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Thread: Register type

  1. #1
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    Register type

    We are about to have a new Mitsubishi Zuba 3-ton central heat pump installed. We will make use of the existing duct system which has been confirmed to be adequate except for insulation which will be upgraded.

    We have 10 registers, 7 of which are ceiling mounted near windows and 3 are wall mounted (one high, two low (attic room)) The registers are all 12x6. Originals have multiple dampers, but several have been replaced with the type that has just one large damper/baffle. I think these may be wall registers? (pics of registers attached)

    Partly for cosmetic reasons and partly to improve flow patterns, I feel I should replace some of the registers. In our town, nobody stocks this size, so I will have to buy on-line.

    My question relates to the louvre orientation. Apparently I can buy 1,2,3 or 4 way registers. Are there guidelines as to which way should the air flow be directed given that they will be used mainly for heating?

    Pics of two typical rooms attached.
    Attached Images Attached Images     

  2. #2
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    I like the better quality commercial style registers that ar 2 or 4 way and allow you to adjust hte luvers manually. They also have less resistance and therefor eflow mor eair and have better throw for good mixing. However too much throw can make a room feel drafty depending on register location.


    the ones with the large single camper are intended for walls I believe. They are very cheap and can be pretty noisy if you have too much airlfow throguh them. It sounds like you however have a good number of dampers, so your velocity probably isn't too high.

    If youre near a wall I think you usually just want 2-way dampers that throw air to the sides and center.

  3. #3
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    Quote Originally Posted by motoguy128 View Post
    I like the better quality commercial style registers that ar 2 or 4 way and allow you to adjust hte luvers manually. They also have less resistance and therefor eflow mor eair and have better throw for good mixing. However too much throw can make a room feel drafty depending on register location.


    the ones with the large single camper are intended for walls I believe. They are very cheap and can be pretty noisy if you have too much airlfow throguh them. It sounds like you however have a good number of dampers, so your velocity probably isn't too high.

    If youre near a wall I think you usually just want 2-way dampers that throw air to the sides and center.
    Would these be similar to type you are recommending?:

    http://www.map-hvac.com/RepSupport/S...x?PDF=GR-2.0_B

    I can see benefit of being able to adjust vanes manually so one register type might suit all locations.

    Our total air flow will be 1200cfm and have a mix of duct sizes (4"-7") feeding registers. Larger ones may have fairly high velocity if flow is say 140cfm.

    Any good sources on-line for this type of register? (We are in Canada). I think I will buy 7 new ceilng units and use the existing multi vane ones on the walls.

  4. #4
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    Yes, like those. Much better quality and airflow characteristic. You can in some cases flow almost twice the CFM without any noise compared to basic stamped steel grills. I think they look better too. But they do cost 2-3x more so it's not suprising that few installers use the better ones unless they are clearly specified.

  5. #5
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    pic 4, is a room directly over head of the diffuser? If so watch what you buy, they may be to deep to fit all the way up in the supply boot.
    Always here

  6. #6
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    Quote Originally Posted by energy star View Post
    pic 4, is a room directly over head of the diffuser? If so watch what you buy, they may be to deep to fit all the way up in the supply boot.
    Good point - I am aware of problem because the cheap units with single damper I posted pic of do not fully open in some outlets.

  7. #7
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    I gotta get back to work, but first I would like to say, just get something you can adjust the face of. I would not worry about the damper. Have your HVAC pro install a damper back at the main trunk. I also noticed some mold around a diffuser in one of the pics. That may be one on the second floor, I would check to make sure the boot is sealed tight to the ceiling and it's insulated in the attic properly.
    Always here

  8. #8
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    Quote Originally Posted by energy star View Post
    I gotta get back to work, but first I would like to say, just get something you can adjust the face of. I would not worry about the damper. Have your HVAC pro install a damper back at the main trunk. I also noticed some mold around a diffuser in one of the pics. That may be one on the second floor, I would check to make sure the boot is sealed tight to the ceiling and it's insulated in the attic properly.
    I checked with local HVAC wholesaler - They can order very nice commercial registers, but they will cost about $60 each! Ouch. I stopped at Lowes on way home and they had 12x6s for $17.98. Just stamped in aluminum - type with 2-way louvres on front and multi vanes behind. Not bad, but I think I need to do some more research!

