Vaillant Training/Logical Fault Finding Guide for allCOMBlcompact and THERMOcompact models

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~ VaillantHEATING,CONTROLS,HOT WATER.

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Contents

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Guidance Notes

IICD

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Room Sealed Fan Flued Models (RSF)COMBlcompactVCW 242E, 282ETHERMOcompactVC112E, 142E, 182E, 242E, 282E

Ii)

)r:-'.'-:14

.Balanced Flue & Open Flue ModelsCOMBlcompactVCW221, 240, 280THERMOcompactVC110, 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 workthrough one step at a time.

3.AII guides deal with central heating (C/htg) first, thenhot water (D.HW.)Do the same when following guides.

4. When checking 240v AC mains voltage use terminal 1on appliance terminal strip as the neutral test point.

~ 5. When checking D.C. voltage use terminal 9 onappliance terminal strip as the negative test point.(All D.C. voltages are low voltage).

10

56

1

Q7

Note 1 It is law* that any work carried out on a gasappliance must be carried out by a competent personwho is registered with CORGI (Council for RegisteredGas Installers).Note 2 All work involving electricity must be carriedout by a competent person who is responsible forelectrical safety checks.

*Gas Safety (Installations and Use) Regulations 1984Gas Safety (Installations and Use) AmendmentRegulation 1990

6.ln order to use this fault finding guide ensure that theoperating mode of circulating pump is set to operatingmode (I) (selector plug adjacent to appliance terminalstrip makes electrical connection to contact one) seediagram.T

IISI0Gro GroG

7. Note that illustrations and pictures are shown onlyonce and are not duplicated again in this guide.Each illustration/picture has been given a referencenumber.

93

FRONT CONTROL PANEL

Key1. Yellow neon indicating power to operator.2. Green neon indicating operation of Diaphragm pump.As voltage decreases to diaphragm pump so neon losesluminosity.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 flowtemperature only.9. Red neon rocker switch for power on.10. Central heating rocker switch (not fitted on VCappliances) .

42

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Room Sealed Fan Flued Models (RSF)

guidance note 6)

Q.

11

+

YES

+

1

:g~....

f...l

~

~YES

~

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[!]

(c) Check appliance not in time

delay (isolate power, wait 5seconds and restore).

(d) Check anti surge fuse(0.16 amp)....

~$J

Inoe. pU\pPrun1

tYES,

[ Go ill 4

~Check hydraulic operation OK ?1. Hydraulic diverter valvemoves left closes microswitchM2 (VCWonly)T

~

2. Differential valve opens.T Pic14

[Go to 5

4

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~NO"(a) Check 240v AC acrosspump terminalsT Pic10

(b) Check pump free to rotateand not stuckT Pic11

~.

I tvIf(a) and (b) are OK.- changepump.

I~NO

(a) Check appliance andsystem full, pressurised andvented of air.

(b) Check servo valve is inC/htg position, return springholds carn down (VCWonly).T

(c) Check for dirt, sludge,flux or inhibitorcausTngfrothing in systemaffecting:-1. Pump performance2. Hydraulic diverter valve(VCW only)3. Servo valve (VCW only)4. Connecting tubes5. Main heat exchanger6. Differential valve

Pic 12

M3OPEN G

Rear view

I

~Does applianC1ignition?T

~(yellow neon glowing frontcontrol box)

0

YES

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~ VaillantHEATING,CONTROLS,HOTWATER.

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I~O~ (a) Check microswitchM2(20v DC)is makingcontactand closed circuit(VCWonly).T

(d) Check combustionchamber seals.(e) Cneck airswitcn"tubeskinked and Sl

., top cover plate clear.T

Pic 15

(b) Check fan pressureswitch oper9tes (240v AC:from both sides of switch toneutral terminal 1) if notcheck C to FT Pic 16

(c) Check flue installation:- Joints correctly located- Flue not blocke(- Terminal position

(1)Check fan workingcorrectly.If all above OK change fanpressure switch.

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Does burner light and

remain alight?

