brand-new; there was a fine oily residue of dust on the blower blades that I really couldn't get off with the vacuum cleaner (Wasn't the right tool). But it's not thick at all, it doesn't even completely cover the blades themselves, it's just "spotty". My guess is that blowers themselves have more resistance to buildup due to increased air pressure or something. :) Air flow isn't really a problem tho, just thought I'd give it a cleaning while I was up there. :)
As for the burner assembly, the assembly itself was sparkling clean after vacuuming; it appears to be made out of stainless steel, and the pan under it (which caught all the rust flakes & dust) is coated with a plastic/rubber compound. Once it was vacuumed, it looked brand-new. (I was surprised, considering its age; I have no idea if the unit is the original one that came with the house or was replaced at some point during the last 24 years).
The flue at the top of the exchanger was more of a "hood" that leads to a pipe extending out of the roof; the underside was open. I pulled it off to check that area for dirt/dust/rust and found it relatively clean. Maybe 2-3 teaspoons worth of material that I vacuumed out.
The majority of the accumulation under the burners WAS a fine dust, but there were a lot of "flakes" as well; some as big around as a half-dollar, and ALMOST as thick. There for a while I was wondering if maybe it wasn't SUPPOSED to be there, as some type of insulation for the burners. *Snicker* -- I just couldn't see how THAT much trash could accumulate under those burners.. I would just guess that it's "never" been cleaned.
At any rate, thank you SO much for the advice & comments. I'll grab a carbon monoxide detector tomorrow, and depending on the results of that (and the mirror check, if I can do that; the access port for the burners is pretty darn narrow!) I'll call a pro out. You think that if I called someone out to perform a duct cleaning that the same person would be qualified to check that exchanger for cracks?
Also, I have an American Home Shield warranty; would the replacement of that exchanger be covered, you think?
Thanks again!
Southern
When I stated that the blower assembly was "surprisingly" clean, I won't say that it looked brand-new; there was a fine oily residue of dust on the blower blades that I really couldn't get off with the vacuum cleaner (Wasn't the right tool). But it's not thick at all, it doesn't even completely cover the blades themselves, it's just "spotty". My guess is that blowers themselves have more resistance to buildup due to increased air pressure or something. :) Air flow isn't really a problem tho, just thought I'd give it a cleaning while I was up there. :)
As for the burner assembly, the assembly itself was sparkling clean after vacuuming; it appears to be made out of stainless steel, and the pan under it (which caught all the rust flakes & dust) is coated with a plastic/rubber compound. Once it was vacuumed, it looked brand-new. (I was surprised, considering its age; I have no idea if the unit is the original one that came with the house or was replaced at some point during the last 24 years).
The flue at the top of the exchanger was more of a "hood" that leads to a pipe extending out of the roof; the underside was open. I pulled it off to check that area for dirt/dust/rust and found it relatively clean. Maybe 2-3 teaspoons worth of material that I vacuumed out.
The majority of the accumulation under the burners WAS a fine dust, but there were a lot of "flakes" as well; some as big around as a half-dollar, and ALMOST as thick. There for a while I was wondering if maybe it wasn't SUPPOSED to be there, as some type of insulation for the burners. *Snicker* -- I just couldn't see how THAT much trash could accumulate under those burners.. I would just guess that it's "never" been cleaned.
At any rate, thank you SO much for the advice & comments. I'll grab a carbon monoxide detector tomorrow, and depending on the results of that (and the mirror check, if I can do that; the access port for the burners is pretty darn narrow!) I'll call a pro out. You think that if I called someone out to perform a duct cleaning that the same person would be qualified to check that exchanger for cracks?
Also, I have an American Home Shield warranty; would the replacement of that exchanger be covered, you think?
Thanks again!
Southern
resercon
11-10-01, 04:45 PM
I don't recommend duct cleaning and getting a pro out is prudent. It probably be cheaper to replace the unit than an exchanger and if the unit is covered by your insurance that's what they would do. You should check the burners at least annually.
PHnd
11-10-01, 04:52 PM
All I'm gonna say is I gave you sound advice. If you think a $7 monoxide detector is the thing to do, go for it.
11-10-01, 07:28 PM
Actually, called AHS about 10 minutes after I posted that and they have a tech coming out Monday. :)
Thanks again!
Southern
Thanks again!
Southern
PHnd
11-11-01, 04:28 AM
I'm glad to see your doing the right thing.
That kind of dirt in a furnace is not normal. Natural gas is clean burning and so the inside of the furnace should be also. Rust is caused from moisture which is a product of combution. Chances are the flue is not drafting properly so here are a couple things you can measure to help determine if it drafts properly. As a rule (1) the horizontal run of pipe cannot be any more than 75% of the vertical. (2) The vertical rise above the roof needs to be, measured at the highest point of penetration through the roof, 2' up with 10' around from any obstruction. (3) The horizontal run needs a rise of 1/4" per foot. (4) If the flue penetrates the roof within a few feet of the peak you'll want it to extend a minimum 2' above the peak even if the 2' above penetration rule is met.
That kind of dirt in a furnace is not normal. Natural gas is clean burning and so the inside of the furnace should be also. Rust is caused from moisture which is a product of combution. Chances are the flue is not drafting properly so here are a couple things you can measure to help determine if it drafts properly. As a rule (1) the horizontal run of pipe cannot be any more than 75% of the vertical. (2) The vertical rise above the roof needs to be, measured at the highest point of penetration through the roof, 2' up with 10' around from any obstruction. (3) The horizontal run needs a rise of 1/4" per foot. (4) If the flue penetrates the roof within a few feet of the peak you'll want it to extend a minimum 2' above the peak even if the 2' above penetration rule is met.