Carrier infinity – zone control

[serik]

I am in a desperate need of an advice here…
We are about to have a sheet metal ducts made and put in and have to decide if they need to be configured for zoning.

Originally it was a single story ranch, we are adding a 2nd story in the attic, on top of the middle portion of the house. It spans all the way from one gable end to another and adds 600sf to the original 1,800; so 2,400 sf total

No money for zoning equipment this year though I would like to have a ductwork which would support it. I would break it into 3 zones: A-masterbedroom and two 1st floor bedrooms, B- greatroom, dining room and den (those are all connected and don’t have individual doors), C - 2nd story rooms. Each 1st floor zone would have 6 supply registers, 2nd floor 4 or 5 registers.

Am I right that the ductwork would have to support a minimum CFM on each zone individually? And it means 910 CFM in low fire mode, divided by 5 = 182 CFM per register. I think this is awfully too much, even at 100cfm per register system is uncomfortably loud.

Am I missing something? Or should I give up on zoning?

[wildbill99]

I am in a desperate need of an advice here…
We are about to have a sheet metal ducts made and put in and have to decide if they need to be configured for zoning.

Originally it was a single story ranch, we are adding a 2nd story in the attic, on top of the middle portion of the house. It spans all the way from one gable end to another and adds 600sf to the original 1,800; so 2,400 sf total

No money for zoning equipment this year though I would like to have a ductwork which would support it. I would break it into 3 zones: A-masterbedroom and two 1st floor bedrooms, B- greatroom, dining room and den (those are all connected and don’t have individual doors), C - 2nd story rooms. Each 1st floor zone would have 6 supply registers, 2nd floor 4 or 5 registers.

Am I right that the ductwork would have to support a minimum CFM on each zone individually? And it means 910 CFM in low fire mode, divided by 5 = 182 CFM per register. I think this is awfully too much, even at 100cfm per register system is uncomfortably loud.

Am I missing something? Or should I give up on zoning?

I did not see any mention of RETURNS.

I am a HO with an engineering background. From what I have experienced in my own home and others and complaints of people 2 story houses the having returns on the 2nd floor having high returns is very critical to get good cooling on the 2nd floor.

And best to have some ways of controlling the amount of air going to each level.

Some of this has to do with the specific loads that you have in each area. And that depends on the number and types of windows, insulation (since this a remodel the 2nd story might be much better than the first) and the number of people that use the space.

I will let the pros answer the more specific questions.

Right now an installer is tearing out my old sytemS. I am replacing separate downstair and upstair system with a new single one with multi-staging HP and modulating furance. I am go to try to manual zoning, but add automatic later if that does not work out.

[dash]

A Manual J load calculation will determine the cfms required for each room ,for cooling and heating.

The ducts need to be sized,by Manual D, for 125% of the required cfms,for each zone and branch duct.

You would not need to size each zone to handle 100% of the required cfms for the system.The zoning bypass damper or a great zoning system,like the Carrier Infinity will do just fine.

[serik]

I have all the numbers from manual J, CFM requirement came out to 1200 total. However the furnace is existing and it is 1500 CFM high fire / 720 CFM low fire.

Also no bypass damper is needed or recommended with Carrier Infinity. I am just curious if it will go lower than 720 CFM or it will be my minimum, no matter how many zones are active?

[serik]

this came directly from SYSTXBBUIZ01-B manual:

Design Considerations
The Evolution Zone system is unique because a bypass damper
must not be used. This is possible due to the intelligence of the
system and variable speed motor technology. For trouble--free
applications, the following parameters should always be met:
1. Zones should be sized so that each zone can deliver at least
the minimum airflow for the system in both heating and
cooling modes.
2. Oversize duct work by 25% to avoid excess noise at minimum
zone airflow.
3. Be aware that heating airflow may be higher than cooling
airflow depending on equipment combination.

#1 forces me to make zones larger than they need to be and to use less zones, than i could. Currently noise is a big concern, especially at the room adjacent to the garage (thats where indoor unit is located). High heat noise is unbearable. I am afraid to make it even noisier with the new sheet metal ducts and zoning...