SIME FORMAT WALL HUNG BOILERS
MODEL 34i AND MODEL 34e
REF: INSTALLATION INSTRUCTIONS
19/02/04
15
3.2 PCB Features
a)
POT.ACC. Bridge.(
see Fig 9
) This modifies the ignition pressure programme of
the gas valve. With the bridge disconnecting, the ignition pressure varies in a linear
manner from low to the maximum set heating pressure. With the bridge connected,
the pressure varies in a linear manner from 50% to the maximum set heating
pressure.
When the boiler is operating on Propane, it is recommended that
the bridge be connected to improve the ignition function (quicker
cross-lighting) (
see Fig 9a
).
b) Natural Gas/ LPG Selector Bridge
. With the bridge disconnected, the
boiler will operate correctly for Natural Gas. With the bridge connected, the
boiler will operate correctly for LPG gas. Failure to use in the correct
position for either gas will mean that the required maximum and minimum
gas pressure cannot be obtained.
3.3
Temperature
Control
Temperature control is provided by modulation of the gas burner
pressure, and thus the input of the boiler. The water temperature is
sensed by N.T.G. thermistor located on the outlet of the heat
exchanger. The varying voltages thus produced by the PCB will
operate the modulating coil on the gas valve, and move the servo
regulator accordingly.