Vaillant Training/Logical Fault Finding Guide for all COMBlcompact and THERMOcompact models

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HEATING,CONTROLS,HOT WATER.

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HEATING,CONTROLS, OTWATER. H

Contents

Guidance Notes

IICD l'

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Room Sealed Fan Flued Models (RSF) COMBlcompact VCW 242E, 282E THERMOcompact VC112E, 142E, 182E, 242E, 282E
Balanced Flue & Open Flue Models COMBlcompact VCW221, 240, 280 THERMOcompact VC110, 180, 240, 221.

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Guidance Notes (should be read before using this fault finding guide)
1. Check you are using correct guide for your appliance. See index and check model number. 2.Always start at the beginning of guide and work through one step at a time. 3.AII guides deal with central heating (C/htg) first, then hot water (D.HW.) Do the same when following guides. 4. When checking 240v AC mains voltage use terminal 1 on appliance terminal strip as the neutral test point. 6.ln order to use this fault finding guide ensure that the operating mode of circulating pump is set to operating mode (I) (selector plug adjacent to appliance terminal strip makes electrical connection to contact one) see diagram. T

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5. When checking D.C. voltage use terminal 9 on appliance terminal strip as the negative test point. (All D.C. voltages are low voltage).
7. Note that illustrations and pictures are shown only once and are not duplicated again in this guide. Each illustration/picture has been given a reference number.
FRONT CONTROL PANEL Key 1. Yellow neon indicating power to operator. 2. Green neon indicating operation of Diaphragm pump. As voltage decreases to diaphragm pump so neon loses luminosity. 3. 0.16 amp anti surge fuse. 4. Time delay adjustment (factory set 5 minutes, adjustable 1-12 minutes). 5. Fault suppression button (ignition lockout). 6. Indicating neon (lockout). 7. 2 x 2 amp fuses (L&N). 8. Variable potentiometer controlling central heating flow temperature only. 9. Red neon rocker switch for power on. 10. Central heating rocker switch (not fitted on VC appliances).
Note 1 It is law* that any work carried out on a gas appliance must be carried out by a competent person who is registered with CORGI (Council for Registered Gas Installers). Note 2 All work involving electricity must be carried out by a competent person who is responsible for electrical safety checks. *Gas Safety (Installations and Use) Regulations 1984 Gas Safety (Installations and Use) Amendment Regulation 1990

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Room Sealed Fan Flued Models (RSF)

guidance note 6)

+ YES +

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(c) Check appliance not in time delay (isolate power, wait 5 seconds and restore). (d) Check anti surge fuse (0.16 amp).

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HEATING, CONTROLS, OTWATER. H

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~NO"
(a) Check 240v AC across pump terminals T Pic10
(b) Check pump free to rotate and not stuck T Pic11 ~.

Go ill 4

and (b) are OK.- change
Check hydraulic operation OK ? 1. Hydraulic diverter valve moves left closes microswitch M2 (VCW only)
(a) Check appliance and system full, pressurised and vented of air. (b) Check servo valve is in C/htg position, return spring holds carn down (VCW only). T Pic 12
(c) Check for dirt, sludge, flux or inhibitorcausTng frothing in system affecting:1. Pump performance 2. Hydraulic diverter valve (VCW only) 3. Servo valve (VCW only) 4. Connecting tubes 5. Main heat exchanger 6. Differential valve

M3 OPEN

2. Differential valve opens. T Pic 14

Rear view

Go to 5
Does applianC1 ignition? T
(a) Check microswitchM2 (20v DC) is making contact and closed circuit(VCW only). T Pic 15

(d) Check combustion chamber seals. (e) Cneck air switcn"tubes kinked and Sl., top cover plate clear. T
(yellow neon glowing front control box) (b) Check fan pressure switch oper9tes (240v AC :from both sides of switch to neutral terminal 1) if not check C to F T Pic 16
(1) Check fan working correctly. If all above OK change fan

pressure switch.

(c) Check flue installation: - Joints correctly located - Flue not blocke( - Terminal position
Does burner light and remain alight?
N;B. For lockoat (Black button & Red Neon) problems when no flame is visible check A to F. T

~ YES ~ t

\)~rnenflame is visible prior to lockout checkFto H only (a). Check gas supply to appliance live and purged. (b). Check differential valve open (if no return to Q4). (c). Check20v DC across gas operator, if available but operator fails to open (audible click) change operator. T
(d). Check central heating' overheat thermostat and connection (should be closed circuit, if open change component). T b" Pic22

71 I~O~

I (a) Check standing and working gas pressure at appliance inlet. T Pic25 (c) Check voltage across diaphragm pump (approx 6v DC) withNTC disconnected. T Pic27

Go to 8

(b) Check diaphragm pump operating tubes and throttle jet clear.

T Pic26

(d) Check burner pressure settings low and high fire rate. T Pic 28
(e) Check and/or replace gas operator.

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(a) TestNTC/Elebtronic board. Pull off NTC wire (from D.H.W. overheat) touch it on chassis, if burner goes off, change NTC. T Pic29 If burner stays on change electronic board. (The gas operator may be stuck open eg debris. This symptom is very unlikely but can be checked by pulling off the wire to operator. Ifburner remains alight then change operator).
(a) Check demand for hot water-tap open and supply pipes correct way round. (b) Check water section moves servo valve cam - if not check venturi/diaphragm of water section. (d) Check hy valve moves microswitch r open no eTec through switch).