~YES

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~VaillantHEATING,CONTROLS,HOTWATER.

~NO~ N;B. For lockoat (Blackbutton & Red Neon)problems when no flame isvisible check A to F.T

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\)~rnenflame is visible priorto lockout checkFto H only(a). Check gas supply toappliance live and purged.(b). Check differential valveopen (if no return to Q4).(c). Check20v DC acrossgas operator, if availablebut operator fails to open(audible click) changeoperator.T

t

(d). Check central heating'overheat thermostat and

connection (should beclosed circuit, if openchange component).T b " Pic22

71

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~YES

~Go to 8

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YES

~ VaillantHEATING,CONTROLS,HOTWATER.

I~O~(a) Check standing andworking gas pressure atappliance inlet.T Pic25

~

(c) Check voltage acrossdiaphragm pump (approx 6vDC) withNTC disconnected.T Pic27

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(b) Check diaphragm pumpoperating tubes and throttlejet clear.T Pic26

NO~ (a) TestNTC/Elebtronicboard.Pull off NTC wire (fromD.H.W. overheat) touch iton chassis, if burner goesoff, change NTC.T Pic29

(d) Check burner pressuresettings low and high fire rate.T Pic28

(e) Check and/or replace gasoperator.

If burner stays on changeelectronic board.

(The gas operator may bestuck open eg debris. Thissymptom is very unlikelybut can be checked bypulling off the wire tooperator. Ifburner remainsalight then changeoperator).

~ VaillantHEATING,CONTROLS,HOTWATER.

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(a) Check demand for hotwater-tap open and supplypipes correct way round.(b) Check water sectionmoves servo valve cam - if

not check venturi/diaphragmof water section...

~o~

~YES

!

Pic 30

(c) Check microswitCh M3(20v DC) is making contactand closed circuit... Pic31

(d) Check hyvalve movesmicroswitch r

open no eTecthrough switch)...

M3CLOSED ~

(e) If Dcheck gas -

pressure at& burner pr'Pic 25 & Pic 28.

(1) If water fl<insufficientc 0

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

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Balanced Flue and Open Flue ModelsCOMBlcompact VCW221 , 240, 280

THERMOcompact VC11 0, 180, 240, 221

Red Rocker switch - Set to ON position

Heating Switch - Set to ON position (VCW only)

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

~ First check central heating operation (All external controls on)

11

Can pilot light be lit and

established? I~NO~(a) Check gas supply toappliance live and purged.(b) Check pilot injector,burner and supply tubes.... Pic33

(d) Check thermocoupleand connections.... Pic35

~+

YES

+

~

(c) Check piezo ignitor,leads and electrodes.... Pic34

(e) Check central heatingoverheat thermostat and

connections (should beclosed circuit, if openchange component).Refer to Pic 22

(f) If intermittent pilotoutage occurs check flueintegrity (balanced flue)ventilation or draughts(open flue).

Go to 2

9

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Does red neon glow inmain switch?

+YES

tGo to 3

~Does pump run?

+YES

tGo to 4

~VaillantHEATING,CONTROLS,HOTWATER.

~o~

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~o~

I

(a) Check 240v AC acrossterminals 2 (L) and 1 (N)Refer to Pic 1.

(b) Check 2 x 2 ampappliance fuses.Refer to Pic 2.

(c) Check 3 amp spur fuse.

If fuses OK and poweravailable but neon fails to

light, replace front MotherBoard.

~

(a) Check 240v AC acrosspump terminals (if not checkC to F).Refer to Pic 10.

(b) Check pump free torotate and not stuck - If A &

B are OK change pump.Refer to Pic 11.

(c) Check 240v AC availablefor external controls at

terminal 3, if not changeMother Board.Refer to Pic 5.

(d) Check demand forheating - external controlson, and 240v AC back toterminal 4.

(e) Check anti surge fuse(O.16amp). Refer to Pic 4.

