MHS Boilers Ultramax 73 Installation and operation manual

Ultramax Floor Standing Condensing Boiler
Operating & Maintenance Manual
For Models 73 - 287
MHS Boilers Ltd
35 Nobel Square
Burnt Mills Industrial Estate
Basildon Essex
SS13 1LT
01268 591010 Telephone [phone] Fax
WWW.MHSBOILERS.COM
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Contents
UltramaxTechnicalData
UltramaxDimensions
1 Introduction
1.1 General
1.2 Supplier
1.3 This document
1.4 Service
1.5 General restrictions
2 Description
2.1 General
2.2 Main components
2.2.1 Description of principal components
2.3 Boiler control
2.4 Safety aspects
3 Safety
4 Delivery and transport
4.1 Delivery
4.2 Packaging
4 .3 Transport
5Installation
5.1 Regulations
5.2 Boiler room
5.2.1 General
5.2.2 Set up
5.2.3 Ventilation
5 .3 Connections
5.3.1 Gas connection
5.3.2 Electrical connection
5.3.3 Water connections
5.3.4 Combustion air supply
5.3.4.1 General
5.3.4.2 Air supply pipe
5.3.5 The Flue system
5.3.5.1 General

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5.3.5.2 Chimney
5.3.6 Condensate discharge
5.4 Hydraulic system
5.4.1 General
5.4.2 Water flow
5.4.2.1 Flow rate and resistance
5.4.2.2 Pump characteristics
5.4.2.3 Isolating valves
5.4.2.4 Valves
5.4.2.5 Water flow protection
5.4.3 Water pressure
5.4.3.1 Operating pressure
5.4.3.2 Boiler expansion tank
5.4.3.3 System expansion tank
5.4.3.4 Water pressure protection
5.4.4 Water temperature
5.4.5 Water quality
5.4.6 Examples of hydraulic systems
6 Operating instructions
6.1 Function
6.2 Regulation
6.3 Control module
6.4 Fault indications
6.5 Start-up
6.6 Shut-down
6 .7 Warnings
7Commissioning
7.1 General
7 .2 Commissioning
8Maintenance
8.1 Safety
8.2 General
8.3 Procedure
8.4 Cleaning the burner and heat exchangers
8.5 Cleaning the filter/screen in the gas combination block
8.6 Ionisation measurement
8.7 Service

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Ultramax Technical Data.
Type 73 90 115 146 192 241 287
Nominal heat output
Nominal heat input (nett. CV)
Minimum heat input
kW
kW
kW
70
74
16
86
91
20
114
121
23
139
147
29
185
194
39
230
243
49
274
289
58
Gas consumption
natural gas H (10.9 kWh/m3 )
propane (12.8 kWh/kg ) m3/h
kg/h
6.79
5.78
8.35
7.11
11.10
9.45
13.49
11.48
17.80
15.16
22.29
18.98
26.51
22.58
Gas inlet pressure natural gas (min.)
natural gas (max.) propane (min./max.) mbar
mbar
mbar
17
50
30/50
17
50
30/50
17
50
30/50
17
50
30/50
17
50
30/50
17
50
30/50
17
50
30/50
Water capacity Max. working pressure dm3
bar
13
6
15
6
17
6
19
6
36
6
39
6
42
6
Flue connection
Air supply
D
D1
mm
mm
100
100
100
100
130
125
150
125
180
150
200
180
200
180
Gas connection GR 3⁄4" R 3⁄4" R 3⁄4" R 3⁄4" R 1" R 11⁄2" R 11⁄2"
Water connections WR 11⁄2" R 11⁄2" R 11⁄2" R 11⁄2" R2" R2" R2"
Power supply
Frequency
Fuse
V
Hz
A
240
50
10
240
50
10
240
50
10
240
50
10
240
50
10
240
50
10
240
50
10
Max. electrical power
consumption
pump (option) maximum
unit total
W
W
W
128
245
373
128
245
373
391
245
636
391
245
636
397
380
777
397
380
777
397
380
777
Boiler weight, empty, ± 5 % kg 120 140 160 180 250 270 290
Ultramax Dimensions

