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  1. #1
    Join Date
    Jul 2004
    Location
    Kent, WA
    Posts
    129
    I just got a new Evolution system installed, and it can certainly blow much harder than the old oil furnace I had before. In looking at the air handler parameters on the thermostat, it tells me the current CFM, Fan RPM, and Static Pressure. Does anyone know where this static pressure is measured? I'm assuming it can't know the return duct static, and it could know about filter static but I'm not sure if it does with this value. The value is about 0.33" with a CFM of 1400. Any idea as to whether I'm near the limits of the fan at this value?

  2. #2
    Join Date
    Mar 2004
    Posts
    1,042
    Infinity/Evolution measures the total system ESP by doing some clever math on the blower RPM and blower current. The number includes everything.

    The ESP limit on those systems is 0.8" (except for some of the very first ones, maybe?); you are doing great.

  3. #3
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    wyounger is correct,you are doing just fine .

  4. #4
    Join Date
    Feb 2005
    Posts
    35
    Nice, Without a filter I'm .5 at 1400.

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,599
    suemarkp,
    did they do any additional duct work when they installed your system.
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    How-to-apply-for-Professional

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

  6. #6
    Join Date
    Jul 2004
    Location
    Kent, WA
    Posts
    129
    Not really. I had them move the air handler from the corner of the basement to the center. This allowed about 20' of return duct to be removed and will make access to one of the main trunks easier so I can eventually get more air upstairs. I considered my duct marginal via manual D, but it seems to be fine. I was assuming I only had 0.2 IWC to work with though. My main trunk is 10x24. I have 11 6" take offs and 2 7" takeoffs. Return air is 10x30. Everything is hard metal duct.

    I also have a 16x25x4 media filter and the thermostat idicates that it is 60% used. Maybe I'll go with a higher MERV filter since I have more static to work with.

  7. #7
    Join Date
    Apr 2004
    Posts
    7,680
    Close, it uses math based on blower curves and RPM but rather than current it measures torque.

    EMC motors are great arent they? You need to consider something before you go restriciting the system. And that is the motors are very ineffeicient when demanding higher statics. The watts to drive it are considerably higher when you load them up. I would stay below 0.5" if it were me and this is from an operating cost view and a noise level view. One way to reduce the over all static is to increase your duct sizes if you end up over 0.5".

  8. #8
    Join Date
    Jul 2005
    Posts
    133
    Originally posted by docholiday
    .

    I would stay below 0.5" if it were me and this is from an operating cost view and a noise level view. One way to reduce the over all static is to increase your duct sizes if you end up over 0.5".
    Since I'm getting one of these, can you predict what you're going to get based on the duct size you currently have?

  9. #9
    Join Date
    Apr 2004
    Posts
    7,680
    I am not sure you can but a sold contractor can, the duct is supposed to be designed to the overall and room by room loads and the proper equipment to match. In no way should one assume just by sticking a air handler in place the problems will be solved. The whole kit and kaboodle is the system and the system only works when designed properly. The trick is finding the contractor that will look at the system as a whole and not be afraid to propose making any deficiency in the exsisting part of the system (meaning the distribution). Once he does that, virtually any brand will accomplish the mission.

  10. #10
    Join Date
    Apr 2003
    Posts
    248
    One question comes to mind as I read this thread.

    Is the strain on a motor due to high static pressure proportional to the blower speed. Lets say a blower running on high at 1400 cfm has a static of 1.0 (above recommended levels). But on low it runs at 800 cfm and static is 0.4.
    Is the blower motor struggling at the lower speed? Or is it that being above 0.5 at any speed is bad?

    BTW, my 58mvp060 furnace has a static of 0.68 on high speed (1074 cfm) and static is 0.12 on low (450 cfm).

    [Edited by seadragon on 09-02-2005 at 10:22 PM]

  11. #11
    Join Date
    Apr 2004
    Posts
    7,680
    Well, yes it is proportional because the restriction (ductwork) is consistant. If at 1400 you see a 1.0" static, the static will be reduced if you slow the fan down, then again so will your airflow.

    Static, think of a basketball, the pressure in that ball is static pressure, pushing out in all directions. If I pump it up, the static increases, if I lower the volume of air, it the stati decreases.

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