Multi F Installation Manual

72
MULTI F / MULTI F MAX Outdoor Unit Installation Manual
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MULTI
F
MAX
MULTI
F
Amount of
Factory-Charged
Refrigerant per
Outdoor Unit
Amount of
Additional
Refrigerant
Trim Charge
Refrigerant Concentration Limit (RCL) Calculations
To calculate total refrigerant amount per system:
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ASHRAE Standards 15 and 34 offer guidelines that address refrigerant safety and the maximum allowable concentration of refrigerant in an
occupied space. Refrigerant will dissipate into the atmosphere, but a certain volume of air is required for this to occur safely. For R410A re-
frigerant, the maximum allowable concentration is 0.026 lbs./ft
3
per 1,000 ft
3
of air in an occupied space. Buildings with twenty-four (24) hour
occupancy allow half of that concentration.
1
ASHRAE Standards 15 and 34 assume that if a system develops a leak, its entire refrigerant charge will dump into the area where the leak
occurs. To meet ASHRAE Standards 15 and 34, calculate the refrigerant concentration that may occur in the smallest room volume on
the system, and compare the results to the maximum allowable concentration number (see below for information on how to calculate the
refrigerant concentration).
1
Also consult state and local codes in regards to refrigerant safety.
1
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ASHRAE Standard 15 / 34 and addenda current as of the date of this publication.
Take appropriate actions at the end of HVAC equipment life to recover, recycle, reclaim or destroy R410A refrigerant according to applicable US
EPA rules.
Total System
Refrigerant
Charge
 =
To calculate the potential refrigerant concentration level (RCL):
1. Measure the occupied space dimensions (in feet).
2. Calculate the cubic foot volume of air in the smallest occupied
space. (To obtain a detailed overview of the RCL, perform the
same calculations to the second smallest zone, the third smallest
zone until the RCL is obtained for all zones. Also, pay special
attention to areas such as basements, etc., where refrigerant
cannot dissipate easily.)
3. Divide the refrigerant charge of the Multi Zone system serving the
area in pounds by the results of step 1.
4. If the calculation indicates that the potential refrigerant concen-
tration level is higher than the allowed RCL, increase the cubic
volume of the smallest occupied space or modify the piping
system design.
5. The allowable RCL limit for most applications must be equal to
or less than 0.026 lbs./ft
3
. However, in special occupied spaces,
such as hospitals and nursing homes, where occupants may have
limited mobility, the allowable RCL limit is cut in half. See ASHRAE
Standard 34 and local codes for detailed information.
1
RCL (lbs./ft
3
) =
Total System Refrigerant Charge (lbs.)
Volume of Smallest Occupied Space (ft
3
)
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Outdoor Unit
Direction of Refrigerant Flow
Indoor Unit
Zone into which the
entire charge of
refrigerant leaks.
Indoor Unit Indoor Unit
Indoor Unit
Figure 111: Example of R410A Refrigerant Leak Location.
CAUTIONS FOR REFRIGERANT LEAKS