All in one a/c unit...

[Printer Mike]

First of all, please excuse if this has already been adressed. This post is concerning a small new lake cottage that has approx. a 24' x 40' footprint with open ceiling with about a 350 sq. ft. loft bedroom and bathroom.

To save space the builder plans to install a all in one outside unit(no air handler in the interior. So there will be air supply and return ducts going to the a/c unit on the exterior of the cottage.

I tried to find information about advantages and disadvantages of this type of system on the internet without much luck. I am thinking 'less efficiency.'

Any comments/advice welcomed. Thanks in advance!

 

[mike_s]

I've NEVER been a fan of exterior installed ducts.

They are just asking for water leaks and insulation in the ducts getting wet.


Wet insulation produces mold and mildew and causes breathing problems. I'm spend the extra money for a "split system" and get away from an exterior duct. Yeah I know people do it... I'm just not a fan of it.

(I'm assuming the unit will be on the ground and will be ducted upwards at least 10 feet vertically and into the attic space above the first floor, beside the upper loft area. )

 

[jimp]

I have a outdoor unit on my shop. You can take care of the water issue, just look at all the commercial units and trailers.

The one thing to consider is you can only get a 80% eff. unit (91 or 95% have condensate in the heat exchanger and can not be allowed to freeze). If you want a 91 or greater it has to be inside if the temperture drops below freezing. If 80% is ok I don't see a problem.

 

[Printer Mike]

This cottage will most likely be my wife's and my last and permanent residence. We will be living on a fixed income. Having the lowest possible heating and cooling bill is important. It does get very hot and cold here in Georgia. We are paying extra for foam insulation in the ceiling.

The builder assures me that this system is the way to go.(??????)

 

[green.bubbly]

Most trailers use this type of setup and the house I am in right now has the same type unit. It is under a covered patio so water is not an issue. It is probably not a bad choice but for a little more money, I multi-zone mini split might be even better. This would probably be more efficient as you can heat and cool zones instead of the entire house.

A little more upfront but bigger savings down the road.

 

[danski0224]

First of all, please excuse if this has already been adressed. This post is concerning a small new lake cottage that has approx. a 24' x 40' footprint with open ceiling with about a 350 sq. ft. loft bedroom and bathroom.

To save space the builder plans to install a all in one outside unit(no air handler in the interior. So there will be air supply and return ducts going to the a/c unit on the exterior of the cottage.

I tried to find information about advantages and disadvantages of this type of system on the internet without much luck. I am thinking 'less efficiency.'

Any comments/advice welcomed. Thanks in advance!

This cottage will most likely be my wife's and my last and permanent residence. We will be living on a fixed income. Having the lowest possible heating and cooling bill is important. It does get very hot and cold here in Georgia. We are paying extra for foam insulation in the ceiling.

The builder assures me that this system is the way to go.(??????)

No air handler? Then are we to assume that you will use a heat pump and resistive backup? (no gas, propane or oil furnace)

You will want a variable speed or ECM motor for air movement (an ECM motor is not necessarily variable speed). Not sure if you can get that from the factory in a package unit. An ECM motor can be retrofitted.

A package unit can be outfitted with economizer and enthalpy controls that can provide for "free cooling" (no compressor operation) if the outdoor temperature and humidity is low enough.

You can get higher SEER combinations using a traditional split system (outdoor unit and indoor air handler/coil) than a package unit.

Be aware that you do not get high SEER combinations to work unless the ducting and airflow is correct.

Poor ducting on a variable speed blower will cost you more money to operate.

Generally speaking, a builder does not know much about HVAC systems. The builder does know how to get something installed for the lowest price, and mark up "upgrades".

If you are having the home custom built, you should be able to speak with the HVAC contractor, or use your own. That is the only way to get your concerns properly addressed.

 

[thooks]

Mike,

There's nothing wrong with using a packaged system and running the ductwork through the crawl space. I've seen it a million times. I, myself, have a packaged unit at my house on one part. It actually serves the bed and bathroom above the garage addition, with the ducts running up the side wall and into the ceiling space of the garage.


I strongly recommend adding an additional cover of galvanized sheet metal over the insulated, sealed supply and return ducts.

But.....let me try to guide you in a different direction....high-efficiency mini-splits. These are the newest and latest technology in HVAC, at least in the US. The rest of the civilized world has been using them for years as the primary HVAC source.

Daikin has a 1-1/2 and 2-ton split system that is sort of "conventional", but you get all the goodies from the latest technology- http://www.daikinac.com/residential/productsDaikinInverter.asp?sec=products&page=57

They also have multi-port, single-phase systems where you can mix and match several (4) indoor units to a single outdoor condensing unit. I can't find info on this on their website, but I can hook you up with a Daikin rep in the ATL area.

This is what I will install in the next house I build (or any replacement). These types of systems are all variable-speed...the compressor is variable speed, the indoor fan is variable speed and it is all soft-start.

With the multi-port units, one room could be calling for cooling and the rest not...leaving the occupants comfortable.

They also have a 3-5 ton variable refrigerant flow system with the capability of serving several indoor units and allowing heating AND cooling at the same time. Say the East side wants some cooling in the morning, while the West side is chilly and momma wants some heat in the sewing room. No problem. No energy is wasted on that, either.

These heat pumps will produce good heat down to 0°F or less with no problem. Let me know if you want more info. No, I'm not a Daikin employee, rep, or related to one. I just feel they make some good equipment.

 

[Charles (in GA)]

I see those units shoved up to old houses all the time, I assume ducts underneath the house connecting it to the rooms. Looks ugly as sin. I would never consider doing this on a new construction. They are largely intended for use in retrofits where there is no place to install an air handler.

Charles

 

[danski0224]

I see those units shoved up to old houses all the time, I assume ducts underneath the house connecting it to the rooms. Looks ugly as sin. I would never consider doing this on a new construction. They are largely intended for use in retrofits where there is no place to install an air handler.

Charles

Don't go to Arizona... Those units are installed on the roof.

Ugly *and* hard to service.