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Old 07-11-2008, 10:23 AM   #16
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Can a non-HVAC guy install an AC?


The only way for anyone to figure out what size you need is to run a manual J on the space. This would take into account the insulation, windows, doors, etc. I would call around and find someone willing to do this so you can get the correct sizing. Otherwise its just a guess like you have been getting. It also shows if the contractor knows a little more about what they are doing. I would not let them come out if they are unwilling to do this.

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Old 07-11-2008, 12:16 PM   #17
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Can a non-HVAC guy install an AC?


Around twenty five years I installed one in my house myself but I had existing ductwork (gas forced air furnace) and at that time they sold DIY assemblies with precharged lines etc so you didn't have to do any brazing, vacuuming, charging etc. It worked great for the 5 years I lived there.

However, the EPA rules have changed and I don't think you can find any DIY assemblies that won't require you to hire someone appropriately licensed to do the lineset brazing and charging. Usually the people licensed to do that are your local HVAC installers who tend to charge a little more for this type service to make up for the profit they lost in not selling you the unit so it usually ends up with you doing more work without saving much $. And you run the risk on the warranty.

But hiring a pro is not without risk. Someone earlier said hire a pro because there are so many bad installations out there. Well 99% of those bad installations were done by a pro so that's not a very good argument. A lot of pros don't do a manual J and a manual D and rely on rules of thumb. The answer is hire a "good" pro.

If it was a house I'd say find that good pro. But if you already have a licensed guy and know what he will charge you to do the final hookup and are comfortable with the warranty situation then the garage is a pretty low risk situation to DIY. Should be pretty straightforward to install minimal duct work. For a garage setting I would set up your ductwork so the registers actually blow where you'll be when doing most of your work. That way your main work areas will be comfortable much faster.

As far as the size goes I think you probably understand what your getting. If you were keeping it cooled all summer the pro that told you 3.5 tons are probably right. And the pro who told you 5 tons is probably right in that he took into consideration how you will be using it. But both probably planned on a conventional distribution system of ductwork. If you design the ductwork to focus on your work areas you might get by with a smaller unit. Why cool 1800 ft if your going to only be in the 150 ft workbench area.
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Old 07-11-2008, 03:04 PM   #18
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Can a non-HVAC guy install an AC?


I believed my post was the one referred to. I may have miss typed or you miss read so I will try to make it more clear. I was trying to convey that if there are pro's out there that mess some of these jobs up what realistic hope is there for a layman. I thought that the quotation's around pro would make that clear sorry
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Old 07-11-2008, 03:48 PM   #19
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Can a non-HVAC guy install an AC?


600sqft per ton, 400cfm per ton. If it was mine, I would go with the 5 ton.

Did you use the calculator on the website you posted? They offer a manual J load calculation. Bet they come up with 5 ton also. I will try it later. There are more effective load calculating sites and information.

I really dont get what all the fuss is about.

Last edited by 8 Ball; 07-11-2008 at 03:53 PM.
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Old 07-21-2008, 10:48 AM   #20
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Can a non-HVAC guy install an AC?


I am a non-HVAC guy. My background is electrical/electronic/DIY. I got four estimates from 'professional' HVAC types and concluded they were unaware and under educated. I could talk about this almost forever.
I researched air conditioning on the internet for several months - learning how to design a duct system took a lot of effort. I designed my entire system, bought material almost exclusively on the internet, and worked some long and difficult hours installing the hold thing. I learned many tricks of the trade. My DIY saved me over $5000 and I know how to repair and keep the system working. That will save a minimum of $300 yearly.
My advice:
Think about why would a 'professional' give good advice on a DIY site?
If you are willing to learn long term, you can DIY.
You will save about half the cost of a 'professional' job even if you make costly mistakes.
You will save money for a lifetime because you are not at the mercy of the 'professionals'.
You will work hard putting the system in.
Approach the task step by step:
1.Decide on type of system - split/packaged air only/packaged heat pump.
2.Decide on duct system - round/rectangular/flex - in crawl space/attic
2.Decide on size - the calculators on the internet (acdirect.com for example) worked for me. I previously used 3 ton of window air conditioners to cool my house, the internet calculators estimated 2.6 ton, one contractor estimated 2.5 ton, another estimated 3 ton, I installed a 3 ton heat pump - works great!
3.Design duct system - a lot to learn here. I used all round metal duct with flex duct at junctions.
4.Research best sources for material. Home Depot/Lowes has some round metal components in the 6 to 8 inch size.
5.Install
Best Regards
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Old 07-21-2008, 02:58 PM   #21
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Can a non-HVAC guy install an AC?


