Home AC installation

[mikester]

What's it take to install AC into a house without it?


I do have central heat with brand new duct work which was done just a couple of years ago.

What needs to be done to put in AC though? Can I use the same duct work?

I'm just curious - we have had a hot summer this year and it gets pretty miserable in the house. Last year was hot too and if next year follows we'll be miserable again for a few months. I want to see if it is cost effective to upgrade or not.

[dad911]

It should be relatively simple if the ductwork is there. Need a compressor outside, wired to 220, evaporator coils mounted in the ductwork of the furnace/air handler, and 2 copper lines for refrigerant connecting them.

[Superman]

Depends on what you have there. For a heat pump system, you'd need to put evaporator coils in the "can" where your furnace is. Heat pumps want fairly large ducting and good air movement, which is probably what you have.

I can tell you that it's worth it, even if you just turn it on long enough to take the moisture out of the air in your house. Much more comfortable.

[futuresoptions]

Sadly, when you install central heat only, the duct size is generally undersized for A/C. The reason this is, is because heat usually runs at a lower CFM / Fan speed and they have to make the duct smaller to keep the static pressure up. Depending on who did your install, I am going to guess that you would need new duct. A/C units usually run on high fan speed while heat runs on low speed. If you would like to know for sure, it is best to have a reputable company come out and inspect your duct work and see if it would supply the appropriate CFM needed for each room. It may be simple to work around and may only require a few more vents in a few places/rooms.

[look 171]

I am afraid Bill is right. The other issues is the big old return air duct. How much room do you have in that attic again? I remember you said it was somewhat small. Give me a call Mike, I can send you to the right people. There are a couple of way to do this. I will walk you through it.

[mikester]

Originally Posted by look 171

I am afraid Bill is right. The other issues is the big old return air duct. How much room do you have in that attic again? I remember you said it was somewhat small. Give me a call Mike, I can send you to the right people. There are a couple of way to do this. I will walk you through it.

Right now I'm just looking for information. We just finished this landscaping project and it's been hot as heck here...

I want to understand the components and what not.

[look 171]

Originally Posted by mikester

Right now I'm just looking for information. We just finished this landscaping project and it's been hot as heck here...

I want to understand the components and what not.

I will find out from the mouth of the guru next week or two. I have to see my HVAC man because I have to pay my bills.

[KFC911]

Hey Mikester, is humid at all where you live? If so, you might want to consider a dehumidifier (or two) to make it more bearable. I think that's a lot of the "comfort factor" for an a/c anyways...

[onewhippedpuppy]

On top of the required equipment, which many wholesale shops won't sell to an individual, you'll also need a vacuum pump to evacuate the system and the correct refrigerant, which requires a license to obtain. You could probably do the install then hire a pro to evacuate and charge. Are you ok with running wiring and copper tubing through your house? Sweating copper tube? As the others mentioned you'll need to insure that your heater ductwork and fan are up to the task, and you'll probably need to change out the control box at the heater. You'll also need to properly size your A/C compressor and A-coil based on house size, windows, insulation, etc. It's not rocket science, but there are some nuances to doing it right.

I've installed systems in a past life, but still hired someone this year to replace both units.

[mikester]

Originally Posted by onewhippedpuppy

On top of the required equipment, which many wholesale shops won't sell to an individual, you'll also need a vacuum pump to evacuate the system and the correct refrigerant, which requires a license to obtain. You could probably do the install then hire a pro to evacuate and charge. Are you ok with running wiring and copper tubing through your house? Sweating copper tube? As the others mentioned you'll need to insure that your heater ductwork and fan are up to the task, and you'll probably need to change out the control box at the heater. You'll also need to properly size your A/C compressor and A-coil based on house size, windows, insulation, etc. It's not rocket science, but there are some nuances to doing it right.

I've installed systems in a past life, but still hired someone this year to replace both units.

Not interested in doing it myself - just want to understand the system so that if I do decide to upgrade the house I know what I'm being sold.

[peppy]

We did this last year. The unit on the right is a self contained unit, just hook up power/thermostat and duct work and everything is ready to go. The crawl space under the house is very small.

The unit on the left is a split system and the air handler and evaporator(cold part) is in the attic. The line set going up to the attic has since been wrapped in white metal, so it doesn't look to bad.

Both of these are 2.5 ton heat pumps with electric backup.

