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Old 08-30-2010, 03:52 PM   #1
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Time for a new central A/C!


Hello! My wife and I just purchased the home I grew up in from my parents! It's a great house, but needs a ton of work. The electric bill is crazy high. We're pretty confident part of the problem is the 30yr old central a/c unit.

I'd really like to replace this thing. It works, but takes forever to cool off the house. I can't imagine it's running at peak efficiency, even at 1980 standards. I was just curious how difficult it is to replace these. I'm a pretty competent guy, but I've honestly never had to deal wit this before. Any advice? Can this be done myself? How about brand recommendation?

Thanks!

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Old 08-30-2010, 06:38 PM   #2
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Not trying to be smart, but if you have to ask, you should probably leave it to a pro. You need specialized equipment and supplies to do the job properly and the average homeowner/handyman won't have these. And if you buy them you'll likely never need them again, so the cost might have been better spent paying a pro in the first place.

Having said that, there's a boatload of hack installers out there, so do your homework before you hire anyone!

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Old 08-30-2010, 07:31 PM   #3
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as an experienced DIY'er and homeowner who has done relatively major HVAC work and spent a few hundred dollars on tools, i can tell you it's a pretty big learning curve and a LOT of work for someone who doesn't have the expertise of a pro. believe me, i have spent hours and hours doing work that would take a pro much less time. however, i enjoy doing it and i have saved a couple thousand dollars in labor and parts mark-up by doing it myself.

bottom line, it's not easy and not the best way to get started on DIY work. it's a lot of hard work and there are a lot of things you need to learn before you can do it yourself. however, the cost of tools is nothing compared to what you will pay in labor and parts mark-up to have a good pro do a full installation job.
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Old 08-30-2010, 08:45 PM   #4
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and if you purchase off the internet you won't have a warranty. HVAC manufacturers have recently added an exclusion voiding the warranty if bought on line.

There is also the fact that that since last year all units have the new refrigerant (freon). You may find any dealer reluctant to sell to you since you have to be certified certified for the new freon.

You would also need an EPA card that allows to handle and buy refrigerants.

If you don't have one you would be breaking federal law.
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Old 08-31-2010, 04:03 AM   #5
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It depends on the size of your house in which size of a/c unit you'll need.

I have a 1800 sq ft home and I replaced my old r22 unit when it burnt the compressor with a new 3 ton 410a unit. At the same time, I replaced the A coil and installed a 93% effecient furnance as well. I also replaced all of the copper supply and return lines as well.

The cost savings just in my electric bill (summer) and gas bill (winter) has already paid me back for the entire cost of the new system.

My dad is HVAC certified, so we did all the work ourselves and saved a ton! And, by being able to purchase wholesale, saved me even more. Total cost for the complete system was about $1500. In a year, the energy savings has already paid me back.

One option is to contact a HVAC pro and see if they will do it on their off time for you, which would save you some money.

I can proudly say that my new a/c unit puts out so much cold air that I actually have to turn it off sometimes.

Plus, when I go to sell my house, the new owners will not have to worry about the HVAC system. So, that's a huge selling point.

Last edited by pioneerurban; 08-31-2010 at 04:06 AM.
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Old 08-31-2010, 04:11 AM   #6
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It depends on the size of your house in which size of a/c unit you'll need.

I have a 1800 sq ft home and I replaced my old r22 unit when it burnt the compressor with a new 3 ton 410a unit. At the same time, I replaced the A coil and installed a 93% effecient furnance as well. I also replaced all of the copper supply and return lines as well.

The cost savings just in my electric bill (summer) and gas bill (winter) has already paid me back for the entire cost of the new system.

My dad is HVAC certified, so we did all the work ourselves and saved a ton! And, by being able to purchase wholesale, saved me even more. Total cost for the complete system was about $1500. In a year, the energy savings has already paid me back.

One option is to contact a HVAC pro and see if they will do it on their off time for you, which would save you some money.

I can proudly say that my new a/c unit puts out so much cold air that I actually have to turn it off sometimes.

Plus, when I go to sell my house, the new owners will not have to worry about the HVAC system. So, that's a huge selling point.

So cold you have to turn it off? Some body did not size the ac correctly.
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Old 08-31-2010, 04:19 AM   #7
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Originally Posted by hvaclover View Post
So cold you have to turn it off? Some body did not size the ac correctly.

What do you mean? I'm not a expert. but my dad is HVAC certified and we did the work ourselves.

Thanks.
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Old 08-31-2010, 04:22 AM   #8
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What do you mean? I'm not a expert. but my dad is HVAC certified and we did the work ourselves.

Thanks.
What type of load calc did you do?
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Old 08-31-2010, 04:30 AM   #9
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What type of load calc did you do?
Unfortunately I am not able to answer that.... I'll have to ask my dad later on today and I'll post this evening.

Thank you for your help.

Sorry to hijack your thread OP.
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Old 09-01-2010, 04:59 AM   #10
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Quote:
Originally Posted by Pineapple View Post
Hello! My wife and I just purchased the home I grew up in from my parents! It's a great house, but needs a ton of work. The electric bill is crazy high. We're pretty confident part of the problem is the 30yr old central a/c unit.

I'd really like to replace this thing. It works, but takes forever to cool off the house. I can't imagine it's running at peak efficiency, even at 1980 standards. I was just curious how difficult it is to replace these. I'm a pretty competent guy, but I've honestly never had to deal wit this before. Any advice? Can this be done myself? How about brand recommendation?

Thanks!
Your current system may have undersized duct work. And that can be a cause of it taking a long time to cool off the house. Also, letting the house get hot, and then turning on the A/C, it will take a long time to cool the house off.

