Morco FEB-24E UK User manual

1
FEB-24E UK SUPERCOMPACT
COMBINATION BOILER
TECHNICAL & FAULTFINDING GUIDE
Morco Products Ltd
Riverview Road, Beverley, East Yorkshire, HU17 0LD
Telephone [phone] Fax [phone]

2
Contents
1. Quick Guide to Trouble Shooting
2. Electrical Components
3. Central Heating Logic Programme
4. Explanation of Self Diagnostics
5. Self Diagnostic Flow Charts
ISSUE NUMBER 1.0

3
1. Quick Guide to Trouble shooting
This section outlines the most common problems and helps to guide you through the rest
of the workshop manual. (Read this section first, before you make any adjustments. It
will save you time.)
CHECK HOT WATER SYSTEM FIRST, BEFORE THE CENTRAL HEATING CIRCUIT
HOT WATER SYSTEM
Here are some common problems:
GAS REGULATORS
Single appliance low capacity gas regulators plus 3/8” flexible low pressure pipe, will
reduce the efficiency dramatically. Ensure gas regulators and pipes are capable of
delivering 37mbar at the inlet under full load. A 2.5mbar drop is acceptable.
WATER FILTER
Check for contamination with foreign objects such as sawdust, plastic pipe swarf, etc. The
water filter is located inside the cold water inlet fitting under the boiler. Any blockage will
reduce flow and may prevent the boiler firing up.
HOT AND COLD WATER CONNECTIONS
Connections may be reversed at the boiler inlet/outlet fittings, resulting in the boiler failing
to commence ignition sequence. This is because the hydraulic valve operates in one
direction only.
THERMOSTATIC SHOWER MIXER VALVE
Faulty non return valves within the mixer tap may allow mains cold water to enter the
domestic hot water pipe work. The boiler will react to the situation according to the
amount of mains water entering the system. In severe cases a high percentage of mains
cold water will exit the hot water tap in place of hot water, as water will always take the
path of least resistance. This will result in no hot water flow, or a very restricted flow
through the boiler. This will result in no ignition occurring or the boiler will modulate at very
low gas pressure, followed by the boiler eventually shutting down as insufficient flow
passes through the boiler.

4
QUICK PLUMBING CHECK
A simple solution if cross contamination of hot and cold water is suspected, is to
disconnect the hot water outlet pipe from the boiler (under the van), this procedure
eliminates faulty mixer valves and crossed pipes from the system and will allow the boiler
to operate without any water starvation or back pressure. If it works, you now know the
plumbing system is at fault and not the boiler.
WATER SUPPLY
The FEB24E Combination Boiler delivers up to 10 litres/minute of hot water. Many sites
depending on occupancy levels and season do not have a mains system capable of
supplying a constant pressure/flow rate to the boiler. Should the pressure/flow rate of the
incoming mains cold water fall below the minimum specified values, the boiler will shut
down due to the domestic hot water (DHW) thermistor detecting a temperature greater
than 70 deg C or the micro-switch deactivating under low flow. Pressure at the cold water
inlet can be checked using a gauge attached to the filling loop valve on the installation pipe
work. The pressures should be checked when the domestic hot water flow is at maximum
(10 litres/min). This can be adjusted at the faucet. If max flow cannot be achieved through
the faucet, there is either a blockage or the water supply is inadequate.
CENTRAL HEATING SYSTEM
Check the following first:-
ROOM THERMOSTAT – (if fitted)
Faulty connections or incorrectly wired room thermostats result in the central heating not
working. The fault is usually at the room thermostat, but can also occur at the connector
block on the boiler, due to the insulation not being removed from the conductor wire or a
loose feed wire (2 black) at the base of the connector.
LOW PRESSURE ON GAUGE
Incorrect or too low a pressure in the heating circuit will disable the boiler in both central
heating and hot water modes. FEB24E boilers are fitted with a pressure switch, should the
pressure within the heating circuit fall below 0.8 bar the switch will become open circuit
and the boiler will lock out. Fault code 2 will be displayed via the LED. This will prevent
damage to the boiler in the event of the heating system leaking, or in some cases due to
accidental drain down of the heating circuit.
Important- The accuracy of pressure gauges may vary and can provide a general
indication of pressure within the boiler only. Pressure will also vary according to
temperature. The normal operating pressure when cold should be 1.6bar.

