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Lennox direct vent

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ChrisJ
ChrisJ Member Posts: 15,673
in Gas Heating
My parents have a Lennox direct vent forced hot air furnace from around 2006 and occasionally its giving an error which indicates not enough flow through the vents.



My understanding is either the blower could be bad, a sensor could be bad or there may be a restriction in one of the vent pipes.  Thats all fine but what I'm curious about is why isn't there mesh on the intake and exhaust to keep mice from getting in, and why isn't there a union or a coupler on the pipes so they can easily be unhooked from the furnace and cleaned?



I would think mesh on both pipes as well as a convient way to disconnect them would be a must during installation no?  We want to add this but I'm worried there may be something I'm overlooking and perhaps they are not there for a reason.
Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment

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  • icesailor
    icesailor Member Posts: 7,265
    edited November 2011
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    No (low) flow

    A stupid question but have you changed or checked the air filters? If they are dirty or clogged, you get a low flow error.



    As far as "unions", hot air furnaces are usually only disconnected to replace them. Most things can be changed without removing the unit. If the heat exchanger is cracked or damaged, a new unit is in order. A new unit seldom is a slide in job unless it is the exact same unit. There is usually some adaptation to a change out.
  • ChrisJ
    ChrisJ Member Posts: 15,673
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    low flow

    The flow flow error is in the direct vent setup not the heating system.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Rich_L
    Rich_L Member Posts: 81
    edited November 2011
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    Screens

    Screens can be added and I have in the past if blockages from animals tends to be problematic. I had one particular case that the birds loved to nest in. For these I usually add 1/2" hardware cloth (screen with rather large openings) to keep out the rodents but allow plenty of airflow. You need to be careful though. Under certain atmospheric conditions the screens will tend to frost over and too tight of a mesh will completely block the air flow. Cut the screen to the same outside diameter as the pipe and then just push a coupling over top, no need to glue. It will hold the screen in place. Unless you can find stainless steel for the exhaust you'll need to replace it every couple of years. It will rust out that often.



    One reason for no unions, the flue pipe needs to be sealed completely from the discharge at the heat exchanger to the outside of the structure. If there were a union and it worked itself loose and allowed venting in the living space... I just cut the pipes if necessary for cleaning and re-glue with couplings afterwards. On the intake you can just push it back together dry and then take it back apart in the future if needed for cleaning. Good luck, Rich
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