what size would you do.

[jim147]

I'm stuck with the duct.

Then bid out what the duct will take and make the customer sign off on it or walk away.

Most times it's better to get out of a job instead of looking for a fix for something you know is not going to work.

jim

[ironpit]

THAT is exactly what I want to do! But this is my accountant and I do a lot of work for him.
Would hate to lose the account. Appreciate what you guys have said. I don't mean to minimize the load calc, I use Lennox calc sheets. But SO many times the existing ductwork in houses around here are way off.

You can't just throw the right sized equipment on the wrong size duct.
I sub for a couple of dealers and have worked for others.

The returns are sized from .1 to .05 . That is a huge difference.

Actually, it gets frustrating at times.I bust my butt to study, and it gripes me sometimes what I run across.
Thanks for your time.

[mgenius33]

What about using a lower rpm motor? Maybe an Evergreen, or something. Then pull one lead off a 5kw strip, and use turning vanes in the supply T.
If you're worried about the heat, use a two stg stat and set the differential high. Even at 15kw / 800 cfm it will only be about a 60* rise.

[gapfaff]

So, how old is this modular? shouldn't the manufacturer have some obligation to correct this? Warranty? Your Accountant has the pull to get this done as the selling dealer. I know the present owner doesn't want the floors cut for additional vents but they could be swayed to see the long term benefits? Is it on a crawl space? It could be done and insulation sealed back up properly but, labor intensive which is why the manufacturer should bare some financial responsibility.

[ironpit]

Brand new home. They just set it. Has a crawl. It's about sixty miles from here... and anywhere else. wet crawl and cut gravel. I notice that the duct under the furnace extends about a foot and a half past the furnace closet. There is no way to install the line set and condensate line without going thru the ductwork. It is impossible. I have no idea why they ran the duct like that. It serves no purpose that I can see.

I think I am going to walk away from this one.

Not familiar with Evergreen.

[gapfaff]

then the answer is simple...it's the manufacturers responsibility to make it right. Can't be done to code not having supplies in 3 rooms? In Wisconsin these modulars are inspected before and occupancy permit is given and that would not pass up here. Modulars are different than mobile home standards up here. Don't know about codes where you are located.

Brand new home. They just set it. Has a crawl. It's about sixty miles from here... and anywhere else. wet crawl and cut gravel. I notice that the duct under the furnace extends about a foot and a half past the furnace closet. There is no way to install the line set and condensate line without going thru the ductwork. It is impossible. I have no idea why they ran the duct like that. It serves no purpose that I can see.

I think I am going to walk away from this one.

Not familiar with Evergreen.

[gapfaff]

Don't blame you! homeowners should probably get a lawyer if the manufacturer doesn't agree to fix it. Sounds like they just threw in an airhandler they had in stock and didn't worry about sizing it properly. I have a similar horror story about a mfr venting a 92% TRANE furnace in a mod home. they used any pvc fittings they had lying around...tees in place of elbows etc. I was the TRANE tech they had to pay to correct the problem. So, if this mfr is reputable they'll get this resolved to the homeowners satisfaction. good luck.

[southshorejohn]

Then bid out what the duct will take and make the customer sign off on it or walk away.

Most times it's better to get out of a job instead of looking for a fix for something you know is not going to work.
jim

Ditto, been there, done that down the road when it doesn't work right guess who's fault it will be no mater what,

[ironpit]

Thanks guys. If you get the time, you should google indiana's hvac license requirements.

It's not like I don't know how to do a job from scratch in a professional manner, it's crap like this that frustrates me. Load calcs are obviously the right way to do a job, but they mean little of nothing if the ductwork is wrong.

There is a business in b'town that had a 5 ton a/c package unit installed 7 years ago. It has one 16 x 8 duict ran to the building. I have replaced two 1 hrse blower motors in the last couple of years. Now the compressor is acting up. I have told these guys repeatedly, duct work is killing you. Finally, they are going to change the ductwork.

[stopro1]

What you have is an oversized return and undersized supply for the 2.5-3T system you think is needed. With the oversized blower, and total static of the combined supply/return/registers there, you may end up with the 1000-1200 cfm you need. I would think that your 1600 nominal cfm blower, with as high as .8"-.9" of total esp imposed, could deliver a net cfm in the acceptable size range. Check the blower curve of the ahu. As far as your six supply registers go, assuming they are fed with 6" runouts.....they could deliver as much as 200cfm a piece with that kind of pressure built in the supply duct system. Noisy, yes....impossible, no.

With this type of home, minimal supply duct size is a necessity. It may be the very reason the return and blower were oversized.

[beenthere]

She'll change her tune about more supplies come winter when those rooms get cold.

[ironpit]

Stoppro1 You might be right. But that laundry room is gonna freeze. Thanks for the info.

[carmon]

install more supply vents or walk away... home owner will get over a few registers.... if not let them sweat