Stuart Turner Mikrofill ETHOS 350 Guide

ETHOS 350 & 550 FLOOR STANDING CONDENSING BOILERS
TECHNICAL DOCUMENTATION
2023/02REV. 00
CONDENSING BOILERS

TABLE OF CONTENTS
01. Technical Data 04 07. Operating Instructions 22
Operation
02. Dimensions 05 Controls
Boiler Module 23
03. Safety Guidelines 06 PCB Symbol Key
Conditions Switching On the Appliance 24
General Guidelines Switching Off the Appliance
Service 07 Information Display 25
General Restrictions DHW Operation
Heating Operation
04. Description 08 Displaying Information
General Table Parameter List
Working Principle and Design History Mode 26
Application Features Possible Error Codes
Main Components 09 Possible Error Codes continued. 27
Rear Connections
Boiler Control 10 08. Commissioning 28
Safety Aspects General
Reference Value for Maximum Load
05. Delivery & Transport 11 Reference Value for Minimum Load
Delivery Maximum Load Adjustment 29
Transport Minimum Load Adjustment
Moving Setting the CO2Value for the ETHOS Range 30
Access Requirements Conversion from Natural Gas to Propane 31
06. Installation 12 09. Cascade Set-Up 31
Regulations Auto Detection Mode
Installation Guidelines Cascade Test Mode 32
Ventilation 13
Gas Connection 10. Maintenance 33
Water Connections Safety
Electrical Connections Servicing Schedule
0 - 10 V Control Removal of Gas Valve and Venturi 34
Internal Controls Breakdown (Main PCB) 14 Removal of Fan and Burner Assembly 35
Internal Controls Breakdown (Control Fascia) 15 Setting / Checking of Electrode and Probe Gaps 36
External Controls Breakdown (Din Rail)
Controls and Options 16 11. Component List 37
Flue Connection 17 Casing and Electrical Components
Condense Removal Core Components 38
Flue Length 18
Calculation of Diameter and Length 12. Conversion Formulae & Factors 39
Condense Connections 19
Safety Valve Connection 13. Notes 41
Hydraulic System
Shut-Off Valves 20
Valves (Boilers in Cascade Arrangement)
Draining and Cleaning
Water Circulation System
Water Pressure 21
System Expansion Vessel
Water Pressure Protection Device
Water Temperature
Water Quality
Water Hardness 22
TECHNICAL DOCUMENTATION 03

TECHNICAL DATA
GENERAL
Dimensions (Height x Width x Depth)[1] mm 1300 x 750 x 1100 1300 x 750 x 1500
Model ETHOS 350 ETHOS 550
Water Content of Appliance litre 25 30
Weight (Empty) kg 234 370
Flow / Return Connections BSP DN50 PN16 Flange DN65 PN16 Flange
Gas Connection BSP 1½” 1½”
Flue Connection mm 150 180
Power Consumption W 558 898
Electrical Supply V 230 230
Frequency Hz 50 50
Fuse Protection A 10 10
Maximum Fan Speed RPM 6100 9200
Minimum Fan Speed RPM 1300 1950
HEATING PERFORMANCE
Nominal Heat Input (Nett) kW 17.5 - 350.0 27.5 - 550.0
Nominal Heat Output at 80/60°C kW 17.2 - 343.0 27.0 - 539.0
Nominal Heat Output at 50/30°C kW 18.9 - 378.0 29.7 - 594.0
Maximum Gas Consumption
G20 m3/hr 35.5 56.1
G25 m3/hr 40.4 62.1
G31 m3/hr 13.6 20.9
TECHNICAL DATA
Flue Gas Dew Point °C 52 52
Flue Temperature at 80/60°C (at ambient temperature of 20°C) °C 75 75
Flue Material Temperature Class T 120 T 120
Permitted Maximum Resistance of Flue System[2] Pa 200 250
Condensation pH Value 3.0 - 5.5 3.0 - 5.5
Maximum CH Flow Temperature °C 90 90
CH Water Pressure (Minimum / Maximum) bar 0.5 - 6.0 0.5 - 6.0
Minimum / Maximum Gas Pressure
G20 mbar 17 - 20 17 - 20
G25 mbar 17 - 20 17 - 20
G31 mbar 30 - 50 30 - 50
ENVIRONMENTAL DATA
NOXLevels mg/kW 31.0 31.0
Maximum Efciency (Nett Non-Condensing) % 98.1 98.3
Maximum Efciency (Nett Condensing) % 108.9 108.6
Seasonal Efciency % 95.6 95.6
[1]
[2]
Depth dimensions are taken from the front to the rear of the casing and do not include the external pipework. Height dimensions are
taken from the bottom of the boiler and do not include the height of the supplied adjustable feet.
With this resistance value the heat output will remain within the specications indicated on the dataplate; if the resistance is higher,
the heat output will be reduced.
04 TECHNICAL DOCUMENTATION

