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  1. #1
    Join Date
    Jul 2008
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    5

    2S Heating / 1S Cooling Question...

    OK....
    I have just had a new Amana System Installed...and since it has been@ 100-108 Degrees lately..the Heating side of things has NOT COME UP!.

    My Furnace is an Amana 2 Stage GHD80-70 Gas downflow furnace..

    The cooling is strictly single stage..and that suits me fine..

    The 2 Stage heat seems to be controlled by the furnace itself and is selectable through a DIP switch in the furnace rather than a W1/W2 wiring to the tstat to regulate staging.

    When the system was initially installed..I noticed that they left it in single stage heating.

    At my request.... (And after reviewing their SALES PITCH back to them) they changed it to 2 stage heating.

    My question is...why is the furnace deciding to operate in first or second stage?

    Shouldn't that decision come from the tstat??

    Thanks for the Info..you guys are the best!!!!

    Larry

  2. #2
    Join Date
    Nov 2000
    Location
    Eastern PA
    Posts
    68,933
    Before anyone else jumps on this, what you have is an Amana Distinctions furnace which is a Goodman furnace with an Amana Distinctions label on it. There is nothing wrong with this.

    That particular type of two stage control has advantages as well as disadvantages when compared to a thermostatically controlled two stage system.

    Some of the advantages are that by utililizing an alogorythmic logic system, that furnace board monitors the amount of heat loss your home has over any given period of time in order to adjust how long the high and low fire stages of the furnace operate.

    Contrary to what many people believe, the low fire operation of a two stage furnace is not more efficient then the high fire is. Multistaged equipment has comfort benefits, but are not more efficient. If they were more efficient, the manufacturer's would be screaming about it in their advertising.

    A furnace that operates only in low fire can develope condensate issues in the the heat exchanger. Your furnace does not allow that to occur by forcing the furnace into high fire at least every 12 minutes of operation.

    One thing that consumers have complained about with that furnace is that it seems to operate erratically. The more erratic the HO, the more erratic the furnace. I say this because the furnace does tend to go in and out of low and high fire as it seeks a balance point according to the past calculations of how long previous run times were. If a HO hears the furnace go into high fire when they feel it shouldn't, or vice versa, some HOs have a tendency to then adjust the thermostat to account for what they think the furnace should be doing. This just messes up the algorythmic calculations.

    Set it and forget it and enjoy your new system.
    Government is a disease...
    ...masquerading as its own cure…
    Ecclesiastes 10:2 NIV


  3. #3
    Join Date
    Jul 2008
    Location
    Alabama
    Posts
    658
    In my opinion it works best when the stat controls staging.

    If the furnace does it , its mostly timed.
    This lets 2nd stage come on even if not needed.

  4. #4
    Join Date
    Mar 2001
    Location
    North Carolina
    Posts
    428
    Yours has 5 minute low fire then goes into high fire controlled by time only. The GMV95 for instance uses a two stage thermostat and is controlled by the thermostat.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    67,875
    Well, in the OP's case, I'd be more worried about getting the burner set up right, then weather its controled by the stat, or a timer.

    Obviously, if they set it as a single stage burner. They never checked or adjusted it in first stage, if they even did for second stage.
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  6. #6
    Join Date
    Mar 2001
    Location
    North Carolina
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    428
    Quote Originally Posted by beenthere View Post
    Well, in the OP's case, I'd be more worried about getting the burner set up right, then weather its controled by the stat, or a timer.

    Obviously, if they set it as a single stage burner. They never checked or adjusted it in first stage, if they even did for second stage.
    I agree if they left in in single stage before and didn't realize what they did that they could not have possibly set it up correctly for both stages. I was just answering his question.

    My question is...why is the furnace deciding to operate in first or second stage?

    Shouldn't that decision come from the tstat??


    Long day yesterday was to tired to type beyond the minimal answer lol

  7. #7
    Join Date
    Aug 2003
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    466
    Quote Originally Posted by obxtech View Post
    Yours has 5 minute low fire then goes into high fire controlled by time only. The GMV95 for instance uses a two stage thermostat and is controlled by the thermostat.
    I believe you are mistaken. The Goodman "H" series (hybrid) furnaces are not timer operated, but rather work from a continuosly self regulating algorythmic control board. You may be thinking of models that are designed to operate with a two stage thermostat that are using a single stage thermostat and board timer. There are other furnace manufacturer's using this type of control including, I believe, Carrier. This control has the benefit of keeping furnaces from having condensate issues from only operating in low fire. Not much different then the type of controls used to operate York and even Rheem modulating furnaces.

