Filter
Top Products
H2iSD-38
2010 Hyper-heating Y-SERIES SYSTEM DESIGN (Sept. 2010)
2010 H2i
®
Y-SERIES
SYSTEM DESIGN
6. CAUTIONS
R410A refrigerant is harmless and incombustible. R410A is heavier than the indoor air in density. Leakage of the refrigerant in a room
has possibility to lead to a hypoxia situation. Therefore, the critical concentration specified below shall not be exceeded even if the leakage
happens.
Critical concentration
Critical concentration is the maximum refrigerant concentration at which no harm would occur if immediate measures are taken
when refrigerant leakage happens.
Critical concentration of R410A: 0.30kg/m
3
(The weight of refrigeration gas per 1 m
3
[1 ft
3
]
air
conditioning space.);
The critical concentration is per ISO5149, EN378-1 (other codes and standards may establish different values for critical concentration).
For CITY MULTI systems, the concentration of refrigerant leaked should not exceed the critical concentration in any situation.
[0.0187 lbs./ft
3
]
The maximum refrigerant leakage concentration (Rmax) is defined as the result of the possible maximum refrigerant weight (Wmax)
leaked into a room divided by its room capacity (V). The refrigerant weight includes itsoriginal charge and additional charge at the site.
The additional charge is calculated according to "
PUHY-P-T(S)HMU/Y(S)HMU's refrigerant charging calculation
", and shall not be
over charged at the site
.
Procedure 6-2-1~3 tells how to confirm maximum refrigerant leakage concentration (Rmax) and how to take
Refrigerant pipe
to Outdoor unit
Indoor unit
Opening
Ventilation air supply fan (always ON)
Indoor space
(Floor)
Fig. 6-2. air supply always ON
Refrigerant pipe
to Outdoor unit
Indoor unit
Opening
Sensor for refrigerant leakage (Oxygen sensor or refrigerant sensor).
[At 0.3m height from the floor]
Ventilation air supply fan
Indoor space
(Floor)
Fig. 6-3.
air supply upon sensor action
Note 1. Countermeasure 3 should be done in a proper way in which the ventilation air supply shall be on whenever the leakage happens.
Note 2. In principle, MITSUBISHI ELECTRIC requires proper piping design, installation and air-tight testing after installation to avoid leakage happening.
In the area should earthquake happen, anti-vibration measures should be fully considered.
The piping should consider the extension due to the temperature variation.
Outdoor unit (No.1)
Flow of refrigerant
Indoor unit
Maximum refrigerant leakage concentration (Rmax)
Outdoor unit (No.1) Outdoor unit (No.2)
Indoor unit
Flow of refrigerant Flow of refrigerant
Rmax=Wmax / V
Maximum refrigerant leakage concentration (Rmax)
Rmax=Wmax / V
where, Wmax=W1+W2
W1: Refrigerant weight of Outdoor unit No.1
W2: Refrigerant weight of Outdoor unit No.2
Fig. 6-1 The maximum refrigerant leakage concentration
6-2-1.Find the room capacity (V),
If a room having total opening area more than 0.15% of the floor area at a low position with another room/space, the two rooms/space are
considered as one.The total space shall be added up.
6-2-2.Find the possible maximum leakage (Wmax) in the room. If a room has Indoor unit(s) from more than 1 Outdoor unit, add up the refriger-
ant of the Outdoor units.
6-2-3.Divide (Wmax) by (V) to get the maximum refrigerant leakage concentration (Rmax).
6-2-4.Find if there is any room in which the maximum refrigerant leakage concentration (Rmax) is over 0.30kg/m
3
If no, then the CITY MULTI is safe against refrigerant leakage.
If yes, following countermeasure is recommended to do at site.
Countermeasure 1: Let-out (making V bigger)
Design an opening of more than 0.15% of the floor area at a low position of the wall to let out the refrigerant whenever leaked.
e.g. make the upper and lower seams of door big enough.
Countermeasure 2: Smaller total charge (making Wmax smaller)
e.g. Avoid connecting more than 1 Outdoor unit to one room.
e.g. Using smaller model size but more Outdoor units.
e.g. Shorten the refrigerant piping as much as possible.
Countermeasure 3:
As the density of the refrigerant is bigger than that of the air.
Ventilation air supply solution refers to Fig. 6-2~3.
countermeasures against a possible leakage.
Ventilation air in from the ceiling.
Ventilation air from the ceiling is better than air exhausting from the ceiling.
Ventilation Ventilation
[0.0187 lbs./ft. ].
3
e.g. Remove unit from space.
6-1. Refrigerant Properties
The installer and/or air-conditioning system specialist shall follow local safety regulations and standards regarding refrigerant leakage. The
following standard may be applicable if a local regulation or standard is available.
6-2. Conrm the Critical Concentration Levels and Perform Countermeasures