DIMENSIONS
▲ FIGURE 01. DIMENSIONS OF THE ETHOS FLOOR STANDING BOILERS.
ETHOS 350 ETHOS 550
A in 1” 1”
B mm Ø 32 Ø 32
C in 1½” 1½”
D in 2” 2½”
E mm Ø 150 Ø 180
F mm 1100 1500
1300
750
400
95
180
110
655
995
415
715
840
170
400
E
D
D
A
B
C
F
• All dimensions are in millimetres unless
otherwise specied.
• Depth dimensions are taken from the front
to the rear of the casing and do not include
the external pipework.
• Height dimensions are taken from the
bottom of the boiler and do not include the
height of the supplied adjustable feet.
• Data may deviate slightly due to fabrication
tolerances.
• We reserve the right to make changes
without prior notication.
TECHNICAL DOCUMENTATION 05

SAFETY GUIDELINES
CONDITIONS
Mikroll Systems Ltd. shall not be liable for any damages caused by non-compliance with this manuals
instructions. Only original parts must be used for service purposes.
GENERAL GUIDELINES
The appliance is not intended for use by persons (including children) with reduced mental, physical or sensory
capabilities, or lack of experience or knowledge, unless they have been given supervision or instruction
concerning the use of the appliance by a person responsible for their safety.
It is a statutory requirement that all gas appliances are installed in accordance with the manufacturers
instructions and all regulations in force. All instructions should be fully read before installing or using the
appliance. All installations should be carried out by competent persons as described in the Gas Safety
(Installation and Use) Regulations i.e. Gas Safe registered and holding current certication.
The manufacturers instructions MUST NOT be taken in any way as overriding statutory obligations.
This boiler has been tested and certied to comply with all necessary European directives, latest building
regulations and efciency requirements, is CE marked and complies with;
• 2009/142/EC Gas Appliance Directive.
• 2014/30/EU Electromagnetic Compatibility Directive.
• 2014/35/EU Low Voltage Directive.
This boiler should be installed in compliance with;
• Building Regulations.
• Building Regulations (Scotland-Consolidated).
• Building Regulations (Northern Ireland).
• The Health and Safety at Work Act.
• Gas Safety (Installation and Use) Regulations.
• Water Fittings Regulations or Water By-laws in Scotland.
• Local Water Company By-laws
The boiler should not be modied in any way. Any modications will invalidate the gas approval and invalidate
the warranty.
ATTENTION: HIGH VOLTAGE!
Before opening the boiler casing for maintenance or servicing, the 230 VAC main supply
to the boiler must be disconnected!
06 TECHNICAL DOCUMENTATION