5
Important - Leaks on the heating circuit can occur anywhere on the system. It is important
to locate and rectify any leak however small it may be. One way of detecting minute leaks
is to pressurise the boiler to 2.0bar. Using toilet or tissue paper, wipe around any joints on
the system. If any moisture is present then the tissue will change colour becoming darker.
Check the following if low pressure is shown:
Radiator air vent screws and blanking plugs
Radiator valves all joints and unions
Filling loop double check valve
(This may not be visible without removing inspection panels)
Boiler connections including safety valve (check discharge pipe)
Automatic air vent bleed screw (located on top of pump)
Drain plugs and connections under the van. Any leaks are usually indicated by
dark patches on the concrete or gravel, or look for patches of dead grass.
Loss of pressure from expansion vessel (see section under expansion vessel)
If the leak is impossible to detect then the last resort is to introduce a proprietary leak
sealing chemical into the system such as Fernox LS 3.
TIME CLOCK
Check that the time clock is calling for heat, the white tappets should be in the outer
position at the arrow head.
IMPORTANT. The specification of time clocks on boilers after serial number 050512656
incorporates a three position selector switch located at the base of the clock. There are
three positions as follows:
1. Switch to the left overrides timed positions and heating is on constant.
2. Switch in the centre position heating is on or off according to tappet timed
positions on the clock
3. Switch to the right heating is off.
HEATING SLOW TO REACH TEMPERATURE
The main burner may ignite for short periods only and the radiators may be slow to heat.
This can be caused by a blocked filter on the central heating return pipe. (Right hand
pipe). Access to the filter requires draining down the boiler, and removing the pipe fitting
from the boiler. The filter can then be removed for cleaning and MUST be replaced to the
boiler.

6
Another associated problem with sluggish radiator performance can be attributed to un-
circulated undiluted anti freeze in the boiler and pipe work. This problem is usually worse
in cold conditions. In order to cure the problem, try the following method.
1. Turn off one radiator valve on the largest radiator. Increase the pressure in the
system to 2.0bar. Now release 0.5 litre of fluid from the air vent cap on the radiator
into a container.
2. Close the vent and re-pressurise the heating circuit to 2.0bar and open the radiator
valve which was closed on the initial purge. Close the valve previously open (you
will need a screw driver and adjustable spanner to open and close the lock shield
valve). Release another 0.5 litre of fluid from the air vent cap. This procedure
should have cleared any concentrated anti freeze from the pipe work.
3. Re-pressure the boiler to 1.6bar and open both the radiator valves fully and run the
heating. Once the boiler has established full heat at the radiator, close one of the
valves on the working radiator. Other radiators should now slowly start to heat up.
Radiators which fail to heat up may require purging as above.
4. If time is not a problem, simply leave the heating on. After an hour or two the
problem will clear itself.
COLD RADIATORS
These usually appear in pairs, due to crossed pipe work, i.e. one radiator is fed with two
flow pipes with a second radiator fed with two returns, and consequently neither radiator is
capable of circulation and remains cold.
Always check that the valves are open. Some systems are not heat tested before
despatch, and it is possible that the valves may be closed very tightly. If in doubt check by
removing the plastic head and use a spanner to open the valve.
THINGS TO CHECK BEFORE MAKING ANY ADJUSTMENTS
1. Mains cold water supply valve fully open.
2. Gas installation correct. Regulator/pipe size correct/UPSO/OPSO working
correctly.
3. Gas supply valves open/isolation valve on boiler fully open.
4. Power supply to boiler socket present.
5. Air pressure switch test point cap fully located. (Black rubber cap on the right hand
side on the top of boiler)
6. Correct water pressure is in the heating circuit (1.6Bar when cold)

