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5.1 GAS SUPPLY INSTALLATION

Inspect the entire installation including the gas meter, test for 

tightness and purge. Refer to BS 6891 (I.S. 813 in ROI) for 

specific instruction.

5.2 THE HEATING SYSTEM

The appliance contains components that may become damaged 

or rendered inoperable by oils and/or debris that are residual 

from the installation of the system, consequently it is essential 

that the system be flushed in accordance with the following 

instructions.

5.3 INITIAL FILLING OF THE SYSTEM

Ensure both flow and return service valves are open, remove 

appliance casing as described in 4.7.1, identify the automatic air 

release valves (AAV) and loosen the dust cap/s by turning the 

cap anti-clockwise one full turn. Ensure all manual air release 

valves located on the heating system are closed. Connect the 

filling loop as shown in fig. 5, slowly proceed to fill the system 

by firstly opening the inlet valve connected to the flow pipe, and 

then turning the lever on the fill valve, to the open position. As 

water enters the system the pressure gauge will begin to rise. 

Once the gauge has reached 1 BAR close both valves and begin 

venting all manual air release valves, starting at the lowest first. 

It may be necessary to go back and top-up the pressure until 

the entire system has been filled. Inspect the system for water 

tightness, rectifying any leaks.

5.3.1 MANUAL AIR RELEASE (fig. 19)

When the boiler has been filled for the first time or the system 

has been drained and refilled, it will be necessary to release 

any air that may have become trapped within the appliance heat 

exchanger.  Slacken the bleed screw until water is released 

and then close.

IMPORTANT, THERE ARE NO OTHER MANUAL AIR RE-

LEASE VALVES LOCATED ON THE APPLIANCE.

5.4 INITIAL FLUSHING OF THE SYSTEM

The whole of the heating system must be flushed both cold 

and hot as detailed in 5.8. Open all radiator or heating valves 

and the appliance flow & return service valve. Drain the boiler 

and system from the lowest points. Open the drain valve full 

bore to remove any installation debris from the boiler prior to 

lighting. Refill the boiler and heating system as described in 5.3.

5.5 PRE-OPERATION CHECKS

Before attempting the initial lighting of the appliance, the fol-

lowing checks must be carried out:

•  ensure all gas service valves from the meter to the appliance 

are open and the supply pipe has been properly purged;

Fig. 19

•  ensure the proper electrical checks have been carried out, 

(see 7.8) particularly continuity, polarity and resistance to 

earth;

•  ensure the 3 AMP fuse – supplied with the appliance – has 

been fitted;

•  ensure the system has been filled, vented and the pressure 

set to 1 BAR;

•  ensure the flue system has been fitted properly and in ac

-

cordance with the instructions;

•  ensure all appliance service valves are open.

5.6 INITIAL LIGHTING

Ensure the electrical supply to the appliance is switched on. 

Ensure any external controls are switched to an ‘ON’ position 

and are calling for heat. Move the selector switch to the ON 

position, the appliance will now operate as described in 1.2. 

Should the appliance fail to ignite, refer to 5.6 and/or section 7 

(mode of operation, parameter setting & faultfinding).

5.7 CHECKING GAS PRESSURE AND COMBUS-

TION ANALYSIS

The appliance is factory set so should require no additional 

adjustment once installed. However to satisfy the require-

ments of GSIUR 26/9 (I.S. 813 ROI), it will be necessary to 

gas rate the appliance using the gas meter that serves the 

appliance and carry out a combustion analysis check in accor-

dance with BS 7967 (UK)  to ensure that correct combustion is 

occurring, see flow chart on page 32.

Additionally, if the gas valve has been adjusted, replaced, or 

the appliance has been converted for use with another gas 

type, then it becomes necessary to carry out a combustion 

analysis check to ensure that correct combustion is occurring.

If there are no means to carry out a combustion analysis 

check, then it will not be possible to complete the commissio-

ning procedure.

Details on how to carry out the combustion analysis can be 

found in section 7.

IMPORTANT

It’s imperative that a sufficient dynamic – gas – pressure is 

maintained at all times. Should the dynamic gas pressure fall 

below an acceptable level, the appliance may malfunction or 

sustain damage.

