7
Combi 90 Outdoor Module
When the hot tap is closed and the diverter valve flow
switches sense that hot water is no longer required, if the
remote timer is set to either TIMED or CONSTANT, the
boiler will return to the central heating mode, with the
pump and burner running. If the timer is not calling for
central heating, the pump is turned off but the burner will
continue to run for a short period until the water in the
boiler reaches the required temperature ready for another
hot water operation.
1
A hot water flow rate of up to 17 litres/min is
available, dependant on mains water pressure. To
maintain a longer and more consistent hot water
temperature, a flow restrictor is factory fitted to
limit the flow rate to approximately 15 litres/min.
The flow restrictor is located in the outlet side of
the cold water inlet isolating valve.
2
The incoming mains water pressure should be
between 1 and 8 bar to ensure efficient operation.
If the pressure is above 8 bar a pressure reducing
valve must be fitted.
The boiler may still operate down to a pressure of
1.0 bar but with a reduced flow rate. Below 1.0 bar
the hot water flow switch will turn the boiler off.
The minimum flow rate needed for the flowswitch
to operate is 3 litres/min.
3
To ensure economic use, the pipe runs between the
boiler and hot taps should be in 15 mm copper pipe
and be as short as possible. Where possible the
pipework should be insulated to reduce heat loss.
4
All taps and mixing valves used in the domestic hot
water system must be suitable for operating at a
mains pressure of up to 8 bar.
5
If required, a shower may be fitted in the domestic hot
water system. It is recommended that thermostatically
controlled shower valves are used to protect against a
flow of water at too high a temperature. If a fixed
head type shower is used, no anti-syphonage devices
are required. If a loose or flexible head type shower is
used, it must be arranged so that the head cannot fall
closer than 25 mm above the top of the bath, thereby
preventing immersion in the bath water. If this is not
practicable, an anti-syphonage device must be fitted
at the point of the flexible hose connection.
6
The supply of hot and cold mains water direct to a
bidet is allowed (subject to local Water Undertaking
requirements) provided that the bidet is of the over-
rim flushing type. The outlets should be shrouded and
unable to have a temporary hand held spray attached.
Arrangements for anti-syphonage are not necessary.
3 - GENERAL BOILER INFORMATION
7
Before the mains water supply pipe is connected to the
boiler, it should be thoroughly flushed out to avoid the
danger of dirt or foreign matter entering the boiler.
8
The mains water connection to the boiler must be
the first connection from the mains supply.
Note: Hard Water - A water hardness test kit is supplied
with the boiler. Should the total hardness of the water
supply exceed 125 ppm, an in-line scale inhibitor or
water softener (both available from Grant UK) should
be fitted in the cold water supply to the boiler. Consult
the local Water Undertaking if in doubt.
Important: Do not immerse the test strip in running
water and avoid contact.
Fill a clean container with a sample of water from the
mains cold water supply to the boiler.
Immerse the test strip in the water for approximately one
second, ensuring that all the test zones are fully wetted.
Shake off the surplus water and wait for one minute.
Assess the colouration of the test zones using the
following chart.
Domestic hot water system
3.6
To use the water hardness kit
3.7
Green areas
4
3
2
1
0
Violet areas
0
1
2
3
4
Hardness
very soft
soft
medium
hard
very hard
Total hardness mg/l (ppm)
<50 mg/l calcium carbonate
>70 mg/l calcium carbonate
>125 mg/l calcium carbonate
>250 mg/l calcium carbonate
>370 mg/l calcium carbonate
Note: (1 mg/l = 1 ppm (part per million)
If the hardness reading is found to be in the medium to
very hard range (the shaded area), it is essential that some
form of water conditioner or softener is fitted to reduce
scale formation within the combination boiler. Failure to
do so may invalidate both the manufacturers warranty
and any extended warranty covering the appliance.
The water conditioner or softener should be fitted to
the cold water supply serving the appliance and in
accordance with the manufacturers instructions. Grant
Engineering (UK) Ltd. cannot be held responsible for
any damage or misuse caused by the fitting of any
water conditioning device.
Please protect the domestic hot water system from
the harmful effects of scale.