SAFETY GUIDELINES
SERVICE
Should you require any assistance during installation or in the unlikely event of a product failure please do not
hesitate to contact our technical department on 03452 60 60 20.
GENERAL RESTRICTIONS
Mikroll products should always be used, installed and maintained in accordance with the statutory
requirements, specications and standards applicable to these installations. Mikroll cannot be held
responsible for any losses or damage whether direct or consequential that have arisen as a result of incorrect
or poor installation.
WARNING!
Particular attention must be given to the safety guidelines as non-compliance will render
the warranty void and may constitute an illegal installation.
Detailed recommendations are contained in the following Standards and Codes of Practice:
• BS 5854
• BS 6644
• BS 6880
• IGE/UP/1
• IGE/UP/2
• IGE/UP/10
Flue and Flue Structures in Buildings.
Installation of Gas Fired Hot Water Boilers of Rated Inputs between 70kW and 1.8MW
(net) (2nd and 3rd Family Gases).
Low Temperature Hot Water Heating Systems of Output greater than 45kW.
• Part 1: Fundamental and Design Considerations.
• Part 2: Selection of Equipment.
• Part 3: Installation, Commissioning and Maintenance.
Soundness Testing and Purging of Industrial and Commercial Gas Installations.
Gas Installation Pipework, Boosters and Compressors on Industrial and Commercial
Premises.
Installation of Gas Appliances in Industrial and Commercial Premises.
TECHNICAL DOCUMENTATION 07

DESCRIPTION
GENERAL
The Mikroll ETHOS oor standing boilers are environmentally friendly gas red heating boilers with a modulation
range between approximately 10% and 100% of their maximum output. The appliances have low NOXand
CO emission, which satises the most stringent environmental requirements.
The ETHOS range has received UKCA and CE approval for all relevant countries
and has been registered under the Product Identication Number 86CL109.
The boilers may only be used on open (type B23) systems.
The boiler is delivered fully wired, fully assembled, tested and preset complete with emissions report.
WORKING PRINCIPLE AND DESIGN
Air is drawn in as required, via a variable speed fan. The gas valve measures the negative pressure (draught)
in the venturi and modulates the gas valve in response. The gas and air is then thoroughly mixed in the correct
ratio in the fan housing and red directly into the burner.
The boiler management system compares the actual water ow temperature to the required water
temperature. The management system computes the load required and adjusts the fan speed. This is a
continual process during operation.
The heat transfer takes place in a stainless steel triple heat exchanger block. The burner res into the primary
heat exchanger whilst the second heat exchanger (condenser) is connected downstream in such a manner
that the condense water cannot enter the primary heat exchanger, all heat exchangers consist of several
smooth pipes in the form of a coil and are connected using stainless steel water distribution manifolds.
APPLICATION FEATURES
The design of the boiler incorporates the following:
• Full Operation and Fault Diagnostics via LCD.
• Control / High Limit Sensors.
• Integral DHW Control (DHW Input Signal Required).
• Integral Safety Relief.
• Integral Weather Compensation (Optional External Sensor Required).
• Frost Protection.
• Pressure Read Out.
• Compatible with most External BMS Options.
08 TECHNICAL DOCUMENTATION

DESCRIPTION
FRONT VIEW: BACK VIEW:
BOTTOM CONNECTIONS:MAIN COMPONENTS:
01 Burner #00 Control Unit
02 Burner #01 Control Unit
03 Combustion Fan
04 Control Fascia
05 Electrical Connections
06 Gas Valve
07 Heat Exchanger and Burner Package
08 Flap Valve
09 Venturi
REAR CONNECTIONS:
10 Condense Outlet
11 Flow Connection
12 Gas Connection
13 Pressure Relief Valve Outlet
14 Return Connection
09
08
03
07
08
04
06
06
03
09
13
11
14
12
10
01
05
02
TECHNICAL DOCUMENTATION 09

