VOKERA unica he Release note

Installation
& Servicing
Instructions
THESE INSTRUCTIONS
TO BE RETAINED
BY USER
Vokèra is a licensed member of the Benchmark scheme
which aims to improve the standards of installation and
commissioning of domestic hot water systems in the UK.
Unica HE
High efficiency combi boiler

Contents
Design principles & operating sequence Page
1.1 Principle components 3
1.2 Mode of operation (at rest) 3
1.3 Mode of operation (heating) 3
1.4 Mode of operation (Hot water) 3
1.5 Safety devices 3
Technical data Page
2.1 Central heating 4
2.2 Domestic hot water 4
2.3 Gas pressures 4
2.4 Expansion vessel 4
2.5 Dimensions 4
2.6 Clearances 4
2.7 Connections 4
2.8 Electrical 4
2.9 Flue details (concentric) 4
2.9A Flue details (twin pipes) 4
2.9B Flue details (80/125) 4
2.10 Efficiency 4
2.11 Emissions 4
2.12 Pump duty 5
General requirements (UK) Page
3.1 Related documents 6
3.2 Location of appliance 6
3.3 Gas supply 6
3.4 Flue system 6
3.5 Air supply 6
3.6 Water circulation 6
3.7 Electrical supply 7
3.8 Mounting on a combustible surface 7
3.9 Timber framed buildings 7
3.10 Inhibitors 7
3.11 Showers 7
General requirements (EIRE) Page
3A.1 Related documents 8
3A.2 Location of appliance 8
3A.3 Gas supply 8
3A.4 Flue system 8
3A.5 Air supply 8
3A.6 Water circulation 8
3A.7 Electrical supply 9
3A.8 Mounting on a combustible surface 9
3A.9 Timber framed buildings 9
3A.10 Inhibitors 9
3A.11 Showers 9
3A.12 Declaration of conformity 9
Installation Page
4.1 Delivery 10
4.2 Contents 10
4.3 Unpacking 10
4.4 Preparation for mounting the appliance 10
4.5 Fitting the flue 10
4.6 Connecting the gas & water 14
4.7 Electrical connections 15
Commissioning Page
5.1 Gas supply installation 16
5.2 The heating system 16
5.3 Initial filling of the system 16
5.4 Initial flushing of the system 16
5.5 Pre-operation checks 16
5.6 Initial lighting 16
5.7 Checking gas pressure & combustion analysis 16
5.8 Final flushing of the heating system 17
5.9 Setting the boiler operating temperature 17
5.10 Setting the system design pressure 17
5.11 Regulating the central heating system 17
5.12 Final checks 17
5.13 Instructing the user 17
Servicing Page
6.1 General 18
6.2 Routine annual servicing 18
6.3 Replacement of components 18
6.4 Component removal procedure 18
6.5 Pump assembly 18
6.6 Safety valve 19
6.7 Lower automatic air release valves 19
6.8 Water pressure switch 19
6.9 Primary thermistor 19
6.10 Return thermistor 19
6.11 Printed circuit board 19
6.12 Gas valve 19
6.13 Electrodes and condense sensor 20
6.14 Flue fan & mixer 20
6.15 Burner 20
6.16 Main heat exchanger 20
6.17 Automatic by-pass 21
6.18 Expansion vessel 21
6.19 Condense trap removal 21
6.20 Flue collector removal 21
Checks, adjustments and fault finding Page
7.1 Checking appliance operation 23
7.2 Appliance modes of operation 23
7.3 Appliance fan speed 24
7.4 Checking the CO2& adjusting the valve 24
7.5 Combustion analysis test 25
7.6 Checking the expansion vessel 25
7.7 External faults 25
7.8 Electrical checks 25
7.9 Fault finding 26
7.10 Component values & characteristics 26
7.11 Final fault codes 26
7.12 Boiler configuration 26
Wiring diagrams Page
8.1 External wiring 27
8.2 Typical control applications 27
8.3 Other devices 27
8.4 Vokera twin-channel programmer 27
Exploded diagrams Page
9.1 Table 1 29
9.2 Table 2 30
9.3 Table 3 31
9.4 Table 4 32
9.5 Table 5 33
L.P.G. instructions Page
10.1 Related documents 34
10.2 Technical data 34
10.3 Converting the appliance gas type 34
10.4 Gas supply 34
10.5 Gas supply installation 34
10.6 Adjusting the gas valve 34
10.7 Appliance fan speed 35
Benchmark 36

1
The Unica HE comprises a range of high-efficiency
combination boilers with outputs to DHW of 28kW, 32kW,
and 36kW respectively. These appliances – by design
– incorporate electronic ignition, circulating pump,
expansion vessel, safety valve, pressure gauge, and
automatic by-pass.
The Unica range is produced as room sealed, category
II2H3P appliances, suitable for internal wall mounting
applications only. Each appliance is provided with a fan
powered flue outlet with an annular co-axial combustion air
intake that can be rotated – horizontally – through 360
degrees for various horizontal or vertical applications. The
Unica HE can also be used with the Vokera twin flue
system.
The Unica HE is approved for use with C13 & C33 type flue
applications.
These appliances are designed for use with a sealed
system only; consequently they are not intended for use
on open vented systems.
This booklet is an integral part of the appliance. It is
therefore necessary to ensure that the booklet is handed
to the person responsible for the property in which the
appliance is located/installed. A replacement copy can
be obtained from Vokera customer services.
INTRODUCTION
The Unica HE is approved for use with C13 & C33 type flue applications.
fig. 1
General layout (fig. 1)
1 Three porte valve actuator
2 Drain valve
3 Safety valve
4 Pressure switch
5 Pump
6 Bottom auto air vent (AAV)
7 Injector
8 Condense trap
9 Return sensor
10 Flue gas analysis test point
11 Flue outlet & air intake
12 Ignition transformer
13 Top AAV
14 Flow sensor
15 High limit thermostat
16 Limit thermostat
17 Sensing Electrode
18 Spark Electrode
19 Cylindric Burner
20 Condensate level sensor
21 Main heat exchanger
22 Top AAV pipe
23 Fan assembly
24 Mixer
25 Expansion vessel
26 Domestic hot water sensor
27 Domestic hot water heat exchanger
28 DHW flow switch
29 Gas valve
30 Condensing drain
R Heating return connection
F Heating flow connection
G Gas connection
O Hot water outlet
I Cold water inlet
R F G O I
R F G O I

