IBC Technologies SL 80-399 - Water Pressure Sensor

INSTALLATION AND OPERATION INSTRUCTIONS
5-4
SL 80-399 MODULATING GAS BOILER
Next,conrmthatthecircuitisproperlypowered.Thesupplyvoltagetothe
sensor should be 13.8 VDC; to check, the simplest technique is to measure the
circuit on the face of the controller circuit board (vs. an attempt to splice into the
harness / connectors). See previous page for a presentation of the measurement
points.
Finally, to measure the sensor output, connect a DC volt meter between points
“J501-33” (located on the footprint of the 34 pin connector – immediately below
the right leg of the LCD display - second pin from bottom right) and GND (see
above). With the fan off, the measure should read 0.5VDC. With a Fan Pressure
of approx. 300, the meter will read 1.5v (approx.). Note:- this component is a
sensor, not a switch; do not over-pressurize by blowing into the air reference
lines. Maximum pressure capacity is 40” w.c. @ 20 C but only 10” w.c. @ 5C.
5.2.4 Water Pressure Sensor
Go to the Advanced Diagnostics screen, and check the top display line — Inlet
Pressure. With the pumps at rest and system pressure of 12.5 psi, the Inlet
Pressure sensor value should read 235 +/- 5.
Check operation of the sensor by isolating the boiler from its system piping,
closingthesystemllvalvethencrackingthepressurereliefvalve;thesignal
shouldreectdecliningpressure.Ifitremains“xed”,drainboilerandreplace
sensor, or dislodge any blocking debris from sensor inlet channel and reinsert.
5.2.5 Hi-Limit Switches (water and vent UVHL)
Check resistance between leads. If resistance is very low, temperature should
be acceptable. If resistance is very high, temperature should be out of bounds.
A simple means of checking whether a high limit switch is open is by measuring
the AC voltage across the device. If the reading is 24 VAC the switch is open. If a
0VAC reading is shown, it is closed. NEVER connect an ohm-meter or continuity
checker across a live circuit.
5.2.6 Fenwal Ignition Module
Whentheboilerfailstoignite,ortheameignites,butgoesoutattheendofthe
ignitiontrial,theproblemcouldbeintheamesensingcircuit.
Connectanelectricaltestmeter-settoreadMicroamps(symbolμA)tothetwo
test pins at the top right of the ignition module. Recycle the boiler so it enters
anothertrialforignitionandmonitortheamecurrentreading.Whentheburner
ignites, a steady reading of between [3 and 5] Microamps should be measured
by your meter. The control will lock out if the reading drops below 0.7 Microamps.
(see Section 5.3.1 - “Control Module - Maximum ignition trials error”, and Section
5.3.2 - “Ignition problems”).
Do not blow into sensor ports
Air pressure sensor mounting
Water pressure sensor
Fenwal ignition module - Microamp
(μA) test points are shown at top
leftt corner of module (beside red
L.E.D.)