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  1. #1
    Join Date
    Jan 2008
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    5

    Question Honeywell based multi zone system ballencing question

    (you'll have to excuse me, I'm learning how this system works as i go)

    I have a 2 zone setup, one zone runs basically the whole house, the second just feeds a media room and equipment closet.

    media room is less than 10% of home, and is sealed with no windows and an exterior type door with weatherstrip joining it to the rest of the home. there is a HVAC return in the room.

    On each of the main ducts that feed each zone there are 2 wire normally open electric dampeners, and there is a gravity balancing dampener that feeds back into the return (balancing dampener is before the electrics, it will dump into the return if both electrics close).

    The whole house seems to work fine, my concern lies with the media room. when just the media room is running, there is too much flow in the room. there is too much airflow noise, and the room short cycles. (it pressurizes to where the door whistles loud enough you can hear it in the next room)

    If i adjust the media room electric dampener down to its minimum open position (seems to be still 60 or 70% open still id guess) i can get it down to where i can adjust the weight on the balancing dampener to where the flow is at least acceptably slowed (slight whistle through door, and you can hear air blowing through the vents).

    My concern is when i have the balance dampener set that light, am i hurting efficiency when the whole house is running?

    Can i reduce the balance weight more, or would i be better served by adding some additional (manual/fixed) restriction in the feed to the media room after the electric dampener to slow down the flow to that room so i can run the balancing dampener with less bypass when the whole house is on? (this will raise total system pressure, particularly when just the media room is running. is this bad?)

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,069
    The zone is too small.
    You can have your contractor add 1 or 2 more supplies to that room, that will slow the air flow down in the supplies. Then add more return( alot more) to that room so it doesn't blow through the door. You don't have enough, thats why its pressurizing the room.

    Another option, do you have an area that is not conditioned. That a dump zone can be run to. Then when the small zone is calling, the excess air would go there instead.
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  3. #3
    Join Date
    Jul 2004
    Location
    Massachusetts
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    6,837
    Your issues could serve as a lesson for all those who seek to install or have installed, individual zones. Zones for air systems have been around for a long time but it's only relatively recently that they've become mainstream. Unfortunately, most installing companies are woefully short on the knowledge to do it properly. I agree with beenthere. A 10% zone is WAY too small as a separate zone. Is it really necessary for that zone, being so small, to be able to call the furnace or AC unit on by itself? One possible solution to such a small zone is to make it a "non-voting" zone. That is, the damers are installed and are operational but he end switches that turn the equipment on & off are not connected. Therefore, that zone/room only gets heating/cooling when the main zone is calling. That means you'll never have the issue of huge air volumes limited to coming out only the supplies in that room because the rest of the house is also using the air from the appliance. When the room heats up or cools down to the thermostat setting, the damper(s) close. Should the room need heat or cool before the main house does, it will not get any air until the main house calls for heat or cool. This is a common practice in systems where there's a small office or bathroom that's being made an individual zone for some reason.

    Your installers should have known there'd be a significant problem with a 10% zone before it was even installed.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  4. #4
    Join Date
    Nov 2007
    Location
    Chicago
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    76
    The system can work with a small zone, but it needs to be controlled correctly. The bypass damper should be sized for the full air flow minus the smallest zone. Lets just say you have a 3 ton air handler with 1200 cfm and your smallest zone is 200 cfm, that bypass needs to be sized for 1000 cfm. The air handler should also be controlled so that it turns the fan on with a call for cooling/heating but cycles the gas or a/c based on discharge air temperature.