DESCRIPTION
BOILER CONTROL
If there is a heat demand, and if all necessary conditions have been fullled and all safety devices are
satised, the boiler will start. This heat requirement will arise if:
• the ow temperature of the boiler is less than the required ow temperature.
• the frost protection has been triggered independently of the operating conditions.
The boiler control unit adjusts the boiler output by changing the fan speed such that the desired temperature
is attained and maintained. The actual ow temperature is controlled within 4°C of the target temperature.
SAFETY ASPECTS
The following safety devices are installed on the boiler:
• Temperature Monitoring System.
• High Limit Temperature Monitoring System.
• Limit Temperature Monitoring System.
• Flame Monitoring by means of Ionisation Measurement.
• Fan Speed Monitoring.
• Flow Monitoring using a Flow Water Temperature Sensor.
If one of these safety systems is activated, the boiler will go to an interlocking or lockout condition and will
be switched off. Lockout conditions can only be reset by pressing the reset button, after rectifying the fault.
10 TECHNICAL DOCUMENTATION

DELIVERY & TRANSPORT
DELIVERY
The boiler is delivered fully assembled, tested and packed.
• Check the boiler for damage upon receipt.
• Check whether the items delivered are correct and in accordance with the items ordered.
TRANSPORT
The packing should only be removed after transportation.
MOVING
Each boiler is packed in its own carton. Refer to the technical data for dimensions and weights in order to
work safely within the Health and Safety guidelines when handling these products.
ACCESS REQUIREMENTS
The dimensions are such that all ETHOS oor standing boilers can be transported through a standard doorway.
TECHNICAL DOCUMENTATION 11

INSTALLATION
REGULATIONS
The appliance should be installed by a competent installer in accordance with the applicable national and
local standards, rules and regulations (please refer to pages 06 and 07 for safety guidelines).
INSTALLATION GUIDELINES
The following guidelines should be complied with;
• The device should be installed in a frost free room due to the risk of freezing of the condensate
drain.
• The built-in protection system is activated when the temperature of the central heating water falls
below 5°C.
• Ensure that there is sufcient room around the device for maintenance and the replacement of
components if necessary.
• Ensure the base / oor has sufcient load bearing capabilities for the boiler and any other equipment
when full of water.
The recommended minimum clearances are as follows:
• 1000mm to the front (to allow free space for movement).
• 400mm above.
• 100mm at the sides.
12 TECHNICAL DOCUMENTATION

INSTALLATION
VENTILATION
The ventilation of the installation room should conform to current gas regulations.
GAS CONNECTION
The gas connection is located on the rear of the appliance (see page 09). It should be installed by a competent
installer in accordance with the applicable national standards.
A suitable isolation valve should be installed for each boiler and should be in an accessible position. Care
should be taken when sizing the pipework to ensure the supply is sufcient for the maximum load operation
of the boiler.
The pressure on the inlet side of the appliance should be reduced to 20 mbar for natural gas (G20) and no
more than 50 mbar for propane (G31). Under full load conditions the measured gas pressure at the gas valve
should be no less than 17 mbar for natural gas (G20) and 30 mbar for propane (G31).
WATER CONNECTIONS
The boiler is designed for sealed systems only and should not be used for open vented systems. For information
and sizing of sealed system equipment, please refer to our pressurisation management brochure.
It is recommended that manually operated valves should be installed between the boiler ow and return
connections and the system.
It is also recommended that the ow and return pipes are securely xed with brackets. This prevents damage
and makes maintenance easier.
ELECTRICAL CONNECTIONS
The electrical connections should be installed by a competent installer in accordance with applicable
national standards.
The appliance is fully wired in accordance with the electrical diagrams delivered with the appliance.
Electrical terminal connections are located at the top of the boiler and are accessed by removing the boiler
top panel. Suitable cable entry points are supplied in the form of cable glands.
The appliance is suitable for a 230 V 50 Hz power supply with live / neutral / earth and is polarity sensitive. The
installer should use a local two pole isolating switch with a contact opening of at least 3mm in the 230 V supply
to the boiler. A permanent earth must also be installed. In order to prevent problems due to electromagnetic
radiation, screened cables should be used for all control wiring between the boiler and external management
systems. The screening should be earthed on both sides in accordance with current EMC directives.
As the boiler incorporates electrical equipment there is an obligation to the installer to ensure that the boiler
is correctly earthed.
0 - 10 V CONTROL
If using the 0 - 10 V control, please ensure that the voltage is driven down to 0 V to disable the boiler(s) and
that the 0 - 10 V connection to terminals 12 and 13 is not broken; if broken, the boiler can re on low re due
to a voltage differential between terminals 12 and 13. Please note that the 0 - 10 V control will override the
boiler set point and control via the burner modulation i.e. 10 V = 100%. Please ensure that the control voltage
is modulated to prevent the boiler over shooting the required set point.
TECHNICAL DOCUMENTATION 13