Pic 30

CLOSED

(e) If D check gas

(c) Check microswitCh M3 (20v DC) is making contact and closed circuit. Pic31.
pressure at & burner pr' Pic 25 & Pic 28. (1) If water fl<

insufficient c

adequate cold water mainO, supply and/or blockage in water section or DHW

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Balanced Flue and Open Flue Models
H' COMBlcompact THERMOcompact VCW221 , 240, 280 VC11 0, 180, 240, 221
Red Rocker switch - Set to ON position - Set to ON position (VCW only)

Heating Switch

Circulating Pump - Operating mode position one (I) (see guidance note 6)

First check central heating operation (All external controls on)
Can pilot light be lit and established? (a) Check gas supply to appliance live and purged. (b) Check pilot injector, burner and supply tubes. Pic33 (d) Check thermocouple and connections. Pic35

Go to 2

(e) Check central heating overheat thermostat and connections (should be closed circuit, if open change component). Refer to Pic 22 (f) If intermittent pilot outage occurs check flue integrity (balanced flue) ventilation or draughts (open flue).

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(c) Check piezo ignitor, leads and electrodes. Pic34
Does red neon glow in main switch?
(a) Check 240v AC across terminals 2 (L) and 1 (N) Refer to Pic 1. (b) Check 2 x 2 amp appliance fuses. Refer to Pic 2.
(c) Check 3 amp spur fuse. If fuses OK and power available but neon fails to light, replace front Mother Board.

Go to 3

Does pump run?
(a) Check 240v AC across pump terminals (if not check C to F). Refer to Pic 10. (b) Check pump free to rotate and not stuck - If A & B are OK change pump. Refer to Pic 11. (c) Check 240v AC available for external controls at terminal 3, if not change Mother Board. Refer to Pic 5.
(d) Check demand for heating - external controls on, and 240v AC back to terminal 4. (e) Check anti surge fuse (O.16amp). Refer to Pic 4. (f) Check safety isolating transformer 240v AC primary (black/grey) and approx. 17v AC secondary (brown/blue). Refer to Pic 9.

Go to 4

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Check hydraulic operation OK? 1. Hydraulic diverter valve moves left closes microswitch M2 (VCW only). Refer to Pic 13. or 2. Differential valve closes microswitch T M4 (VC's only) Pic36

NO"

(a) Check appliance and system full, pressurised and vented of air. (b) Check servo valve is in C/htg position, return spring holds cam down (VCW only). Refer to Pic 12. (c) Check differential valve and tubes. (d) Check for dirt, flux sludge or inhibitor in system causing frothing affecting :1. Pump performance. 2. Hydraulic diverter valve (VCWonly). 3. Servo valve (VCW only) 4. Connecting tubes. 5. Main heat exchanger. 6. Differential valve.

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Does burner light?

Go to 6

(a) Check variable potentiometer (boiler stat) setting on maximum. (b) Check appliance not in time delay (isolate power wait 5 seconds and restore). (c) Check Domestic Hot Water overheat thermostat (VCW only) - pull off bottom white wire, if burner lights Replace DHW overheat. Refer to Pic 7. (d) Check NTC - (pull wire off NTC sensor, if burner lights change NTC. Refer to Pic 8. (e) Check operation and adjustment of microswitch M2 20v DC (VCW only). Refer to Pic 15. (f) Check differential valve closes microswitch M4 20v DC (VC only). T Pie3?

(h) Check for continuity through gas section microswitch M5 (20vDC) T Pic38
(i) Check for continuity through main heat exchanger overheat thermostat. T Pic39
(9) Check 20v DC across gas operator, if available but operator fails to open (audible click) change operator. Refer to Pic 21
0) Check small p.c.b. bridge located bottom rear of Mother Board. T
Does burner modulate up to high
fire rate after approx 5 seconds?

I~O"

, YES ,

Go to 7

(a) Check standing and working gas pressure at appliance inlet. Refer to Pic 25. (b) Check diaphragm pump operating tubes and throttle jet clear. Refer to Pic 26. (c) Check voltage across
diaphragm pump (approx 6v DC) (NTC disconnected Refer to Pic 27. (d) Check burner pressure settings low and high fire rate. Refer to Pic 28. (e) Check and/or replace gas operator.

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fDoes appliance modulate down to low fire (ignition rate) and go off? To test Put appliance thermostat to no. 6, fire appliance for central heating. Burner should now modulate down and shut off at approx 60C (see temperature gauge).
(a) Test NTC/Electronic board. Pull off NTC wire (from DHW overheat) and touch it on chassis, if burner goes off change NTC. Refer to Pic 29 If burner stays on change electronic board.
(The gas operator may be stuck open e.g. debris. This symptom is very unlikely but can be checked by pulling off the wire to the operator. If burner remains alight then change operator).
If COMBlcompact VCW Go to 8
If THERMOcompact End of job
For VCW only - is D.HW operation OK?
(a) Check demand for hot water - tap open and supply pipes correct way round. (b) Check water section moves servo valve cam - if not check venturi/diaphragm of water section. Refer to Pic3(). (c) Check microswitch M3 (20v DC). Refer to Pic 31. (d) Check hydraulic diverter valve moves right opening microswitch M1 (with M1 open no electrical continuity
through switch). Refer to Pic 32. (e) If DHW not hot enough check gas supply working pressure at appliance inlet & burner pressure. Refer to Pic 25 & Pic 28. (f) If water flow rate insufficient check. for adequate cold water main supply and/or blockage in water section or DHW heat exchanger. End of job.

End of job

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2nd edition February'94

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Designed and Produced by IMPACT Image Management 0622 721144
Vaillant cannol accept responsibility for damage as a resull 01non-observance 01this Fault Finding Guide. Subject to alteration. (2194).
HEATING,CONTROLS.HOT WATER.