Install Instructions

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© 2019 tekmar 671
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D - 08/19
Pulse Width Modulation Zone Operation
The control operates the system pump to operate continuously
during melt, idle and storm operation. The boiler relays and heat
pumps relays operate on a 20-minute pulse width modulation
cycle. The relay on time is determined by the calculated slab
target and by the measured slab temperature reading. As
the slab temperature reaches the slab target, the on time per
cycle of the relay is reduced to prevent the slab temperature
from overshooting. If no slab sensor is installed the heat relay
remains on 100% of the time until the Melt circle has completed.
When connected to a tekmarNet system, the 671 can operate
a boiler (Boiler Type set to Enable) or it can call for heat from
the tekmarNet boiler control (Boiler Type set to Control)
Relay operation:
• System pump — operates continuously during melting,
idling or storm
• Heat relay — cycles on/off using Pulse Width Modulation to
control the slab temperature
• Boiler — cycles on/off using Pulse Width Modulation to con-
trol the slab temperature