[kdean1]

Does the package unit have round duct connections? Don't shoot yourself in the foot by making a reduction of a rectangular duct connection to round pipe.

 

[mikel7829]

I see alot of people that sizes mobile homes as they would a house..most of the time the unit can keep up until the sun comes out. Mobile homes are like a magnet for the sun.Also keep in mind the placement of the registers they tend to be in the middle of the home not exactly where they normally would be in a regular structure.They we're place we're they are for the manufacturers convince not for preformance.Personally I would oversize a tad bit due to heat loss,ect. Due to the way MOST are insulated and sealed their not going to preform top notch regardless.I would also try to get another return in on the other side of the home from where the original return is at.Also where is the t-stat going to be located? In a mobile home this can be a pain as well trying to get it to function like it should.

 

[customheating]

Someone was quick to say,mobile homes have inferior insulation. That may be true on older models, but if you look at them now days, they are 2x6 outside walls with r-19, and also the floors are insulated well, with a thick tarp like material. Also,I've found,the company's that you buy a new mobile from, DO NOT want to hire any local contractor, so since they do not know how to install a split system, they install a package a.c., what's important but rare,is when using the factory furnace,with package a.c., your supposed to tab in a gravity damper, it keeps the heat from running back through the package supply and out the return of the package unit. Then they also sell self piercing coils,outdoor units,and linesets, that are pre-charged. No vacume or charge needed, the extra length on copper they leave rolled up underneath. They have o rings,and are notorious for leaking.

 

[DavidDeBord]

See if this helps

:cheers:

 

[DavidDeBord]

They have flex going from the package unit to the supply and return and it isn't in the best of shape either

There's part of Your Problem.

Any duct coming from a Package Unit,for Mobile Home/ Modular applications absolutely needs to protected from the Weather, & have minimum restriction for air-flow.

 

[DavidDeBord]

It's a doublewide and they currently only had one return and it was a 12 by 20. I was planning on increasing that one

"12 by 20" Floor Grill, or 12 x 20 Duct?

If it's a floor grill, what size duct is connected to it?

 

[DavidDeBord]

Also the doublewide doesn't have the vapor barrier underneath and most of the insulation is gone that's why I waa leaning toward a 3 ton and i was going to replace the flex with round pipe

Your Load Calculations have to be for what is "Existing", which has to include the floor insulation falling down. The original unit "may" have been correct for when the insulation was intact, but, now it is inadequate.

Installing Metal piping is an excellent improvement but, it should at the least be 26G, with External, Weather resistant insulation. All in all, Your local Building Department, can tell you want they want to see at the job-site.

 

[kdean1]

Yes it did but If I change it out I'm going to replace it hard round pipe

Hard round pipe is good. BUT far too often I find an opening that is 12"x18" which has been covered with sheet metal and a 10" or 12" round collar installed. Ask yourself why the manufacturer made the opening so big in the first place and what will happen when it is reduced.

 

[DavidDeBord]

That 12" x 18" can be converted to Round Pipe, but in most cases, it's going to be far larger than 10", or 12" Round pipe.

And I Agree Kdean, ... If an Installer intentionally reduced the Duct Size specified by the Manufacturer , just to save a $, or did it out of a Lack of Knowledge, ... then Many Problems are soon going to occur.