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Type 73 90 115 146 192 241 287
B mm 500 600 700 800 600 700 800
B1 mm 360 420 490 560 470 550 600
D mm 100 100 130 150 180 200 200
D1 mm 100 100 125 125 150 180 180
G R 3⁄4" R 3⁄4" R 3⁄4" R 3⁄4" R 1" R 11⁄2" R 11⁄2"
H1 mm 160 160 170 176 197 197 197
H2 mm 497 488 501 486 556 549 537
H3 mm 943 943 921 921 921 921 921
L mm 685 685 685 685 895 895 895
L1 mm 50 50 50 50 85 85 85
L2 mm 160 160 160 160 160 160 160
L3 mm 80 80 90 90 100 100 100
L4 mm 445 445 445 445 655 655 655
L5 mm 525 525 525 525 735 735 735
L6 mm 95 95 135 120 130 120 120
W R 11⁄2" R 11⁄2" R 11⁄2" R 11⁄2" R 2" R 2" R 2"
Conditions applicable to table above:
- Nominal capacity measured at: 60 - 80°C.
- Gas consumption at: 1 013 mbar, 15°C, dry
- Gas category: 22H3P
- Appliance category: B23, C53, C33 or C63
- Protection degree: IP20

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1 Introduction
1.1 General
Through their unique construction, the Ultramax range of central heating units are renowned for their:
- high thermal efficiency
- environmental friendliness
- light weight and small dimensions
- durability
- low noise production
- large regulating range
- available with many different options.
Active and market required research enables MHS Boilers Ltd to offer solutions for the most
provocative heating demands.
1.2 Supplier
MHS Boilers Ltd are proud to supply and technically support the Ultramax Range of boilers throughout
the United Kingdom.
For advice or more information please contact your local sales representative or our head office via
01268 591010.
1.3 This document
This documentation has been written to aid the following target groups:
- the consulting engineer
- the heating installer
- the service engineer
- the user.
Because these target groups require mostly similar information and also specific information, our
technical documentation has been integrated to provide these target groups with the necessary
general and specific information to install, service and operate this product.
If additional information is required please contact your local representative or our head office via
01268 591010.
The following aspects will be explained:
- general description
- technical specifications
- necessary services for system design and unit installation
- example systems
- maintenance instructions.
Operating instructions for the user can be found on the unit. See also chapter 6.
1.4 Service
For commissioning and assistance in maintenance matters, please contact the Technical Services
Department via 01268 591010.

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1.5 General restrictions
The application, installation and maintenance of MHS products must always be carried out
in accordance with the requirements (legal or otherwise), specifications and standards applicable
to such installations.
All data, information and suggestions provided by MHS Boilers Ltd. in relation to its products are
based on careful investigation. Nevertheless, neither MHS Boilers Ltd. nor any other organisation
connected with MHS Boilers Ltd. accepts any liability for application, installation or exploitation
that occurs outside its sphere of influence.
Changes may be incorporated without prior notice. MHS Boilers Ltd. accepts no obligation to
adapt previously delivered products to incorporate such changes.
2 Description
2.1 General
The Ultramax series are environmentally friendly modulating gas fired heating boilers with variable
outputs from 20% to 100% of maximum capacity.
The Ultramax series consists of 7 types in a range from 73 to 278 kW.
The units have an extremely low emission of NOx and CO, so that this boiler satisfies the most
stringent European requirements.
The Ultramax series have CE approval for all relevant European countries. The series are registered
under the product identification number 0063BL3354.
The boilers are standard supplied as a standard (category B23) or a room sealed (categories C53,
C33 or C63) appliance.
Working principle and construction
Air is blown into the appliance, as required, by a speed-controlled fan and thoroughly mixed with
gas in the correct proportions.
A temperature controller compares the desired water temperature with the temperature of the water
flow. If required, the controller will vary the load and the fan will emit a speed feed back signal
to maintain the correct heating capacity.
The gas/air mixture so formed is passed through the cooled premix burner and ignited. The
premix burner is constructed of finned bimetallic pipes (inside stainless steel, outside aluminium)
and cast iron water headers. (Replaced with Stainless Steel On The Water Heater Versions.)
Heat transfer takes place in three heat exchangers. The first heat exchanger is constructed from
smooth stainless steel pipes, while the second heat exchanger is fitted with laser-welded, stainless
steel finned pipes. The third heat exchanger is fitted with smooth stainless steel pipes.
All heat exchangers are fitted with cast iron water headers (stainless steel for water heater) which
guarantee an optimum water flow through the appliance.
The burner and the heat exchangers are connected in series.
The Ultramax units have a small water capacity so that it can rapidly adjust to changing conditions.
It can be installed without any restrictions to the return water temperature. The necessary water

