Allowable CR limit to avoid abnormal sound level risks in heating operation
f
If the CR exceeds 130%, in a specific case of heating operation, an indoor unit may have higher sound level than
the level specified in the technical documents.
f
In order to minimize the sound level, the system minimum operation ratio needs to be verified and considered as
follows:
※
Operation Ratio(%), OR
• Heat Pump system, H/P
OR (H/P) (%) =
Sum of nominal capacity of indoor units running in heating mode
* 100%
Sum of nominal capacity of indoor units
• Heat Recovery system, H/R
OR (H/R) (%) =
Sum of nominal capacity of indoor units running in both cooling & heating mode
* 100%
Sum of nominal capacity of indoor units
The Minimum Operation Ratio should be determined during the project design stage using Fig. 2.
Fig. 2 Allowable CR with respect to indoor unit type as operation ratio increases
Combination Ratio (Connection Ratio)
Outdoor unit
All capacities of H/P & H/R (Single, Dual and Triple Module Systems)
Indoor unit
All indoor unit types
*)
except Wall-Mounted
Wall-Mounted
Operation Ratio
Nominal Capacity ≤ 18kBtu/h
Nominal capacity > 18kBtu/h
All capacities
10%
150%
158%
141%
20%
161%
170%
155%
30%
171%
184%
173%
130%
140%
150%
160%
170%
180%
190%
200%
5%
10%
25%
30%
All
ow
ab
le
Ex
tended
C
ombi
nati
on
Rati
o
15%
20%
Minimum Operation Ratio in Heating
Nominal Capacity
≤
18,000Btu/h
Nominal Capacity > 18,000Btu/h
Wall-mounted(all ranges)
Design Procedure & Combination Ratio