Mini-Split AC basics and how we got started on our project

We have been planning on getting some supplemental heating and a source of cooling for our ranch style home in the SF Bay Area for a long time. Since I travel to Asia on business a few times a year, I have been used to seeing these units parked in apartment balconies all the time.

For the past year we have been contemplating what solution would work best for us given our requirements, budget and our focus on efficiency.

Talkng to a few contractors it became clear that most of them were steering me towards what they could install rather than listening to what I wanted installed. One of the options we could have looked into involved the whole house AC, which in my opinion lacked localized controls on heating and cooling.

Our house currently has a gas furnace for forced air heating and the one thing I hate the most is that I am forced to heat the whole house whether I need it or not. Since this was already built into the house when we purchased it, it didn't make much of a sense to rip it off and replace it with something else. But since we are looking at other options now I wanted to make sure we get what we want.

During my research I started looking more closely at mini-split units which were insanely efficient (23 SEERS & 11.5 HSPF) and were being used widely across the world in Europe and Asia. In the United States, these units surprisingly weren't popular at all and a few contractors I had been in touch and no experience installing such units.

Mini-Split AC units consist of a compressor which is installed outside the house and one or more evalorator units which cool/heat the house, installed on the wall. The exterior and the interior units are connect by 2 pipe called the Liquid Line (LL) and the Gas Line (GL), togather with a control wire and a drain hose.

Since because of the LL and the GL these need no duct work and hence they are also called ductless AC systems. This makes them ideal for use in older homes where new duct work is not an option and also in homes where you just do not have any ducts.

Upon further investigation on efficiency, operating costs and the way these operated, we decided that this would be best suited for our home. The weather in SF Bay area is pretty moderate with average lows at 40 F and average high at 82 F - Moderate SF Bay Weather

The system we were installing was primarily for the few months a year where we wanted a few rooms in our home cooled a bit and an option of provided localized heat when necessary.

Once we had narrowed down on what was needed, we proceeded with contacting some local contractors to get this installed at our place. After a few weeks of getting quotes and working with a few local contractors as well as established HVAC companies it was clear that our expectations and what the contractors had to offer, had an unbridgeable gap. It was then I turned into checking out what options the web provided for us, especially since we are avid DIY'ers and have competed quite a few of our home projects.

Considering our home square footage and our requirements we needed the following

• Ability to cool 2(or 3) of our bedrooms and one living room
• Ability to control cooling in each of these rooms
• Option to heat if available
• Efficiency of at least 15 SEERS
• Ability to take advantage of 30% Federal tax credit ending in Dec 2010

A few of our contractors came up with quotes ranging from $5K for central cooling (which did not meet our criteria) to about $10.5K for a name brand mini-split heat pump installation and various figures between the 2 numbers. In fact the cheapest quote meeting our requirements was $9K which I found to be on the higher side considering the work involved. These quotes did not include any of the electrical work.

HVAC for the longest time has been a very regulated industry - meaning the manufacturers and distributors work closely with contractors directly (for good reasons). Since the refrigerants are regulated by EPA, you need a special permit to work with these refrigerants (Section 608 Technician Certification credentials). This is because of the ozone-depleting effect that these refrigerants have if released out in the open. Proper recovery and disposal of refrigerant is a must and is reuired by law in many cases.

The flip side is that in cases ( like mini-splits) where you could potentially install and where an installation could be a DIY, people face problems with outlets refusing to sell equipment directly to end users. In this case you have the option of either getting help from your contractor friends or if you are like me who does not have a contractor friend, you could check things online. Please bear in mind that in most cases manufacturers do need the installation finalized by a licensed HVAC technician but in this case you could still do the 80-90% of the installation and pay a small fee (< $150) for a technician to finalize your install.


Finally a word on EPA restrictions on new generation refrigerants like R410A


Complying With The Section 608 Refrigerant Recycling Rule | Ozone Depletion - Regulatory Programs | U.S. EPA 

Refrigerant Sales Restrictions

The sale of ozone-depleting refrigerant (such as R-11, R-12, and R-22) in any size container has been restricted to technicians certified either under the program described in Technician Certification above or under EPA's motor vehicle air conditioning regulations. The sales restriction covers ozone-depleting refrigerant contained in bulk containers, such as cans, cylinders, or drums.

The restriction excludes refrigerant contained in refrigerators or air conditioners with fully assembled refrigerant circuits (such as household refrigerators, window air conditioners, and packaged air conditioners), and HFC refrigerants (such as R-134a and R-410A).

So its perfectly legal to purchase an AC unit with R410A but its not clear if you need a special license from the EPA to activate your mini-split.