I have worked cleaning HVAC in my area for almost 5 years. I always do a thorough inspection and cleaning, providing before and after photos. I have completed some jobs where I felt that it was not entirely necessary, but ultimately what the customer wanted. With that being said, I have endless photos of unspeakable horrors. Hotels are usually nasty, post construction mess is certain, pets and kids create lots off debris, bugs congregate and die, then spiders set up and die, I have even had one supply that was nearly plugged with sand!
Tip – Be careful with change-outs. Ductwork deteriorates and sometimes has to be replaced.  It is only if the ductwork is in fantastic condition that you should get a change-out without ductwork (Remember – the ductwork has already been there for 15-20 years, and now it will be there another 15-20…it has to be in good shape). However, many HVAC installation companies like to push change-outs because the ductwork is the most time consuming part of the job, and a change-out is quick, easy money. Realize that it’s only about 15-20% of the jobs that qualify for a change-out, so be careful.
I'd have to disagree with all of your statements. Not only are they derived from no experience in the field, you are missing keys facts. Ducts even if air tight will get dirty. If they are not getting dirty, it means they are not working. Your returns side of the duct work is always under negative pressure when the system is operational.Therefore it is always drawing air in. Seeing how dust is made up mostly from dead skin humans shed daily. Around 1.6 Pounds of skin a year per human. Living in your home anything that is air born will be drawn back towards the cold air returns. That is what they are designed for, to draw stale air back to the system to be filtered and sent back through the house.Homes with carpet will actually have cleaner duct work than home with all tile or hardwood. This is because carpets hold onto dust particles and you vacuum them up. Whereas on hardwood or tile, dust can run freely back to the returns. Even if a duct system was sealed 100%, which is next to impossible to achieve 100% would still need to be cleaned. The cleaning may only have to be every 7-10 years for example. Most homes require every 5-7 years. And that's if it was done properly the first time. If you constantly hire people that have no or minimal knowledge of duct cleaning, You home would require cleaning more often. Every 2 years. That's a trade secret, The longer they recommend before the next cleaning, the odds are they did it right. That's not to say there aren't people that lie, because there are. Just have your duct cleaner take pictures before and after cleaning. Not just an outside view. Get in there, picture entire joist liners, Whole main runs and even long round pipes. Also it helps to have a company that guarantees their work. If it's not done right, they will come back and do it until it is. Most companies that do this make sure it is right the first time. Your not getting paid to do the job twice.
If you think duct cleaning might be a good idea for your home, but you are not sure, talk to a professional. The company that services your heating and cooling system may be a good source of advice. You may also want to contact professional duct cleaning service providers and ask them about the services they provide. Remember, they are trying to sell you a service, so ask questions and insist on complete and knowledgeable answers.
Quality and price should come hand in hand, a too-good-to-be-true price for an efficient air duct cleaning will not give you the quality that you wanted. To make sure you are getting your money’s worth, check reviews of air duct cleaning companies, certifications from industry since this work requires continuous learning due to new techniques and research breakthrough from time to time. Make sure to shop around and get written estimates first.
BIG THANK YOU for being honest, and advising us that for some reason the fuse/switch was in the reverse position so the AC unit would not properly turn on.   The unit turned back on immediately, and began cooling the house.   And then providing advice that the AC/Heating system needed some TLC, and giving us options to save money by purchasing a maintenance plan that included the filters plus cleaning services since we were already being charged for the service today.
When central air conditioning service fails during a heat spell, you may have to wait days for an HVAC repair technician or an ac contractor to show up, and you'll probably pay at least several hundred for the repair. But if you're comfortable working around electricity and are willing to spend about $50 on parts, you can probably repair your air conditioning service yourself in about two hours and save about $225 on parts markup and labor.
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