Ductless A/Cs and General Thoughts

[lncoop]

Can't seem to find any unbiased opinions on the internets (shocker!:lol. Context: 2000 square foot split, beds baths and kitchen up, big bonus room down. Condenser in the shade just outside the bonus room, evaporator and guts in little mechanical room between bonus room and garage with pretty shoddy duct work all through the attic. Downstairs can be kept ice cold regardless of conditions but upstairs not so much. System was likely adequate before POs added to the master suite, but now it's just not quite up to the task. Does okay if highs don't exceed ninety or so, but it struggles with the typical Arkansas summer temps and humidity. My electric bill is a heart stopper. I could have someone clean up the duct work, improve the return air system and up-size capacity for around $10k IF, and it's a big if, the mechanical room can accommodate the larger footprint. That said, I do think just improving the air flow and adding insulation would help even if we weren't able to increase capacity. Air flow is extremely unbalanced with the weakest being on the far side of the master which is the square footage that was added.

What made me think of the ductless systems was what I assume to be their advantage in a situation like mine when space is an issue (not just in the mechanical room, but also in the attic, especially over the additional space). Don't plan to do anything immediately (if ever; might just replace the house instead) but would like to hear your thoughts on all the above. So, what y'all think?

 

[rbh]

2 thoughts come to mind Coop- first make sure that all vegetation is away from the outside unit so that it can expell the heat and the cooling lines are well insulated so they do not get ice building up on them (100 degrees outside and the lines have an inch of ice built up around them from the condensation)

As well as you said the basement is an icebox, so shut off the registers downstairs and force the cold air to other areas-the cold air will settle to the basement naturaly

 

[alldodge]

The ductless work fine, main issue for me is there a bit noisy. You basically have a wall mounted air conditioner, but are quitter then a window mounted. They are easy to install for those who have mechanical skills, and come precharged with Freon.

In-law installed one in there sun room and they work pretty well. That said, once any AC try's to work when temps are above 90 or so, they all have trouble unless you have geo-thermal.

Added insulation in most all cases is a good thing. AC needs lots of air flow to get best results, so redoing ducts to better move air to hotter areas is good so long as CFM stays up

 

[Tnstratofam]

If the unit is undersized and the ductwork or insulation or both aren't up to par then you are going to have problems on the hottest and the coldest days. 2000 square feet should be a 4ton system, with good ductwork design and insulation you might squeak by with a 3 and 1/2 ton, but it will still strugle on 90+? days especially with lots of humidity.

Have the ductwork and insulation taken care of then see where you stand. You may only need a small ductless unit for the larger master.

Controlling temps on multiple levels with a single system can be tough unless it is zoned. Just closing vents in areas that are over cooled waists energy as you will generaly only increase airflow out of the remaining open vents by about 5%. The rest of the conditioned air is simply stuck in closed ductwork.

Also the insulation on the suction line is there due to condensation. It isn't there to keep the line from freezing. If your suction line is forming ice then you either have an airflow problem with the system like a dirty filter, to restrictive of a filter, or your ductwork is improperly sized. Or a refrigeration issue such as low refrigerant or a bad metering device. Your suction line should never freeze, or have frost on it for more than a few seconds.

Heating season a heatpumps condenser coils will freeze and get defrosted this is normal.

P.S. I've benn a heating and air contractor for 20 years, and with todays higher efficiency equipment air flow is key to a good working system. It can't be rule of thumb anymore your system needs to be designed based on a good load calculation done on your house.

 

[thumpar]

I have only had a few experiences with it. It is a good retrofit and nice to have the flexibility of different cooling zones.

 

[jbcurt00]

Controlling temps on multiple levels with a single system can be tough unless it is zoned. Just closing vents in areas that are over cooled waists energy as you will generaly only increase airflow out of the remaining open vents by about 5%. The rest of the conditioned air is simply stuck in closed ductwork.

But w adequete access to install them, inline dampers, at the main/feeder trunk junction, does a better job redistributing air then closed registers do though, correct?

Good luck Coop, better decide soon, dog days of summer are rapidly approaching

 

[Tnstratofam]

But w adequete access to install them, inline dampers, at the main/feeder trunk junction, does a better job redistributing air then closed registers do though, correct?

Good luck Coop, better decide soon, dog days of summer are rapidly approaching

Yes this is an acceptable way to redistribute air. Most zone systems work this way by shutting off dampers at the main trunk line. By closing dampers at the main trunk you are increasing static pressure in the main line which will in turn increase air flow to the open zones. There is a catch though the zone must be balanced ( Usually through either a dump zone or variable speed air handler and condenser.) to allow excess static pressure to be dealt with.

Using dampered take offs at each branch line is also a good way to balance air flow in a system. They allow you to dampen the runs with excessive air flow thereby increasing air flow to weaker runs. This needs to be done using either a manometer or magnahelic, as well as a cfm meter to measure the individual supply vents and cold air returns.


Closing the vents in the rooms is not the same as closing a damper at the main trunk line.