2
Fig. 1A
MODE SELECTOR
SWITCH
RED LED
GREEN LED
HEATING
TEMPERATURE
SELECTOR
2-digit LED
display
HYDROMETRE
DHW
TEMPERATURE
SELECTOR
Hot water only Select this position if you want the boiler to supply hot water only (no heating)
Boiler at OFF/standby Select this position when you want the boiler to be switched off or short
periods (days) or if the boiler requires to be reset (refer to users handbook)
Heating & hot water (economy) Select this position when you want the boiler to respond to a heating request
from the time-clock/programmer
Heating & hot water with pre-heat Select this position when you want the boiler to respond to a heating request
from the time-clock/programmer (comfort) and you want the domestic hot
water to be pre-heated
DHW temperature selector Move the selector clockwise to increase the hot water outlet temperature, or
counter-clockwise to reduce the temperature
Heating temperature selector Move the selector clockwise to increase the heating outlet temperature, or
counter-clockwise to reduce the temperature
2-digit LED display Displays the current outlet temperature of the boiler. During a fault condition,
the appropriate fault code will be displayed (refere to the users handbook for
instructions regarding fault codes)
Green LED lit Boiler is working/responding to a heating/hot water request
Red LED lit Boiler has identified a fault and has failed-safe. Refer to users handbook for
instructions on how to reset
Pressure gauge Ensure the system pressure is set correctly (minimum 0.5-bar)

3
SECTION 1 DESIGN PRINCIPLES AND OPERATING SEQUENCE
1.1 PRINCIPLE COMPONENTS
•A fully integrated electronic control board
featuring electronic temperature control, anti-
cycle control, pump over-run, self-diagnostic
fault indicator, full air/gas modulation.
•Radial aluminium heat exchanger.
•Electronic ignition with flame supervision
•Integral high-head pump
•Fan
•Expansion vessel
•Water pressure switch
•Condensate level sensor
•Pressure gauge
•Safety valve
1.2 MODE OF OPERATION (at rest)
When the appliance is at rest and there are no
requests for heating or hot water, the following
functions are active:
•Frost-protection system – the frost-protection
system protects the appliance against the risk
of frost damage both for CH and DHW. For CH
line, if the main temperature falls to 6°C, the
appliance will function on minimum power until
the temperature on main reaches 35°C.
Moreover if the DHW temperature falls to 4°C,
the appliance will function on minimum power
until the temperature on main reaches 55°C.
•Anti-block function – the anti-block function
enables the pump and divertor valve actuator to
be energised for short periods, when the
appliance has been inactive for more than 24-
hours.
1.3 MODE OF OPERATION (Heating)
When there is a request for heat via the time clock
and/or any external control, the pump and fan are
started, the fan speed will modulate until the
correct signal voltage is received at the control
PCB. At this point an ignition sequence is
enabled.
Ignition is sensed by the electronic circuit to
ensure flame stability at the burner. Once
successful ignition has been achieved, the
electronic circuitry increases the gas rate to 75%
for a period of 15 minutes. Thereafter, the boiler’s
output will either be increase to maximum or
modulate to suit the set requirement.
When the appliance reaches the desired
temperature the burner will shut down and the
boiler will perform a three-minute anti-cycle (timer
delay).
When the request for heat has been satisfied the
appliance pump and fan may continue to operate
to dissipate any residual heat within the appliance.
1.4 MODE OF OPERATION (Hot water)
When there is a request for DHW via a hot water
outlet or tap, the pump and fan are started, the
fan speed will modulate until the correct signal
voltage is received at the control PCB. At this
point an ignition sequence is enabled.
Ignition is sensed by the electronic circuit to
ensure flame stability at the burner. Once
successful ignition has been achieved, the
electronic circuitry increases the gas rate to
maximum or will modulate output to stabilise the
temperature.
In the event of the appliance exceeding the desired
temperature (set point) the burner will shut down
until the temperature drops. When the request for
DHW has been satisfied the appliance pump and
fan may continue to operate to dissipate any
residual heat within the appliance.
1.5 SAFETY DEVICES
When the appliance is in use, safe operation is
ensured by:
•A water pressure switch that monitors system
water pressure and will de-activate the pump,
fan, and burner should the system water pressure
drop below the rated tolerance.
•Fan speed sensor to ensure safe operation of
the burner
•A high limit thermostat that over-rides the
temperature control circuit to prevent or interrupt
the operation of the burner.
•Flame sensor that will shut down the burner
when no flame signal is detected.
•A sensor that interrupts the operation of the
appliance if the condense pipe becomes blocked.
•A safety valve which releases excess pressure
from the primary circuit.
Fig. 2
Expansion
vessel
Safety
valve
Pump
Return
temperature
sensor
Main heat
exchanger
Bottom
AAV
Pressure
switch
DHW heat
exchanger
Diverter
valve
Drain
valve
DHW
temperature
sensor
Flow temperature
sensor
Top AAV
Automatic
by-pass
DHW
nonreturn
valve
Flow
regulator
CH
return
CH
flow
DHW flow
switch
DHW
inlet
DHW
outlet