1. Design Procedure & Combination Ratio
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.
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 ≤ 4.5kW Nominal capacity > 4.5kW All capacities
10% 131% 145% 135%
20% 137% 153% 141%
30% 149% 162% 151%
130%
140%
150%
160%
170%
180%
5% 20% 25% 30%
Allowable Extended Combination Ratio
10% 15%
Minimum Operation Ratio in Heating
Nominal Capacity ≤ 4.5kW
Nominal Capacity < 4.5kW
Wall-mounted(all ranges)
Fig. 2 Allowable CR with respect to indoor unit type as operation ratio increases
Combination Ratio (Connection Ratio)
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