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RT-SVX096A-EN
Minimum Room Area (A
min
) Adjustments
Use equation below to adjust the minimum room area, as
applicable, based on the unit’s installation height, altitude,
and occupancy level it serves.
A
min.adj
= Nameplate A
min
x Altitude Adj x Height Adj x F
occ
Multiply the altitude adjustment factor in the table below by
A
min
listed on the unit nameplate or in the Installation,
Operation, and Maintenance (IOM) manual.
Table 3. Altitude adjustment factor
Altitude (ft)
Sea Level
to 2000
2001 to
4000
4001 to
6000
6001 to
8000
8001 to
10000
10001 to
12000
12001 to
14000
14001 to
15000
Over 15000
A
min
Adjustment
1 1.05 1.11 1.17 1.24 1.32 1.41 1.51 1.57
In addition, A
min
can be adjusted if the unit is installed in a
room at a height that is higher than the minimum height
shown on the unit. To adjust A
min
, multiply by the ratio of
the unit minimum release height (in meters) / actual release
height (in meters). Use 0.6 m in the ratio for unit minimum
installation heights less than or equal to 0.6 m.
For institutional occupancies, ASHRAE Standard 15
applies an additional adjustment factor F
occ
to the amount
of a charge allowed in a space. To calculate the adjusted
A
min
for institutional occupancies, multiply the A
min
on the
nameplate by two.
EXAMPLE 1: 20 Ton Packaged Rooftop Multi-Zone VAV
System Serving an Institutional Occupancy Space
The packaged unit serves 7600 ft
2
of a nursing home
located at an attitude of 4000 ft. The unit has two equally
charged 10 ton refrigeration circuits. Each circuit has 12 lbs
of refrigerant with a minimum room area requirement of
180 ft
2
with a 2.2 m release height.
TA
min.adj
= 180 ft
2
x 1.05 x 2 = 378 ft
2
No additional ventilation is required.
EXAMPLE 2: 10 Ton Split System Serving a Single
Commercial Occupancy Space
The split system serves a 1500 ft
2
manufacturing space at
5000 ft altitude. The final installed charge of the single
circuit 10 ton unit is 20 lb. The unit has an open return with
a release height of 1 m and ducted supply air. The unit
A
min
is 660 ft
2
.
A
min.adj
= 660 ft
2
x 1.11 = 733 ft
2
No additional ventilation is required.
Determining Room Area (A or TA)
The room area (A) is the room area enclosed by the
projection to the floor of the walls, partitions, and doors of
the space that the equipment serves. For ducted systems,
total room area (TA) of all rooms connected by ducts, may
be used instead of A.
Rooms connected by drop ceilings only are not considered
a single room.
Rooms on the same floor of the building, and connected by
an open passageway, can be considered part of the same
room if the passageway is a permanent opening, extends
to the floor and is intended for people to walk through.
Adjacent rooms on the same floor of the building and
connected by permanent openings in the walls and/or
doors between rooms (including gaps between the wall and
the floor), can be considered part of the same room if the
openings meet the following criteria.
• The opening is permanent and cannot be closed.
• Openings extending to the floor, such as door gaps,
need to be at least 20 mm above the floor covering
surface.
• Natural ventilations opening areas must meet the
requirements of ANSI\ASHRAE Standard 15-2022,
Section 7.2.3.2.
Rooms that are connected by a mechanical ventilation
system can be considered a single room area if the
mechanical ventilation system meets the requirements of
ANSI\ASHRAE Standard 15-2022, Section 7.6.4.
Leak Detection System
(Refrigerant charge greater than 3.91 lb
per circuit)
The leak detection system consists of one or more
refrigerant detection sensors. When the system detects a
leak, the following mitigation actions will be initiated until
refrigerant has not been detected for at least 5 minutes:
• Energize the supply fan(s) to deliver a required
minimum amount of circulation airflow.
• Disable compressor operation.
• Provide an output signal to fully open all zoning
dampers, such as VAV boxes.
• Provide an output to energize additional mechanical
ventilation (if needed).
• Units without airflow proving will disable electric heat
sources.
Building fire and smoke systems may override this function.
If the refrigerant sensor has a fault, is at the end of its life,
or is disconnected, the unit will initiate the mitigation
A2L Information
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