VOKERA Maxin 24e Release note

Installation
& Servicing
Instructions
THESE INSTRUCTIONS
TO BE RETAINED
BY USER
24e & 28e
British Gas Service Listed
G.C. No. 47 094 22 (24e)
G.C. No. 47 094 23 (28e)

1
MAXIN 24e & 28e
These appliances are designed for use with
a sealed heating system only and are not
intended for use on an open vented system.
The provision of stored domestic hot water is
possiblebytheadditionofanindirectcylinder
with 'S' or 'Y' plan controls.
A range-rating facility is incorporated in the
boiler for the central heating system in
conjunction with the electronic burner modu-
lation. The domestic hot water (dhw) service
utilisesadifferentialwaterpressurecontrol
combinedwith a 3 port diverter valveto give
hotwaterpriority.
TheVokèraMAXIN24e&28earecombined
centralheatinganddomestichotwater
appliances.By design they incorporate full
sequenceelectronicignition,circulating
pump,expansionvessel,safetyvalve,tem-
peraturegauge,pressuregaugeand3port
divertervalve.
Theyareproduced asaroomsealedappli-
ancessuitableforwallmountingapplications
only.Theyareprovidedwithafanpowered
flueoutletwithanannular co-axial combus-
tion air intake which can be rotated through
360 degrees. A vertical & twin flue option is
available, and they are also suitable for S.E.
duct installation.
SECTION 1 INTRODUCTION
Fig.1 General Layout
1 Flue Outlet
2 Air Intake & Restrictor Ring
3 Pressure Differential Switch
4 Silicone Pressure Tubes
5 Expansion Vessel
6 Main Heat Exchanger
7 Flame Sensing Electrode
8 Spark Electrode
9 Automatic Air Release Valve
10 Pump
11 Safety Valve
12 Domestic Heat Exchanger
13 Domestic Microswitch
14 Ignition Reset Button
15 Central Heating Temperature Control
16 Hot Water Temperature Control
17 Mode Selector Switch
18 Timeclock Aperture (optional)
19 Temperature/Pressure Gauge
20 Temperature Sensor (thermistor)
21 Diverter Valve
22 Domestic Distribution Manifold
23 Flow Switch (boiler)
24 Gas Valve & Ignition Control
25 Fan Overrun Thermostat
26 Safety Thermostat
27 Modulator Coil
28 Main Burner
29 Combustion Chamber
30 Fan Assembly
31 Air Chamber (with front removed)
32 Flue Gas Analysis Test Point
1
2
3
4
5
6
7
8
9
10
11
12
13
17
16
19
18
22
23
24
26
25
27
28
29
30
31
32
14
20
21
15

2MAXIN 24e & 28e
SECTION 2 DESIGN PRINCIPLES AND OPERATING SEQUENCE
Fig. 2
12
3
Note 2
Note
1
CHR
Notes
1. Differential pressure unit. Senses water
flow rate through the pump & main heat
exchanger and operates the flow
switch.(23)
2. Differential pressure unit. Senses domes-
tic hot water flow which operates the 3
port valve and domestic microswitch.
(13).
KEY:
CHF CentralHeatingFlow.
HWO Domestic Hot water outlet.
CWI Cold Water Inlet.
CHR CentralHeatingReturn.
2.1 Fig.1 illustrates the general layout of com-
ponents. Fig.2 illustrates the operating
principles described below.
2.2 Central Heating Mode
2.2.1 When the various switches and controls
impose a demand for heat, the pump is
started. The flow of water from the pump
operates a flow switch. This in turn ener-
gises the electronic circuitry. The fan is
started,the gas valve is energised at an
intermediaterateandtheelectronicignition
goesthroughanignitionattempt.
2.2.2 The burner ignition is checked by the elec-
troniccircuitrytoensurecorrectignitionof
the burner, once successful the electronic
control will allow the full rate of gas to flow
through the gas valve.
2.2.3 As water temperature increases this is
sensed by the temperature sensor on the
hydraulic section which modulates the
burner to the minimum set pressure.
2.2.4 Depending on the load, either the water
temperature will continue to rise, where
upon the burner is switched off, or the water
temperature will fall and the burner will
return to the maximum set pressure.
2.3 Domestic Hot Water Mode
2.3.1 The appliance will operate in domestic hot
water mode whenever the mode selector
switch is on regardless of mode selector
switch position and any demand for central
heating.
2.3.2 Opening a draw off tap will operate the dhw
differentialpressuredevicewhichin turn
operates the 3-port valve (21) and the dhw
flowswitch.
The three port valve diverts boiler water to
thedhwheatexchanger.
2.3.3 The dhw flow switch transfers control of the
burner to the dhw temperature control
potentiometer (15) which modulates the
burner output between high and low flame to
maintain an average heat input to suit the
dhwoutputrequired.
2.3.4 A fan overrun is incorporated in the boiler in
both c/h & dhw modes. The fan overruns
until the boiler water cools to approximately
80°C (176°F).
2.4 Safety Devices
2.4.1 In both central heating and hot water modes
safe operating is ensured by
A. Differential pressure units in both pri-
mary and dhw circuits which prevent burner
operation if water flow rates are too low.
B. A safety thermostat, which interrupts the
control circuit shutting off the gas valve. At
the same time the fan will still operate.
C. A Pressure differential switch in the flue
system to check the fans operation before
allowing ignition.
2.4.2 A safety valve is provided to relieve excess
pressure from the primary circuit.
CHF HWO CWI
10
24
5
6
30

