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  1. #1
    Join Date
    Mar 2008
    Posts
    657

    need opinions on residential lennox overnight setback

    ok here's the situation. changed out old carrier furnace for new lennox g61 vaiable sp. 2 stage furance {135,000btu} with arzel zoning system. upstairs has two zones on wireless stats. first floor is it own zone. this is a newer home with proper insulation. customer sets 1st floor stat back to 55 degrees overnight, 1st floor is set to come on at 6:00 am set to 72 degrees. customer is disappointed that temperature of 1st floor does not come to 72 within an hour, but it does reach 68 degrees. i guess my question is, is the 55 degree setback at night too much for the temp rise of 17degrees in the first hour. comments, suggestions, info appreciated!

  2. #2
    Join Date
    Mar 2004
    Location
    Grottoes VA
    Posts
    5,856
    No more than a couple degrees setback is too much.

    A HVAC system is designed to maintain space temp.
    Karst means cave. So, I search for caves.

  3. #3
    Join Date
    Aug 2003
    Location
    Lincoln, Nebraska
    Posts
    1,051
    I tell people 2-5 degrees is OK

    17 degrees is way to much and will take a long time to recover. They are probably loosing savings instead of saving money.
    Its a good Life!

  4. #4
    Join Date
    Mar 2008
    Posts
    657
    yeah you guys are both correct but i can't get the customer to understand that he isn't saving any money by doing this. and that the setbac is way to severe. oh by the way@ 730AM the temp is for 62 degrees. this guy is killing me, and holding final payment. so i guess i'm gonna have to bring lennox tech support into it to prove to this guy that i'm not trying to get over on him!

  5. #5
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,708
    adaptive recovery stat??

  6. #6
    Join Date
    Mar 2008
    Posts
    657
    enlighten me t527

  7. #7
    Join Date
    Mar 2008
    Posts
    657
    nevermind did my homework and yes it has adaptive recovery, but the customer will not let the stat be set up in the proper manner. he thinks he's an engineer (know it all) and i guess i have to break out some literature and let him read it for himself, because he's not believing me or maybe he doesn't have the money and is delaying the payment. i don't know?

  8. #8
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,708
    if dumb@ss won't let stat be set up right then add another supply blowing on stat...........

  9. #9
    Join Date
    Jun 2007
    Location
    Round Rock
    Posts
    3,520
    I'll bet he doesn't have the money. We had some biotch a few years ago who wanted her master to cool down to 60 at night because she slept better. She then would get up take a shower and wanted her bathroom to be 80 when she got out so she wouldn't be cold. All this in a matter of 20 minutes. We ended up putting a zoning system on the downstairs, it was 1 unit, cooling about 1400 sq. ft. downstairs where her bedroom was. Her master bedroom/bathroom was about 500 sq. ft. Bedroom zone 1, rest of downstairs zone 2. As far as warming up 20 degrees. I told her to buy a portable heater and put it on the floor. Customers can be such a pain in the arse when they don't want to pay.

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,755
    Do you have your load calcs for the first floor.
    If so, show him the load calcs and at what OD temp the furnace will no longer be able to raise the first floor temp 17* in an hour.

    Might point out to him, that a function of the 2 stage is long run times. And what he wants it to do, is the opposite of what he paid for.
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  11. #11
    Join Date
    Jan 2002
    Location
    Ft.Worth,Tx
    Posts
    4,584
    Tell the homeowner that if he wants more than 12* you would need to redesign system for liebert and cost would go up to 15,000.00 for the changes.

    Normal residential equipment can not make that much recovery in (1) hour. Air changes per hour are limited and with that much swing in temperature he will not be saving any money just costing more to achieive the same goal.

    Normal residential equipment can make between 4-5 degrees of set-back within 1-1 1/2 hours.
    "Everyday above ground, is a good day".
    "But everyday that you have made a difference in someones life, may insure you stay above ground a little longer".<aircooled>

  12. #12
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,755
    Normal residential equipment can make between 4-5 degrees of set-back within 1-1 1/2 hours.


    Since we're talking about a gas furnace, the temp rise per hour will depend on the OD temp.

    At 20*F OD temp, my oil furnace does about 4* rise an hour recovering.
    At 50*F OD temp, it does atleast 12* rise an hour. I have it down fired, or it would be more.
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