Thats right we are out there giving free advice in order for you to follow it mess up and there by generating work for us. The simple fact is unless you had some help in the tool department there is no way you saved 5k , or if you did there is no way you did the job right. let me guess you soldered your joints (wrong) if you brazed which i doubt I know you didnt purge the lines and trickled nitrogen . How many micron's where in the system when you charged it dont know , big suprise. And better yet how did you charge it do you own a phycrometer and calculate the nessasary super heat and subcool. did you install a filter dryer. The tool cost's alone make it worth it to hire a pro. ductwork ill give you because just about anybody can calculate static pressure and cfm . I seriously hope you dont live in my service area , because we cant tell you that you messed you whole system up .
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Old 07-21-2008, 07:41 PM   #22
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Can a non-HVAC guy install an AC?


I remember the last posts concerning sizing of the unit. If I remember correctly, he was only going to use the unit occasionally. just to cool the garage down when he was working there. Hence, the oversized unit.

If you can get a packaged unit, they usually come pre-charged with refrigerant. You can get them at least two different ways, depending on where you'll mount it. The side-draft type mounts on a pad outside at ground level. The ducts penetrate an outside wall. You'd need to design and install some ductwork above the ceiling. Electrical is usually easy, thermostat is even easier.

The other type mounts on the roof. You'd need to verify that the roof structure can hold it (usually not a problem), and build some type of curb to get it level. Then, you'd need to cut some pretty good sized holes in the roof sheathing, and properly flash the curb to the existing roofing material. On this type, obviously the ducts point down, and you'd again need to design and install some ductwork. Unless you're certified in rotary wing, and have access to a helicopter, you'll need a crane to get the unit on top of the roof. lol. Electrical and thermostat are just as easy as with the padmount.

This would be a pretty serious DIY project, the ductwork would be the biggest challenge. If you get an HVAC company to install it, you might be able to save a few bucks by doing the electrical yourself. There's at least a half-dozen guys over on the electrical forum who can help.

Rob

P.S. Obviously ,you drive 73's. I have an ATP, about 5400 hrs, typed in DC7's and Merlin Metro's, but about 20 years ago due to an eye problem, I can only get a 3rd class medical, thus ending my career of herding tin. Oh well, pulling wire isn't all that bad!!

Rob
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Old 08-19-2008, 04:47 PM   #23
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Can a non-HVAC guy install an AC?


Ill tell you what go to the store like Home Depot Lowes or what is closes to you and gat about 3 ac unit that goes in window or wool cut out perfect hole in the wool
And install them you will be happy that you did and you are going to save big money you can duet everything by your self good luck
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Old 08-19-2008, 04:49 PM   #24
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Can a non-HVAC guy install an AC?


I think the wool would be itchy.
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Old 10-29-2008, 11:54 AM   #25
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Can a non-HVAC guy install an AC?


There might be an insurance factor too.

If the worst happens, and your house burns down because of an improper installation, I am not sure if your insurance will cover you.

If you have an installer do it, will all of the permits and inspections I "think" you would be pretty safe ( in more ways than one ) ...
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Old 10-29-2008, 01:29 PM   #26
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Can a non-HVAC guy install an AC?


I guess it all boils down to your skill level and competency with tools and understanding some basics in compression and expansion of gases.

It appears that you are a 737 driver, yes nothing gets by me, and being that you are not a dummy. Knowing how much runway you have to have to get of the ground in 100 degree weather is a lot different than getting off the ground in 0 degree weather. My guess is that you have to use a lot of runway often where you are. When I flew in Alaska I don't need much more that a large parking lot.

AC is no different in the learning curve.

The key in sizing is matching the cfm of the air handler, the size of the A coil and the output of the unit.

Getting the electricity to the unit is easy. Just follow code and wiring size.

The length of your line set, the size of your A coil and the output of your unit will determine the amount of refrigeration. In Oregon anyone can buy that stuff over the counter.

You would need to do a vacuum test on your connections for sure and fix any leaks. If you are good then there won't be any.

Unless you can borrow some of the equipment you will have to buy or rent some.

Can it be done? Yes it can is the short answer.
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Old 10-29-2008, 05:02 PM   #27
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Can a non-HVAC guy install an AC?


Your biggest worry is will it void your warranty with the manufacture, most will require a licensed installer to honor warranty.

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