3
MAXIN 24e & 28e
SECTION 3 TECHNICAL DATA
3.1 Units Dimensions and values are given in
the preferred Sl Units with Imperial units in
brackets where applicable.
3.2 Dimensions and Contents
Height 820mm (32.2in) appliance only.
980mm (38.7in) inc.horizontal flue.
Width: 450mm (17.7in)
Depth: 322mm (12.6in)
Weight empty 49kg (108lb)
full 52kg (114lb)
Water content: 3 litres (.66 gals)
for further dimensions see figs 12 - 16
3.3 Connection sizes
Heating flow and return: Threaded tail for
22mm bent tap connector (supplied).
Cold water inlet: Nut and olive for 15mm
o.d.
Hot water outlet: Nut and tail for 15mm
compression or capillary.
Gas Service: Rc ½ (½in BSP int)
Safety valve outlet: 15mm compression or
capillary.
Flue outlet/Air inlet: nom dia 60/100mm
specially supplied with boiler (concentric).
Flue outlet/Air inlet: nom dia 80/80mm
specially supplied with boiler (twin).
3.4 Installation Requirements
3.4.1 Clearances (Horizontal or Vertical Flue)
Minimum - above casing 225mm (9in)
Minimum - below casing 200mm (8in)
Minimum - In front 600mm (24in)
Minimum - At sides 12mm (½in) from
casing)
3.4.2 Maximum heating system contents approx.
76.4 litres (16.8 gals) Acceptance capacity
of expansion vessel 8 litres (1.8 gals).
3.4.3 Means of filling sealed system: To accord
with BS and/or local Water Authority re-
quirements.
3.4.4 The standard concentric horizontal flue
allows a maximum length of duct as fol-
lows:
Rear flue: 731mm (wall thickness)
Side flue: 890mm (to centre line of boiler).
Using extension tubes the flue may be
extended to the following lengths.
Concentric
24e: 4.5 metres max. (horizontal)
28e: 3.4 metres max. (horizontal)
24e 5.25 metres max. (vertical)
28e 4.4 metres max. (vertical)
Twin
24e& 28e 14/14 metres max. (horizontal)
24e&28e14/14metresmax.(vertical)
plusthehorizontalorverticalconcentric
terminal.
Thereductioninfluelengthforeachbend
used is listed opposite.
3.5 Electrical Details
Mains supply 230v ~ 50Hz Fused 3A
Internal fuse rating F2A
Power consumption: 125w.
3.6 Performance and Limitations 24e
Max. input 26.3 kW (89,735 Btu/h)(net)
Min. input 11.2 kW (38,225 Btu/h)(net)(c/h)
Min. input 9.8 kW (33,447 Btu/h)(net)(h/w)
Max. input 29.2 kW (99,658 Btu/h)(gross)
Min. input 12.4 kW (42,320 Btu/h)(gross)(c/h)
Min. input 10.8 kW (36,860 Btu/h)(gross)(h/w)
Max. output 23.7 kW (80,864 Btu/h)
Min. output 9.3 kW (31,740 Btu/h)(c/h)
Min. output 8.1 kW (27,645 Btu/h)(h/w)
Central Heating output range
Max. 23.7 kW (80,864 Btu/h)
Min. 9.3 kW (31,740 Btu/h)
3.7 Performance and Limitations 28e
Max. input 31.0 kW (105,802 Btu/h)(net)
Min. input 11.9 kW (40,614 Btu/h)(net)(c/h)
Min. input 10.5 kW (35,836 Btu/h)(net)(h/w)
Max. input 34.4 kW (117,406 Btu/h)(gross)
Min. input 13.2 kW (45,051 Btu/h)(gross)(c/h)
Min. input 11.6 kW (39,590 Btu/h)(gross)(h/w)
Max. output 28.0 kW (95,563 Btu/h)
Min. output 9.9 kW (33,788 Btu/h)(c/h)
Min. output 8.7 kW (29,692 Btu/h)(h/w)
Central Heating output range
Max. 28.0 kW (95,563 Btu/h)
Min. 9.9 kW (33,788 Btu/h)
3.8 Designed temp rise 20°C
Max. flow temperature 85°C
Fig.22 shows the relation between burner
pressure and input/output (N/G).
NOTE: Use gross input values when gas
rating the appliance (N/G).
3.8.1 L.P.G. instructions are to be found on pages
57 & 58.
BEND
90°
45°
REDUCTION IN FLUE
LENGTH FOR EACH
BEND
1000 mm
500 mm
CONCENTRIC FLUE:
BEND
90°
45°
REDUCTION IN FLUE
LENGTH FOR EACH
BEND
1000 mm
1000 mm
TWIN FLUE:

4MAXIN 24e & 28e
Working Pressures Heating System Hot Water System
Maximum 1.5bar/15m.wg/50ft wg 6.0bar/90psig
Minimum 0.5bar/5m.wg/16ft wg 0.6bar/7psig
Safetyvalvesetting 3bar/30m/102ft
Flow Rates
Min. water flow (dhw) 2.8 litres/min (0.6 gal/min)
Min. central heating flow rate through appliance 350 litres/h (1.28 gal/min).
Gas Control Valve: Basic Honeywell VK4105A 1027 1 220/240v CVI (Combined Valve and Ignition)
This unit is modified. The modification comprises a coil carried by the main burner regulation screw. For
full flame a voltage of approx. 12.5v dc is applied to the coil. For central heating max. rate the max.
voltage to the coil is restricted by an on site adjustment of a potentiometer.
3.9 Nominal hot water production
3.10 Central Heating Pump Duty
Min.GasRate
Max.GasRate 3.27 m3/h 115.8 ft3/h
1.10 m3/h 39.0 ft3/h
28e
24e
3.12 Burner Details (N/G)
Burner Pressure Min. C/H
24e 28e
PolidoroNP12 PolidoroNP14
12x 1.35 14 x 1.35
10.1 mbar 10.1 mbar
3.11 Gas Rates (N/G)
TEMPERATURE
RISE °C
35
30 11.3
9.7 11.5
13.4
24e 28e
FLOW RATE LITRES/MIN.
Fig. 3
Water
flow
l/h
Water
pressure
mbar
Burner Pressure Max.
1.9 mbar 1.6 mbar
Burner Pressure Min. DHW
MainBurnerInjectors
MainBurner
1.5 mbar 1.3 mbar
1.02 m3/h 36.37 ft3/h
2.78 m3/h 98.3 ft3/h
Pump pressure
Residual Pressure
Boiler pressure loss
0250 500 750 1000 1250
0
100
200
300
400
500

5
MAXIN 24e & 28e
SECTION 4 GENERAL REQUIREMENTS
4.0 General Requirements
This appliance must be installed by a compe-
tent person in accordance with the Gas
Safety(Installation&Use)Regulations1998.
4.1 RelatedDocuments
The installation of this boiler must be in
accordance with the relevant requirements
of the Gas Safety (Installation & Use)
Regulations1998theLocalBuildingRegula-
tions, the current l.E.E. Wiring Regulations,
theby-lawsofthelocalwaterundertaking,
and in Scotland, in accordance with the
BuildingStandards(Scotland)Regulation.In
Irelandthelocalbuildingregulations(IE).
It should be in accordance also with any
relevantrequirementsofthelocalauthority
andtherelevantrecommendationsofthe
followingBritishStandardCodesofPractice:
4.2 Location of Appliance
Thecombinationboilermaybeinstalledin
anyroomorinternal space,althoughparticu-
lar attention is drawn to the requirements of
the current l.E.E. Wiring Regulations, and in
Scotland,the electrical provisions of the
Building Regulations, with respect to the
installation of the combination boiler in a
roomor internal space containing a bath or
shower.
Wherearoom-sealed applianceisinstalled
in a room containing a bath or shower, any
electricalswitchorappliancecontrol,utilising
mains electricity, should be located in such a
position that it cannot be touched by a
person using the bath or shower.
The location chosen for the boiler must
permit the provision of a satisfactory flue and
termination. The location must also permit an
adequateair supply for combustion purposes
and an adequate space for servicing and air
circulationaround the boiler.
Where the installation of the boiler will be in
an unusual location special procedures may
be necessary and BS 6798:1987 gives
detailed guidance on this aspect.
Pipework from the meter to the boiler must
be of adequate size. Pipes of a smaller size
than the boiler inlet connection should not be
used.
The complete installation must be tested for
soundnessasdescribedintheabove code.
N.B. If the gas supply for the boiler serves
other appliances ensure that an adequate
supply is available both to the boiler and the
other appliance when they are in use at the
same time.
4.4 Flue System
The terminal should be located where
dispersal of combustion products is not
impeded and with due regard for the damage
or discoloration that might occur to building
productsinthevicinity(seefig 4).
The terminal must not be located in a place
where it is likely to cause a nuisance.
In cold and/or humid weather water vapour
may condense on leaving the flue terminal.
The effect of such ‘steaming’ must be
considered.
A compartment used to enclose the boiler
must be designed and constructed specifi-
cally for this purpose. An existing cupboard
or compartment may be used provided that
it is modified for this purpose.
Detailsofessentialfeaturesofcupboard/
compartment design including airing cup-
boardinstallationsaregiveninBS
6798:1987. This appliance is not suitable for
externalinstallation.
4.3 Gas Supply
A gas meter is connected to the service pipe
by the local gas supplier.
An existing meter should be checked,
preferably by the gas supplier to ensure that
the meter is adequate to deal with the rate of
gassupply required for all appliances it
serves.
Installationpipesshould be fitted in accord-
ancewithBS6891:1988.
BS 6891 1988 Low pressure installation pipes
BS 6798 1987 Boilers of rated input not exceeding 60kW.
BS 5449 Part 1 1990 Forced circulation hot water systems
BS 5546 1990 Installation of gas hot water supplies
for domestic purposes (2nd family gases).
BS 5440 Part 1 1990 Flues.
BS 5440 Part 2 1989 Flues & Ventilation.
BS 7074 Part 1 1989 Application, selection & installation of expansion
vessels & ancillary equipment for sealed water
systems.

