Rooftop Packaged Heat Pump Configuration

[jason62082]

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.

[sammy37]

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.

[timebuilder]

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.

[Southern Mech]

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.

[jason62082]

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?

[BaldLoonie]

Has it been recommended to get a unit with a louvered grille over the coil to prevent future hail damage?

[jason62082]

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.

[sammy37]

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.

[Southern Mech]

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.

[jason62082]

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?

[sammy37]

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.

[sammy37]

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.

[jason62082]

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.

[sammy37]

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.

First off, an adjustable store bought roof curb requires no skill from the contractor. A good contractor will measure the pitch of your roof, measure your existing ductwork on the roof and have a sheet metal shop custom fabricate new metal.

The shingles need to be on top of the bottom flashing around the curb, otherwise when they tear out your existing roof jack and pull the duct up through the roof, you will have a leak. This is why you see in some pics, all the messy roof tar around the curb.

You will notice in a couple of those pics, the roof around the unit is shot. If I come accross something like this, I recommend that the HO replace the roof at the same time and most will.

[sammy37]

I dont know what the norm is in Mesa Jason but in Vegas, the only people using these adjustable curbs are mostly hacks and that is so they can get in and get out quick. Like I said in my last post, they require no skill and I've yet to see one properly done here.

I've been told in the past on this site that I need to catch up or die. Well, I dont care if this new adjustable roof curb is the great new thing or not, I will not use one!
I will use an existing elbow and have a new stand made, it does not disturb the roof.
If a customer wants to go down shot, I will still use a stand and have a custom transition made and it still does not disturb the roof.

[jason62082]

First off, an adjustable store bought roof curb requires no skill from the contractor. A good contractor will measure the pitch of your roof, measure your existing ductwork on the roof and have a sheet metal shop custom fabricate new metal.

The shingles need to be on top of the bottom flashing around the curb, otherwise when they tear out your existing roof jack and pull the duct up through the roof, you will have a leak. This is why you see in some pics, all the messy roof tar around the curb.

You will notice in a couple of those pics, the roof around the unit is shot. If I come accross something like this, I recommend that the HO replace the roof at the same time and most will.

I'm guessing you mean the shingles should look like this: http://hvac-talk.com/vbb/showthread.php?t=89277

I also see in that thread that the contractor uses a custom curb and an adjustable curb in the second set of photos.

[sammy37]

Yes, those look nice. I especially like the first one with the non adjustable curb.
Also, some residential units provide a little less airflow when mounted downshot. The Goodman GPG is the worst for that, the evap coil and drain pan sit right on top of the downshot opening.