5.8 FINAL FLUSHING OF THE HEATING SYSTEM

The system shall be flushed in accordance with BS 7593 (I.S. 

813 ROI). Should a cleanser be used, it must be suitable for 

Aluminium heat exchangers. It shall be from a reputable manu-

facturer and shall be administered in strict accordance with the 

manufacturers’ instructions and the DWTA code of practice.

NOTE

Chemicals used to cleanse the system and/or inhibit corrosion 

must be pH neutral, i.e. they should ensure that the level of the 

pH in the system water remains neutral. Premature failure of 

certain components can occur if the level of pH in the system 

water is out-with normal levels.

5.8.1 INHIBITORS

See Section 3 “General Requirements”.

5.9 SETTING THE FLOW OUTLET TEMPERA-

TURE

The flow outlet temperature can be adjusted between 40 °C - 

80 °C for standard CH system by using the Heating thermostat 

knob (see fig.1).

5.9.1 SETTING THE DHW OUTLET TEMPERATURE

The DHW outlet temperature can be adjusted between 37 °C 

- 60 °C via the DHW thermostat knob (see fig.1).

5.10 SETTING THE SYSTEM DESIGN PRESSURE

The design pressure should be a minimum of 0.5 BAR and a 

maximum of 1.5 BAR. The actual reading should ideally be 1 

BAR plus the equivalent height in metres (0.1 BAR = 1 metre) to 

the highest point in the system above the base of the appliance 

SECTION 5 - COMMISSIONING

Summary of Contents for Excel 25

Page 1: ...S TO BE RETAINED BY USER Vok ra 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 Excel High ef...

Page 2: ...3A 5 Air supply 11 3A 6 Water circulation 11 3A 7 Electrical supply 11 3A 8 Mounting on a combustible surface 11 3A 9 Timber framed buildings 11 3A 10 Inhibitors 11 3A 11 Showers 11 3A 12 Declaration...

Page 3: ...el boiler has been designed to meet and exceed the very latest standards in gas central heating technology and if cared for will give years of reliable use and efficiency Please therefore take some ti...

Page 4: ...et temperature or counter clockwise to reduce the temperature range 37 C 60 C Boiler at OFF standby Select this position when you want the boiler to be switched off for short periods days or if the bo...

Page 5: ...may be necessary to reduce the flow of water at the hot water outlet tap NOTE If the appliance fails to ignite during the ignition sequence it will enter a lockout condition Should this occur please a...

Page 6: ...switch in the bottom position To select OFF mode move the selector switch in the upper position APPLIANCE STATUS LED AND FAULT CODES Fig 3 4 WHAT IF 5 SETTING THE VOK RA Advice for homeowners Please c...

Page 7: ...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...

Page 8: ...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...

Page 9: ...ume 74 litres Pre charge pressure 1 bar 2 5 Dimensions Excel 25 Excel 29 Height mm 715 Width mm 405 Depth mm 250 Dry weight kg 28 29 2 6 Clearances Excel 25 Excel 29 Sides 12mm Top 150mm from casing o...

Page 10: ...ain pipe etc 25 mm E Below eaves 25 mm F Below balcony car port roof etc 25 mm G To the side of a soil drain pipe etc 25 mm 60mm for 80 125 5 flue H From internal external corner 25 mm 60mm for 80 125...

Page 11: ...n vessel to accom modate the increased volume of water when the system is heated It can accept up to 8 litres of expansion from within the system generally this is sufficient however if the system has...

Page 12: ...is to be fitted on a wall of combustible material There is no requirement to protect the wall 3 9 TIMBER FRAMED BUILDINGS If the appliance is to be fitted in a timber framed building it shouldbefitte...

Page 13: ...W PRESSURE SEALED SYSTEM An alternative method of filling the system would be from an independent make up vessel or tank mounted in a position at least 1 metre above the highest point in the system an...

Page 14: ...plane see2 9 Areductionmustalsobemadetothemaximumlength see table below when additional bends are used Reduction for additional bends Bend Reduction in maximum flue length for each bend 45 bend 1 0 me...

Page 15: ...e installation of the 80 125mm concentric flue system please refer to the instructions supplied The vertical flue terminal can be connected directly to the ap pliance flue outlet Alternatively an exte...