INSTALLATION
INTERNAL CONTROLS BREAKDOWN (MAIN PCB)
01 02 03
04 05 06
01 02 03 04 05
06 07 08 09 10
01 02
03 04
01
02
03
04
05
06
07
08
09
10
11
12
13
14
01
02
03
04
05
06
07
08
01
02
03
04
05
06
01
02
03
04
01
02
03
04
0510
09
08
07
06
X18 F00 F01
X16 X17
X13
X12
X15
X14
X11
X02 X01 X00
• X00 Pin 01: Power to Main PCB
• X00 Pin 02: Power to Main PCB
• X01 Pin 01: Boiler Run Signal
• X01 Pin 02: Pump
• X01 Pin 03: 240 V Output[1][2]
• X01 Pin 04: 240 V Output[1][2]
• X01 Pin 05: Fan Mains
• X01 Pin 07: Pump
• X01 Pin 08: 240 V Output[1][2]
• X01 Pin 10: Fan Mains
• X02 Pin 01: Transformer
• X02 Pin 02: Transformer
• X02 Pin 05: Gas Valve Rectied
• X02 Pin 06: Gas Valve Rectied
• X11 Pin 01: AC Fan Interface
• X11 Pin 02: AC Fan Interface
• X11 Pin 03: Flap Valve
• X11 Pin 06: AC Fan Interface
• X11 Pin 07: AC Fan Interface
• X11 Pin 08: Flap Valve
• X13 Pin 01: Pressure Sensor[2]
• X13 Pin 02: Pressure Sensor[2]
• X13 Pin 04: DHW Sensor
• X13 Pin 05: Return Sensor
• X13 Pin 06: Supply Sensor
• X13 Pin 07: Flue Gas High Limit Switch
• X13 Pin 08: Pressure Sensor[2]
• X13 Pin 11: DHW Sensor
• X13 Pin 12: Return Sensor
• X13 Pin 13: Supply Sensor
• X13 Pin 14: Flue Gas High Limit Switch
• X14 Pin 01: Link to X14 Pin 05[3]
• X14 Pin 02: Link to X14 Pin 06[3]
• X14 Pin 05: Link to X14 Pin 01[3]
• X14 Pin 06: Link to X14 Pin 02[3]
• X15 Pin 01: Main PCB to Control Fascia[2]
• X15 Pin 02: Main PCB to Control Fascia
• X15 Pin 03: Main PCB to Control Fascia[2]
• X15 Pin 04: Main PCB to Control Fascia
• X15 Pin 05: Main PCB to Control Fascia
• X15 Pin 06: Main PCB to Control Fascia
▲ FIGURE 02. TOP VIEW OF MAIN PCB.
[1] Used to either power additional pump or motorised valve.
[2] Only used on Burner #00.
[3] Only used on Burner #01.
14 TECHNICAL DOCUMENTATION