6MAXIN 24e & 28e
For protection of combustibles, refer to BS
5440:1 where the terminal is less than 2m
(6.6ft) above a pavement or platform to
which people have access (including any
balcony or flat roof the terminal must be
protected by a guard of durable material).
AsuitableguardisavailablefromVokèra Ltd.
Part No 018, G.C. No. 301 106
Thisguardmustbefittedcentrallyoverthe
terminal.Markthepositions ofthefixings,
drill the wall and secure using wall plugs and
3 of 1½" No.8 plated screws.
4.6 Water Circulation (Central Heating)
Detailedrecommendationsare given in
BS 6798:1987 and BS 5449:1:1990 (for
smallbore and microbore central heating
systems).
4.6.1 Thefollowingnotesaregivenforgeneral
guidance.
4.6.2 Pipework
Copper tubing to BS 2871:1:1971 is recom-
mended for water pipe. Jointing should be
either by capillary soldered or with compres-
sionfittings.
Where possible, pipes should have a gradi-
ent to ensure air is carried naturally to air
release points and water flows naturally to
draintaps.
It should be ensured as far as possible that
the appliance heat exchanger is not a natural
collecting point for air.
Exceptwhereprovidingusefulheat, pipes
should be insulated to prevent heat loss and
toavoidfreezing.Particular attention should
bepaidtopipespassing through ventilated
spaces in roofs and under floors.
4.6.3 By-Pass
An automatic by-pass is incorporated in the
boiler and systems should be designed to
ensure that with only one radiator turned on a
flow rate of at least 350 litres/hour (1.28 gals/
min)isachievedthroughthe boiler see6.9.4
4.6.4 SystemDesign
Figs 5 & 5a illustrates typical system lay-
outs showing options of either, pipe connec-
tion from below as fig. 5, or pipe connection
from above utilising the purpose made duct
in the rear frame of the appliance.
4.6.5 Draining Taps
These must be located in accessible posi-
tions to permit the draining of the whole
system. The taps must be at least 15mm
nominal size and manufactured in accord-
ancewithBS2879:1980.
Fig. 4
4.5 Air Supply
The following notes are intended for general
guidance.
Theroomsealedfanfluedboilerdoesnot
require a permanent air vent for combustion
airsupply.
Where installed in a cupboard or compart-
ment ventilation is not required.
Terminal position for fan assisted boiler
(minimum distance) mm
A - Directly below an open window or other 300
opening (e.g. air brick)
B - Below gutters, soil pipes or drain pipes 25
C - Below eaves 25
D - Below balconies or car port roof 25
E - From vertical drain pipes and soil pipes 75
F - From internal or external corners 25
G - Above ground or below balcony level 300
H - From a surface facing a terminal 600
I - From a terminal facing a terminal 1200
J - From an opening in the car port (e.g. door
window) into dwelling. 1200
K - Vertically from a terminal on the same wall 1500
L - Horizontally from a terminal on the same wall 300
M - Horizontally from a vertical terminal to a wall 300
N – Horizontally from an opening, airbrick, openable
window, etc. 300
NOTE: The flue must be terminated in a place not likely
to cause a nuisance.

7
MAXIN 24e & 28e
N.B. Vokèra Ltd recommend a 2-pipe system. Single pipe systems are more liable to be troublesome unless
carefullly designed and installed.
Fig. 5a
Shower
Boiler Hot Water
Outlets
Radiator
Fig. 5
Gas Supply
Pipe Cold Water
Inlet
Radiator
Shower
Cold Water
Inlet
Gas Supply
Pipe
Boiler
Hot Water
Outlets

8MAXIN 24e & 28e
Fig. 6
Cold Water
Inlet Central Heating
Return
Fig. 6a
Hot Water
Outlet
C/H Flow
Valve
Cold Water
Inlet Stop-
cock
Gas
Cock
Bent Tap
Connectors
(special) C/H Return
Valve
4.6.6 Air Release Points
These must be fitted at all high points where
air will naturally collect, and must be sited to
facilitate complete filling of the system.
4.6.7 Theappliancehasanintegralsealedexpansion
vessel to accommodate the increase of water
volume when the system is heated. It can
accept up to 8 litres (1.8gals) of expansion
water. If the appliance is connected to a
system with an unusually high water content.
Calculate the total expansion and add addi-
tional sealed expansion capacity as appropri-
ate.
In general, modern systems will present no
problem.
4.6.8 Filling Point
A method for initially filling the system and
replacing water lost during servicing must be
provided, and it must comply with local water
authority regulations.
A method is shown in fig. 6 using the Vokèra
filling loop which is acceptable in most areas.
In the event that this method is not suitable in
a particular area, contact the local authority
for preferred methods.
Analternativemethodwouldbefrom an inde-
pendentmake up vessel or tank mounted in a
position 1m higher than the highest point of
the system & with a minimum static head
(from the top of the boiler to the water level of
the feed tank) of 5m. The cold feed pipe must
have an approved non return valve and stop-
cock so the tank can be isolated from the
system after filling. The feed pipe should be
connectedtothecentralheatingreturnpipeas
close to the boiler as possible.
4.7 Electrical Supply
The appliance is supplied for operation on
230V ~ 50Hz electricity supply. It should be
protected with a 3-amp fuse.
THIS APPLIANCE MUST BE EARTHED.
The method of connection to the mains elec-
tricity must allow complete isolation from the
supply.
The preferred method is by using a fused
double pole switch with a contact separation
of at least 3mm.
The switch must supply ONLY the appliance
and immediate electrical control circuits (e.g.
programmer/room thermostat)
Alternatively, use an unswitched shuttered
socket outlet with a fused 3-pin plug both
complying with BS 1363.
4.8 Showers
If a shower control is to be supplied from the
combinationunititshouldbeofthetypewhich
incorporates a thermostatic control and by
design is suitable for use with a combination
boiler.Checkapplicationwithshowermanufac-
turer.

