How often do central AC units need to be charged?


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Old 06-10-09, 05:40 PM
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How often do central AC units need to be charged?

Hello,

We bought out house last year and it has an Amana central AC unit that is about 12-14 years old. We've turned it on just a few times between last fall and this summer, and it doesn't seem to cool the house very fast, at least not as fast as the AC at our old house.

I'm not sure the last time it was serviced, but how often do AC units need charging? And about how much might something like that cost to have done?

Thanks.

Mark
 
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Old 06-10-09, 05:51 PM
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Never.

We have older 80's Tempstar units still working in a multi-unit condo, and other similar aged rentals, that nobody has had to work on, to the best of my knowledge. Albeit we live where they are only run maybe a few months, intermittantly throughout the summer months, not subjected to pressure charge differences as much.

Refrigerators are the same way. They should last years and years without ever needing any charge from some leak.

First you need to find out if you are getting perhaps around a 17 degree differential between the cold air return air and the first register where the cold air blows out of. Use a (the same) thermometer at each location. Get back with us on this.
 
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Old 06-11-09, 04:16 AM
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"They should last years"

The operative word is SHOULD.

My answer is your experience history will dictate it.
I've had systems that went many years with no loss of cooling.
The one I have now goes about three years. I recently had it checked and one lb of freon added, cost me $107, but that can vary ALOT.
 
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Old 06-11-09, 04:21 AM
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The refrigerant circuit is a sealed system, if it needs refrigerant it has a leak. Your best bet would be to contact a good local HVAC company and have them perform annual maintenance. That should pin point any problems the system may have. Call Amana and they will tell you who is an authorized dealer in your area.
 
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Old 06-11-09, 05:21 AM
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12-14 years old I wouldn't put too much into it. It's at the end of its usefull life.

Like said though check the temp drop between supply and return. Also post the numbers you get. There may be nothing wrong with it. A properly sized a/c can take up to 24 hours or more to get a house to set-point from a dead start.
 
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Old 06-11-09, 07:29 AM
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Originally Posted by mattison
12-14 years old I wouldn't put too much into it. It's at the end of its usefull life.
But wouldn't an a/c's useful life in NY be different from that say in Florida or the southwest desert?
 
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Old 06-11-09, 10:21 AM
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Originally Posted by ecman51`
First you need to find out if you are getting perhaps around a 17 degree differential between the cold air return air and the first register where the cold air blows out of. Use a (the same) thermometer at each location. Get back with us on this.
Originally Posted by mattison
Like said though check the temp drop between supply and return. Also post the numbers you get. There may be nothing wrong with it. A properly sized a/c can take up to 24 hours or more to get a house to set-point from a dead start.
So to check the temp differential, just set a thermometer next to the cold air return vent closest to the furnace fan, get a reading, and then put the same thermometer next to the closest register to the furnace fan and get a reading there? And that should be at least 17 difference?

As far as not dumping a lot of money into this unit, I'm in total agreement, but since we're in the final stages of a kitchen remodel, I don't really have money laying around for a new unit this year. Being in upstate NY, we only need AC a few months a year, and then maybe only 20-30 days during those months. I really want to get this unit to last (but also work properly) until next year when maybe I can replace it.
 
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Old 06-11-09, 11:14 AM
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Originally Posted by ecman51`
But wouldn't an a/c's useful life in NY be different from that say in Florida or the southwest desert?

I was looking at his username. Yeah you should get a bit more but it's still up there.
 
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Old 06-11-09, 04:57 PM
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Originally Posted by Indiana627
So to check the temp differential, just set a thermometer next to the cold air return vent closest to the furnace fan, get a reading, and then put the same thermometer next to the closest register to the furnace fan and get a reading there? And that should be at least 17 difference?
About that - give or take a couple degrees. For example, if the house is 79 inside and you wished it were 74, so you turn on the a/c, and you then measure say 75 at the floor level at the return grill -and then find that you are getting 58 degrees cold air blowing out, you are close to what you can expect.
 
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Old 07-28-09, 04:51 PM
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Finally hot enough here to turn on the CA again. I set a thermometer next to the closest cold air return to the furnace fan and let it sit for 15 minutes. It read 73. I then set the same thermometer next to the closest register to the furnace fan for 15 minutes. It read 66. So only 7 differnece, no where near the 17 that I should be getting. What does this tell you guys? Thanks.

Mark
 
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Old 07-28-09, 05:49 PM
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When was the last time it was serviced?
 
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Old 07-29-09, 01:59 PM
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I called the company the previous owner's used (we just bought the house last year) and they said 2006 was the last CA service. The unit was installed in 1995.

If I get a new unit that sits outside, will I be able to reuse the coil that's in the furnace duct work? Or would it all have to be replace? Thanks.

Mark
 
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Old 07-29-09, 04:12 PM
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A/C systems should never need to be charged unless they are leaking - in which case, find and fix the leak.
Doug
 
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Old 07-29-09, 04:41 PM
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Originally Posted by Indiana627
I called the company the previous owner's used (we just bought the house last year) and they said 2006 was the last CA service. The unit was installed in 1995.

If I get a new unit that sits outside, will I be able to reuse the coil that's in the furnace duct work? Or would it all have to be replace? Thanks.
Mark
Except for cleaning filters, what does the service company do on a routine basis? I don't think that issue explains your problem.

But, I think you need to call a service person to correct your problem.

It's way to soon to decide to replace the compresser. But if you have to, you can use a properly sized, new compresser with your existing evaporator.
Doug
 
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Old 07-31-09, 01:15 AM
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Best to match condensor & coil

Originally Posted by Indiana627
Finally hot enough here to turn on the CA again. I set a thermometer next to the closest cold air return to the furnace fan and let it sit for 15 minutes. It read 73. I then set the same thermometer next to the closest register to the furnace fan for 15 minutes. It read 66. So only 7 differnece, no where near the 17 that I should be getting. What does this tell you guys? Thanks.

Mark
Due to age of system, todays seer ratings, & refrigerant changes...you would be wise to change both. Especially with R410A being only manufactured equipment starting in 2010. Plus, matching a new 13+ seer unit on old coil would decrese its efficiency, especially if it has a piston instead of TXV metering device. If you switch to R410A, make sure company flushes the copper lines out with a flush agent, like quickflush or RX11 flush, and pulls a good deep vacuum. Oils are different in both refrigerants and don't mix good at all. Plus, R410A is very moisture sensitive. This is where a deep vacuum helps & a good 16 cubic inch liquid line filter drier. Hope this info helps you make an educated decision. Good luck
 
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Old 08-05-09, 03:15 PM
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Originally Posted by B2LExperts
...you would be wise to change both. Especially with R410A being only manufactured equipment starting in 2010.
Since his system was installed in 1995, it must be charged with R-22. R-22 will be manufactured up to 2020 for use in existing, legacy A/C units (and likely will be available after that date). Info here:
What You Should Know about Refrigerants When Purchasing or Repairing a Residential A/C System or Heat Pump | Ozone Depletion - Regulatory Programs | U.S. EPA

Also, tests show that the performance of R410A systems degrade worse than R22 systems with increasing outdoor temps. Info here: http://www.fire.nist.gov/bfrlpubs/bu...PDF/b02186.pdf

I wouldn't replace either the compressor or the evaporator - I would try to get the unit repaired. Have you called a repairman yet? No sense agonizing until you get somebody qualified to look at it. You shoudn't have to replace your whole central A/C every 15 years, in my opinion.
Doug
 

Last edited by gilmorrie; 08-05-09 at 04:43 PM.
 

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