INSTALLATION AND OPERATION INSTRUCTIONS
5-4
VFC 15-150, VFC 45-225 MODULATING GAS BOILERS
5.2.5 Hi-Limit Switch (water and vent)
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 Ignition Module
There are two approved ignition modules - Fenwal (grey) and Capable Controls
(white). Each have a red LED lamp providing the following signals: Fenwal – 1
rapid ash on 1st entering Pre-purge, 3 rapid ashes upon Failure to Ignite After 3
Attempts; the Capable Controls module provides a single ash at the start of each
Purge and Interpurge cycle, continuous rapid ashes during the 4 second spark
interval, solid illumination following successful ignition until burner shutdown, and
a slow on/off cycle with a 3-try failure.
Flame current can be monitored on the Fenwal. 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
2-7 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”). For
conversion from Fenwal to the Capable Control, specify IBC part# 240-049 – that
provides the module plus added wire lead and instructions.
Fenwal ignition module - Microamp
(μA) test points are shown at top
right corner of module (above red
L.E.D.)
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