A guide to purchasing residential air conditioning & heating !
Comfort is the key
Many items are in more detail at the "MENU Selection & other site pages"

All material & labor is part of your cost. So what one installs are DOES NOT install can affect your price?

Existing - replacement - add on
Start with: Appointment or meeting
The air conditioning & heating contractor should have conversation with the home owner, architect, engineer, preferably the home owner since they will be living in the home and will expect their comfort to be maintained. The purpose of this meeting is to get their ideas and what the complete,( units, ducts, grilles, supply & return air, etc ),air conditioning & heating design can do. Of course cost will play into the discussion. Not an estimate yet but some cost of various items will have an affect on the final result. Physical sizes & locations for various related items should be discussed as well.
1. Did the existing system keep your family comfortable in it's performance days or were there any rooms that were uncomfortable during heating or cooling?
2. During heating or cooling did the humidity level seem to be ok or was it to dry or to humid?
3. Are we going to contemplate a change of equipment say from gas or oil to a heat pump with maybe auxiliary heat?
4. Is there anything about the system you didn't like in the location of electrical wiring, electrical disconnect, drain (condensate) line, refrigerant lines, or any other item you would change if you could?
5. Why is the existing equipment being replaced?
6. Were there any additions made to the home (conditioned or unconditioned)?
7. Was a calculation done on your home for heating & cooling BTU's? Was this calculation done in accordance with Manual "J" or was it a general rule or rule of thumb (so many tons per the square footage)?
8. If items were added especially more electrical was the electrical service and main panel ever increased?
9. Any of the supply grilles ever sweat?
10. Any supply grilles not have sufficient air? (to cold during winter operation and for summer operation to warm).
11. Do you or any member of the family have allergies, hay-fever, or breathing ailments?
12 If you want to oversize your air conditioner for a future addition then a moisture problem could very well happen. It is highly suggested the addition is going to proceed quickly.
Equipment and BTU loads are selected & sized according to the existing home's Design Temperature - BTU's  and can play some moisture havoc, (humidity too high),  when they are too greatly oversized.
Before your home is examined are you familiar with the quantity of hours that are in a given year and the number of hours per a temperature (see Answers-Questions-Tips at the Menu, then select hours per year).? These hours will help in the operation cost of various types of equipment such as gas, oil, electric heat, heat pump and efficiency ratings of cooling & heating equipment.
Maintenance & repair cost (see  also at the Menu select Answers-Questions-Tips) through the years will also be a part of your future cost but not the initial cost. Systems last a good number of years but that depends a lot on how they are installed & maintained.

These questions & other input should be supplied in order that an appropriate system could be designed & installed.

