Siemens Maxum II Reference Manual page 75

The PECM provides the voltage to the two pairs of 1400-Watt AC Air Bath heater power
switching circuits located on the rear wall of the electronic enclosure. A dedicated cable
connects the PECM to the relay assembly. Each circuit has two solid-state relays connected
in series.
One series-connected relay controls the 1400-Watt AC heater functions to maintain controller
initiated set point temperature. In conjunction with the control signal, the air bath heater
pressure switch enables the relay. The second series-connected relay is used for safety
purposes. It performs an emergency analyzer system shutdown if an over-temperature
condition is detected. Both relay circuits are completely independent of each other. However,
in order for the power switching to occur both relays must be enabled. Temperature controls
are monitored on the Detector Personality Module located in the SNE and routed to the PECM
via a dedicated cable. No other functions are connected to the temperature control circuit.
Figure 2-38
Medium Wattage SSR
A medium wattage version of the Solid State Relay (SSR) module is available. The original
assembly included four large relays suitable for switching two of the 1400 watt air bath oven
heater elements. However, many Maxum GCs do not require that much power. Therefore, a
new SSR Module was added to the Maxum spare part offering. The newer board provides
smaller relays which are capable of controlling the new 500 watt air bath heater assembly
described previously. In addition, the "medium power" SSRB can be used to control the two
250 watt heaters used in the Maxum airless oven configurations. The newer board can also
be used to control the low wattage heaters in the heated Flame Ionization and Flame
Photometric detector housings or in heated sample injection valves.
The relays on the medium wattage SSR cannot be replaced individually. However, the module
is easily replaced. Another difference between the high wattage SSR and medium wattage
SSR is that the medium wattage version does not required heat dissipating fins on the back
of the enclosure. The relays are equipped with heat sinks on the front of the module as shown
in the photograph below.
Maxum II Reference Manual
Manual, 7/2017, 2000596-001
Electronic Compartment Component Descriptions and Maintenance Procedures
3
4
1
2
3
4
1
2
Air Bath Heater Relay Schematic
Schematic A
3
Rc
Zero
Control
voltage
LED
Voltage
detect
4
2.7 Solid State Relay Module
1 Load
AC
or
Line
2
Load
75