7
AT THE BOILER, REMOVE THE FRONT COVER AND CHECK THE FOLLOWING:
The 2 white modulation solenoid wires are connected
The spark generator is attached to the gas valve correctly
Both the H.T leads from the spark generator are attached correctly
Look for wires and components not connected or plugged incorrectly, especially the
clip on central heating thermistor which should be attached to the heating flow pipe
and not the gas pipe!
IMPORTANT: Boilers with serial numbers 050410747 onwards will have the central
heating thermistor located on the left hand side of the main heat exchanger.
Important Things You Will Find in the Technical and Faultfinding Manual
Domestic Hot Water Ignition Sequence (Page 28)
This flow diagram represents the general operating system in the domestic hot water
mode and the sequence of events if temperatures exceed the specified limits which are
pre-determined by the PCB.
Central Heating Ignition Sequence (Page 29)
This flow diagram represents the general operating system in the central heating mode
and the sequence of events if temperatures exceed the specified limits.
Please note that following the initial 30 seconds of minimum output, modulation may not
occur for a further 5 minutes if the central heating logic programme is operating. This is
because the boiler will not fire on full power if it has detected it is serving a system with a
low load. This is the case in most caravan holiday homes. For more detailed information
please see the note on central heating logic programme. (Page 25)
Lighting Up Sequence Flow Diagram (page 27)
The lighting up sequence is common for both the central heating and domestic hot water
modes. Once the flame is established the relevant regulation on modulation takes place.
Explanation of Self-Diagnostics (Page 30)
Whenever a fault develops in the boiler that is likely to affect its safe operation it will lock
out and show a fault code via a flashing sequence on the red LED on the control panel.
Lock out faults will require a component to be replaced or service work to be carried out.
Identify the fault by reading the flashing LED sequence (self diagnostic fault code). Each

8
fault code has a description as to the cause of the problem in the workshop manual – read
this carefully.
N.B. there will be a time delay of between a few seconds and 3 minutes between the boiler
locking out and showing the self diagnostic fault code. The workshop manual shows each
component of the boiler, a functional description and the operating voltages where
applicable. By reading this information and testing before replacing components the
correct diagnosis can be reached ensuring that the wrong part is not replaced
unnecessarily.
Fault Finding Flow Diagrams (Pages 39 – 46)
These diagrams help diagnose problems that are not related to the safe operation of the
boiler and hence are not subject to the “lock –out” mechanism and the corresponding self
diagnostic fault code. The diagrams are to be used as a guide only and in conjunction with
the more detailed information on each component found elsewhere in the workshop
manual.

9

10

11
2. Electrical Components
Electrical Circuit Diagram

12
1. Electrical Filter page 14
2. Mains Connection page 14
3. Earth page 14
4. Fan page 14
5. Circulation Pump page 14
6. Spark Generator page 15
7. Gas Valve Solenoid EV1 page 15
8. Gas Valve Solenoid EV2 page 15
9. Front Panel Control PCB page 15
10.Hydraulic Unit 3 Way Valve Microswitch page 16
11.Air Pressure Switch page 16
12.Room Thermostat
13.Room Thermostat Connection Block page 17
14.Clock Connection
15.Modulating Gas Solenoid page 17
16.Ionisation Electrode page 18
17.High Limit Thermostat page 18
21.Domestic Hot Water Thermistor page 18
22.Central Heating Thermistor page 19
23.Central Heating Low Pressure Switch page 20
25.Green LED Burner On page 20
26.Red LED Lockout/Fault Indicator page 21
30.Time Clock page 21
S1 Boiler Model Selector Bridges (FEB-24E Make)
S2 Boiler Model Selector Bridges (FEB-24E Make)
S3 Boiler Model Selector Bridges (FEB-24E Open)
S4 Gas Type Selector Bridge (Propane Make, Natural Open)
P1 Maximum Power Potentiometer
P2 Ignition Power Potentiometer
P3 Central Heating Power Potentiometer (set at 60% max power)
J12 Auto Test Point

13

14
The Heading Numbers refer to the Electrical Circuit Diagram
1. ELECTRICAL FILTER
This cleans the incoming mains supply voltage to the PCB
It is wired as follows: L2 Live In (Brown)
N4 Neutral In (Blue)
U1 Live Out (Grey)
3U Neutral Out (Grey)
= Earth to Chassis (Green & Yellow)
2. MAINS SUPPLY
This is provided via a 3 core flex to the electrical filter, fitted to a 3 amp fused supply on the
plug and must be earthed.
3. EARTH CONNECTIONS
Four earth connections must be connected to the following terminals:
Boiler Chassis
Gas Valve
Fan
Central Heating Pump.
The clock requires no earth.
4. FAN
The fan draws 55 watts and runs on 220/230v ac. It is operated by relay number 1 and fed
from J10 (blue & brown wires, non- polarised). It must be earthed at the fan and at the
PCB
5. CENTRAL HEATING CIRCULATION PUMP
The pump operates in both central heating and domestic hot water modes. Supply voltage
is 230V ac fed from J9 on the PCB (blue & brown). Always operate at number 3 speed.
If power is supplied to the boiler and the pump has not run for 24 hours the PCB will power
up the pump for 1 minute. In addition, should the temperature at the central heating
thermistor fall to 6 degrees Celsius, the pump will run until a temperature of 9 degrees
Celsius is achieved. This is classed as first stage frost protection. For further details on
pump overrun times see box charts on D.H.W. and C.H. service (page 26)

