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  1. #1
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    Old furnace - Chimney liner brick shredding

    I bought the current house 2 years ago. The chimney liner that is used by furnace and water heater is slowly shredding, no cracks In the exterior brick.

    Called up a chimney servicing company and was recommended to get a high efficiency furnace that will vent through PVC pipe since the water heater and furnace are using the chimney vent causing too much condensation.

    So my plan is to first replace the furnace and see if the brick will stop shredding and then replace the chimney liner.

    The house has a single stage Lennox 80,000 BTU from 2005. I am looking up several options for the furnace and noticed that Goodman is recommended for value for money by ASM Air.

    So I got two quotes for GMVC96 two stage variable speed furnace, one dealer gave me a quote which is as high as Tran ($) and the other one gave me a quote 30% lower than the former ($).

    1. Is this manufacturer and model somebody here can recommend
    2. Is the low quoted price too good to be true

    This is the first time I am posting here. I will remove the quotes if they are against the forum rules.
    Last edited by BaldLoonie; 10-22-2019 at 10:10 AM. Reason: removed pricing

  2. #2
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    May 2000
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    Indianapolis, IN, USA
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    The 80% furnace has cool exhaust and because your installer didn't install a metal liner kit, the furnace damaged the inside of said chimney. Going to 90+ furnace is fine BUT the appropriate size metal liner must be installed in the chimney for the water heater to vent in. If not, you will continue the damage.

    I had to remove your prices due to site rules but the low quoted price would scare me. That's dirt cheap. If you get a 2 stage furnace, be sure to get a nice 2 stage thermostat. The GMVC is communicating and Goodman has a matching stat that would give you the most control of the furnace.

  3. #3
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    Mar 2018
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    Chico, Ca #StateofJefferson
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    Before you replace any equipment, find a contractor that will use manual j to size the homes load. Did the 2 contractors qoute 80k btu furnaces as well? Who measured ducting static pressure to verify that the ducting could handle the higher airflow of a 96% furnace versus your 80% furnace?

  4. #4
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    Quote Originally Posted by BaldLoonie View Post
    The 80% furnace has cool exhaust and because your installer didn't install a metal liner kit, the furnace damaged the inside of said chimney. Going to 90+ furnace is fine BUT the appropriate size metal liner must be installed in the chimney for the water heater to vent in. If not, you will continue the damage.

    I had to remove your prices due to site rules but the low quoted price would scare me. That's dirt cheap. If you get a 2 stage furnace, be sure to get a nice 2 stage thermostat. The GMVC is communicating and Goodman has a matching stat that would give you the most control of the furnace.
    Sorry, I thought my post did not get approved and never made it here, so could not reply earlier. Thank you for the advice. I will avoid the contractor who quoted the dirt cheap price, it was very odd to see that price.

    The room with the furnace is small and I also use it as my laundry room, can I continue to vent the high efficiency HVAC through the chimney after I install the aluminium liner.

    I got a quote for Trane furnace, aluminium chimney liner, and humidifier from Abt (the electronic retailer) which was very reasonably priced.

    I have an Ecobee3 Lite, I am hoping it will be able to handle the 2 stage.

    I know this is more of a masonry question, can I cover the shredded part of the brick with mortar to retain structural integrity or just let it be?

  5. #5
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    Quote Originally Posted by Makeitcold View Post
    Before you replace any equipment, find a contractor that will use manual j to size the homes load. Did the 2 contractors qoute 80k btu furnaces as well? Who measured ducting static pressure to verify that the ducting could handle the higher airflow of a 96% furnace versus your 80% furnace?
    Thank you for these suggestions, I did not even realize that the existing ducts may not be able to handle the air flow from the bigger HVAC. I will follow up on this with the contractors.

    All of them suggested 80,000 BTU, I wonder whether they did it just because they are replacing an existing one.

  6. #6
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    Aug 2009
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    Beatrice, NE
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    Why not just line the chimney and keep the current equipment till it dies. That gives yo a liner for the water heater in the future, it give you time to research companies and get Man J done along with proper sizing, and then it can be determined if you have a duct size issue or not.

  7. #7
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    Quote Originally Posted by BNME8EZ View Post
    Why not just line the chimney and keep the current equipment till it dies. That gives yo a liner for the water heater in the future, it give you time to research companies and get Man J done along with proper sizing, and then it can be determined if you have a duct size issue or not.
    I was considering just replacing the liner as you are suggesting.

    The furnace is already 14 years old, very loud, and will probably have to offer credit to the buyer if I decide to sell the house. So thought I could use this as an opportunity to get a calmer furnace and use the 48 month financing option.

