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  1. #1
    Join Date
    Oct 2007
    Location
    Southern California
    Posts
    27

    Variable Speed vs. Modulating

    Can someone define the difference? It seems like Rheem and York are the only mfg with Modulating. Is that correct?

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,727
    Yes, that right.

    But your confusing terms I think.
    Variable speed refers to the blower.
    Modulating, refers to the burner.

    York makes their mod in both VS, and Multispeed blower configuration.
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  3. #3
    Join Date
    Nov 2006
    Posts
    1
    Coleman also makes a modulating unit with multi speed and v drive.

  4. #4
    Join Date
    Apr 2004
    Posts
    7,680
    Coleman is york.

    As mentioned VS refers to the blower, meaning specificly an ECM motor. In a typicle 2 stage furnace, the ECM delivers two specific CFM's (airflow volume) for high and low fire. A modulating furnace has a variable burner and the ECM motor delivers the correct airflow at the given firing rate.

    ECM's (Variable speed) also allow you to gain some efficiency for cooling mode and enable the technician to do some things with dehumidification should you need it.

    Modulating furnaces vary. The Rheem or Ruud Mod, uses a special thermostat which adjusts the heating output based on room temperature. The York/Coleman uses algorithems and timing to adjust the heat output.

  5. #5
    Join Date
    Oct 2007
    Location
    Southern California
    Posts
    27

    Smile Thanks, guys!

    Now I've got it.

  6. #6
    Join Date
    Mar 2003
    Location
    PA/DE area
    Posts
    1,535
    Carrier is coming out with one soon.
    It's NOT the BRAND,it's the company that installs it!!!!!

  7. #7
    Join Date
    Jul 2006
    Posts
    15

    Hmm Got some questions and a few answers

    You guys are talking modulated vs. variable speed and assuming it only means the blower. If you look at the Nordyne/Maytag IQ drive 23 seer it has a variable speed compressor and drive to allow the system to only produce the amount of cooling you need and not cycle to match the load.

    Modulation usually means more than one capacity step on the system which Carrier, Lennox, Goodman(Amana), Nordyne, Rheem, Trane and York all have. There are multiple designs out there to create modulation in a system. A lot of them use Copeland Scroll UltraTech (2-steps of modulation), some use Bristol TS (Twin single) (2-Step recip) and Trane 19 SEER are tandem recips to get 2 steps of modulation.

    Can you guys tell me what Carrier is coming out with soon? I haven't heard about any new system yet!

  8. #8
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,727
    Are yu talking about the Carrier 3 stage furnace.
    40%, 65%, and high is 100%.
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  9. #9
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,727
    jayhvac.

    He was asking about furnaces, not A/C's or heat pumps. So thats why our answers are only for furnaces.
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  10. #10
    Join Date
    Oct 2007
    Location
    Southern California
    Posts
    27

    So only Rheem and York have a Mod furnace?

    Right?

  11. #11
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    33,898
    Lennox has one coming out. It's 1/2 way between York & Rheem. It should use a 2 stage thermostat so it has more input from the space as to room temp vs setpoint to decide how to fire. The guy I talked to at the Lennox booth at Comfortech wasn't too sure beyond that how it was controlled.

  12. #12
    Join Date
    Jul 2006
    Posts
    15

    Oops!

    I figured that out last night around 10! Sorry.

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