Install Instructions

117
IM-PR 566442 1114 (Design Manual)
• Diverting Valve – A diverting valve is
controlled by a non-electronic actuator that
sends out a xed water temperature. This
control maintains a xed water temperature
by adjusting the volume of return water being
diverted back into the supply stream.
• Injection Mixing – This variable temperature
control option uses either a single-speed
or variable-speed injection circulator that
receives a signal from a reset control to
vary the volume of hot water injected into
secondary piping. These small injected
amounts of hot water mix with the water in the
secondary piping, increasing the temperature
as needed. One advantage to using an
injection mixing system is that a large amount
of Btus can be carried using a relatively
small diameter and a low-wattage circulator.
Injection mixing can be a good solution on
large systems with high ow requirements,
since specifying a circulator instead of a
mixing valve can avoid the extra head from
the mixing valve. Remember, when selecting
mixing balancing valves, choose valves with
a high Cv rating. For mixing valves, select
a valve with a Cv rating that is as close as
possible to the design ow rate through the
valve. This will optimize performance of the
valve (good control at reduced head).
• Modulating Heat Source – The heat source
is controlled by a reset control to vary the
supply water temperature based upon the
outdoor and/or indoor temperatures, thus
potentially eliminating the need for additional
mixing devices. Depending on the heat
source type and manufacturer, modulation
methods may vary. Multiple temperature
systems may require secondary mixing
in addition to boiler modulation. Based
on large heat load requirements for snow
melting systems, most snow melt systems
will require a dedicated boiler. If low return
water temperatures and high slab water
temperatures are a concern, additional controls
and mixing devices may have to be added.