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Old 02-12-2013, 06:31 AM   #1
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Help Assessing HVAC System Before Purchase


In the process of purchasing the house I've lived in for the last year. Two story home with separate upstairs/downstairs units. Downstairs unit is older and does a fair job of keeping the house cool in the summer - but not a good job. Is there a way to measurably demonstrate the system is getting old and or needs replacement?

Current owner says system was in when he purchased, so it's unknown how old it is.

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Old 02-12-2013, 06:45 AM   #2
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Help Assessing HVAC System Before Purchase


get a experienced reputable Pro in to check the heat exchanger for cracks and other problems and be there to see it. don't call Joe's heat em and cheatem.

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Old 02-12-2013, 06:47 AM   #3
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Help Assessing HVAC System Before Purchase


What's the model and serial number?

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Old 02-12-2013, 07:02 AM   #4
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Help Assessing HVAC System Before Purchase


Quote:
Originally Posted by lateracer View Post
Is there a way to measurably demonstrate the system is getting old and or needs replacement?
Temperature change: Measure room temp (intake to AC) at X degrees.
Then measure cooled air at (several) outlet registers.

Quote:
Current owner says system was in when he purchased, so it's unknown how old it is.
Assume they both are on their last legs and will nee to be replaced within one year. Budget for that work and adjust offer accordingly -or- insist that the owner replace them as part of the sale -subject to inspection-.
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Old 02-12-2013, 07:23 AM   #5
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Help Assessing HVAC System Before Purchase


If you post the make and model and serial # someone here can tell you how old it is.
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Old 02-12-2013, 08:29 AM   #6
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Help Assessing HVAC System Before Purchase


call a pro and have them check the following and make recomendations as to the "fixes" and have them estimate the costs for remediation.

1. subcool and superheat (this is related to how well the system is "charged" with relationship to your install (ie ductwork)
2. delta t (how much temperature change there is as the air passes through your system)
3. static pressue (how hard your air handler is working to move air. most mfgrs state .5 iwc is max)
4. air flow to each room (this relates to comfort and if there is enough air flow to keep each room, based on size, cool.)
5. system size (this relates to manual J and will dictate your max design temps as well as the cost to run your system)


with that info, your professional should be able to advise you what, if any, issues you have and provide you a number that you can use in negotiations with the seller.
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Old 02-12-2013, 09:43 AM   #7
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Help Assessing HVAC System Before Purchase


Bobs correct, I did not notice we are talking AC here as mostly it is furnace questions. AC compressors wear like a car engine and lose capacity so an experienced Pro should be able to check the compression ratio and freon level etc. Bear in mind you are buying a used unit and very few sellers will give you any compensation as it is as is.

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