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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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A person is interested in buying a home built in the 90's

Customer Question

a person is interested in buying a home built in the 90's with central A/C. the prior owner had 2 dogs. the new owner is allergic to dogs. The ducts are seen to be the flexi ducts with the silver insulation wrap. What is the best way to decontaminate the duct system? can polishing the inside of the flexi ducts work? Also on a central A/c system where is there any fresh air coming in from outside or is it just recirculating the house air? What does the big unit with the fan outside do? does it suck in air or just cool the Freon, which goes to the air handler in the attic which cools the house air? Lastly, on a split unit is there any outside air from this type?
Submitted: 11 months ago.
Category: HVAC
Expert:  Rick replied 11 months ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

The only way to remove contaminates from the system is to have a professional duct cleaning service clean the ducts. You can't "polish" the inside of the ducts. Installing a filter designed to remove allergens will help keep the allergen levels in the house down.
In a typical AC system the air is only re-circulated. No air comes form outdoors.

The outdoor unit is the refrigeration unit that condenses the refrigerant and dissipates the heat from the house to the outdoors (the purpose of the fan). This is the essential aspect of the cooling system.

Also no outside air from a split system.

Customer: replied 11 months ago.
okay, how are they going to clean the ducts if they are flexi ducts? the old type of ducts where sheet metal boxes that the roto brush could clean. I've seen pictures online for this but here the ducts look like bellows of an accordion and it would be impossible to get all the pet dander of of those creases. Should I plan on going into the attic and replacing the ducts up there cutting them ans splicing into the old as they go down the wall chase?
Expert:  Rick replied 11 months ago.

They typically use a large vacuum suction machine. It pulls air through the ducts with a lot more force than the blower on the system. So anything that doesn't get sucked out is not going to blow out the vent at much lower air pressure. You can replace the ducts if you want and they are accessible. But it usually isn't necessary. New families move into houses all the time that have allergens that didn't bother the previous occupants. Duct cleaning usually is all that's needed.

Customer: replied 11 months ago.
ok thanks
Expert:  Rick replied 11 months ago.

You're welcome.

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