I find that how difficult something is to do. Is dependant on how skilled a person is, and their meaning/perception of difficult.
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Old 09-01-2010, 10:35 AM   #11
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i found it challenging and i do everything myself. however, the twist was the fact that i was working in a 120+ degree attic with little to no airflow and a lot of insulation. that takes conditioning and a suck-it-up and just do it attitude. i don't care how good you are at anything, that takes something else.
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Old 09-01-2010, 12:13 PM   #12
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I posted this awhile back. It reflects my actual DIY experience. Maybe it'll help you decide if DIY is right for you.

I did end up installing a 4T split system (Rheem RPNE/RSHA) and did 100% of the work myself.

My out of pocket expenses were about $3000 - $3500 including supplies and specialized HVAC tools. At the time contractor quotes were $8000 - 12,000.

Here are my observations for what they're worth:
1. There is a lot of homework involved in DIY HVAC. (ex: Reading technical manuals backwards and forwards, studying EPA to get certified, practicing brazing technique, practicing sheet metal work, doing vacuum pull dry runs, learning how to use the specialized tools and equipment.) This was far more time consuming then the actual installation work. (as it should be if you're a DIYer)

2. HVAC is not well suited for general DIY. It would be tough for a typical homeowner/DIYer to becomes proficient in general HVAC. However it's feasable for some homeowners to become experts on their homes particular HVAC system.

3. There will be some surprises along the way. None were too tough to solve but don't assume it's a matter of "plug and play":

(ex) My new air handler was throwing a breaker - I thought I screwed up - It turned out the old breaker was weakened from the repeated throws on and off during installation.

(ex) I heard a loud hum from the air handler. It turned out to be harmonic resonance from the metal cover over the LV transformer that was solved by beefing up the cover. Once again I thought I screwed up something.

(ex) My HP wouldn't come on when I cycled power. It was a flakey defrost board.

(ex) The Rheem HP manual didn't say that the error codes showed that last known state and don't automatically toggle to normal after the 5 minute delay. That caused me some confusion.

4. I didn't solicit help from a contractor. I think it's best to either do this 100% solo or contract it all out. I don't think the "top shelf" pros will be eager to do co-op installs. You'll likely find "hacks" but who wants them touching your installation.

5. There generally is warranty support. The online supplier I used made good on a warranty claim. (Rheem RPNE Ranco defrost boards had a problem where they'd get confused if there was a power glitch and have to be reset by shorting the test pins). However warranty support is kind of a PIA. They'll send you new parts and bill you first. Once they receive the defective part they'll issue you credit.

I saved so much money that even if I have a future part warranty issue that's denied I can pay out of pocket and still be way, way ahead.

6. You can get anything you want online but it helps to be able to buy certain items from the local supply houses. Some of them are not eager to sell to homeowners. The EPA cards goes a long way to get your a COD account.

Summary:
My system has been running great for the past 2.5 yrs and I don't regret going the DIY route. I saved a bundle of money, learned alot, had fun doing it and performed an installation that I feel is far better then a pro rushing to complete a job.

However HVAC work can be unforging to errors and the devil is in the details. It's not "cookie cutter" work and there will be surprises/complications that you'll have to deal with and you likely won't have the luxury of experience to draw on. Preperation is far more time consuming then the actual work for a DIYer.

I'm trying to tell it like it is and going through this process gave me a lot of respect for the guys that do this stuff day in and day out. (laying on your back threading refrigeration lines thru a crawlspace is not exactly fun)

Last edited by hennyh; 09-01-2010 at 12:17 PM.
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Old 09-01-2010, 12:46 PM   #13
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i echo a lot of what hennyh said. you better be persistent and have a never give up attitude. take your time doing your research and spending the time up front learning as much as you can about servicing HVAC before you start doing anything. doing anything hastily can result in causing further damage to your system that will just add to the repair bill. keep reminding yourself that you are saving thousands of dollars and even if you make a few mistakes and it costs you a bit more in time and materials, you will still save money.

i think it's well worth it in the end if you are willing to put in the time up front. i now feel comfortable servicing my A/C and doing any job necessary. in texas, A/C systems fail all the time and it is such a financial headache for a lot of homeowners. my buddy just recently spent 18 grand (yes, crazy) on an 18 SEER Trane system when he could have replaced his evaporator coil and it would have been fine. he got caught up in the marketing hype and being convinced that his builder's special A/C (Goodman) was complete junk. i am relieved that i can do it on the cheap and don't have to worry about it from a financial perspective. plus, i know the job that i did and i know my system, so if something goes wrong i know where to begin with troubleshooting.
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Old 09-01-2010, 04:49 PM   #14
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Your current system may have undersized duct work. And that can be a cause of it taking a long time to cool off the house. Also, letting the house get hot, and then turning on the A/C, it will take a long time to cool the house off.

I find that how difficult something is to do. Is dependant on how skilled a person is, and their meaning/perception of difficult.

Been, your response is a good example of what is happening wide spread thru the resi side of HVAC right now.

We are getting slammed with calls of "the ac won't hold temp". Nothing wrong it's just the OD ambient is exceeding design temps.

I have found a common thread to a considerable proportion of theses complaints: New roofs. A lot of the homes affected had old roofs when we installed the ac.

I've been told the new shingles today are much thinner than the old ones.

You think cause of the new roofs with thinner shingles is causing a higher radiant load?
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Old 09-01-2010, 05:19 PM   #15
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Right now, my attic is around 10 degrees warmer than the outside temp (78), with a humidity level of 35 in the attic, 77% outside. The warmest I have seen it get is around 110 with outside at around 92. I would say that shingles have nothing to do with air temp in the attic, but ventilation does.

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