Taking A/C boxes to the next level: multi-ton split systems

[micro gro]

Mini split's are superior not only because of the higher energy efficiency ratings but more importantly because they don't exchange air by their split design nature. Most (if not all) window units do, even though the cold and hot sides are technically separated. My window unit cost me a lot of extra money to operate because of added cost of CO2 (more CO2 lost = more refills, more often) and electric consumption. Even with a generator it would have been easily more expensive if not in LP/NG costs, then in electric costs since the A/C will cycle more from the generator heat, and the generator will cycle more because the A/C is losing more CO2...

I think the lowest rating you'll find on a mini split is something like 13 SEER, as high as 18 (I might have seen 21's). On a window unit that is probably on the higher end of your ratings. High 9's and low 10's are common for window units. Whatever you do, get one with an Energy Star rating (I think minimum is 10.x to qualify for Energy Star).

I'm far from a HVAC tech or anything but I'd guess "obviously" that 2 smaller units will be less energy efficient due to the overhead required, but I'm not so sure.

PS - Look for units with DC inverters.

 

[hoosierdaddy]

My window unit has the cool air separated and has it's own plastic chamber. All air is retained within the cool side, and none gets exhausted past the hot coils.
Most units that do not have a fresh air vent, have separate air flows. The ones that do have fresh air vents, can easily be glued shut and caulked up tight.

 

[Securityfirst]

Building one in a downstairs bedroom

Building one in a downstairs bedroom

Hi Micro! How goes it? Here is my Vegg room. At the end you can see the drape and a wall, behind that wall is a deck. After reading your thread I dont see any reason why you could not build an A/c room near that wall do you?

 

[micro gro]

Securityfirst, call S and we can discuss.

 

[Philosophelon]

2 questions for ya micro:

Where do you exhaust the 12" blower in the A/C compressor room?
Also, from where are you drawing the intake air in the compressor room?

Sorry if I missed it earlier in the thread.

 

[micro gro]

Philosophelon, exhaust through roof, intake from windows.

 

[NorCal]

has the air exchange been enough to keep the condenser running efficiently? In my experience (in running a 2.5 hp chiller in its own 12x12 room) we originally had no exhaust and the room was getting terribly hot (like 110 deg) then I installed a 12" h/o vortex (2050 cfm) and it definitely helped the issue, unfortunately one of the pumps from the rez to the chiller failed (actually the no flow no go switch failed) and screwed the entire water cooled system up its literally a disaster.

either way im looking into the 5 ton excel air stealth system and was trying to utilize the same concept, leaving a room for the condenser and exhausting it like you did. My main concern is whether or not i could just exhaust the unit itself (like run a top plenum with 16" ducting from the top of the condenser and just let it push its own air out of the room via a 16" exhaust hole going outside ) or just have the hot air blowing into the room and then exhausting that w/ a 12" vortex h/o with a big scrubber attached to it.

if the condenser is located close to the flower room and exhausted w/o an exhaust fan and scrubber will the odors escape also?

sorry for so many questions but ive been racking my brains trying to get this design done and im really trying to keep this as a sealed room, no noisy fans or air going out and it seems like youd be able to help me out with your knowledge and experience

 

[hoosierdaddy]

NorCal, you would be far better of dong what you are thinking and ducting the top of the unit right out of the room. If you keep the duct the same size it will probably push out with the unit fan just fine.
Allowing that hot air into the lung room only decreases the units efficiency.

 

[vancityj]

It states on the Excel Air website (http://excelair.ca/XL Installation.pdf) that, 'The fan on the outdoor condensing unit is not designed to move air through any ductwork. Additional blower must be installed for this. Required amount of air is 550 CFM per Ton'. How well do the mini-splits work? I'm skeptical that they work as well in a larger room as they have less than half the CFM movement as a blower; a three-ton mini split is about 500 CFM, no? Vs, 1200 CFM with a blower based AC.
Here's part of an e-mail I received from an HVAC seller regarding CFM on a 30,000btu/2.5 Ton unit, 'As for the CFM ratings on both, we have posted them below for your review. In our opinion, If the room is that small you would be much better off with the Mitsubishi Mini Split instead of the water cooled system.
Water Cooled System CFM Rating: 1070
Mitsubishi CFM Rating:
AirFlow Dry 296-431-568
AirFlow Wet 265-385-508'.

 

[hoosierdaddy]

It states on the Excel Air website (http://excelair.ca/XL Installation.pdf) that, 'The fan on the outdoor condensing unit is not designed to move air through any ductwork. Additional blower must be installed for this. Required amount of air is 550 CFM per Ton'.

I agree that when you duct the exhaust you normally will need a fan to help. However, the fan of a 5k-10k unit will be about the same size as the fan for a 20,000btu unit. And if the ducting out of the back is the same size as the back, you can essentially run it for a good ways straight and even have a 90 deg turn in it without needing a fan to help. Only when you choke down that size to a ducting size will you need help getting the air out.
I use a 250 CFM to get rid of the air ducted from my 5050btu.

*if you have a (proper) AC box, you can essentially push air into the intake side with a fan, and do the same as you would adding a fan to the exhaust.