Furnace 1ZONE, AC 2 ZONES Same System

Marc Finn

We are putting a new variable speed furnace for the 2nd floor only. The second floor was previously only electric heat and the house is in Rockland County, New York. This is our first full year in the house. Currently we have a 15 year old a/c which is for the 2nd and 1st floor.

My main concern is a quiet heating system. This is why I am going for the variable speed furnace. Now we are thinking of adding a new a/c to the new furnace at the recommendation of the contractor. The new furnace would only heat the 2nd floor. THe a/c which would be linked to the new furnace would however cool both the 1st and 2nd floor. The contractor said assuming the size of my current air conditoning is 3 tons or less then he could combine the a/c and furnace from the attic. He mentioned putting in some kind of damper so the furnace would not heat the 1st floor but the air conditioning be linked to the furnace and cool both the first and the second floor.
Does this make sense to you? The issue is using a heating or cooling system with a constant volume of air that during certain seasons will have that volume directed to a portion of the house that does not need that much air. The result is noise from the
airflow through the ducts and registers and drafts from too much air.

the contractor says he can design the system so it will not be noiser by having the new a/c combined with the new furnace.

The contractor came over yesterday and said that the way to prevent increased noise is in the design and he said that it will be necessary to set the fan to different settings meaning the fan will be set differently for a/c than when it is used for heat.


I am confused. Any advise appreciated. For me it is not worth getting the a/c along with the furnace if having the a/c cool both the 1st and 2nd floor will make the use of the furnace which will heat only the 2nd floor noisier.

I am confused. However, if the contractor is right in that combining the a/c with the furnace will not make the noise from the furnace any louder then it would be worthwhile to put in the a/c as well.

Any advice appreciated.

heaterdude

it could work....

if laid out properly. Most v-speed products have different cfm settings for heating and cooling and reduced speed options of either. You could run full capacity airflow when cooling and drop to a minimum airflow in heating, all automatically from the thermostat demand. Combined with an electric zone damper for the first floor that opens only when cooling(again, automatically)and some good design, you could be in business. Good luck!