[Zeke]

Originally Posted by mikester

Not interested in doing it myself - just want to understand the system so that if I do decide to upgrade the house I know what I'm being sold.

Very good outlook. And you can find many independents that will do the work. I always like to work with smaller owner operated companies preferring to hire ones where the boss hisself is on the job.

On the duct work, even though what has been said is generally true, the ducts won't be that much smaller, if smaller at all. Many installers go with duct sizes that will handle A/C at a later date. Frankly, with the calculations needed to properly size ducting and placing boots, most seem to miss the mark one way or the other a bit or have to compromise because of the overall layout.

Ideally, A/C and heating would occupy separate systems with heating boots at the floor and A/C vents in the ceiling. But since they typically share the same air handler, that is not the usual case.

The point is I've seen many convoluted duct systems do the job adequately. 100% efficient, no, but what is? It's all a matter of degree. Balancing within the ducts will help distribute the conditioned air in the home. You can add inline boosters too. There's one I know of that is dead quiet with a variable speed fan.

[look 171]

Inline booster and electronic dampers are really trick stuff. Most people (residential jobs)do not want to pay for them and are sometimes talk out of it all together by the HVAC contractor due to cost. If they can sell you a system without boosters and fancy dampers, and get the job, why not. So its less efficient, big deal, it still works. Most home owners would never hire a engineer to do the calc or design on an HVAC system to begin with. They just go after the installers. Most installers I found lack the real knowledge about their craft or the engineering aspects of it. Then there's the aesthetic one must deal with. That I know they are not good at it. Part of my job is fine that middle of the road for the placement of grills and outlets.

[ShakinJoe]

Go ductless.

Fujitsu General America

[dad911]

Originally Posted by ShakinJoe

Go ductless.

Fujitsu General America

Why when the ducts are there. Hang 3' wide units in each room, and multiple outside units? Perhaps if you just want to do 1 room or office.

Zeke's got it right. If it's a relatively new unit the ducts should be fine, maybe add a few, or make some high/low on the wall to circulate air better in the summer. Get a pro to look at it, you should be fine.

[Zeke]

There are online calculators. I used one for a big remodel 3 years ago. I fired the HVAC guy and ended up having to do all the duct work myself as a reward. Works perfectly to this day.

[johnsjmc]

Depending on the location Your local building permit office might also require heat loss/ gain and duct sizing calculations . These would add a few hundred to an install . I replaced the AC in a small Florida house last year .changed from straight cool to a heat pump. I had 2 local quotes around $6500 and then found a small licensed company 20 mi away thru Craigslist which did the whole thing (with permit and inspection ) for $3600

[red-beard]

Originally Posted by dad911

Why when the ducts are there. Hang 3' wide units in each room, and multiple outside units? Perhaps if you just want to do 1 room or office.

Zeke's got it right. If it's a relatively new unit the ducts should be fine, maybe add a few, or make some high/low on the wall to circulate air better in the summer. Get a pro to look at it, you should be fine.

You can get systems with a single outdoor unit which handles three or four indoor units. These units also use variable frequency drive technology which ramp the outdoor unit up and down with need. Each indoor unit has an indivdual control, so you only cool where you need at the time you need. And many of the better units have SEER rating of 24 or better.

Mike, how much cooling do you need? How "hot" did it get in the summer? My Parents installed a 3 ton A/C unit in upstate NY which was fine for 2800 sq feet. I have 3300-3400 here in Houston and 7 tons of cooling with 2 separate A/C units.

A good professional A/C person will evaluate your insulation, cooling requirements, etc. I would get a few people too look.

In Texas, the price of electricity means the super-duper efficient units won't pay back enough in energy savings. California, with the much higher price of electricity, you will need to evaluate the operational costs vs. installed cost.

[ShakinJoe]

Originally Posted by dad911

Why when the ducts are there. Hang 3' wide units in each room, and multiple outside units? Perhaps if you just want to do 1 room or office.

Zeke's got it right. If it's a relatively new unit the ducts should be fine, maybe add a few, or make some high/low on the wall to circulate air better in the summer. Get a pro to look at it, you should be fine.

You can use the "ducted" heads too with these systems. Shooter duct runs equal less loss equal more efficiency. Plus you can use multiple heads with one condensing unit.

[Baz]

If it's just a couple-few months out of the year - I wonder if a couple window units would accommodate your needs, Mike. That would be easier and less expensive than trying to retrofit an existing central system.