INSTALLATION
INTERNAL CONTROLS BREAKDOWN (CONTROL FASCIA)
X06
X01X04
X03
X05
• X01 Pin 01: Control Fascia to Main PCB[1]
• X01 Pin 02: Control Fascia to Main PCB[1]
• X01 Pin 03: Control Fascia to Main PCB[1]
• X01 Pin 04: Control Fascia to Main PCB[2]
• X01 Pin 05: Control Fascia to Main PCB[2]
• X01 Pin 07: Control Fascia to Main PCB[1]
• X01 Pin 08: Control Fascia to Main PCB[1]
• X01 Pin 09: Control Fascia to Main PCB[1]
• X01 Pin 10: Control Fascia to Main PCB[2]
• X01 Pin 11: Control Fascia to Main PCB[2]
[1] Only used on Burner #00.
[2] Only used on Burner #01.
• X03 Pin 02: Communication with Master
• X03 Pin 04: Communication with Master
• X03 Pin 05: Communication with Master
• X04 Pin 01: 0 - 10 V DC Input
• X04 Pin 02: OpenTherm
• X04 Pin 03: OpenTherm
• X04 Pin 04: External Sensor
• X04 Pin 05: External Sensor
• X04 Pin 06: 0 - 10 V DC Input
• X04 Pin 07: CH Cascade Sensor
• X04 Pin 08: CH Cascade Sensor
• X04 Pin 09: Room Thermostat
• X04 Pin 10: Room Thermostat
• X05 Pin 01: Alarm Output
• X05 Pin 02: Alarm Output
• X05 Pin 05: Reset
• X05 Pin 06: Reset
• X06 Pin 02: Communication with Slave
• X06 Pin 03: Communication with Slave
• X06 Pin 04: Communication with Slave
▲ FIGURE 03. TOP VIEW OF CONTROL FASCIA.
EXTERNAL CONTROLS BREAKDOWN (DIN RAIL)
▲ FIGURE 04. FRONT VIEW OF DIN RAIL.
ALive, Earth and Neutral: Incoming Supply HConnections 14 and 15: OpenTherm
BConnections 1 and 2: Room Thermostat[1] IConnections 16, 17 and 18: Communication with Slave
CConnections 3 and 4: External Sensor JConnections 19, 20 and 21: Communication with Master
DConnections 5 and 6: DHW Thermostat[1] KConnections 22 and 23: CH Cascade Sensor
EConnections 7, 8 and 9[2]:DHW Output[3] LConnection 24[4]:Burner #00 Boiler Run Signal
FConnection 11[4]:Alarm Output Connection 25[4]:Burner #01 Boiler Run Signal
GConnections 12 and 13: 0 - 10 V DC Input[5] MLive, Earth and Neutral: Supply to External Pump[6]
[1] Volt Free Connection (UNDER NO CIRCUMSTANCES MUST VOLTAGE BE APPLIED TO THESE CONNECTIONS).
[2] 240 V Output in no DHW Load Condition.
[3] Used to either power additional Pump or Motorised Valve.
[4] 240 V Output.
[5] Factory tted link, do not remove unless utilising 0 - 10 V control.
[6] 240 V Output (0.8 A).
If the current requirement for the external pump supply exceeds 0.8 A, a contacter / relay will need to be
used as appropriate.
A B C D E F G H I K MJ L
TECHNICAL DOCUMENTATION 15

INSTALLATION
CONTROLS AND OPTIONS
The boiler features an automatic fully modulating control system and as such can be used as a ‘stand alone’
appliance.
The standard controls include;
• 0 - 10 V Input ready.
• Condense Trap Blockage Cut Out.
• Domestic Hot Water Priority Control.
• Frost Protection.
• Low Pressure Cut Out.
• Shunt Pump Overrun Timer.
• Weather Compensation (Optional Sensor Required).
16 TECHNICAL DOCUMENTATION