Page 16: ...ir 2000mm 0225840 45 bend pair N A 0225845 90 bend pair N A 0225850 Twin bracket 5 N A 0225855 Single bracket 5 N A MOUNTING THE BOILER The fixing holes for the wall mounting bracket should now be dri...

Page 17: ...wards the appliance 17mm per 1000mm Fig 13c Fig 14 4 6 CONNECTING THE GAS AND WATER The appliance is supplied with an accessory pack that includes service valves Theservicevalvesareforwelding Theacces...

Page 18: ...circuits please refer to section 8 for detailed instructions ANYEXTERNALCONTROLOR WIRING MUST BE SERVED FROM THE SAME ISOLATOR AS THAT OF THE APPLIANCE The supply cable from the isolator to the appli...

Page 19: ...d properly and in ac cordance with the instructions ensure all appliance service valves are open 5 6 INITIAL LIGHTING Ensure the electrical supply to the appliance is switched on Ensure any external c...

Page 20: ...tres flow restrictor 5 12 FINAL CHECKS ENSURE ALL TEST NIPPLES ON THE APPLIANCE GAS VALVE ARE TIGHT AND CHECKED FOR TIGHTNESS ENSURE THE APPLIANCE FLUE SYSTEM IS FITTED CORRECTLY AND IS PROPERLY SECUR...

Page 21: ...ved from the appliance Replace carefully in the reverse order 6 6 SAFETY VALVE fig 22 Carry out component removal procedure as described in 6 4 Disconnect the outlet pipe G from the safety valve remov...

Page 22: ...omponent removal procedure as described in 6 4 Remove the air chamber front cover Disconnect the electrode leads and ancillary wiring from their respective connectors Re move the retaining screws V fo...

Page 23: ...ibed in 6 4 Remove the locking pin Q1 that secures the cover R1 to the hydraulic manifold Using a hooked piece of wire carefully withdraw the by pass cartridge S1 and or DHW non return cartridge T1 En...

Page 24: ...onnectthewiringtotheDHWflowswitch Slacken and unscrew the inlet connection Unscrew the nut E2 Lift the DHW flow switch housing from its seating If necessary remove the locking pin F2 from the DHW flow...

Page 25: ...sed for more that 20 minutes 7 2 3 HEATING MODE With the selector switch in the heating hot water position and any additional controls time clock programmer room thermostat etc calling for heat the ap...

Page 26: ...ut the component removal procedure as described in 6 4 You must ensure that the boiler is completely drained of water Using a suitable pressure gauge remove dust cap on expansion vessel and check the...

Page 27: ...letion of any task that required the disconnection and re connection of any electrical wiring or component these checks must be repeated 7 8 FAULT FINDING Before attempting any faultfinding the electr...

Page 28: ...c information on the suitability of a particular control Further guidance on the recom mended practice for the installation of external controls can be found in CHeSS HC5 HC6 www energyefficiency gov...

Page 29: ...oiler lock out CN1 CN15 Connectors CN5 Room thermostat 24 Vdc S W CO2 function button F S 1 Flame sensor F1 Fuse 3 15A T F External fuse 3 15A F M3 Terminal strip for electrical connection hight power...

Page 30: ...yellow led blinking gas valve maximun setting press twice burner running at maximum DHW yellow led blinking red led fixed gas valve minimum setting press three time burner running at minimum yellow l...

Page 31: ...3 However if the CO2 reading is incorrect the minimum gas pressure must be adjusted as follows locate the minimum adjustment screw fig 37 using a suit able screwdriver remove the protection plug using...

Page 32: ......

Page 33: ......

Page 34: ...to stabilise YES Is CO less than 350ppm AND CO CO2 ratio less than 0 004 NO Boiler is operating satisfactorily No further actions required Ensure test points are capped boiler case is correctly repla...

Page 35: ......

Page 36: ...s vokera co uk www vokera co uk www vokera ie Sales General Enquires T 0844 391 0999 F 0844 391 0998 Vok ra Ireland West Court Callan Co Kilkenny T 056 7755057 F 056 7755060 Vok ra Limited reserve the...

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