15
6. SPARK GENERATOR
The spark generator is located as a separate component on the gas valve and has two
functions.
1. To produce a high tension voltage to produce an ignition spark at the electrode
2. To supply the 230V ac from the PCB to the main gas valve solenoids. (See section
7&8)
The 230V ac fed from J8 (brown) is transformed to HT voltage by the spark generator and
the maximum duration of the spark is 18 seconds in 3 x 6 second sequences. The supply
voltage to the spark generator from the PCB ceases as soon as the ionisation electrode
detects the main burner flame has been established. The unit can be removed from the
gas valve by removing the forward facing self tapping screw located on the top of the unit,
this will then allow the unit to be unplugged from the gas valve.
N. B. Care must be taken when replacing the unit not to damage or bend the pins on the
gas valve solenoid.
7. & 8. GAS VALVE SOLENOIDS
The gas valve is fitted with twin solenoids moulded into a single removable unit. In order
for the gas valve to open and allow gas to the burner, both of the solenoids must be
energised. The supply voltage for this action is 230V ac and supplied from J8 (red / black)
on the PCB
To remove the solenoid from the gas valve remove the spark generator (see above) then
remove the central locating screw, this will allow the solenoid to be pulled away from the
gas valve.
N.B. faulty solenoids can be replaced, without the need to replace the complete gas valve.
(Part Number FCB 1501).
Nominal resistance values for the solenoids can be taken from the disconnected spark
generator plug J8.
EV1 = 0.84 kOhms (nominal) between black and blue (pins 4 and 3 on solenoid).
EV2 (small) = 7.00 kOhms (nominal) between red and blue (pins 1 and 3 on solenoid).

16
9. TEMPERATURE CONTROL P.C.B.
The temperature control PCB provides three types of functions for the boiler as follows.
1. on /off selection for domestic hot water / central heating /reset boiler after lock out
2. Temperature selection for either domestic hot water/central heating.
3. LED displays for standby / burner on / lockout display.
Maximum resistance value for P1 D.H.W is 5.20kΩ.
Maximum resistance value for P2 C.H. is 5.20kΩ.
Voltage is supplied to the PCB from J1 black at 5V dc.
Voltage readings between black/ blue (P1), range from 0V dc in off position to 4.20V dc in
the max position.
Voltage readings between black/ brown (P2), range from 0V dc in the off position to 4.20V
dc in the max position.
10. HYDRAULIC UNIT THREE-WAY VALVE MICRO SWITCH
This is located on the 3 way valve to the left hand side of the brass diaphragm housing. In
the central heating (C.H.) mode the switch is kept closed, as the tip of the switch rests on
the diaphragm push rod. When hot water is demanded the disc and push rod both move.
This releases the micro switch. Once this occurs the boiler is operating in the D.H.W.
mode.
In standby mode the supply voltage to the switch is 22V dc from J4 (blue)
In operation the voltage is 12.2V dc returning to the P.C.B. to J4 (brown)
11. AIR PRESSURE SWITCH
The air pressure switch proves that the fan is running and creating enough air flow through
the boiler for combustion. The correct operation of the switch is dependant on the plastic
venturi which is located at the top of the fan housing outlet.
In normal operation the fan creates an air flow though the venturi causing a pressure drop
inside the venturi. This is transmitted to the air pressure switch via the connecting tubes.
This causes the contacts within the switch to make, and the ignition process begins.
Voltage is supplied to the switch from J4 (21V dc) 3rd black from left
Voltage returns to PCB from the switch. J4 (21V dc) 4th black from left. This occurs when
switch contacts are closed.
If the contacts in the switch jam and remain in the closed position after the fan has stopped
running. Then the boiler will fail on the next ignition sequence and fault 1 will be displayed
after 15 seconds.
Connections of the air tubes to the switch are as follows.
Top tube from venturi to P2 on air pressure switch (left hand side) provides negative
pressure to switch from venturi

