Install Instructions

IM-PR 566442 1114 (Design Manual)
20
Example Equation: A 300 ft² room has a heat loss of 40 Btu/hr/ft² of floor area. The design calls for 30% of
the heating loss to be supplied through the wall and 70% of the heating loss to be supplied through the floor.
The room design temperature is 68°F. Available surface area for the radiant panels is 100 ft² of wall area and
300 ft² of floor area. What surface temperature is required for the wall and the floor to satisfy the heat load?
1. Find the total heat loss of the room in Btu/hr by multiplying the floor area by the heat loss per
floor area: 40 Btu/hr/ft² x 300 ft² = 12,000 Btu/hr
2. Find the heat loss supplied through the wall and floor on a per-square-foot basis.
a. Floor: (70% x 12,000 Btu/hr)/300 ft² = 28 Btu/hr/ft²
b. Wall: (30% x 12,000 Btu/hr)/100 ft² = 36 Btu/hr/ft²
3. Identify ∆T between floor and room and wall and room.
a. Floor: Find 28 Btu/hr/ft² on the vertical axis of Figure 1-12, and move to the right until
you intersect the line labeled “Floor.” From this intersection, move down to the horizontal axis
and read the ∆T between the room temperature and the floor surface temperature. The result
is 14.7°F.
b. Wall: Find 36 Btu/hr/ft² on the vertical axis of Figure 1-12 and move to the right until you
intersect the line labeled “Wall.”From this intersection, move down to the horizontal axis and
read the ∆T between the room temperature and the floor surface temperature. The result
is 25.7°F.
4. Add the ∆T for the floor and the wall to the room temperature to determine the required
surface temperature.
a. Floor: 14.7°F + 68°F = 82.7°F
b. Wall: 25.7°F + 68°F = 93.7°F
5. Verify that surface temperatures are within design limitations.
a. Wall: 93.7°F is below the maximum recommended surface temperature range for walls.
b. Floor: 82.7°F is below the upper limit of the acceptable surface temperature for floors, which
is 85°F.
c. Result: Design surface temperatures are less than or equal to the upper limit of the acceptable
surface temperatures; the room heat load can be met successfully and comfortably with these
design temperatures.
Figure 1-16 Heat load supplied per square foot of floor or wall emitter area based on ∆T between the room
set point temperature and the emitter surface temperature
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10
20
30
40
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70
0510 15 20 25 30
Btu/hr/2 of Panel Surface Area
Temperature Difference (°F) between Room Temperature and
Panel Surface Temperature
Floor
Wall
Ceiling