INSTALLATION
FLUE CONNECTION
The ue gas discharge outlet system should be installed by a competent installer according to applicable
national and local standards and specications. Care should also be taken to ensure compliance with the
Clean Air Act.
The boilers are suitable for open type ue systems.
• Type B23: Open type appliance without draught stabiliser, air supply from the room, ue gas
discharge outlet above the roof.
The ue gas outlet is located at the rear of the appliance and is designed for direct connection to a corrosion
resistant ue pipe.
The ue gas discharge pipe to be used should be air tight and water tight at the joints and connections, or
should be seamless. Horizontal components in the ue pipe should be installed sloping in the direction of the
appliance (minimum 25mm per metre).
The maximum permissable draught on the boiler is 20 Pa.
Care should be taken when making joints to ensure that the seals are not damaged and the joints must be
sited to enable access / inspection (GasSafe TB 008 Ed. 2.1).
A direct connection to a brick chimney is not permissible unless a suitable liner is installed.
The following table gives the ue gas data for all types:
ETHOS 350 ETHOS 550
Average Flue Gas Temperature at Full Load °C 70 70
Quantity of Flue Gas at Full Load m3/h 651 1023
kg/s 0.18 0.28
Maximum Permissable Flue Resistance Pa 200 250
▲ FIGURE 05. FLUE GAS DATA / LOAD 100% / FLOW TEMPERATURE 80°C / RETURN TEMPERATURE 60°C.
CONDENSE REMOVAL
Drains should be tted to all ue systems to eliminate excessive condense running through the boiler.
TECHNICAL DOCUMENTATION 17

INSTALLATION
FLUE LENGTH
Since the boiler is equipped with a ‘premix burner’ with a fan, an over pressure is created in the boiler. This
over pressure is sufcient to overcome the resistance of the burner, the heat exchanger and the chimney.
The back pressure on the boiler depends on:
•the resistance of the ue pipe.
• the degree of cooling of the combustion gases.
• the resistance of the discharge outlet.
The degree of cooling of the combustion gases depends on the following:
•the insulation value of the ue.
• the ambient temperature.
•the ue system and outlet.
There is a maximum over pressure of around 2.0 mbar (200 Pa) for the ETHOS 350 and 2.5 mbar (250 Pa) for the
ETHOS 550 in the boiler for the ue gas discharge system.
The maximum draught permissible is 0.2 mbar (20 Pa), this should be checked with the flue warm and boilers
not firing. Exceeding these figures will be detrimental to both the performance and warranty of the
appliance.
CALCULATION OF DIAMETER AND LENGTH
For the calculation and control of the inner diameter of a discharge system with mechanical discharge,
please refer to the applicable national and local standards and regulations.
18 TECHNICAL DOCUMENTATION

INSTALLATION
CONDENSE CONNECTIONS
The boiler includes an anti syphon condense trap enabling the condense pipework to be taken directly to
drain. The condense water is slightly acidic (pH 3.0 - 5.5) and should be run in a standard drain pipe material,
e.g. acrylonitrile-butadiene-styrene (ABS), polypropylene (PP), polyvinyl chloride (PVC), cross-linked polyvinyl
chloride (PVC-C) or unplasticised polyvinyl chloride (PVC-U).
The condensate pipe should ideally run and terminate internally to a soil stack or waste pipe. Alternatively,
the condensate can be discharged in to the rainwater system or a purpose-made soakaway. Whichever
method is used must conform to applicable national and local standards and regulations. All connecting
drainage pipework should have a fall of at least 2.5° to the horizontal, or approximately 25mm per metre of
pipe run. If the drainage pipe has external run it should be kept to a minimum length with a minimum diameter
of 22mm and be insulated in order to minimise the effects of freezing. It should be noted that connection of
a condensate pipe to a drain may be subject to building controls.
SAFETY VALVE CONNECTION
The discharge pipe from the safety valve shall be self draining and terminate in a visible position where the
discharge cannot result in hazard to any person or to the plant. The size of the discharge pipe shall be no less
than the nominal size of the valve outlet.
HYDRAULIC SYSTEM
The minimum required water circulation over the boiler should be maintained at all times (equivalent to ΔT
25°K at full load). The minimum required water circulation should not be adversely affected by the use of
valves, non-return valves, systems in which several boilers are connected to a common distribution pipe etc.
The maximum water ow is achieved at ΔT 15°K.
ETHOS 350 ETHOS 550
ΔT 20°K Nominal Flow Rate (Q) m3/h 14.99 23.57
Boiler Resistance Nominal Flow (R) kPa 40 35
▲ FIGURE 06. WATER FLOW QUANTITY FOR THE FLOOR STANDING ETHOS RANGE.
The boiler has a pump control circuit to operate an external shunt pump. When the boiler is enabled, the
pump is switched on. If the boiler is disabled, the pump will continue to run for a few minutes. The standard run
on time is ve minutes, but this can be adjusted.
TECHNICAL DOCUMENTATION 19

