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  1. #1

    Rooftop Packaged Heat Pump Configuration

    I have a two story (3/12 gable roof) house in Mesa, AZ with a 5-ton packaged heat pump on the roof. I am having the unit replaced by an HVAC pro and have a few questions.

    1) Is it better to use the current sideflow w/elbow configuration, or switch to a downflow w/curb configuration? It seems like most companies want to go sideflow with an elbow.

    2) Does brand really matter (besides Goodman)? I'm currently looking at comparable American Standards and Rheems (14 Seer, single stage comp, var blower).

    3) I currently have two 14x25 stamped filter returns, one on each floor. It'll be hard to change the size of the 1st floor return, but I can easily have the second floor changed out to a 14x30. I can also select the bar style grills. Will one 14x25 and one 14x30 bar face return be okay for a 5-ton unit?

    4) How do I find a quality installer in Mesa? There aren't any listed on the locator map.

    Some other details: My house was built in 1978. It has rigid metal ducts. The airflow to the 1st floor is poor. The supply ducts are average leakage. The return is a little above average leakage.

  2. #2
    Join Date
    Feb 2007
    Location
    Las Vegas,NV
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    745
    Some will argue that mounting the unit downshot is better, maybe I would prefer to do it with a stand and not a roof curb. In the future when someone has to replace that unit, it will be easier to swap a stand and transition the ductwork, than to have to tear out a curb that doesnt match the dimensions of the replacement unit.

    As far as brand goes, it doesnt matter. You need to find a reputable contractor to do your install and sometimes asking neighbors who they use, is a good place to start.

    Go ahead now and pay the extra money to fix your airflow issues to the downstairs.

  3. #3
    Join Date
    Nov 2006
    Location
    Southeastern Pa
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    18,342
    Many package units retain the same footprint from year to year. When a matchup is needed, a curb adapter works well. I'm a fan of downflow, since it it what makes medium commercial units easy to change out.

    I would start with having a company do a Manual D to see if the ductwork can supply the airflow you need. Since the home is from 1978, have a heat load calculation done to assure you that you will have a properly sized unit for your area climate.

    I also recommend having the ductwork corrected FIRST.
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  4. #4
    Join Date
    Dec 2010
    Location
    Down by the river
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    1,650
    Quote Originally Posted by sammy37 View Post
    Some will argue that mounting the unit downshot is better, maybe I would prefer to do it with a stand and not a roof curb. In the future when someone has to replace that unit, it will be easier to swap a stand and transition the ductwork, than to have to tear out a curb that doesnt match the dimensions of the replacement unit.

    As far as brand goes, it doesnt matter. You need to find a reputable contractor to do your install and sometimes asking neighbors who they use, is a good place to start.

    Go ahead now and pay the extra money to fix your airflow issues to the downstairs.
    down flow with a roof curb. in the future for replacement you can have an adapter curb made up that mates up with original dimensions and meets the new. no need to rip out anything, it's done all the time.

    spend the money now and get ductwork straight, on a 2 level home it may be wise to look at a zoned sytem. No new construction 2 level homes can have only 1 zone. The reason, you can't keep a 2 story home's temps = both heating and cooling with 1 controlling zone.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  5. #5
    I didn't mention it in my original post, but the reason I am replacing my heat pump is because of hail damage. I have an insurance settlement to replace my roof and heat pump. I am planning to improve the ducting at the same time. The main problem, from what I've been told, is that the supply is split into two trunks at the jack (one for each floor). The second floor duct is less than half of the length of the first floor run and has less bends in the branches. The first floor is a sub-optimal design and can't really be fixed without building a new house. It's been recommend that I install a Y adapter for the two trunks and add a damper for the second floor run. Does this seem reasonable?

  6. #6
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,084
    Has it been recommended to get a unit with a louvered grille over the coil to prevent future hail damage?

  7. #7
    Quote Originally Posted by BaldLoonie View Post
    Has it been recommended to get a unit with a louvered grille over the coil to prevent future hail damage?
    Not by anyone I've talked to yet, although I had thought about this myself. So far, I've been quoted an American Standard Heritage 14 that has the louvers.

  8. #8
    Join Date
    Feb 2007
    Location
    Las Vegas,NV
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    745
    Quote Originally Posted by Southern Mech View Post
    down flow with a roof curb. in the future for replacement you can have an adapter curb made up that mates up with original dimensions and meets the new. no need to rip out anything, it's done all the time.

    spend the money now and get ductwork straight, on a 2 level home it may be wise to look at a zoned sytem. No new construction 2 level homes can have only 1 zone. The reason, you can't keep a 2 story home's temps = both heating and cooling with 1 controlling zone.
    I have no problem with a curb adapter on a commercial building when it's done right.
    As far as residential, most hacks around here are using adjustable pre made roof curbs and not even properly fitting them under the shingles.
    I would not want to come along and put a curb adapter on one of those setups, not to mention it would just set the unit that much higher.

  9. #9
    Join Date
    Dec 2010
    Location
    Down by the river
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    Quote Originally Posted by sammy37 View Post
    I have no problem with a curb adapter on a commercial building when it's done right.
    As far as residential, most hacks around here are using adjustable pre made roof curbs and not even properly fitting them under the shingles.
    I would not want to come along and put a curb adapter on one of those setups, not to mention it would just set the unit that much higher.
    agreed. and a good point for the OP if he goes this route, is to make sure the job gets done properly and permanently.
    It's hard to stop a Trane. but I have made one helluva living keeping them going.

  10. #10
    Quote Originally Posted by sammy37 View Post
    I have no problem with a curb adapter on a commercial building when it's done right.
    As far as residential, most hacks around here are using adjustable pre made roof curbs and not even properly fitting them under the shingles.
    I would not want to come along and put a curb adapter on one of those setups, not to mention it would just set the unit that much higher.
    So do these installations look good or hacky?
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  11. #11
    Join Date
    Feb 2007
    Location
    Las Vegas,NV
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    745
    Quote Originally Posted by jason62082 View Post
    So do these installations look good or hacky?
    I've seen his stuff and I think he advertises on craigslist. Thats what I would consider kind of Hack.

  12. #12
    Join Date
    Feb 2007
    Location
    Las Vegas,NV
    Posts
    745
    In all of the pics, those roof curbs are sitting on top of the shingles. Those adjustable curbs need to be slid under the shingles.

    I'm not a fan of pulling flex duct through the roof and attaching it to a curb, just seems like a crap way to do work.

    In most cases, the elbow on your roof is in two pieces, where as you have the roof jack on the roof and the elbow is fitted on to that. If you want to go downshot, your contractor can remove the elbow and have a transition made to fit your roof jack and then all you will need is a new stand.
    By doing it this way, your roof is not disturbed and it makes it easier for future changeouts down the road.

  13. #13
    Quote Originally Posted by sammy37 View Post
    I've seen his stuff and I think he advertises on craigslist. Thats what I would consider kind of Hack.
    I don't know that this company advertises on craiglist. From the untrained eye, this looks fine to me. What exactly looks hacky? Is it that the shingles don't go over the bottom lip of the sides and bottom of the curb? Is it the curb itself?

    I do appreciate your input. I'm just trying to prepare myself to be the inspector after the job is complete. If I I don't, who will? Thanks.

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