9
MAXIN 24e & 28e
SECTION 5 INSTALLATION
5.1 Delivery (fig. 7)
The appliance is delivered in a heavy duty
cardboard carton.
Lay the carton on the floor with the writing the
correct way up.
5.2 Unpacking (fig. 8)
Pull both sides of the carton open. Do not use
a knife. Unfold the rest of the carton from
around the appliance.
Lay the appliance with the black frame on the
floor.Removethetwo polystyreneblocksone
at the top and the other at the base of the
appliance.
Remove the hanging bracket from the top
polystyrene block and the box containing the
fixing kit from the lower polystyrene block.
The fixing kit contains
1-Hangingbracket
1 - Fittings pack containing:
Central heating valves & tap connectors (2)
Gas service tap (1)
Cold water stopcock (1)
Hot water outlet (1 nut & tail)
Variouswashers
Flue Kit supplied in separate carton.
5.3 Preparing for Mounting
5.3.1 Remove the 2 screws securing the front con-
trol panel and remove the 2 screws securing
thelower part of the casing to the case frame.
5.3.2 Slightly lift the casing and slide it gently to-
wards the top of the appliance to disengage
thecasefromthetop suspension hooks.(Fig.
9)
5.3.3 Ensure the casing and screws are put to one
side in a safe place.
5.3.4 Loosely fit (hand tight) the valves and fittings
using the washers supplied (Figs. 6a & 10).
C/H
Flow
D/H/W
Outlet Cold
Water
Inlet
C/H
Return
Safety
Valve
Outlet
Gas
Fig. 7
Fig. 8
Fig. 9
Fig. 10

10 MAXIN 24e & 28e
5.4 Preparation for mounting the appliance
Theapplianceshouldbemountedonasmooth,
vertical surface, which must be capable of
supportingthefullweightoftheappliance. Care
should be exercised when determining the
position of the appliance with respect to hidden
obstructions such as pipes, cables, etc.
When the position of the appliance has been
decided–usingthetemplatesupplied–carefully
markthepositionofthefixingjig/mountingbracket
assembly(seefig.11)andflue-hole(ifapplicable).
5.4.1 Important
Thereare two holes on the template. Thelower
hole should be used with the telescopic flue kit
(part no. 0225705 & 0225710). The upper hole
is for use with all other horizontal flue kits.
5.4.2 Maximum flue lengths
5.5 Fitting the fl ue
The top flue outlet permits both horizontal and
vertical flue applications to be considered,
alternatively, the Vokera twin flue system can be
utilised if longer flue runs are required.
5.5.1 Concentric horizontal flue
(For concentric vertical flue, see 5.5.2)
(For twin flue applications, see 5.5.3)
The appliance flue outlet elbow can be rotated
through360ºonitsverticalaxis. Inadditiontheflue
may be extended from the outlet elbow in the
Fig. 11
type 1 = centre of rear flue hole
using only 0225705 or
0225710 flue
type 2 = centre of rear flue hole
for all other flues
Reduction for bends
Bend Reduction in maximum flue length
for each bend
45º bend 0.5 metre
90º bend 1.0 metre
Flue system Maxin 24e Maxin 28e
Concentric Horizontal 3.4m 4.5m
Concentric Vertical 4.4m 5.25m
Twin flue 14m/14m 14m/14m
+ terminal + terminal
Horizontal flue terminals and accessories
Part No. Description Min-Max Length
0225705 Standard telescopic flue 380mm – 600mm
(Dimension ‘X’)
0225710 Extended telescopic flue 600mm – 920mm
(Dimension ‘X’)
2359029 Horizontal flue kit 833mm
For use with add. (Dimension ‘X’)
Bends & extensions
2359069 750mm extension 750mm
2359079 1500mm extension 1500mm
2359049 45º bend (pair) N/A
2359059 90º bend N/A
0225760 Wall bracket (5) N/A
horizontalplane(see5.4.2),howeveriftheflueisto
beextendedoradditionalbendsaretobefitted,the
standard horizontal flue kit (part no. 2359029)
must be used. A reduction must also be made to
themaximumlength (seetable)whenadditional
bends are used.
U sing the template provided (see 5.4.1), mark
anddrilla125mmholeforthepassageoftheflue
pipe. The hole should have a 1º drop from the
boiler to outside, to eliminate the possibility of
rainwater entering the appliance via the flue.
The fixing holes for the wall-mounting bracket &
jig should now be drilled and plugged, an
appropriatetypeandquantityoffixingshouldbe
used to ensure that the bracket is mounted
securely.
Once the bracket & jig has been secured to the
wall, mount the appliance onto the bracket.
FITTING THE TELESCOPIC FLUE KIT
(0225705 & 0225710)
Carefullymeasurethedistancefromthecentre
of the appliance flue outlet to the face of the
outside wall (dimension ‘X’ see fig. 12). Add
50mm to dimension ‘X’ to give the overall flue
length (dimension ‘Y’). Using the complete
telescopic flue assembly adjust the length to
suit dimension ‘Y’. Once the telescopic flue
terminal has been adjusted to the correct
length, secure the flue assembly with the
screw supplied.
NOTE
The flue restrictor ring (see fig. 1) must be
removed or discarded prior to attaching the
flue bend to the appliance.

