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v1.0 10/2007 Page 3 of 16
Service Call Overview
Important: Read the information on pages 1 and 2 before using this guide. This guide assumes the reader is
familiar with the Vitodens product manuals and the Quick Start-up Guide (QSG).
When burner fault indicator (red LED) is lit, the boiler is in lockout mode and needs to be reset.
When a fault is flashing on the programming unit’s display, but the red light is not lit, the boiler need not be
reset and will resume operation as soon as the fault is acknowledged or corrected.
Item Field Service Calls Suggested Solution
Section 1: Unusual boiler operation
1 Boiler does not start and
no fault code is
displayed on
programming unit’s
screen.
Model 6-24/8-32
Water pressure switch did not close (WB2-24C, -24, -32).
Check system pressure (must be above 12 psig).
Power on boiler and enter installer set-up. Go to Relay Test #10. If
boiler has stalled with no fault code displayed, remove wires from
pressure switch and jumper it. If boiler starts, replace the switch.
If boiler does not start, check for other probable causes, such as
incorrect voltage, defective VR20 board, LGM board etc.
2 Boiler does not start and
no fault code is
displayed on
programming unit’s
screen.
Model 11-44/15-60
Water flow switch did not close. Follow procedure as in item 1.
If boiler does not start, verify #20, #21 and #20A plugs for pump
connections in both PPM and orange boiler relay pump box.
If plug #20 was incorrectly used as system pump (#20A), change it
to #20A plug; boiler should then start (see QSG for pump diagrams).
If boiler does not start, check for other probable causes, such as
incorrect voltage, defective VR20 board, LGM board etc.
3 Boiler short cycling
Check for proper grounding of the boiler (dedicated ground, check
building ground).
Check for air in the system – purge until system is entirely free of air.
Check for proper water flow in the system (check for proper sizing of
pump(s) and pipes).
Low gas pressure while boiler is running. Check inlet gas valve
screen. Increase gas supply pressure if it is below the required
minimum.
Check for blocked air inlet on concentric venting system. (For testing
purposes only: remove burner cover to eliminate venting air intake
and to allow room air for combustion).
Flue gas leakages on concentric system (see flue gas test procedure
in Venting System Installation Instructions)
4 Boiler short cycling
Model 6-24/8-32
When in DHW call for heat: ensure solenoid valve is installed straight
into the diverting valve against the seat, even if solenoid pulls in and
out normally as per Relay Test #04).
DHW coil resistance is high, especially with non-Viessmann tank.
Order PN 7134599.
Check for zone valves in the system. If present, they require a
separate pressure-activated bypass – Vitodens 200, WB2-24, -32
internal bypass is not designed to handle system flow. It is only used
for boiler pump protection. Use of Low Loss Header will help in this
situation.
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