Basement AC air return?

[grantgoold]

I have a 3 ton basement AC I am ready to install. The unit does not require recirulation of the interior air but I am thinking it might be better than dirty outside air or worse yet air not previously cooled. I am considering placing two or three floor registers on each side of the middle bay and using that closed system for air recirculation. The middle bay would provide more that enough air flow. The registers would be lovered so during non-function would be closed.  The unit needs about 420 square inches of air flow to make if function correctly.

Any of you out there tried this? Is so, ideas would be greatly appreciated. I am not going to install roof airs at this time. I may even consider another basement unit in the future. MCI 9.

Thanks

Grant

[Nick Badame Refrig/ACC]

Hi Grant,

The return air would be better suited when it is pulling from the interrior. It is more efficient to recool the air that you have allready cooled

to be able to bring the temp down in a timely mannor

Grant, if you have time, look at my setup in my yahoo site. There is a link at the bottom of my postings.    2- 15000 btu's each..


Good uck

Nick-

[Merlin-PV]

I have done exactly what you are sugesting,return air in the raceway in the middle works just fine my unit is only 2 ton and will bring down the temp from 100 deg. down to 75 deg in about 15 min cold air ducts in the ceiling, 4 - 4x12 floor registers in the floor .Insulation is the key!!!

[grantgoold]

Merlin, when you say insulation, do you mean on the duct work or the entire bus. I am not doing a complete conversion at this time so am somewhat dependent on system keeping the bus comfortable. I may add a second unit if needed. I do have the OTR AC system that still works.

Thanks for the input. Any pictures of the system would be greatly appreciated both interior and exterior.

Regards,

Grant

[grantgoold]

Nick, thanks for the quick reply. I sent a response but it looks like it did not make it. I have looked over your Yahoo site and have a few more detailed questions. I have my single ac unit on a sliding joey bed. It sits on the curb side middle bay. I have the condenser coils facing outwards. I would like to build a manifold that encloses the air being pulled from the floor of the coach pass the coils and then like you have the supply air discharge in two ducts for each side of the bay. The condenser coil side is 35 inches wide. I cannot see a hole in the floor that large? How did you open enough floor space to get the air flow. The manual suggests 420 inches of unrestricted air flow for maximum efficiency. I was thinking three or four 6x12 registers and then one or two allowing bay air to enter in as well. Any ideas? Also, I am not doing a complete tear out of the interior at this point so no overhead duct work. Should I just return the cold air via floor registers as well?

Hopefully this isn't a repeat question. Thanks again for your time and expertise.

Grant

[Hartley]

I would reconsider pulling air from inside a bay, You will be pulling dirty, odors and all kinds of creepy stuff in through air leaks
in the plumbing and electrical tunnel. Have you looked in there at the coat of SOOT? It gets sucked from the engine bay
all the way up into the stock a/c air intake if any of the rubber seals are missing.

Also if you have any pass through holes between the bays you may also be pulling a negative pressure in them as well and
there is a lot of stinky stuff down there that honestly you wouldn't be happy about smelling.

Oh, Well... My 2 cents worth.. Cause I been there a few times...

[grantgoold]

Thanks for the reply. At this time, it looks like I might be able to get the return air from just the inside of the bus without using the bay. I agree the smell could be bad.

Thanks

Grant

[Merlin-PV]

Both the coach and the ductwork coach being most important draw return air from inside draw cooling air for your condenser from outside and expel it their also on oposed sides

[Burgermeister]

Nobody has raised the point of ensuring proper "area coverage" by positioning the return air ducts to ensure proper or optimum air exchange. 

Thiis should be considered in both vertical and horizontal aspects.

An extreme example would be supply at floor level front, return at ceiling rear. 

Return would be taking the hot air (that's risen) to the A/C and the cold air would "fill" in the space evauated.  Front to back flow would ensure entire living space is "covered"

I acknowledge, there's an immediate benefit from supplying cooled air high, because of occupant perception, but this is a "strategic decision"  and varies by space and occupant use. 

I was just attempting to illustrate the "physics" of the situation. YM (and use) MV

Onward and Upward

Marc Bourget

[grantgoold]

Thanks Marc for the input. I am trying to spread out the cool air return to help with flow. How is your bus "idea" coming along?

Thanks

Grant