11
MAXIN 24e & 28e
Fig. 13
Fig. 12
Insert the flue assembly into the previously
drilled flue hole and locate the flue bend over
the appliance flue outlet. Push the flue bend
downovertheapplianceflueoutletandensure
thecorrectsealismade. Pulltheflueassembly
towards and over the flue bend – using a
twisting action – ensuring the correct seal is
made.Checkthattheterminalprotrudes past
the finished outside wall by the correct length
(115mm).
NOTE
Youmustensurethattheentirefluesystemis
properly supported and connected.
Sealtheflueassemblytothewallusingcement
or a suitable alternative that will provide
satisfactoryweatherproofing. Theinteriorand
exterior trim can now be fitted
FITTING THE STANDARD (2359029)
HORIZONTAL FLUE KIT (see 5.4.1)
Carefullymeasurethedistancefromthecentre
of the appliance flue outlet to the face of the
outsidewall(dimension‘X’seefig.13). Ensure
theinner(60mm)pipeisfullyinsertedintothe
outer (100mm) pipe (when the inner pipe is
fullyinserted,itstandsproudoftheouter pipe
by7.5mm).Add32mmtodimension‘X’togive
the overall flue length (dimension ‘Y’). The
standardhorizontalfluekit(part no.2359029)
is suitable for a distance (dimension ‘Y’) of up
to 865mm.
NOTE
Dimension‘Y’ismeasuredfromtheendofthe
terminaltotheendoftheouter(100mm) pipe.
The internal trim should be fitted to the flue
pipe before connection of the 90º bend.
If the horizontal flue kit (2359029) requires to
be cut to the correct size (dimension ‘Y’), you
mustensurethattheinner(60mm)pipestands
proud of the outer (100mm) pipe by 7.5mm
(see fig. 13A). Ensure any burrs are filed or
removed and that any seals are located
properly before assembly.
Connecttheinner(60mm)pipeoftheterminal
assembly to the push-fit end of the 90º bend
(supplied) using a twisting action. Insert the
assembledflueintothepreviouslydrilledhole.
Usingtheclips&screwssupplied,connectthe
flue assembly to the boiler, ensuring that the
terminal protrudes past the finished outside
wall by the correct length (135mm).
Youmustensurethat theentirefluesystemis
properly supported and connected.
Sealtheflueassemblytothewallusingcement
or a suitable alternative that will provide
satisfactory weatherproofing. The exterior
trim can now be fitted.
EXTENDING THE HORIZONTAL FLUE
If the horizontal flue requires extension/s or
additional bend/s, the horizontal flue terminal
kit (2359029) must be used. Connect the
bend – supplied with the terminal kit – to the
top of the boiler using the clips, screws, &
gaskets supplied. The additional bends &
extensions have an internal push-fit
connection, care should be taken to ensure
thatthecorrectsealismadewhenassembling
thefluesystem.Connecttherequirednumber
offlueextensionsorbends(uptothemaximum
equivalent flue length) to the flue terminal
using the clips, screws, & gaskets supplied
(see fig. 13 & 13A).
IMPORTANT
The flue restrictor ring (see fig. 1) must be
removed or discarded if the total flue length –
including bends – exceeds 1.0m.
NOTE
Whencuttingthehorizontalflueterminaloran
extension to the required length, you must
ensure that the excess is cut from the plain
end of the terminal or extension, and that the
inner(60mm)pipeis7.5mmlongerthanouter
(100mm) pipe (see fig. 13 & 13A). Remove
anyburrs,andcheckthatanysealsarelocated
properly.

12 MAXIN 24e & 28e
5.5.3 Twin flue system
The Vokera twin flue system enables greater
fluedistancestobeachieved(see5.4.2)than
thatofthestandardconcentricfluesystem. It
can be used for horizontal or vertical
applications, however the twin flue system
mustbeconvertedtothededicatedconcentric
flue kit for termination. It is essential that the
installation of the twin flue system be carried
outinstrictaccordancewiththeseinstructions.
Guidance notes on twin flue installation
••
••
•The flue must have a fall back of 1º back to
the appliance to allow any condensate that
may form in the flue system to drain via the
condensatedrain. Considerationmustalso
Using the dimensions given in fig. 14 as a
reference, mark and cut a 105mm hole in the
ceiling and/or roof.
Fit the appropriate flashing plate to the roof
andinserttheverticalflueterminalthroughthe
flashing plate from the outside, ensuring that
the collar on the flue terminal fits over the
flashing.
Thefixingholesforthe wall-mountingbracket
& jig should now be drilled and plugged, an
appropriate type and quantity of fixing should
beusedtoensurethatthebracketismounted
securely. Oncethebrackethasbeensecured
to the wall, mount the appliance onto the
bracket & jig.
IMPORTANT
Theverticalflueterminalis1.0metreinlength
and cannot be cut; therefore it may be
necessarytoadjusttheheightoftheappliance
to suit or use a suitable extension.
Removeordiscardthefluerestrictorringfrom
theapplianceflueoutlet(seefig.1),ifthetotal
Bend Reduction in maximum flue length for
each bend
45º bend 0.5 metre
90º bend 1.0 metre
Part No. Description Length
2359039 Vertical flue terminal 1.0 metre
0225770 Pitched roof flashing N/A
plate
0225765 Flat roof flashing plate N/A
2359069 750mm extension 750mm
2359079 1500mm extension 1500mm
2359049 45º bend (pair) N/A
2359059 90º bend N/A
0225760 Wall bracket (5) N/A
You must ensure that the entire flue system is
properly supported and connected.
Sealtheflueassemblytothewallusingcement
or a suitable alternative that will provide
satisfactory weatherproofing. The interior and
exterior trim can now be fitted.
5.5.2 Concentric vertical flue
The vertical flue terminal can be connected
directlytotheapplianceflueoutlet. Alternatively,
an extension or bend can be connected to the
appliance flue outlet if desired (see 5.4.2),
howeverifadditionalbendsarefitted,areduction
mustbemadeto themaximumfluelength(see
table below).
Reduction for bends
flue length – including the allowance for any
additional bends – exceeds 1.0 metre.
Connect the vertical flue assembly to the
boiler flue spigot using the 60mm & 100mm
clips, gaskets, & screws (supplied), ensuring
the correct seal is made. The flue support
bracket(suppliedwiththeverticalflue kit) can
now be fitted.
If the vertical flue requires extension/s or
additionalbend/s,connecttherequirednumber
offlueextensionsorbends(uptothemaximum
equivalentfluelength)betweentheboilerand
vertical flue assembly (see fig. 13A).
NOTE
When cutting an extension to the required
length,youmustensure thattheexcessiscut
from the plain end of the extension and that
the inner (60mm) pipe is 7.5mm longer than
outer (100mm) pipe (see fig. 13A). Remove
anyburrs,andcheckthatanysealsarelocated
properly.
Youmustensurethat theentirefluesystemis
properly supported and connected.
Vertical flue terminal and accessories
Fig. 14