Next the examination of the home:
The first item on the agenda is the "Load Calculation" (at Menu see Unit sizing). It should be in accordance with Manual "J" and performed by someone that is familiar with the process.
The process will measure the windows (types & direction), walls (types & amount of insulation), Attic (amount of insulation), Floor (amount of insulation, R values), primarily the envelope of the home and how well it is insulated. Some upgrade insulating (R values) may not be cost effective but the air conditioning & heating contractor should be able to help you in this matter (see Residential Conservation at the Menu of this site).
Once the calculation is done then the amount of heating, cooling BTU's & volume of air can be determined to maintain comfort levels as prescribed in the Design Temperatures which come from the calculation program. The design temperature primarily comes from the 10 year average weather report for given areas. Outside with inside temperatures & moisture is taken into consideration. (see Design Temperature at 2 pages at the Selection Menu. 1 at Load Calculation & the other at Answers-Questions-Tips)
Now that the required unit capacity is known the examination continues.
From the above questions the subcontractor, (with the help of the home owner), can see what type of equipment, lines, drains, vents, ducts with sizes,  electrical wiring and electrical main service, & others that can be physically fitted into areas that will allow performance, service, and installation.
Is this step ever important. The home owner in a lot of cases does not realize the looks or size of items to be installed until they are being installed. Then a problem may occur. Pictures ( a book ) and some samples can be shown to a home owner so that it may cut down on a lot of potential problem areas and any mis-understandings between the home owner & air conditioning / heating contractor.  A book can be developed by the contractor that has pictures of units, (furnaces, a-coils, condensers, package, heat pumps, hours per year for operation cost, thermostat's, refrigerant lines with insulation, drain lines, (condensate), physical sizes of units (even for the contractors use), unit pricing (see one way to do a list under "Answers-Questions-Tips" at the selection menu then select Unit price list). Many things that the customer can see & better relate to. A picture is like a thousand words maybe even better.
Selection of equipment, (select survey at the Menu), should be for it's performance output, (BTU & temperature), from a specification sheet and compare that to the load calculated on the home.
Several units can be suggested as they will vary in initial cost and annual operation cost of heating & cooling (efficiency ratings SEER for cooling & AFUE for heating). A customer needs to see what has a payback in the operation cost department and what that payback maybe ( 5 years & less may be considered a reasonable payback). The Bin Method is one way of doing this ( at the selection Menu select Answers-Questions-Tips then select OC (operating cost)).
Brands will vary in cost but the primary importance is a good & proper installation. We all desire the cheapest but in the long run that is probably the more costly but at the same token the most expensive price may not be the answer either.
A way of evaluating the equipment is it's annual operation cost, repairs, and maintenance over the years. Three major areas of cost & customer evaluation will be the 1. cost of installation, 2. the life of the unit, 3. and repairs & maintenance over the life of the unit.
The installing contractor plays a very big role in the equipments performance and future repairs. If the home owner can, visit the subcontractors place of business. It is not necessarily the size but how clean & organized they may be. That can be reflective of the type of installation.
A lot of home owners will pick the middle to higher middle price and pick the subcontractor that will stand behind their equipment & installation and their warranties & satisfaction guarantees.
There is nothing wrong with 100% satisfaction guarantee & should be noted on the contract (select a sample contract at the Menu). There are companies that are not afraid of it & offer a money back guarantee. Remember it's not the nuts & bolts your buying but comfort.
Examination of the existing duct system as to it's condition, size, connections, type & where it's connected, & those things inside ducts such as extractors, dampers, etc need to take place, ( those things inside the duct can restrict air flow). Sometimes a new duct system is proposed since one can't be sure about the existing ducts. A reason should be spelled out as to why they want to replace the duct work & or grilles (on the contract). In any case existing or replacement, the air distribution system, (duct & grilles), should be in accordance with Manual "D" of ACCA.
Location & physical size of equipment should be part of the home investigation process (along with any ideas the customer may have). Many times (but not all) the customer would like to place equipment THERE (even got a bid from someone else who never measured the space for installation) but the selected units physical dimensions will not allow it to be installed there. Not only is physical dimensions a factor but the ability to properly service or even be able to replace if necessary comes into play. To many times a unit has been installed into an area that it is very difficult to get to the filter, condensate drain, replace larger parts, & more. The installation can take a day or a few days but you have to live with the unit for years.
The outdoor unit may have a patio stone (4) in stead of a full unit support. One corner stone may settle while the others do not thus creating a unbalanced situation and that's not good. Are there vibration pads under this outdoor unit? They are there because of code, to absorb vibration, and they allow air to get under the unit for drying & to eventually keep rusting prolonged.
The location of the outside unit, does it make a noise that can be heard & what rooms will be affected? If the unit is on the roof does it have a roof leak potential? How about the electrical disconnect is it fused or a weather proof box (to turn off power). How about warranties and guarantees? Are they indicated on the contract?
Many items need to be checked by the representative and guaranteed ( in writing on your contract ). Other things the rep should look for, electrical disconnects, (boxes that can turn power off), there location to NOT hinder service, or replacement. Condensate drain piping, (does it not only drain but can a filter be changed?
The main electrical panel should be checked to see if the home has enough electrical to "operate" the existing system, the main wiring & that it is up to code. A lot of times when the building inspector sees that the electrical must be brought up to code, then there is expense with that. It may not have been indicated on the contract but it should be there. One has to look at the size of wire coming to the home, the main panel could be examined & some will say it has a 100 amp capacity but in some homes the electric range may have 40 amp, leaving 60 amp to run all the other items. There have been cases where wiring was doubled up ( 2 items on the same circuit) & the code inspector would not allow it. Now what? Who pays the extra expense now? The main panel inside the home should have it's cover pulled off so that it can be examined properly but be careful that wallpaper or paint doesn't cover it as it very well may cause a chip. There are municipalities that have a form that a calculation can be done of major appliances vs the main panel to see if a change of service will be needed.
Conservation covers the envelope of your home. A lot of times it is the attic area that may need additional insulation. Of course there is a lot more but the professional will and should supply this information. (see Residential Conservation selection at the MENU)
A contract should identify the equipment, BTU calculations, efficiency ratings for heating & cooling, as much of the job as possible (see the sample contract selection at the MENU).
Conservation & a professional survey will take approximately 1 to 1 1/2 hours to properly do & to look everything over.

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