(f) Check safety isolatingtransformer 240v AC

primary (black/grey) andapprox. 17v AC secondary(brown/blue). Refer to Pic 9. '"

~Check hydraulic operationOK?

1. Hydraulic diverter valvemoves left closes

microswitch M2 (VCW only).Refer to Pic 13.or2. Differential valve closes

microswitch M4 (VC's only)T Pic36

\.,

"YES

~Go to 5

tij VaillantHEATING,CONTROLS,HOTWATER.

[!]

NO" (a) Check appliance andsystem full, pressurised andvented of air.

(b) Check servo valve is in

C/htg position, return springholds cam down (VCWonly). Refer to Pic 12.

(c) Check differential valveand tubes.

(d) Check for dirt, fluxsludge or inhibitor in systemcausing 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?

+YES

+Go to 6

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HEATING,CONTROLS,HOTWATER.

(a) Check variablepotentiometer (boiler stat)setting on maximum.(b) Check appliance not intime delay (isolate power wait5 seconds and restore).(c) Check Domestic HotWater overheat thermostat(VCW only) - pull off bottomwhite wire, if burner lights -Replace DHW overheat.Refer to Pic 7.

(d) Check NTC - (pull wire offNTC sensor, if burner lightschange NTC. Refer to Pic 8.(e) Check operation andadjustment of microswitch M220v DC (VCW only).Refer to Pic 15.

(f) Check differential valvecloses microswitch M4 20vDC (VC only).T

(9) Check 20v DC across gasoperator, if available butoperator fails to open (audibleclick) change operator.Refer to Pic 21

(h) Check for continuitythrough gas sectionmicroswitch M5 (20vDC)T Pic38

~(i) Check for continuitythrough main heat exchangeroverheat thermostat.T Pic39

Pie3?

0) Check small p.c.b. bridgelocated bottom rear of MotherBoard.T

.~

Does burner modulate up to highfire rate afterapprox 5 seconds? I~O"

~ ,YES,

Go to 7I

(a) Check standing andworking gas pressure atappliance inlet. Refer to Pic25.

(b) Check diaphragm pumpoperating tubes and throttlejet clear. Refer to Pic 26.

(c) Check voltage across

diaphragm pump (approx 6vDC) (NTC disconnectedRefer to Pic 27.

(d) Check burner pressuresettings low and high firerate. Refer to Pic 28.

(e) Check and/or replacegas operator.

11f-

.~

Does appliance modulatedown to low fire (ignitionrate) and go off?

To test

Put appliance thermostat tono. 6, fire appliance forcentral heating. Burnershould now modulate down

and shut off at approx 60°C(see temperature gauge).

~

YES

If COMBlcompact VCW

Go to 8

If THERMOcompact VC

End of job

~

&For VCW only - is D.HWoperation OK?

::i

YES

+

End of job

tiJVaillant

NO"

NO"

I

HEATING, CONTROLS,HOTWATER.

~

(a) Test NTC/Electronicboard.

Pull off NTC wire (fromDHW overheat) and touch iton chassis, if burner goesoff change NTC.Refer to Pic 29

If burner stays on changeelectronic board.

(The gas operator may bestuck open e.g. debris.This symptom is veryunlikely but can be checkedby pulling off the wire to theoperator. If burner remainsalight then changeoperator).

(a) Check demand for hotwater - tap open and supplypipes correct way round.

(b) Check water sectionmoves servo valvecam - if not check

venturi/diaphragm of watersection. Refer to Pic3().

(c) Check microswitch M3(20v DC). Refer to Pic 31.

(d) Check hydraulic divertervalve moves right openingmicroswitch M1 (with M1open no electrical continuity

through switch). Refer toPic 32.

(e) If DHW not hot enoughcheck gas supply workingpressure at appliance inlet& burner pressure. Refer toPic 25 & Pic 28.

(f) If water flow rateinsufficient check. for

adequate cold water mainsupply and/or blockage inwater section or DHW heat

exchanger.

End of job.

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~ VaillantHEATING,CONTROLS.HOT WATER.

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2nd edition February'94

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).