13
MAXIN 24e & 28e
Bend Reduction in maximum flue length for
each bend
45º bend 1.0 metre
90º bend 1.0 metre
Part No. Description Length
0225805 Horizontal flue terminal 1.0 metre
0225810 Vertical flue terminal 1.0 metre
300 Twin adapter kit N/A
0225770 Pitched roof flashing plate N/A
0225765 Flat roof flashing plate N/A
0225815 Condensate drain kit N/A
0225820 0.25m extension (pair) 250mm
0225825 0.5m extension (pair) 500mm
0225830 1.0m extension (pair) 1000mm
0225835 2.0m extension (pair) 2000mm
0225840 45º bend (pair) N/A
0225845 90º bend (pair) N/A
0225850 Twin bracket (5) N/A
0225855 Single bracket (5) N/A
begiventothefactthatthereisthepossibility
of a small amount of condensate dripping
from the terminal.
••
••
•Ensure that the entire flue system is ad-
equately supported, use at least one
bracket for each extension.
••
••
•The entire flue system must be adequately
insulated to maintain heat within the flue
system thereby reducing the possibility of
condensateproduction.
••
••
•As the exhaust outlet pipe can reach very
high temperatures it must be protected to
prevent persons touching the hot surface.
Reduction for bend
Mounting the boiler
Thefixing holes for the wall-mounting bracket
& jig should now be drilled and plugged, an
appropriate type and quantity of fixing should
beusedtoensure thatthebracketismounted
securely. Oncethebrackethasbeensecured
to the wall, mount the appliance onto the
bracket & jig.
5.5.3.1 Installation of twin adaptor kit (fig. 15)
Twin flue accessories
Fig. 15
•Remove or discard the flue restrictor ring
from the appliance flue outlet (see fig. 1).
•Insertthesmallrestrictorring(suppliedwith
the twin adapter kit) if the total flue length –
including the allowance for any bends – is
less than 8 metres.
•Inserttheexhaustconnectionmanifoldonto
the appliance flue outlet.
•Place the silicone seal (supplied with twin
adapter kit) over the rim of the exhaust
connection manifold.
⇑⇑
⇑⇑
⇑Removeoneoftheblankingplates(located
totheleft&rightoftheappliance flueoutlet)
and–usingthesamescrews–installtheair
baffle.
5.5.3.2 Installation of condensate drain kit
(fig. 16)
Fig. 16
The condensate drain kit must be fitted within
1 metre of the appliance flue outlet. It is
recommended that the condensate drain kit
should be fitted in the vertical plane, however
it can be fitted horizontally with care.
••
••
•Fit the first bend to the condensate drain kit
or exhaust connection manifold by firmly
pushing in to position.
••
••
•Using the two holes in the exhaust connec-
tion manifold as a guide, drill a 3mm hole in
eachandsecureusingthescrewsprovided.
•Connect the air inlet pipe to the air baffle as
above.
•Thetwinfluepipesextensionsandaccesso-
ries can now be installed by pushing to-
gether (the plain end of each extension or
bendshouldbepushedapproximately50mm
intothefemalesocketofthepreviouspiece).
The condensate drain trap must be con-
nectedtothedraininaccordancewithBuild-
ing Regulations or other rules in force.
5.5.3.3 Horizontal termination ( fig. 17)
Thetwinfluesystemmustbeconvertedtothe
dedicated concentric flue kit for termination.
•The horizontal terminal is supplied with a
built-in converter box and cannot be
shortened.

14 MAXIN 24e & 28e
Fig. 18
NOTE
••
••
•Before cutting twin flue pipes ensure allow-
ances have been made for connection onto
thepreviouspieceandontotheconcentricto
twinconverter. Thelasttwinfluepipesmust
be pushed 50mm onto the male spigots of
the concentric to twin converter.
NOTE
Youmustensurethat theentirefluesystemis
properly supported and connected.
When cutting an extension to the required
length, you should ensure that the excess is
cutfromtheplainendoftheextension. Remove
any burrs, and check that both seals are
located properly.
Seal the flue terminal assembly to the wall
usingcementorasuitablealternativethat will
provide satisfactory weatherproofing. The
interior and exterior trim can now be fitted.
5.5.3.4 Vertical termination (See fig. 18)
Thetwinfluesystemmustbeconvertedtothe
dedicated concentric flue kit for termination.
•Theverticalterminalissupplied with abuilt-
in converter box and cannot be shortened.
•A130mmholeisrequiredforthepassageof
the concentric terminal through the ceiling
and/or roof.
Depending on site conditions it may be
preferable to install the terminal assembly
prior to fitting the twin flue pipes.
Fit the appropriate flashing plate to the roof
andinserttheverticalflueterminalthroughthe
flashing plate from the outside, ensuring that
the collar on the flue terminal fits over the
flashing.
Push-fitthetwinfluepipesontotheconcentric
to twin converter ensuring that the exhaust
pipe connects to the exhaust connection on
the concentric to twin converter.
If necessary cut the plain ends (male) of the
Fig. 17
•A130mmholeisrequiredforthepassageof
the concentric terminal through the wall.
Depending on site conditions it may be
preferable to install the terminal assembly
prior to fitting the twin flue pipes.
Markanddrilla130mmholeforthepassage
ofthe horizontal flue terminal, ensuring that
thereisa1ºfallbacktotheboiler(17mmper
1000mm). Inserttheterminalassemblyinto
the flue hole.
Push-fitthetwinfluepipesontotheconcentric
to twin converter ensuring that the exhaust
pipeconnectstotheexhaustconnectionon
the concentric to twin converter.
Ifnecessarycuttheplainends (male) ofthe
twin flue pipes to allow connection to the
concentric to twin converter.
twin flue pipes to allow connection to the
concentric to twin converter.
NOTE
••
••
•Before cutting twin flue pipes ensure allow-
ances have been made for connection onto
thepreviouspieceandontotheconcentricto
twinconverter. Thelasttwinfluepipesmust
be pushed 50mm onto the male spigots of
the concentric to twin converter.
••
••
•Youmustensurethattheentirefluesystem
is properly supported and connected.
••
••
•Ensure that any horizontal sections of pipe
have a 1º fall towards the appliance (17mm
per 1000mm).
••
••
•The convertor box on the vertical terminal
will have to be temporarily removed when
inserting the terminal through the flashing.
••
••
•The condensate trap must be primed with
water prior to commissioning the boiler.
•The condensate drain trap must be con-
nectedtothedraininaccordancewithbuild-
ing regulations or other rules in force.

