Thermal Disinfection; Inspection And Maintenance; Mains Supplies; Inspection And Maintenance Considerations - Worcester Greenstar 4000 Installation And Maintenance Instructions Manual

Inspection and maintenance

7.3

Thermal disinfection

To prevent hot water from becoming contaminated by bacteria such as
legionella, we recommend thermal disinfection after long downtimes.
CAUTION
Risk of scalding:
During thermal disinfection, discharging unmixed hot water can cause
serious scalding.
▶ Run thermal disinfection at the factory default temperature of 70 °C
for a minimum of 3 minutes.
▶ Inform occupants of the premises of the risk of scalding.
▶ Perform thermal disinfection outside of the normal operating times.
▶ Do not discharge DHW unmixed.
To prevent the risk of scalding and to ensure mixed hot water, it is
advisable to fit a thermostatic mixing valve (TMV) at the point of use
(e.g. before the bath hot tap or shower).
Proper thermal disinfection involves the DHW system including the
draw-off points.
▶ Set the thermal disinfection in the service menu or hot water program
of the heating controller ( heating controller operating
instructions).
▶ Close DHW draw-off points.
▶ Set any DHW circulation pump to continuous operation.
▶ Wait until the maximum temperature is reached.
▶ Open all DHW draw-off points, from the nearest to the one furthest
away, and draw off hot water until hot water at a minimum of 70 °C
has flown from all draw-off points for at least 3 minutes.
▶ Restore the original settings.
8 Inspection and maintenance
DANGER
Risk of electric shock!
▶ Isolate electrical components from the power supply (230 V AC)
(fuse, circuit breaker) and secure against unintentional re-
connection before carrying out any work.
Information on safe isolation can be found in the Health and Safety
Executive guidance HSG85.
▶ Check for zero potential before proceeding with work, using test
equipment approved to GS38 to confirm that the electricity supply is
disconnected.
CAUTION

Mains supplies:

▶ Safely isolate both the gas and electrical supply before starting any
work on the appliance and observe all relevant safety precautions.
NOTICE
Personnel and equipment
▶ Any service work must carried out by competent registered
engineers.
▶ Service work must not be attempted if a calibrated CO/CO
and manometer are not available.
58
WARNING
Hot surfaces!
If the appliance has been operating components may be hot.
▶ Ensure precautions are taken when working on the appliance.
CAUTION
Annual maintenance checks:
Annual maintenance checks have to be conducted to ensure the
continued safe and reliable operation of the boiler.
▶ During each maintenance check, the gas valve, all gas joints and test
points should be checked for leakage using an analyser/sniffer.
▶ If a leak is found on the gas valve then it needs replacing as a gas valve
is a non-repairable component.
CAUTION
Component replacement:
▶ After replacement of a gas related component, where a gasket or seal
has been disturbed or replaced, check for gas tightness using a gas
sniffer/analyser.
▶ Also after re-assembly, carry out the following checks:
 Fan pressure.
 Flue gas analysis.
8.1

Inspection and maintenance considerations

• To ensure continued efficient operation the appliance must be
checked at regular intervals.
• The frequency of servicing will depend upon the particular
installation conditions and usage, however, at least an annual service
is recommended.
• The extent of the service work required on the appliance is
determined by the operating condition of the appliance when tested
by qualified engineers.
• After each service, the service interval record sheet at the rear of this
manual, must be completed.
See the following instructions for detail of some of the service
requirements:
▶ Check all joints and connections in the system and remake any that
show signs of leakage. Refill and re-pressurise if applicable as
described in the commissioning section.
▶ When it is frequently necessary to add water to maintain pressure in
the installation, even though no leaks have been discovered, perform
an expansion vessel check.
▶ Check that the condensate system is not obstructed, clean and refill
the condensate siphon.
▶ If the appliance is in a compartment or cupboard check that the
specified clearances around the appliance is clear.
▶ Check that the flue system is unobstructed and undamaged, clean/
replace as necessary.
– If fitted ensure the flue terminal guard is also unobstructed and
undamaged.
▶ Operate the appliance and take note of any irregularities.
– Refer to the fault finding pages for rectification procedure.
analyser
2
Greenstar 4000 – 6 720 891 162 (2020/09)