17
Bottom tube from venturi to P1 on air pressure switch (right hand side) provides positive
pressure to the air pressure switch.
To check for correct operation of the venturi place a manometer on one of test points
located on the top of the boiler. With the fan running note the reading on the manometer
and then take a 2nd reading from the other test point. The difference between the two
readings is the differential pressure.
Minimum differential pressure to activate the switch is 1.4mb.
Switch will deactivate as the differential pressure falls below 0.9 mb
Readings for a 600 mm horizontal flue in still air are:
REAR TEST POINT + 2mb = 3.9 mb
FRONT TEST POINT – 1.9mb
N.B. Contamination of the venturi by insects will prevent sufficient airflow to produce the
required pressure drop and will cause the boiler to lock out. Please see section 4 (fault
code 1) for more details.
13. ROOM THERMOSTAT CONNECTOR
Located within the PCB electronics box is the room thermostat connector block. Access to
the connector is via the small removable panel on the under side of the electronics box.
Voltage is fed from the PCB J4 22V dc (left hand black) and returns to the PCB J4 right
hand black via the time clock terminals 4 and 1. Voltage reduces to 12.5V dc when clock
and thermostat contacts are both closed.
N.B. Loose or poorly connected room thermostat link wires at the connector block will
cause problems with the heating demand, and will not be displayed as a fault code as the
failure is not a safety related mater.
15. MODULATING GAS SOLENOID VALVE
This is located on the main gas valve. It adjusts the burner pressure in proportion to the
temperature selected at the control panel, and the real time temperature values at the
thermistors.
Voltage is supplied from the PCB from J6 (lower 2 whites) as voltage to the solenoid
increases, the burner pressure will increase also. The voltage is measured in parallel at
the terminals at the solenoid.
Nominal figures are;
0.8V dc at minimum burner pressure (4.0 mb)
12.5V dc at maximum burner pressure (35.0 mb)
6.5V dc at ignition pressure (8.0 mb)
Resistance value of the coil with leads disconnected = 78 Ohms
The ignition pressure cuts as soon as the ionisation electrode detects that the main burner
flame has established.

18
16. IONISATION ELECTRODE
The ionisation electrode is located on the left hand side of the burner and is responsible for
detecting that a flame is present across the entire burner.
The electrode is reliant on the ability of the flame to conduct an electric current.
During combustion large numbers of free electrons and ions are present in the burner
flame, which acts as an electrolyte in which a current can flow.
The voltage to the electrode is supplied from the PCB 96V ac (J6 orange)
To check current connect a multimeter in series with the electrode. Select DC micro amps.
With the burner at maximum power expect 5 to 7 micro amps.
When the flame is detected the green neon will change from the solid green to a flashing
green to indicate that a flame has been detected along the full width of the burner.
17. HIGH LIMIT THERMOSTAT
Located on the front of the primary heat exchanger, the fully enclosed bi metal contacts
open if the temperature exceeds 102 degrees centigrade breaking the circuit to the PCB.
Voltage 22V dc is fed from the PCB (J6 second white) and returns to the PCB (J6 top
white) when the contacts are closed (normal position).
The high limit thermostat automatically resets as cooling takes place, but the boiler will
require the lockout (fault 3) to be manually reset at the control panel, before it will resume
normal operation.
N.B. The thermostat is dry mounted on the heat exchanger, (you can remove without
draining down). Never loosen or tighten using the electrical spade terminals.
21. DOMESTIC HOT WATER THERMISTOR
The thermistor screws into a wet pocket (under mains water pressure) at the hot outlet
side on the hydraulic unit and provides the PCB with the temperature of the domestic hot
water exiting the boiler.
As the temperature of the thermistor increases, the resistance decreases. This information
is used by the PCB and ensures that the gas valve modulates to achieve the correct
temperature as selected at the control panel.
In the domestic hot water mode the boiler has an operating range between 35 – 60
degrees centigrade during normal operation. If the thermistor detects a temperature
greater than 70 degrees centigrade then the boiler will shut down and the ignition
sequence will commence when the hot water temperature is lower than the selected
temperature.
If a fault develops on the hot water thermistor (out of range /false temp readings) lock out
will occur and fault code 10 will be displayed, if the thermistor cools to normal values then
the boiler will reset automatically.
If the thermistor fails to return to within normal range then the lock out will not reset and
the thermistor must be replaced.

