While trying to stop the ticking noise coning from my furnace ducts, I accidentally dropped a small piece of fire retardant foam (as you can see in the below photos) in one of the vertical furnace ducts in my basement. I can’t tell how far down it does with my fingers. Is this cause for concern (should I have someone remove it)?
HVAC – Retrieve Dropped Item in Furnace Duct
ductsfire-hazardfurnaceheating
Related Solutions
Check the flame sensor. Sounds like the furnace may not be sensing that the burners are on. Also, consult the manufacturers documentation for trouble code light sequences. The flashing light might be trying to tell you something.
Unconfirmed Trane Error Codes
Codes are displayed using a light (LED) turning on a number of times, followed by a pause. For example:
._._._.___._._._.___
. = On _ = Off
Would be read as 4 flashes, and would mean that one of the limit switches was open.
- Flashing Slow - Normal - No call for heat
- Flashing Fast - Normal - Call for heat
- 2 Flashes - External lockout, retries or recycles exceeded.
- 3 Flashes - Pressure switch error.
- 4 Flashes - Open limit device.
- 5 Flashes - Flame sensed when no flame should be present.
- 6 Flashes - 120V power supply polarity reversed, or poor grounding.
- 7 Flashes - Gas valve circuit error.
- 8 Flashes - Low flame sense signal.
- 9 Flashes - Check igniter.
All right, I found a manual for a nearly-identical unit and cross-referenced what it says with applicable sections of the 2012 International Fuel Gas Code. Now I feel like I have a much better idea of what's going on.
The huge duct is supplying input air for combustion and dilution through the attic, which is code-approved and is sized correctly. There's a hole in the ceiling of the furnace room that I didn't even notice; it's for the output air. It all corresponds perfectly to this illustration in the code:
The alternative is to get the air partially or wholly from inside the conditioned space as long as the building envelope's tightness isn't 0.4 air changes per hour at 50 pascals of pressure or better, which my house most certainly is not (that's Passivehaus-level!). In this case, I would need 50 cubic feet of interior airspace per 1000 BTUs of all interior gas-fired appliances. The furnace draws 125k (waaaay too high), and the gas range is capable of drawing 54k when the oven and all the burners are firing. So the worst-case scenario is that I need 8950 cubic feet (or 1118 square feet) of interior space when all these appliances are in use. I don't have that; the whole interior is only 1100 square feet, and I can't even count bedrooms and bathrooms that have doors, reducing the amount of square footage I can use for combustion air purposes to 650, or 5200 cubic feet, or a maximum of 104,000 BTUs worth of gas drawn by interior gas appliances. Even downsizing the furnace, I will still likely exceed that, and the deficit will get worse as I air-seal the building envelope.
So I have to keep the existing setup, which is all kosher with the code and perfectly safe. And I'll never get carbon monoxide poisoning. So that's good.
The question becomes how to offset the energy penalty of having two huge penetrations into the conditioned space where outside air can flow. I'm thinking that my best option is going to be separating the furnace closet from the rest of the house as much as I can. There are huge holes and thermal bypasses which I'll be sealing up, and if possible, I'm going to add insulation to the stud bays separating the furnace closet from the rest of the house. In essence, I'll turn it into a mini-unconditioned-space within the conditioned space.
Best Answer
There's a much easier solution
On your furnace you have mounted a Aprilaire MK 500. Inside that humidifier is a 9" x 9" opening. You simply need to remove the cover by by depressing the top or bottom tab, pull the 1/4" diameter water line out of the humidifier pad and then pull the humidifier pad out.
You should now be able to see inside the furnace with ease if the foam has fallen down you can run the fan to blow it up and tried to catch it if it didn't already move downstream. If it's not stuck down at the heat exchangers I wouldn't be overly concerned. If it was stuck down on the primary heat exchanger the worst thing you could expect to happen is it would smell a lot like burning foam beyond that it would be unlikely to sustain a flame but not out of the realm of possibility.
For the record bypass humidifiers are supposed to be installed on the return air but it's not the end of the world and this time it worked out to your benefit.