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  1. #1
    Join Date
    Jan 2005
    Location
    Bakersfield, CA
    Posts
    209
    What are the fan speed options on variable speed furnaces, say the Trane XV90 or XV80? Can the unit be programmed to one range of fan speeds when cooling and another range when heating?

    Thanks

  2. #2
    Join Date
    Apr 2004
    Posts
    7,680
    Yes, within a certain limitation. The control board determines which mode the system is in and operates the blower at the designated CFM.

    The ECM motor generally has some flexibility but it also has limitations. For instance, your example of needing 34k heat and 5 tons of cooling it cant be done. hence the need to use the larger furnace

  3. #3
    Join Date
    Jan 2005
    Location
    Bakersfield, CA
    Posts
    209
    Doc, thanks for that answer. I'm now faced with deciding to stay with the zoned system with a significantly oversized furnace or opting for 2 split units. Even there I will be oversized but not as much.

    My contractor said the zoned system configuation he recommends (5 ton XL19i and 5 ton XV90) that he has installed for his own home and others has not resulted in any comfort issues. I asked him about the issue that the furnace will cycle very short run times. He acknowledged that. He also said the Trane unit can be programmed to run fan only at a very low CFM setting between heating cycles. He said that would increase the IAQ as more air would be running through the AprilAire filter.

    He has remained adamant (in a very cordial way) that he has had better customer satisfaction with the XV90 versus the XV80, and also reports of much lower gas bills. This is all anecdotal of course.

    Thanks again.

  4. #4
    Join Date
    Jul 2004
    Location
    NW Arkansas
    Posts
    1,288
    Originally posted by nathan9999


    My contractor said the zoned system configuation he recommends (5 ton XL19i and 5 ton XV90) that he has installed for his own home and others has not resulted in any comfort issues. I asked him about the issue that the furnace will cycle very short run times. He acknowledged that. He also said the Trane unit can be programmed to run fan only at a very low CFM setting between heating cycles. He said that would increase the IAQ as more air would be running through the AprilAire filter.

    Well... the XL19i is a 2 compressor 2 stage unit that that operates on the first stage compressor most of the time. When extra cooling capacity is needed the unit turns off the first stage compressor and brings on the higher BTU output second stage compressor to complete the cooling cycle.

    Two stage units tend to keep the temperature in the comfort zone better than single stage units can. It also helps with the problem of sizing units for the most extreme hot days you will have in your area. A single stage AC is oversized most of the time during the cooling season. The two stage unit is able keep the space more comfortable by using the first stage when the cooling demand is lower and only using the second stage when it is needed.

    He has remained adamant (in a very cordial way) that he has had better customer satisfaction with the XV90 versus the XV80, and also reports of much lower gas bills. This is all anecdotal of course.

    All things being equal, the 90% unit is more efficient than the 80% unit. However, I think it is better to get a two stage XV80 gas furnace than it is to get a single stage XV90 gas furnace. A two stage XV90 gas furnace would be the best choice.

    The variable speed ECM motor will run at 50%cfm output when the fan switch is on. It keeps the air moving, filters it more, and really does not increase the humidity level in the house.

    BTW, If you buy this system, get the 10 year Trane parts and labor warranty.


  5. #5
    BTW, If you buy this system, get the 10 year Trane parts and labor warranty.
    I'd second that recommendation. While I doubt they are terribly prone to major problems, if you do have one with the motor or variable speed controller it's going to be very expensive.

    Just got fixed some very strange issues with the variable speed motor in my XV80 furnace. Just the motor controller board was replaced at a cost of $350 and if the whole motor goes bad it would have been double that.

    The motor and controller are also not something that any company around here stocks either in their trucks or their offices (even though this company recommends these and installed this one here!) so also expect to wait with no heat or AC if the motor goes out.

    I dont mean to sound bitter, in general I've been pretty happy with them, but this last adventure with the motor has soured me on the variable speed just a little bit. Get the warranty.

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,778
    In a pinch you can install a psc motor till you get the mod, or vs motor in.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #7
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    in ten years i only have replaced 1 motor and two control mod. this vs motor seems to have great reliablty and the cost of replace ment is high but if the system is installed correctly and maintaned replacemaent is not much of a factor. the most important thig is to keep the filter clean. get the warrenti because parts cost and you can have ten years of no out put on parts

  8. #8
    Join Date
    Mar 2005
    Location
    Suppy NC
    Posts
    4,513
    forgot to mention
    why cant this contractor size the unit for your house
    a properly sized unit will give you more confort and save you more in the long run. with the proper load calcalations there is no reason a system can not be sized correctly. just because he has been luccky with the five ton unit in his house does not mean he will be in yours.
    have him do a load and size it right or get a neww contractor. just my opinion

  9. #9
    Join Date
    Nov 2003
    Location
    northern mass
    Posts
    411
    I second that....ManJ please.


    And .....i was too lazy to read back throught the thread.....but, is this a new home or an existing home ? What i'm getting at is....are you doing anything like, replacing a boiler with forced air ? Another option is a hydro unit. These are mostly what I install these days, due to other factors that don't concern this thread.

    If that option was available to you, you would have your 5 ton a/c and be able to use a properly sized water coil with the right temp. hot water to give the proper BTU's you desire.

    Again, it's a long shot, but if that option is available to you....there ya go.

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