3M TTS-5-1-OJ, Application Manual

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Most snow melting applications will utilize a 208, 220, or 240 Vac power supply. To ensure maximum snow melting
potential, KSR™ Self-Regulating Heating Cable is for 208/240 Vac. Table 3.3.1 , Cable Selection, shows the circuit
lengths possible with KSR™ Self-Regulating Heating Cable at each voltage. For a specific system, match the branch
circuit breaker size to the KSR™ Self-Regulating Heating Cable circuit length based on:
• The maximum circuit length shown in
Table 3.3.1
• The maximum circuit length required for a given heating cable layout
• The maximum circuit length for a predetermined branch circuit breaker size
Estimating the amount of KSR™ Self-Regulating Heating Cable required, number of circuits needed and the total power
requirements can be accomplished with Formulas 3.1 and 3.2 . These estimates will be useful for coordinating the
material and power requirements of the cable.
Dividing the total KSR™ Self-Regulating Heating Cable estimate by the circuit length shown in
Table 3.3.1
will indicate
how many circuits will be needed for a given branch circuit breaker size.
Notes:
1. Additional heat may be needed if the area will be subject to drifting
or moisture run-off from another source. No allowance has been made
for back or edge loss. Both back and edge loss will occur to varying
degrees on every application. The amount and extent of loss is affected
by soil types, frost line depth, shape and size of the area, plus the
location of the area as it relates to other structures and wind.
2. Spacing as shown in Table 3.2.1 will provide a completely melted
surface for the concrete area under typical snowfall weather conditions:
ambient temperatures between -6°C (20°F) and 1°C (34°F) with wind
speeds of 5 to 24 km/h (15 mph). Should the ambient temperature fall
below -6°C (20°F) during the snowstorm, some snow accumulation
could occur but will be melted at the rate of fall.
Snowfall Severity KSR™ Self-Regulating Heating Cable Spacing
Category Rate of snowfall Non-critical Critical
Light ½"/hour 12" O.C. 7½" O.C
Moderate 1"/hour 9" O.C. 6" O.C.
Heavy 2"/hour 6" O.C. 5" O.C.
Table 3.2.1: KSR™ Self-Regulating Heating Cable Spacing
2
O.C. = on-centre
Formula 3.1: Estimating Quantity of KSR™
Self-Regulating Heating Cable Required
Total KSR™ Self-Regulating Heating Cable required =
area in square feet x (12 ÷ S)
Where: S = KSR™ Self-Regulating Heating Cable
spacing in inches
Formula 3.2: Total Heat Output / Operating Load
P
1
= L
1
x I
1
x E
Where: P
1
= Total heat output (in watts) for system
L
1
= Total installed length of KSR cable
I
1
= Amps per foot multiplier for voltage used
E = Operating voltage
Since the example shown is a public/employee entrance, it would be considered a non-critical area ( Table 3.2.1 ) where
snow removal is convenient but not essential. Additionally, if the example is located in Vancouver, BC, where the
snowfall severity would fall into the “moderate” category of 1 inch per hour, the heating cable should be installed on
9-inch, centre-to-centre spacing.
If the system is to meet ASHRAE requirements, refer to the Cable Spacing Selection Guide on page 39. Based on
this data for Vancouver, 9-inch, centre-to-centre spacing of KSR™ Self-Regulating Heating Cable indicates that for
approximately 84% of snowfall hours the surface will remain clear.
Applications where snow removal is a convenience
but not essential:
• Building entrances
• Loading docks
• Parking garage ramps
Step 3: Determine length of cable required and circuit lengths.
Applications where safe access is essential:
• Hospital emergency entrances
• Train loading platforms
• Fire station driveways