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flow rate is ensured by the presence of an integral water flow switch.
Application possibilities
Because of its construction, the R300 unit is suitable for use in heating systems:
- With a constant supply temperature
- With a weather dependent heating demand
- With low temperature condenser systems
- With optimised condensation
- With control by means of building optimizer/compensator system (2 – 10 Vdc = +10°C – +90°C),
(see 5.3.2 connection terminals).

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2.2 Main components
1 Casing 17 Frame
2 Air pressure switch 18 Filling/drainage valve
3 Control panel 19 Return connection
4 Burner 20 Water flow switch
5 Combustion chamber 21 Water headers
6 First heat exchanger 22 Ignition transformer
7 Second heat exchanger 23 Connecting terminals
8 Third heat exchanger 24 Distribution plate
9 Condensate receptacle 25 Gas valve unit
10 Flue attenuator 26 Fan
11 Condensate discharge trap (V-bend) 27 Gas filter (option)
12 Flue gas discharge 28 Air supply
13 Flow connection A Air
14 Safety valve (option) B Gas
15 Gas connection C Flue gas
16 Adjusting feet D Condensate

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2.2.1 Description of principal components
The boiler is constructed from the following principal components:
Fan [26]
The DC fan, which is equipped with a speed feedback, draws in the combustion air and increases
the air pressure. The speed feedback signal is relayed to the regulator, which adjusts the speed if
need be.
Gas train
The principal component of the gas train is the main gas valve [25]. The quantity of gas is adjusted
in proportion to the quantity of air being supplied. The quantity of air depends on the speed of
the fan. As an option, the unit can be equipped with a gas filter [27].
Burner [4]
After the gas/air mixture has been distributed over the burner using a distribution plate, the mixture
is burnt on the burner surface such that the flame is directed downward. The burner is both
air and water-cooled. The water headers are constructed of cast iron (stainless steel for water
heater), and ensure a two-pass flow through the burner.
Heat exchangers [6, 7 and 8]
The first heat exchanger is constructed of smooth stainless steel pipes and transfers most of the
combustion energy to the system water. The second heat exchanger is constructed of laser-welded,
stainless steel finned pipes. The third heat exchanger is constructed of smooth stainless
steel pipes. The second and third heat exchanger transfer the heat from the combustion gasses to
the system water. All water headers are constructed of cast iron (stainless steel for water heaters),
and ensure a five-pass or three-pass flow through the heat exchangers (depending on the
type). The space between the burner and the first heat exchanger constitutes the combustion
chamber.
Water headers [21]
The water headers are part of the burner and the heat exchangers.
Water connections
These consist of a flow connection [13] and a return connection [19]. Both of these connections are
provided with a filling/drain valve [18]. The flow switch [20] is fitted on the flow line.
Boiler pump (optional)
The boiler pump must be mounted on the return connection to the unit and must be directly connected
electrically to the supplied lead protruding from the rear of the appliance. The capacity and the working
head of the pump must be sufficient to overcome both the resistance of the boiler and some system
resistance. As an option, the pump is supplied as a separate item with the boiler.
Condensate receptacle [9]
A condensate receptacle is fitted underneath the last heat exchanger. This receptacle is equipped
with a condensate and flue gas outlet.

