DriSteem Vapor-logic3, Installation And Operation Manual

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SSR modulation with contactors
With SSR modulation with contactors, the operation
of the unit is the same as it is with TP Modulation. In
this scenario, one of the cycling contactors is replaced
with an SSR. The SSR is now the device that carries
out all of the cycling duties. The contactors will
always be either on or off. Any TP cycling that is
needed will be handled by the SSR stage.
This provides two distinct advantages over standard
TP modulation. First, an SSR can turn on and off
much faster than a contactor can. Therefore, as the
unit modulates around a demand signal, tighter
control is achieved because the cycle time on an SSR
system is factory-set at one second. This means that
every second, the controller can adjust the on and off
times on the SSR to very closely track the desired
demand.
The second major advantage over standard TP
modulation is reliability. With a solid state device like
an SSR, component wear and tear is almost
nonexistent when compared with an
electromechanical device such as a contactor.
Therefore, with the SSR doing all of the heavy
cycling work, the life expectancy of the contactors is
extended.
100
% SSR modulation
The ultimate in electric humidifier modulation is
100% SSR Modulation. With this type of control, all
heat stages are controlled by SSRs. This allows the
output of the humidifier to track the actual demand
very closely because all heat stages can now cycle on
and off at the rapid SSR cycle rate.
With 100% SSR modulation, a contactor is still
provided in series, with the SSR device as an
additional safety feature. This contactor is
energized any time there is demand on the
humidifier, and remains energized until the
demand is satisfied. In this way, if there is a failure
in the SSR device, the contactor is there as a
backup to shut the humidifier down.
Modulation types: SSR modulation.
Operation
Operation:
SSR modulation
VL3-IOM-0301-METRIC.pdf 43 11/19/2009 9:22:39 AM