  8. #8
    Join Date
    Aug 2003
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    466
    Quote Originally Posted by obxtech View Post
    I agree if they left in in single stage before and didn't realize what they did that they could not have possibly set it up correctly for both stages. I was just answering his question.

    My question is...why is the furnace deciding to operate in first or second stage?

    Shouldn't that decision come from the tstat??


    Long day yesterday was to tired to type beyond the minimal answer lol
    A thermostat responds to immediate circumstantial stimuli, such as a door being left open while groceries are being carried in. For such a circumstance, a thermostatically controlled staging system will react to the immediate demand and compensate for the out of the norm heat loss. This type of control may be best for homes that have a lot of occupants running in and out, or for small places of business.

    An algorythmically calculated control learns the average heat loss and anticipates the need for more of less heat. Since there is no efficiency advantage to a furnace operating on low fire, and indeed is less efficient in some instances, why does the furnace operating on high fire more often matter? As I mentioned before, it is not in the best interest of a furnace to run for extended periods on low fire without going into high fire.

    So, each type of system has advantages for comfort under various circumstances. The average home where there is not a lot of in and out door traffic will benefit from an algorythmically controlled staging system. This is why the Rheem modulating furnace is so comfortable. Even though it is through the thermostat that the algorythmic calculations are being made, the Rheem furnace still only has one heat terminal on the furnace board. The thermostat keeps track of heat loss through furnace cycle times and adjusts how much heat is needed at what time.

  9. #9
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    Jan 2004
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    I think if you check. The Rheem mod has 2 heat terminals.
    You can use a 2 stage stat on it, and it becomes a 3 stage furnace. It times to third stage.
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  10. #10
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    Jul 2008
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    Quote Originally Posted by beenthere View Post
    Well, in the OP's case, I'd be more worried about getting the burner set up right, then weather its controled by the stat, or a timer.

    Obviously, if they set it as a single stage burner. They never checked or adjusted it in first stage, if they even did for second stage.


    Ok..I agree...as far as I could see , they did NOTHING to the Furnace side of things other than connect the system, and make sure it "Lit".

    It was @ 103'F when they did the install after all.

    How should I approach this with the company?

    Based on what you are all telling me, they need to come back out in the fall and properly setup the burner in both stages.

    Please give me some advice on the best way/Manner to broach the subject with them.

    This install was not a pleasant one for them, they have been out to service the AC side at least 5 times now...
    It's working properly now after a new Evap coil and TXV valve were installed..

    The original Evap was defective....

    THey told me to call them back this week after the system ran a bit so they could re-check the pressures / charge.


    THANKS!!!!!

    Larry

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    Just ask them to check it this fall.
    Tell them you would like to be sure that the furnace will operate porperly this winter and not condensate in the primary heat exchanger this winter.

    Don't buy into the "that why we set it to single stage" excuse.

    Be polite, but let them know you are concerned.

    I can't tell you the best way to approach it. As I have never been on your side of the fence.


    I've had customers ask me if I checked it in both stages already.
    Thats when I get to say, "yes sir, here are the readings".
    But thats during the install.
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  12. #12
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
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    34,043
    My 2 stage has run on low 98% of the time due to being oversized. I have no condensation issues in the heat exchanger nor the flue pipe. Not finding issues on our customers units who are more appropriately installed.

    The Goodman/Amana units are the only 2 stage units on the market that cannot have a 2 stage stat. I agree that an algorithm beats a fixed timer but still, the unit will time to high in 16 minutes eliminating the best feature of a 2+ stage furnace, long run periods on low in bitter weather. If they are doing this to keep 1st stage run cycles short intentionally then why does the variable speed models encourage the purchase of a 2 stage stat?

  13. #13
    Join Date
    Aug 2003
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    466
    Quote Originally Posted by beenthere View Post
    I think if you check. The Rheem mod has 2 heat terminals.
    You can use a 2 stage stat on it, and it becomes a 3 stage furnace. It times to third stage.
    I am actually only familiar with the earlier models that used the Enerstat fuzzy logic controls, so I could very well be behind the times on the particulars of those controls today. They would still need to use an algorythmic control for modulation or else they would need a lot more heat terminals. The York model I believe is strickly algorythmic control board.

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