  5. #5
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    Jul 2004
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    Massachusetts
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    Quote Originally Posted by hvacconsultant View Post
    The system can work with a small zone, but it needs to be controlled correctly. The bypass damper should be sized for the full air flow minus the smallest zone. Lets just say you have a 3 ton air handler with 1200 cfm and your smallest zone is 200 cfm, that bypass needs to be sized for 1000 cfm. The air handler should also be controlled so that it turns the fan on with a call for cooling/heating but cycles the gas or a/c based on discharge air temperature.
    You're technically correct. The zone can work as you describe but anyone with any experience knows that a 10% zone is going to be trouble. Recirculating 1,000 CFM in your example would quickly run the furnace or AC to it's limit. If you've got your 3-ton AC unit in your example, 0.3 tons is needed for the zone. That's 120 CFM, meaning 1080 CFM of 55 degree air is returned to the unit. Mixed with return air, the average temperature returning to the coil is going to quickly approach 60-degrees INLET. Putting a LAT switch on will cycle the equipment but it will short cycle a furnace and in the case of AC, by the time the unit starts, it'll shut off, do zero dehumidification and with built-in short cycle protection of 3 to 5-minutes, probably be capable of doing very little for comfortable cooling. So yeah, in theory, the number work. But as beenthere already said, the zone is too small. You could do as he suggested and put in more supply but with that solution, the room will roar up to or down to temperature very quickly. So IMO, it's just not a good idea to have a small zone like that calling equipment on. If it were a job we were doing, I'd either advise totally against zoning or put it in as a non-voting zone. Experience is a great teacher.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  6. #6
    Join Date
    Dec 2007
    Location
    oregon
    Posts
    885
    It has been my experiance that anything less then 20% for a zone is going to cause trouble. Already been said. Got to question why it was set up that way to begin with. When zoning and some small zones are to be designed, two stage equipment is important for the longevity of the system, and your comfort. You will need to set up some load shed, or dump zone to help with the overload. Did your installer recommend this set up? My vote is for no vote.
    Genius = The guy who can do anything...except make a living!

  7. #7
    Join Date
    Jan 2008
    Posts
    5
    This was the setup that was recomended. naturally

    The media room contains a video projector and 3.5KW of audio amplification fed by 40 amps of dedicated power. (The subwoofers amp alone generates enough heat at idle to warm the room.) The room defiantly has cooling needs beyond the rest of the home, so it needs a vote in the cooling system. To cool that room in full swing while running the rest of the zones you would have to freeze the rest of the home. There are times in the winter where I'm heating the house, and cooling that room.

    I'm not going to re-do the whole system so back to what is already there. I can dump some excess into somewhere else, but recycling that much back into the main system is going to be too much cold in the inlet? would you just blow it into the attic? (i think ill deal with the whistle before i went that route...)

    Back to my original questions:

    A) am i loosing efficiency in the main house zone by tuning the bypass light enough to get the flow down in the media room?

    B) can i restrict the flow with a manual dampener to the media room to get the flow down?

    If I add more supply's and returns to the media room, it will be quieter yes, but it will magnify the short cycle issue.

    EDIT: is this the solution? ----> maybe just bleed some of the media room air back into the main house? (just enough to stop the whistle and air rushing sound) if i just adjust the stop point on the main house dampener to not allow it to completely close that would accomplish the bleed correct? naturally this is problem on the rare florida day that the rest of the home requires heat- but given the media room isnt used every day i think this would be acceptable.

    So if i may ask, how do you guys deal with a single room with significantly different cooling needs than the rest of the house if not with zones? would you have done a full discrete system for just that room?
    Last edited by TheBeak; 01-12-2008 at 11:14 PM.

  8. #8
    Join Date
    Jun 2001
    Location
    Louisville, KY
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    12,189
    ductless mini split
    Perhaps you should have read the instructions before calling.

  9. #9
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    Jan 2008
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    Quote Originally Posted by jrbenny View Post
    ductless mini split
    those look prety neat (google is your friend). Would you have done the whole house ductless this way, or done the home conventionally with a mini for the one room?

  10. #10
    Join Date
    Dec 2007
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    oregon
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    Quote Originally Posted by jrbenny View Post
    ductless mini split
    Amen brother!
    Genius = The guy who can do anything...except make a living!

  11. #11
    Join Date
    Jan 2008
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    5
    OK, so thats what could have been done. ill remember that for the next house....

    any final words on what to do with this one?

  12. #12
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    Sep 2007
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    NC Coast
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    Quote Originally Posted by TheBeak View Post
    those look prety neat (google is your friend). Would you have done the whole house ductless this way, or done the home conventionally with a mini for the one room?
    No no..... just the one room. But now... what is the load calc on the rest of the house? Is your existing system to big for the load? Or is it withion reason?
    since the one room is approx 10 percent of the house... you may be good just putting in the ductless mini split and leaving the original system alone. (get rid of the supply to that room though.)
    Silent Service........ Death From Below!

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  13. #13
    Join Date
    Jun 2001
    Location
    Louisville, KY
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    Quote Originally Posted by TheBeak View Post
    those look prety neat (google is your friend). Would you have done the whole house ductless this way, or done the home conventionally with a mini for the one room?
    I'd cap your existing duct and remove the zone sensor. Then, install a ductless mini with low ambient controls.

    If you're going to live in a house, you might as well be comfortable and that includes noise issues.
    Perhaps you should have read the instructions before calling.

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