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Hoval STU Wood Pellet Boiler
Maintenance - Inspection & Servicing
A Hoval approved service engineer will be required to carry out work other than
the following: boiler cleaning, inspection of components for damage, initial start-
up combustion check and the specified testing and minor fault rectification.
Always ensure the boiler and stoker are electrically isolated before carrying out
inspections and repairs to the equipment.
No special equipment is required for normal boiler servicing.
Tools for cleaning the boiler heating surfaces are provided with the boiler.
The service engineers' equipment will include any necessary special tools and
also a combustion efficiency test kit.
Periodic Inspection
The following periodic inspections should be made between main servicing periods.
• Examine boiler casing panels for obvious signs
of damage, corrosion or other deterioration, and for security (Badly fitting
casings and damaged insulation materials leads to wasted heat and an increase in the boilerhouse ambient temperature).
• Examine the flue pipe and gasket for obvious signs of damage, corrosion, flue-gas leakage, and for security. Similarly inspect
the cleaning explosion door at rear of boiler.
• Examine the flue and chimney, as far as possible, for partial blockage, debris, etc.
• Ensure that condensation drains at the chimney base are clear and that the boiler flue box drain socket is connected to a drain
pipe with a water trap.
• Keep the boilerhouse floor clear of dust and debris which may be drawn into the stoker and cause damage.
• Examine all fuel and water valves, connection and stoker etc, for obvious signs of damage or leakage, and for security.
In an open-vented heating system, check:
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Level of water in the feed and expansion tank.
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That the ball valve is free to operate correctly.
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All air vents are operating correctly.
Report any occurrences which indicate that the boiler, the firing equipment or the system controls are not operating correctly.
NOTE: No continuous make-up of water should be
taking place (In this event check where a leak may be
occurring or if pumping over is taking place).
Maintenance - Boiler and Stoker Servicing
In addition to the periodic inspections given above it is recommended that a complete check is carried out on all components at appro-
priate intervals.
These checks must be made by a Hoval approved service engineer, ideally under an annual service and maintenance contract.
Hoval Service Department normally provides this service and will be pleased to provide a written quotation on request. This would typi-
cally cover the operation, cleanliness, combustion efficiency etc., of the stoker and associated controls.
Boiler Heating Surfaces
• Check conditions of smokebox cleaning door gasket. Refit door, ensuring it seats correctly on the gasket and tighten
the securing bar nuts.
• Check condition of boiler door ceramic seal. Inspect the lining material on the door. Minor damage to insulating
material can be carefully rectified using a mouldable refractory (e.g. Pyruma) on refractory lined doors. Where a door
is lined with ceramic fibre it is unlikely to suffer damage in normal use but in the unlikely event please consult Hoval.
Any serious damage must be reported to the Service Engineer for repair. Filler material can be repaired similarly.
The door sealing strip must be in good condition and must be replaced when an effective seal cannot be obtained
under normal pressure. Replace sealing strip annually.
• Close the boiler door, and evenly tighten the nuts using a tommy bar/spanner.
• All door nuts and hinge assembly to be greased periodically.
Summer Shut Down
If the boiler is to be out of operation for a long period, e.g. during the summer, the boiler should be thoroughly cleaned.
Atmospheric condensation, activating acidic deposits in the boiler is responsible for considerable corrosion and metal
wastage. Every effort should be made to reduce this by the most thorough cleaning and by keeping the boiler fireside
internals dry.
A tray of absorbing material is placed in the combustion chamber is helpful in this respect. Close the boiler door.
