Should I buy a used A/C outside unit? How can I test this unit to make use it works?

My low income elderly grand parents survived a hot summer without A/C. Their outside compressor malfunctioned. My coworker has a used outside unit (Trane 4 ton) in his garage. He told me it worked %26amp; its for sale.





1. How do I test this unit?


2. My grandparents house is all electric.(No gas)


3 House is 1200 sq ft.


4. Is the unit large enough?

Should I buy a used A/C outside unit? How can I test this unit to make use it works?
You might want to call around and get some pricing. If you purchase a new condensing unit, you get a brand new manufacturer warranty with it and labor warranty with the company who installed it. Depending on the brand name you get, most of them carry at least a 5 year compressor warranty and parts. The contractor who installs it should offer at least a one year labor warranty. Trane, Lennox, and Carrier are good units. Make sure the condensing unit you purchase will be compatible with your inside unit. I would make sure the installer is trained and certified , before you give the ok. To answer your question, you have to install the unit. I would not recommend a used unit. There is alot of risk there. Just call around and see what they can do for you. They might offer financing. If you get me the model number of the unit ( inside and outside) I can get you the tonnage and let you know what you need.
Reply:A 2-1/2 ton (30,000 btu) unit should do the job. Your friend's unit is way too large.





Oversizing a furnace is no problem normally, but oversizing an air-conditioner can be a bummer. A/C's are made to cool but it is more important that they dehumidify. If they don't run very much they will not dehumidify very well. If an A/C unit is oversized it will only run a short while because it will cool the house down very quickly. Too quickly and it will not dehumidify and the comfort level is unsatisfactory. Also the size of the ductwork has to be compatible to the size of the A/C.





Get the serial number and any other information from the label on the outside unit . Give it to one of your local HVAC companies and they'll be able to tell you the size of the old condensing unit. While you're at it, get them to come over and provide you with a free estimate. Old units can be more trouble than they;'re worth. Good luck.
Reply:A four ton unit is way too large for that size of a house. It will not dehumidify properly and will cause mold to form on the inside of the duct work, and this would be very bad. A two and a half ton unit would be plenty big enough. Easier yet, find someone you know and trust and have them order a new compressor for the unit. All the refrigerant will have to be recovered first, then install the new compressor, evacuate the unit down to about 400 to 800 microns, then put the refrigerant back in. Have them check the superheat to make sure the right amount is in it. You may have to add just a little or take just a little out. If you know someone you trust, it's really an easy thing to do and not super expensive like the air conditioning companies will charge you. Good luck.
Reply:You can only properly test pressure when it's connected. You'd need to test low-side pressure and high side pressure, under a proper load of refrigerant. A 1200 sq.ft home would only need a 1 to 1.5 ton unit, depending on how much southern exposure and windows (heat). A 4 ton unit would be overkill and cause more problems than it's worth. If buying a used unit, it is critical to evacuate the system for a long period, with a new filter drier installed... moisture in refrigerant (from sitting in a garage) causes hydrochloric acid, which will kill the unit. I'd spring for a new unit, and put it on your utilities bill... You can in Canada. Call Direct Energy for a quote.
Reply:Only way To Test unit Is To Install It. You Should Only Need 1 1/2 Ton Ac Unit So That one is Way oversized