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Frame [17]
The frame is constructed from steel profile sections and is fitted with vibration absorbing adjusting
feet [16].
Casing [1]
The casing consists of easy-to-remove panels. Once the cover has been opened (using tools), all
other panels can be removed without using tools.
The electrical section
This includes the control and safety circuits for the unit.
Connecting terminals [23]
The boiler power supply, the connecting terminals, the pump connection and the pump relay are
all fitted in the top of the boiler. The terminal strip is located under the cover, on the right hand side.
2.3 Boiler control
The principle employed for the Boiler Management Unit is as follows: The boiler begins operating
on receipt of a heating demand. This heating demand is generated either:
A if the measured supply temperature is lower than the desired temperature.
B as a result of “service operation” mode having been selected
C in standby mode, when the water temperature falls below the frost protection temperature.
After the unit has started up, the PID controller sends a signal to the fan, thus controlling the fan
speed. Depending on the quantity of air displaced by the fan, the proportional pressure regulator
will add the corresponding quantity of gas. In this way, the boiler power is continuously modulated,
enabling the boiler to accurately follow the demand for heat. The fan is equipped with a
speed feedback, enabling an even more accurate control behaviour.
Once the supply water temperature exceeds the desired value, the unit will shut down. As soon as
the supply water temperature falls below the set value, the boiler restarts.
2.4 Safety aspects
The boiler contains the following safety components:
- Flame protection (1x re-start)
- Water flow protection
- Maximum water temperature protection
- Gas valve test
- Fan protection
- Overload and underload protection.
If one of these components operates, this results in a lockout fault. Lockout faults can only be
cancelled by resetting the unit.
3 Safety
Installation instructions
Read through these instructions carefully before starting the installation.

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The appliance must be installed by a recognised installer in accordance with the applicable national
and local regulations.
The installation may only be used for heating systems up to a maximum water temperature of
90°C.
It is expressly stated that these installation instructions must be seen as a supplement to the
above mentioned standards and regulations and that these standards and regulations must take
precedence over any information included in this technical manual.
Maintenance
Work on the electrical installation may only be carried out by an authorised installer in accordance
with the applicable electrical qualifications.
Work on the gas and hydraulic installations may only be undertaken by properly trained personnel
in accordance with the safety regulations for gas installations.
Keep unauthorised persons away from the installation. Do not place any objects on the unit.
Remain out of the area of the hot water connection and the chimney to avoid burns.
Before starting any maintenance or service activities, disconnect the electrical power supply and
close the gas supply valve.
After completing any maintenance or service activity, check the whole installation.
As a supplement to the information provided in this technical manual, all applicable safety regulations
must be consulted to avoid accidents.
All panels forming part of the casing must be mounted. Panels may only be removed for maintenance
or service purposes. After performing maintenance or service activities, ensure that all
panels are replaced.
Safety provisions
The installation may never by switched on if any of the panels have been removed or if any of the
safety devices have been disabled.
Instruction and warning stickers
None of the instruction and warning stickers attached to the installation may be removed or covered
and during the whole of the lifetime of the installation they must remain legible.
Replace any damaged or unreadable instruction and warning stickers immediately.
Modification
Modifications to the installation may only be carried out with the written approval of the manufacturer.
Danger of explosion
When activities are being undertaken in the boiler room, always follow the applicable instructions
“Working in an area where there is a danger of explosion”.