19
Faulty domestic hot water thermistors will allow the boiler to operate in central heating
mode. If a demand for hot water is made during the heating sequence then the boiler will
lock out. (Fault 10). Values of the thermistor can be checked by measuring voltage in
parallel at J2 (black /black) with the power on at the boiler and the plug in situ on the PCB.
To check values by resistance, remove the multi pin plug from the P.C.B and check values
on the (black/ black) using 20 Ωrange.
IMPORTANT. The D.H.W. thermistor on the FEB-24E is the same type as the central
heating thermistor used on the FEB-20E. New thermistors are not supplied with the
sealing “O” ring. Please remove and re-use existing “O” ring.
22. CENTRAL HEATING THERMISTOR
The central heating thermistor is a clip on type, located either on the heating flow pipe
above the hydraulic unit or on later models on the top left hand side of the primary heat
exchanger. Temperature range for central heating is 60°C -85°C.
The thermistor detects the temperature of the heating circuit (primary circuit in D.H.W.
mode) and provides the initial over heat protection for the boiler at 105 °C with fault 6
displayed. A faulty thermistor affects both the central heating and hot water.
A thermistor that is out of range or open circuit will cause the boiler to lock out (fault 12)
As the thermistor cools and re-enters normal operating range reset will automatically take
place, if the thermistor is faulty or open circuit then it must be replaced.
The thermistor also provides frost protection for the boiler if a temperature of 6°c is
detected the pump will run until the temperature reaches 9°C if the temperature continues
to fall until the thermistor reads 3°C Then the boiler will ignite at minimum output until the
heating circuit temperature is 20°C. To check values of the thermistor use the same
procedure as for checking the D.H.W. thermistor, or gain access directly to the thermistor
via the boiler without the need for entering the PCB
TEMPERATURE 0C VOLTAGE (VOLTS) RESISTANCE (K
OHMS)
85 0.92 1.44
80 1.01 1.65
75 1.15 1.91
70 1.28 2.21
65 1.41 2.57
60 1.54 2.99
55 1.71 3.51
50 1.93 4.13
45 2.13 4.87
40 2.34 5.78
35 2.55 6.89

20
23. CENTRAL HEATING LOW PRESSURE SWITCH
Located on the on the return pipe (above the pump) the low pressure switch provides
protection for the boiler in the event of pressure loss in the primary system.
Voltage to the switch (22V dc) is supplied from the PCB junction J4 (left hand red wire)
and returns to the PCB J4 (right hand red wire). Providing the pressure in the boiler is
greater than 0.7 bar the contacts in the switch will be closed and the supply voltage will
return to the PCB J4 (left hand red).
Failure to detect sufficient pressure in the system will result in the boiler locking out with
fault 2 being displayed.
The switch has 3 terminals, however connections with the red wire should be made to
terminals marked “COM” and “NO”.
IMPORTANT. If using an un-insulated screwdriver to lever the terminals from the switch,
voltage from the switch terminals may short to boiler pipe work and damage the PCB.
25. GREEN LED POWER ON & BURNER FUNCTIONING
The green LED has two display modes:
A constant green light indicates the boiler is ready to supply hot water or central heating on
demand.
A flashing green light indicates the burner is firing and operating in either hot water or
central heating mode.
Voltage is supplied to the LED from the PCB J5 22V dc between (black and brown) when
in standby mode.
Voltage changes to pulse mode 22V dc to 0 v dc between (black and brown) when the
main burner flame is detected.
N.B. mains voltage is still present at the PCB until the supply voltage to the boiler is
isolated.
26. RED LED LOCK- OUT INDICATOR
In the event of a boiler malfunction the red LED will flash in a sequence of self diagnostic
fault codes to indicate the relevant fault with the boiler/system or components.
Voltage is supplied from J5 on the PCB 22V dc between (black and red) in the event of
lockout.