15
MAXIN 24e & 28e
5.6 Connecting the Gas and Water
5.6.1 Figs. 10 and 16 show the locations of the
fittings.
5.6.2 Do not over tighten nuts and use another
spanner to apply counter force to avoid
damaging the appliance
5.6.3 Gas Supply
Connectingthegassupply.
Connect a 15mm gas pipe to the gas service
tap and tighten the union nut securing the tap
to the appliance.
5.6.4 Central Heating
Connect the central heating pipework (22mm
o.d) to the respective valves, right hand =
return, left hand = flow, and tighten the
nuts.
5.6.5 Hot Water
Provide a suitable coupling and connect the
hot water draw-off pipe to the 15mm o.d tail.
Tightenthenut.
If the hot water system does not include a tap
below the hot water outlet connection provide
a suitable drain tap to permit draining of the
appliancehotwatersideduringservicing.
5.6.6 Cold Water
Connect a 15mm cold water service pipe to
the inlet stopcock of the appliance. Tighten
thenut.
If the cold water supply is liable to large
pressure fluctuations, a flow/pressure
regulator should be fitted in the supply pipe.
5.6.7 Safety Valve Discharge
The safety valve is located beneath the
pump. Connect discharge pipe to the 15mm
o.d. tail (using a compression fitting).
When connecting, ensure the discharge
pipe does not restrict access to or operation
of the central heating return valve. The
discharge should terminate facing down-
wards exterior to the building in a position
where discharging (possible boiling) water
will not create danger or nuisance; but in an
easily visible position.
5.7 Electrical Connections
5.7.1 The electricity supply must be as specified
in clause 4.7. If controls external to the
appliance are required, design of the
external electrical circuits should be under-
taken by a competent person.
See Section 10 for further advice.
N.B. IT IS ESSENTIAL THAT ALL EXTER-
NAL CONTROL CIRCUITS AND WIRING IS
WIREDFROMTHESAMEELECTRICAL
ISOLATORASSERVESTHEAPPLIANCE.
Factoryfitted internal wiring must not be
disturbed when wiring external controls.
5.7.2 To gain access to the electrical terminals
Remove finger guard by releasing four
securing screws (fig 18a), hinge down the
control fascia. (fig. 19a) until it rests in an
approximately horizontal position.
Remove electrical cover by releasing four
securing screws.
The mains input terminal block is the left
hand block located on the front control facia
(see fig. 19a).
5.7.3 The electricity supply cable from the isolator
and the appliance terminal block must be 3
core flexible sized 0.75mm² (24 x 0.2mm) to
table15-16,BS6500.
Wiring to the appliance should be rated for
operation in contact with surfaces up to
90°C.
Fig. 19
Gas Cock Open
Gas Cock Closed
Fig. 18A Finger Guard
Securing Screws

16 MAXIN 24e & 28e
5.7.4 Pass the cable through one of the cord
anchorage points and connect the wires
Brown to L, Blue to N, and Green/Yellow to
, arrange the cable so that should the
cable slip the anchorage the current carry-
ing conductors become taut before the
earthing conductor.
5.7.5 Securely tighten all terminal screws and
arrange the cable with slack between the
cable anchor and the terminal block.
Tighten the cord anchorage screw until the
cable is secure.
5.7.6 Neatly arrange the external cable in such a
waythat unrestricted opening of the controls
fasciaispossible without strain on the cable.
5.7.7 External controls may be wired from termi-
nals 1 to 2 on the left hand terminal block
mounted on the back of the front fascia panel
afterremovingthefactoryfitted links(seefig.
19A). If a neutral is needed use the terminal
marked N on the terminal strip.
Internal controls (ie. Vokèra time clock) may
be wired from the right hand terminal block
mounted on the back of the front facia after
removing the factory fitted link between 4 &
5. See section 10.
If required pass the external controls cable
through the spare cord anchorage and
arrange the cable so that should the cable
slip the anchorage, the current carrying
conductors become taut before the earthing
conductor.
Fig. 19A
Control panel securing screws
Mains Input &
External Controls
Terminal Block
Internal Controls
Terminal Block

17
MAXIN 24e & 28e
SECTION 6 COMMISSIONING
6.1 Where the text bears identifying numbers in
brackets, refer to figs. 1 and 2 unless other-
wise instructed.
6.2 Gas Supply Installation
Inspecttheentireinstallationincludingthe
meter, test for soundness and purge, all as
describedinBS6891:1988.
6.3 Central Heating Systems
6.3.1 IMPORTANTDONOTRELEASEAIRFROM
THEREDSEALEDEXPANSION TANK.Itis
charged with air at the factory from .75 - .80
bar(11-12psig)
6.3.2 Initial filling of the System
6.3.2.1 See 3.4.3 and 4.6.8
6.3.2.2 Opencentralheatingflowandreturnvalves(if
the indicating line on the square shank is in
line with the valve it indicates open, across
thevalve indicates closed). Unscrew black
cap on automatic air release valve (9) one
fullturn(leaveopenpermanently).
6.3.2.3 Close all air release taps on the central
heating system.
6.3.2.4 Gradually open stopcocks at the filling point
connection to the central heating system until
water is heard to flow. Do not open fully.
6.3.2.5 Startingwiththelowestradiatoropeneach
air release tap in turn closing it only when
clear water, free of bubbles, flows out. In the
same away release air from any high points
inthepipework.
6.3.2.6 Continue filling the system until at least 1.0
bar registers on the gauge then turn off the
filling point stopcocks.
6.3.2.7 Inspect the system for water soundness and
remedyanyleaksdiscovered.
6.3.4 Setting the System Design Pressure
6.3.4.1 The design pressure must be a minimum of 1
barand maximum 1.5 bar.
6.3.4.2 Theactualreadingshouldideally be 1bar
plus the equivalent height in metres to the
highest point of the system above the base of
the appliance up to the maximum of 1.5 bar
total ).
N.B. The safety valve is set to lift at 3bar /
30m / 45psig.
6.3.4.3 To lower the system pressure to the required
value, turn the red knob of the safety valve
(11) a quarter turn to release water until the
required figure registers on the gauge (19).
6.3.5 Filling the Hot Water System
6.3.5.1 Close all hot water draw-off taps.
6.3.5.2 Open cold water inlet stopcock (see fig. 6a)
6.3.5.3 Slowly open each draw-off until clear water
is discharged.
6.4 Checking Electricity Supply
6.4.1 Carry out preliminary checks for continuity,
polarity, and resistance to earth (see page
57),gaining access as required according to
5.7.2 in this manual.
6.4.2 Leavetheappliancewiththecontrolfascia
closedandwiththemainselectricityswitched
OFF
6.5 Lighting the Boiler
6.5.1 Ensureflowandreturnvalvesareopen
(6.3.3.2)
Ifexternaland/orinternalcontrolsarefitted
(e.g Timeclock and/or Room thermostat)
ensure they ‘call for heat’. The commission-
ing of the appliance may be easier if the
external/internal controls are disconnected
and terminals 1 & 2 and 4 & 5 linked. (For
access procedure turn off electricity and
refer to 5.7.2 for instructions).
6.5.2 Switch on the mains electricity and turn the
on/off/mode switch (17) to
6.5.3 Set the c/h control knob (15) to the highest
setting.
6.5.4 The appliance will go through an ignition
sequence and the burner will light.
6.5.5 If during the ignition attempt period (10 secs
approx.) the boiler fails to light, the ignition
control circuit will go to lockout, this is
indicated by the lockout reset button on the
front control panel being illuminated. The
gas valve is de-energised, but leaves the
fan and pump running.
6.3.3 Initial flushing of Pipework
The whole of the heating system must be
flushed both cold and later hot as detailed in
6.10.Openallradiatororheatingvalvesand
theappliancecentralheatingvalves. Drain
the boiler and system from the lowest points.
Openthedrainvalvefullboretoremoveany
installationdebrisfromtheboilerpriorto
lighting. Refill the boiler and heating system
as described in 6.3.2