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Installation
The appliance must be installed by an authorised installer in accordance with the applicable national
and local specifications and regulations. Carefully follow all the safety instructions.
Operation
In the event of a gas leak, switch off the unit and close the gas supply valve. Open doors and windows
and warn the appropriate authorities.
When the installation is re-commissioned, always follow the instructions for use.
Technical specifications
The specifications listed in this technical manual cannot be ignored.
4 Delivery and transport
4.1 Delivery
The unit comes standard fully assembled, tested and packaged.
After delivery and removal of the protective covering, check the appliance for damage.
Check that the equipment delivered is in accordance with the order and the delivery note.
On delivery, check the data plate for the correct boiler type and gas supply pressure.
4.2 Packaging
The unit is supplied in cardboard packaging on a pallet.
For transport, consult the technical details for dimensions and weight.
4.3 Transport
Remove the packaging preferably after transportation and positioning in the boiler room or remove the
panels before transporting the appliance. This is to prevent damage to the casing panels.
Moving the appliance
A pallet truck or fork lift truck used at the front or side of the unit.
Standard door width
The dimensions of the unit are such that after removing the pallet, all types will fit through a
standard width door opening of 80 cm (remove the outside panels of type 287).
Positioning
Once the boiler has been installed, it can be adjusted horizontally using the adjusting feet.
Subsequently, the water, gas, condensate and electrical connections can be made.
Protection against frost
If the unit is out of use during the winter months there is a danger of freezing. Drain the water
from the installation using the filling/drainage valves.

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5 Installation
5.1 Regulations
The appliance must be installed by a recognised installer in accordance with the applicable national
and local specifications and regulations.
Commissioning should be carried out by the Technical Service Department of MHS Boilers Ltd, who
can also determine the composition and quality of the system water.
5.2 Boiler room
5.2.1 General
- The construction of the unit ensures that losses through radiation can be neglected
- Because of the low noise level, additional sound insulation of the boiler room is unnecessary
- Because of the position of the electrical components, a plinth is not required
- The unit is so constructed that the space required for it is small
- The range of applications for the boiler is that much greater because of the possibility to install
it as a room sealed appliance (see Section 5.3.4)
5.2.2 Set up
In order to avoid any difficulties, the following rules apply to the boiler room:
a Install the appliance in a frost-proof room
b Pay particular attention to the positioning of the appliance to ensure protection from freezing
and/or high temperatures. (Consult BS 6644)
c Ensure that the boiler room is sufficiently large, so that there is sufficient space on all sides of
the unit to permit maintenance and possible replacement of components to be carried out.
The absolute minimum free space is:
- 250 mm at both sides
- 1000 mm at the front (space for free movement).
If you do not observe the recommended space requirements, future maintenance might be more
Difficult or impossible.
Hydraulic System Pressure Monitoring
All hydraulic systems connected to the Ultramax range of boilers must incorporate a system water low
pressure switch, in accordance with BS6644.
5.2.3 Ventilation
The ventilation of the boiler room must satisfy the applicable national and local standards and
regulations.
5.3 Connections
5.3.1 Gas connection
The gas connection must be made by a recognised installer in accordance with the applicable

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national and local standards and regulations.
The gas connection is made at the rear of the boiler.
The pressure of the gas supplied to the unit must be reduced to 20 mbar for natural or 37 mbar for
propane with the use of a gas pressure regulator.
The loss of pressure in the connecting pipes must be such that, at maximum boiler capacity, the
pressure must never fall below 20 mbar for natural gas or 37 mbar for propane.
5.3.2 Electrical connection
The electrical connections and provisions must comply with the applicable national and local
standards and regulations.
The units are wired in accordance with the electrical diagram supplied with the appliance.
The electrical connections, the handling brackets and the boiler pump relay are located underneath
the cover, on the right-hand side of the boiler. You can unlock the cover using a 4 mm socket wrench.
You must connect the unit using an all-pole main switch with a contact opening of at least 3 mm.
The cables to be connected (power supply, control) enter the appliance via the rear of the unit,
using cable glands.
The appliance can be switched on and off with the switch on the control panel. The power supply
voltage cannot be removed from the boiler pump relay in this way.
The installer must fit a mains isolator switch in the power supply to the unit within the boiler
room. This can be used to switch off the power to the unit for maintenance purposes or in the
event of a problem.
In accordance with the applicable standards and regulations, an emergency shut-off must be fitted

