Heating, Air Conditioning, Fridge, HVAC/Forced Hot Air Duct


QUESTION: ll of the duct work and redo the basement. I just do not have the funds for something like this.

Can you think of any suggestions? What is i was to increase the duct size to 8in in the basement and then reduce the duct before it goes up the wall into the second floor space. All second floor duct work goes up exterior walls, another reason why these runs are very long.

Furnace wise - we have a 80K BTU 97% variable speed ECM blower. We planned to setup the home for 4tons of cooling. This is what the existing owner had previously had.

Thanks for your help - Mike

ANSWER: Hi Mike, I think part of your question is missing. So I'm not sure what you are trying to do.

Let me know.

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QUESTION: Thanks Jim -

I guess the question is - Where is money best spent to fix-up this undersized duct work.

I think these are my available options. With the idea of keeping costs low because i am tight on funds for now  

1. Add Booster fans to the 6in duct but defeats the energy benefits of the ECM blower fan.

2. Is there any value in changing out the basement duct work to 7 or 8" duct but then it would be reduced to 6" when it travels up the wall.

3. Do I need to start over? Should i open up the walls and replace everything to a larger diameter duct and try to reduce the length of the branch ducts and increase the supply duct length?

The house is 40 years old.... You can tell they struggled with hot and cold spots.

ANSWER: Hi Mike, what has been done to determine that the duct work is to small? Are there any balancing dampers in the ducts? I don't think a booster fan is the answer.

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QUESTION: I had two licensed HVAC guys tell me the ducts could be larger because the 6" duct is carrying air maybe 50ft... 25ft through the basement space and then up to the second floor. The believe there is too much friction for the system to be successful.

Each takeoff has its own damper by the supply. They had tapped off the end of the supply. I had closed that damper and some airflow did improve. I guess the pressure in the supply was really thrown off.

Also, the former owner had a failing humidifier which rusted the takeoffs badly... .In your opinion, is the heavy rust cosmetic or should it be cut back and replaced?

The two technicians had disagreed with what should be done about the rust.

Thanks for your help

Hey Mike, Yes 50' of 6" duct is way to long. When you say 6" duct I assume this is round duct? What size is the supply duct coming off the furnace? Tapping off the end of the duct is a problem. The static pressure in the duct work is probably low. This causes low air flow.

It's hard to picture your duct system, so I can't say to tear it out and start over. As far as the rust goes if it's not leaking then I wouldn't do anything with it.

Hope this helps.

Heating, Air Conditioning, Fridge, HVAC

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Jim S.


I can answer questions on gas or electric furnaces, ac units and heat pumps. I don't work on boilers,chillers,or home appliances.


I have been in the HVAC trade for over 35 years. For the past 15 years I have owned my own business. I am semi-retired so I can answer questions in a timely manner.

I attended trade school for 5 years on weekends and evenings. This was very hard to do, but well worth it!

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