  8. #8
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    Everytime you see a qoute for any furnace size, remember that the btu rating is always the input. An 80k btu 80% furnace will output 64k btu and the same size 96% furnace will output 76,800 btu, does your house need more heat than your current furnace produces? Very unlikely as oversized equipment on undersized ducting is so common this site could operate on nothing else but this complaint from people. Pull your Ecobee off the wall and see if it has a W2 space for a wire and make sure you have an unused wire on the thermostat wiring. Way to many installers will just set 2 stage furnaces to run on high all the time or allow the control boards internal timer to decide when high stage is active, usually after 10 minutes of run time, so make sure you tell them you want the tstat to control the staging

  9. #9
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    Oct 2019
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    Thread Starter
    Quote Originally Posted by Makeitcold View Post
    Everytime you see a qoute for any furnace size, remember that the btu rating is always the input. An 80k btu 80% furnace will output 64k btu and the same size 96% furnace will output 76,800 btu, does your house need more heat than your current furnace produces? Very unlikely as oversized equipment on undersized ducting is so common this site could operate on nothing else but this complaint from people. Pull your Ecobee off the wall and see if it has a W2 space for a wire and make sure you have an unused wire on the thermostat wiring. Way to many installers will just set 2 stage furnaces to run on high all the time or allow the control boards internal timer to decide when high stage is active, usually after 10 minutes of run time, so make sure you tell them you want the tstat to control the staging
    Thank you for all this valuable information, I will make a note of it.

    A HVAC technician just told me over the phone that the high efficiency HVAC cannot vent through the chimney, in fact it will make things worse for the chimney deterioration. I was trying to avoid the PVC pipe in the laundry room because it will make the room visually claustrophobic.

    Wondering whether I should just replace the chimney liner, and be done with the project.

  10. #10
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    Quote Originally Posted by gramesmith View Post
    I was considering just replacing the liner as you are suggesting.

    The furnace is already 14 years old, very loud, and will probably have to offer credit to the buyer if I decide to sell the house. So thought I could use this as an opportunity to get a calmer furnace and use the 48 month financing option.
    National average on a furnace is 20 years so at 14 it should have some life left assuming it has been taken care of and has not been cycling on limit for that time.

    Not always but, often noise is caused by duct work. Upgrades to the duct system can add years to the life of the equipment, lower bills, make the house more comfortable and make it quieter. It can be a much better bang for the buck than equipment.

  11. #11
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    in a house, Appomattox, Va.
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    Like others said, would have an "orphaned"water heater in flue by iyself, which may not vent in summer if the flue wasn't downsized. also, small room with clothes dryer and gravity vent appliances can cause backdrafting of appliances into room.
    Col 3:23


    questions asked, answers received, ignorance abated

  12. #12
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    Aug 2004
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    The chimney must be suitable for the class of service. For CAT I gas appliances that will mean relining with a listed liner. Now, while aluminum liners are approved for this application they must be viewed as temporary because they just don't last. Every one of them we find is full of powdered aluminum oxide as the flue gas acids eat up the liner. They turn to tissue paper in short order when venting 80% furnaces. Get yourself a properly sized 316Ti stainless steel liner with a transferrable forever warranty. Increase the size of the vent connector on the water heater and replace the draft hood with a bullhead tee to a double acting barometric damper with spill switches. Then have your contractor install a 4 minute post-purge cycle on your furnace. That will just about eliminate the condensation issue.

    You can not common vent a CAT IV 90%+ furnace in a chimney with a CAT I appliance. It will just vent out the draft hood into the home and kill you. Get an unlisted low level CO monitor.
    HTH

  13. #13
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    Quote Originally Posted by hearthman View Post
    The chimney must be suitable for the class of service. For CAT I gas appliances that will mean relining with a listed liner. Now, while aluminum liners are approved for this application they must be viewed as temporary because they just don't last. Every one of them we find is full of powdered aluminum oxide as the flue gas acids eat up the liner. They turn to tissue paper in short order when venting 80% furnaces. Get yourself a properly sized 316Ti stainless steel liner with a transferrable forever warranty. Increase the size of the vent connector on the water heater and replace the draft hood with a bullhead tee to a double acting barometric damper with spill switches. Then have your contractor install a 4 minute post-purge cycle on your furnace. That will just about eliminate the condensation issue.

    You can not common vent a CAT IV 90%+ furnace in a chimney with a CAT I appliance. It will just vent out the draft hood into the home and kill you. Get an unlisted low level CO monitor.
    HTH
    Thank you for the advice. I did not receive a notification that you replied to my thread.

    The quotes I got for a stainless steel liner are more than twice my budget. I am going with a aluminium liner and not replacing the HVAC, and hopefully this setup will last a few years.

    To be honest I do not even understand most of the words you posted here. I will confirm with the chimney contractor that he is doing exactly this.

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