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At the exits from the boiler room. In the event of a calamity, the power supply to the unit can be
switched off.
In order to prevent malfunctions occurring as a result of inductive or high frequency signals,
or static electricity, screened cables must be employed for all low voltage and control signals
between the boiler and externally connected units. The screening must be earthed at both ends
of the cable.
Electrical data
Type
Fan, control and
safety components
Pump(option) Total electrical power
consumption (max)
V* W V W** W
73 240 128 240 245 373
90 240 128 240 245 373
115 240 391 240 245 636
146 240 391 240 245 636
192*** 240 397 240 380 777
241*** 240 397 240 380 777
287*** 240 397 240 380 777
* tolerance on voltage: 240 V +10 % /-15 % tolerance on frequency: 50 Hz } 5 %
** the stated pump power is based on the maximum power consumption in pump speed 3
*** 3-phase pump available as an option.
Pumps supplied by others
Control and options
The appliances are fitted with a proportional regulation system. This can be made temperature
dependent with the aid of a 0 – 10 VDC (= -10°C – +90°C) signal. In addition, the boiler regulating
system can be extended by fitting one of the three options described below:
BME Room Temperature Controller Option
This is a weather-compensated regulator with the following possibilities:
- Three on/off periods per day with three different temperatures
- Night-time temperature reduction
- Domestic hot water priority with time programming
- Anti-legionella provision
- Optimum start
- Room-temperature sensor (can be switched off)
- Two-wire communication bus connection
- Multi-language display
- External control.
E6 option
This is a regulator with which two secondary groups can be weather-dependently controlled. In
addition, domestic hot water temperature can also be regulated. All the settings can be adjusted
independently for each group. This E6 regulator can be further extended with an optimizing controller

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for each group (BM). The boiler is then directly weather-dependently controlled.
KKM option
This is a boiler cascade manager permitting up to eight boilers to be switched in cascade. The
KKM also has the same possibilities as the E6 option.
Connection terminals
The operation of the appliance can be influenced by externally generated signals applied to the
appropriate terminals.
Terminal Description
L1-N-PE Boiler power supply; must be fused at 10 A.
8 - 9 Domestic hot water primary pump control. This output provides a voltage (230 V)
when the boiler is operational as a result of a domestic hot water heating demand.
10 - 11 Boiler enable (240 V). Requiring a Volt Free switch. When these terminals are
connected the primary pump will be started and the boiler will be enabled. When there
is an open circuit between them the boiler will be shut down.
The pump will also stop after the set run on time. These terminals can be used,
among other things, for setting the boilers to standby during the summer months
whilst continuing to provide domestic hot water priority.
12 - 13 Operating signal. (240 V) The operating is removed if a fault has occurred more than
2 times within 6 minutes (the fault code will appear in the display with a “3”) or if a
fault is longer than 6 minutes active.
14 - 15 Control voltage for an external gas valve. This output begins to provide 240 V
before the boiler starts up; the voltage ceases after the boiler shuts down. This
output can be used to open hydraulic valves or to operate boiler room ventilation.
16 - 17 Calorifier thermostat (240 V). When these terminals are interconnected the boiler
will try to provide the set flow temperature programmed for the boiler. This input
only functions if terminals 34 - 35 are interconnected.
18 - 19 Interlock input (240 V). If the connection between these terminals is interrupted,
the boiler will be deactivated and wait until the connection is restored (after 6
minutes or if the same fault has occurred three times within 6 minutes, this input
will be interlocked).
20 - 21 Lockout input (240 V). If the connection between these terminals is broken the
boiler will enter the fault mode. Reinstate the connection and press the reset
push-button.
30 - 31 External sensor*. After a suitable sensor has been connected it will be automatically
recognised when the power supply is switched on.
32 - 33 Low velocity header sensor*. This sensor can measure the temperature of a low
velocity header.

