I would appreciate some help evaluating a proposal for renovating an existing central air conditioning system.
The new units provide 3 airflow rates of 17-21-25 m3/min (618-742-883 CFM) and 24-29-34 (847-1024-1201). As I understand it, I have to allocate a proportion of the max airflow based on the ratio of the cooling requirement for each room. The larger unit has a max airflow of 2040m3/h and the room loads are 2kW, 1,5kW, 3kW and 3kW or proportionate flows of 430, 325, 640 and 640m3/h. One room is a bedroom, the rest are used during the day.
The smaller unit has a max airflow of 1500 m3/h and the room loads are 2kW, 3kW, 2kW, 1kW and 1,5kW or proportionate flows of 315, 475, 315, 157 and 236m3/h. The last two rooms are bedrooms.
The old duct is visible and the new proposal varies thus (sizes in metres):
Larger unit 2040m3/h:
0,60x0,20 (actual 0,60x0,20), room 1: 0,20x0,20 (actual 0,30x0,15)
0,50x0,20 (actual 0,54x0,20), room 2: 0,15x0,20 (actual 0,30x0,15)
0,40x0,20 (actual 0,50x0,20), room 3: 0,25x0,20 (actual 0,30x0,15)
Room 4: 0,25x0,20 (actual 0,50x0,15)
Smaller unit 1500m3/h:
0,45x0,20 (actual 0,65x0,20), room 1 0,20x0,15 (actual 0,50x0,15)
0,35x0,20 (actual 0,45x0,20), room 2 0,25x0,15 (actual 0,30x0,15)
0,25x0,20(actual 0,45x0,20), room 3 0,15x0,15 (actual 0,30x0,15)
0,15x0,20 (actual 0,35x0,20), room 4 0,15x0,15 (actual 0,30x0,15)
Room 5 0,20x0,10 (actual 0,30x0,10)
I dont have airflow numbers for the actual units but I guess we can assume that the newer units are better (faster flow, lower power consumption)
How can I evaluate the new numbers? I'm worried that the smaller duct might be cheaper but with more noise.
Also, we are thinking about creating zones the bedrooms, two of which we dont use much (either automatic or manually grills)- should we consider the max airflow for day/ night use and size accordingly? Or as per above, the max airflow if all rooms were to be cooled (ie bedrooms during the day and lounge during the night)
Thanks in advance for any input.