INSTALLATION
SHUT-OFF VALVES
It is recommended that manual valves should be installed between the ow and return connections to the
installation.
VALVES (BOILERS IN CASCADE ARRANGEMENT)
To prevent water ow through non-ring boilers, and hence unnecessary heat loss, a spring loaded non-return
valve may be installed on the return pipework external to the boiler.
DRAINING AND CLEANING
To drain and clean the boiler, a drain valve must be installed between the boiler and the rst valve. Isolate the
water and electrical supplies to the boiler and open the drain valve. As there is an automatic air vent on the
boiler the water will drain naturally. Please note the bottom coils will not drain fully and water will remain. To
clean the water side of the boiler a suitable descaler / desludger can be used. Please contact our technical
department on 03452 60 60 20 for further information.
WATER CIRCULATION SYSTEM
A circulation pump MUST be connected to the boiler and the hot water cylinder MUST be of the indirect
type. The boiler MUST NOT be used for direct hot water supply, and single feed, indirect cylinders are not
recommended and MUST NOT be used on sealed systems. The appliance is NOT suitable for gravity central
heating nor are they suitable for the provision of domestic hot water.
The hot water cylinder and ancillary pipework, not forming part of the useful heating surface, should be
lagged to prevent heat loss and any possible freezing, particularly where pipes run through roof spaces
and ventilated underoor spaces. The boiler must be vented and there must be no low points between the
boiler ow connection and a system venting point, which should be positioned as close to the boiler ow
connection as is possible.
Draining taps MUST be located in accessible positions, which permit the draining of the whole system, including
the boiler and hot water storage vessel. They should be at least ½” BSP nominal size and be in accordance
with BS2879. Do not use the boiler drain tap to drain the system as this can induce sludge into the heat
exchanger.
The central heating system should be in accordance with the relevant standards listed on page 07.
Due to the compact nature of the boiler, the heat stored within the heat exchanger at the point of shutdown
of the burner must be dissipated into the water circuit in order to avoid overheating. In order to allow pump
operation after shutdown, the boiler incorporates a ve minute pump overrun facility. In order to make use
of this, the pump must be supplied from the terminals inside the boiler. Please note that for pumps requiring
greater than 1.0 amp current, they must be connected via a relay / contactor. When sizing pumps, reference
should be made to the hydraulic resistance table on page 19 which shows the boiler resistance against ow
rates, to achieve the required temperature differential.
With the boiler ring at maximum rate, the temperature differential should not be less than 10°C. With the boiler
ring at minimum rate, the temperature differential should not be more than 35°C. Lower ow rates generating
higher temperature differentials may lead to lockouts of the boiler. The lower the return temperature to the
boiler, the higher the efciency. At return temperatures of 55°C and below, the difference becomes marked
because the water in the ue gases starts to condense, releasing its latent heat.
In installations where all radiators have been provided with thermostatic radiator valves, it is essential that
water circulation through the boiler is guaranteed. A low loss header will perform this task.
20 TECHNICAL DOCUMENTATION