  9. #9
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    look at residential rather than commercial.
    hvac supply stores have more choices than lowes hd.

    will hvac company be mastic sealing ductwork as they re-insulate?
    they should also seal boot(supply box) to ceiling gaps.
    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  10. #10
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    Quote Originally Posted by energy_rater_La View Post
    look at residential rather than commercial.
    hvac supply stores have more choices than lowes hd.

    will hvac company be mastic sealing ductwork as they re-insulate?
    they should also seal boot(supply box) to ceiling gaps.
    best of luck.
    I found these ones - priced at about $18.00 each. No local stocker - have to order on-line.

    http://www.dayus.ca/Submittals2010/DAHV_DAVH.pdf

    We are adding to attic insulation using blown in cellulose. Ducts currently have 1" of ~R6 F/G duct insulation with black paper on outside. (dates back to 70's). We will leave it in place (after sealing). Cellulose will fill in around ducts and be mounded over top - should get another R20 at least. Air handler and new tie-in ducts will have R-12 commercial sheet-board insulation.

    Sealing is a bit of a problem in that some parts of ducts are not accessible (24ft of 10x10 duct) They did blow insulation into the cavities that these ducts run through). I had the insulation contractors remove insulation and aluminum tape the joints before they insulated above two of the rooms. The HVAC contractor will do a similar job on other accessible ducts when they are here. Main trunks run on ceiling joists so only three sides can be accessed. Round branches can be accessed. I suspect they are only planning on taping the joints - Will this last?

    I am doing the register openings myself and reaching in to first joint and taping on inside. I have also sealed all openings in boots as well as sealing ceiling cutouts. New registers will come with seals.

  11. #11
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    you'll need every bit of sealing you can do or the fine cellulose particles will
    find every tiny crack and make their way into your house.
    don't limit yourself to just sealing ducts
    seal all penetrations from attic into living space..before adding insulation.
    what you can't get from in attic use caulk to address from inside.

    seal on new register is usually a little foam around edges of grill.

    best of luck.
    The cure of the part should not be attempted without the cure of the whole. ~Plato

  12. #12
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    Quote Originally Posted by energy_rater_La View Post
    you'll need every bit of sealing you can do or the fine cellulose particles will
    find every tiny crack and make their way into your house.
    don't limit yourself to just sealing ducts
    seal all penetrations from attic into living space..before adding insulation.
    what you can't get from in attic use caulk to address from inside.

    seal on new register is usually a little foam around edges of grill.

    best of luck.
    The RETURN ducts that pass through the attic will be new and will be properly sealed by contractor so hopefully no dust will be sucked in. But I think I may ask insulation contractor to only use batts in the attic area that will house the air handler. Might help if there are any remaining leaks on existing supply ducts in that area that might blow dust around.

    Regarding the registers I purchased. One thing I will have given up, is ability to control air flow to individual rooms because of lack of damper. If system require balancing, I guess I may have to deal with that at time

    And yes - we are blocking every possible gap in ceiling - So far the ones we have identified amount to area of an 8" diam hole in ceiling!

  13. #13
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    The selection of the type and size of supply and return nozzles is critical to balance in the heating/cooling system. It's not as easy as picking something that has a particular look and calling it a day. Lowes and other big box outlets definitely do not have the proper products to make an educated decision. I have to admit that I'm a little curious about all the outlets being the same size. Are all the rooms identical with identical exposures? Are all the windows the same size and same orientation regarding sun? I ask because a proper load analysis room-by-room might reveal some issues. You said it's been determined that the duct system is adequate but what about the supply outlets? Manual 'T' or manufacturer's specifications will reveal very different airflows for different size diffusers of the same model number.

    Once again, this is a science, not a guessing game. Too many people think it's just air so it's okay to guess. Nothing could be further form the truth.

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