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35 - 36 Calorifier temperature sensor*. After a suitable sensor has been connected it will
be automatically recognised when the power supply voltage is switched on. The
terminals 35 - 36 must not be interconnected. The purpose of this function, in
comparison with the calorifier thermostat, is to make possible a night time temperature
reduction and an anti-legionella switching (only with BME, E6 or KKM).
37 - 38 External influence (2 – 10 VDC = +10°C – +90°C)*. At voltages below 2 V the
boiler will switch to “constant supply temperature operation”.
41 - 42 SCOM bus connection (make sure to use the correct polarity).
43 - 44 Primary boiler pump control (0 – 10 VDC).
* In order to avoid faults caused by inductive currents, static electricity or high
frequency signals, the use of screened cables is necessary.
5.3.3 Water connections
The appliance must be installed by a recognised installer in accordance with the applicable national
and local regulations. The flow and return connections are made at the rear of the unit.
Water connection supports
We recommend that the supply and return pipes be properly supported using brackets to prevent
mechanically overloading the lines and to simplify maintenance.
The unit is a constant water flow appliance and is suitable only suitable for use with sealed
(pressurised) systems providing the minimum pressure requirements, as per table 10.
The unit must be fitted with a boiler pump that guarantees the required water circulation through the
boiler. The capacity and working head of the pump must be sufficient to overcome both the resistance
of the boiler and the resistance offered by the system.
If the resistance of the system exceeds the available working head of the installed pump, the boiler will
be shut down by the flow switch. In order to prevent this happening, the length and diameter of the
primary pipework between the boiler and the low velocity header must be chosen such that the
remaining working head of the pump (see table 8) will not be exceeded.
It is essential that manually operated valves be fitted between the water connections and
the installation.
In order to limit the losses occurring in a non-operational boiler, a motorised valve can be fitted in the
flow or the return pipe or a mechanical non-return valve is used for this purpose.
Standby losses can be reduced even further by shutting down the boiler via the “boiler enable”
terminals. A properly dimensioned low velocity header ensures that the natural flow through the
boiler can be negated.
5.3.4 Combustion air supply
The unit is supplied as standard to allow room seal operation. This simplifies the possibilities for
installation within the building.

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5.3.4.1 General
Guide lines and installation instructions
The flue gas discharge and the air supply systems must be installed by a recognised installer in
accordance with the applicable national regulations.
The total resistance of the air supply and the flue should not result in a pressure drop exceeding
1.8 mbar (types 73 and 90) or 1.0 mbar (types 115 to 287).
Extreme care must be taken to limit the draught of the attached flue and air supply system to below
15Pa in all firing conditions.
5.3.4.2 Air supply pipe
The air supply pipe may be single-walled and constructed of:
- plastic
- thin-walled aluminium
- flexible aluminium (take account of the resistance)
- stainless steel.
- it is essential that the combustion air intake grille does not allow direct wind attack that could effect
the combustion process of the unit.
Fig. 5 horizontal air supply
Type Air supply diameter D1 (mm)
73 100
90 100
115 125
146 125
192 150
241 180
287 180

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Table 4 Air supply connection
The connection to the air supply pipe is always mounted on the back of the unit.
Multiple units may not be connected to the same air supply or flue pipe.
To prevent snow entering, the air supply pipe must extend at least 300 mm above the roof and
must be fitted with a rain cap.
The flue pipe opening must end at least 1000 mm above the roof, assuming the roof to be flat.
Fig. 6 Heights of air inlet and flue gas discharge
The relative horizontal difference between the flue pipe and the air supply pipe must not be less
than the width of the unit.
Fig. 7 Distance between air inlet and flue gas outlet
To prevent undesirable condensate from forming, we strongly recommend that you insulate the
air-supply duct on the outside to make it vapour tight.