18 MAXIN 24e & 28e
6.5.6 Inthe event of the boiler goingto lockout
depress the lockout reset button. The two
main causes of the boiler going to lockout
during commissioning are electrical supply
polarity reversed, or air in the gas supply.
Check polarity and that the gas supply is
completely purged of air and that gas is
reaching the boiler then repeat from 6.5.2.
6.6 CheckingBurnerPressures
6.6.1 Theheat inputs for high and low gasrates
are factory set to the maximum values given
in section 3.12 for domestic hot water and
central heating but it is necessary to check
themwhencommissioning.
6.6.2 The maximum heat input for the central
heating mode may be reduced by a simple
adjustment to suit the system load. This in no
way affects the appliance maximum which is
alwaysobtainedinthedomestichot water
mode.
6.6.3 Turn off the main electricity supply. Gain
access to the interior as instructed in 5.7.2.
6.6.4 Locatethemain burner pressure test point
(Fig. 20) and slacken the screw half a turn
in an anti clockwise direction. Attach a
suitable pressure gauge. Turn on electricity
supply and fully open a domestic hot water
tap to operate boiler in dhw mode. Adjust
hot water control knob to it's maximum
setting.
6.6.5 The pressure reading for maximum rate
should be.
24e(N/G)
10.1mbar (plus or
minus1.0mbar)
28e(N/G)
10.1mbar
(plusorminus1.0mbar)
If the pressure is wrong it should be adjusted
as instructed in clause 8.23 (N.B. Whenever
the maximum rate is adjusted check and
adjust the minimum rate too)
6.6.6 Reducethe domestic water flow rate to
approx.3-4litres/min,turnthedomestic
control knob slowly to minimum the boiler
output will reduce to the minimum setting. If
low flame cannot be established in this way,
turn off the electricity supply, release the
modulator coil retaining clip and slide the
modulator coil off the brass rod. Switch on
the electricity supply, the boiler will now light
at the minimum setting.
6.6.7 When low flame is established, the pressure
reading should be:
24e(N/G)
1.5mbar
(plusorminus0.15mbar)
28e(N/G)
1.3mbar
(plusorminus0.13mbar)
If it is different adjustment should be made
in accordance with the instructions in 8.23.
6.6.8 Ifthemodulatorcoilwasremovedtocheck
the minimum setting, turn off the electricity
supply and replace the modulator coil
ensuring correct location of clip
6.6.9 Checking Ignition Heat Input (Soft Light
Ignition).
6.6.10 Thesoftlightignitionpressureisfactoryset,
but it is necessary to check it when commis-
sioning.
6.6.11 Turn off the main electricity supply.
6.6.12 Disconnect the sensing electrode lead from
the terminal on the ignition control box (lead
towards the rear going to left side of main
burner).
6.6.13 Turn on the main electricity supply and turn
on a domestic hot water tap to operate the
boiler in dhw mode.
6.6.14 The boiler will now light at a reduced pres-
sure,thereadingshouldbe 4.0mbar (plusor
minus0.4mbar)(N/G)Ifthe pressureis
incorrect it should be adjusted as in 8.23.
N.B. While checking the soft light pressure
the burner will only light for approximately 10
seconds before going to lockout.
6.6.15 Turn off the main electricity supply and
reconnect the sensing electrode lead to the
ignition control box.
Retaining Clip
Fig. 20
Main Burner
Test Point
Incoming Gas
Pressure Test
Point
NOTE: Potentiometers located on main p.c.b. on
front control panel. Access to p.c.b. is obtained by
removing the four cover securing screws.
Fig. 21 Range rating
potentiometer

19
MAXIN 24e & 28e
Fig.22
mbar
12
11
10
9
8
7
6
5
4
3
2
1
0
ins wg
4.8
4.4
4.0
3.6
3.2
2.8
2.4
2.0
1.6
1.3
0.8
0.4
0.0
30
8.8 35
10.2 40 11.7 45
13.1 50
14.6 55
16.1 60
17.6 65 19.0 70 20.5 75 22.0 80
23.4 85
24.9 90
26.4 95
27.9 100
29.3 105
30.8 110
32.2 115
33.7
24e
output 28e
input
24e
input
28e
output
Btu/hx1000
kW
6.6.16 Setting the Maximum Rate for Central
Heating (Range Rating)
Refertofig.22to determinepressureforthe
heatingoutputyou need.Turnontheheating
with the control knob set at maximum, wait
forthe burner to reach main flame, using a
smallscrewdriveradjustthepotentiometer
fig.21 until the required pressure isindicated
on the gauge. Once this pressure has been
fixed it should be indelibly recorded on the
labelprovidedandaffixednexttothedata
badge. This is to ensure that the burner can
beresetwhenanyserviceoperationinvolves
alterationofburnersettings.
6.7 Checking the Flue System
6.7.1 The flue system should be visually checked
for soundness. Check all clamps and fixings
are secure and tight.
6.8 Checking the Heating Thermistor
6.8.1 Allow the system to warm up and manipu-
late the c/h control knob to ensure that the
burner modulates between ‘high’ and ‘low’
and then to ‘off’ and vice versa (scale
range covers approx. 45° - 85°C).
6.9 Regulating the Central Heating System
6.9.1 Fully open all radiator and circuit valves
and run the appliance in the central heating
mode until heated water is circulating. If
conditions are warm, remove any thermo-
staticvalveheads.
6.9.2 If the burner will not light, ensure that water is
in fact circulating See 4.6.3
6.9.3 Adjustradiatorreturnvalvesandanybranch
circuit return valves until the individual
return temperatures are correct and are
approximately equal.
6.9.4 When all is adjusted, progressively close all
radiatorvalves to ensure that the appliance
still operates when flow through the system
is limited.
If the burner cuts out prematurely due to
lack of water flow through the appliance, the
system should be regulated to ensure a flow
rate of at least 350 litres/h (78 gals/h). This
may mean the addition of a small manual
by-pass being fitted to the system if a fully
TRV system is used.
6.10 Final Flushing of the Heating System
6.10.1 Thesystemshouldbeflushedinaccordance
withBS7593: 1992.Turnontheboiler for
centralheatingandallowtheboilerand
systemtoreachtemperature. Turnoffthe
boiler and drain the system whilst still hot.
Refill the boiler and heating system as
describedin6.3.2.
Althoughnotnecessaryforcorrectoperation
of the boiler, an inhibitor may be added at
thispoint.Contacttheinhibitormanufacturer
forfurtherinformationconcerningapplication
anddosage.
6.10.2 Inspect the system for soundness. Turn the
appliance off at the mode selector switch (fig.
1, 17).
6.11 Filling, Testing and Regulating the
Domestic Hot Water System
6.11.1 Startwiththeapplianceswitched onhaving
completedtheproceduresdescribedin 6.4
to 6.10.
6.11.2 Openadomestichot watertap(Preferably
the bath tap).
Ensure cold water inlet stopcock is fully open
and the dhw control knob (16) is set at
maximum.
6.11.3 The flow of water should activate the
differential pressure device and drive the
diverting valve (21) to its other position thus
heating the domestic water flowing through
the dhw heat exchanger. At the same time
the domestic micro-switch (13) is activated
lighting the burner on maximum rate.