20
Maintenance must be carried out by a competent
person.
6.1 Safety Cut-out
The safety cut-out operates if:
1. Wiring is incorrect.
2. The immersion heater thermostat or cylinder
thermostat fails.
3. Thermostat is set too high.
4. Remember before resetting the safety cut-
out or altering the thermostat setting, isolate
electrical supply to the unit prior to removal of
the electrical box lid.
5. Reduce thermostat setting and press the re-
set button. After adjustments are completed,
ensure the lid to the electrical box is replaced.
6. If still out of operation, contact installer.
6.2 Intermittent or slow discharge from tundish
1.
Turn off the electrical supply to the immer
-
sion heaters.
2.
Turn off cold water supply valve.
3. Open a hot tap.
4. Turn the knob on the Temperature and Pres-
sure Relief Valve (5) to the left and hold in this
position for thirty seconds.
5. Attach a foot pump with a schraeder (car
type) valve to the expansion vessel.
6. Pump up to 3 bar
7. Open cold water supply valve.
8.
When water flows through open tap, close
tap
9. Turn on electrical supply to the immersion
heaters.
6.3 Continuous very hot water discharge from
tundish
This indicates a malfunction of a thermal cut-out,
operating thermostat or the combined tempera-
ture and pressure relief valve. Turn off the electri
-
cal supply to the immersion heater and also isolate
an indirect unit from the boiler. Contact the install-
er or competent engineer.
6.4 Expansion vessel maintenance
The expansion vessels do not require annual
maintenance and should not be tampered with
unless an intermittent or slow discharge from the
tundish occurs when water is being heated. In
this situation, maintenance must be carried out
by competent person and the precharge pressure
6. SAFETY AND SERVICING
must be restored to the original value. An annual
visual inspection is recommended. Important: To
check the precharge the expansion vessel must
be completely empty of water. If the precharge
pressure is different from the value shown on
the label it must be restored to the original value.
Do not remove expansion vessel without depres-
surising the cylinder and draining 10 litres of water
from the drain valve at the base of the cylinder.
6.5 Guarantee
Cylinder should be serviced annually and the
log book should be updated in order to validate
guarantee. The log book and service records act
as guarantee document. For terms of guarantee
please see the log book on page
??
6.6 Servicing Procedure:
7.6.1 Expansion relief valve
Ensure that expansion relief valve works by manu-
ally opening to discharge water to tundish.
6.6.2 Pressure reducing valve
Isolate the cold water supply and open a ground
floor cold tap. Unscrew the pressure reducing
cartridge. Clean the filter mesh and the cartridge
under running water. Replace cartridge ensuring
that strainer is correctly located and reassemble
the unit.
6.6.3 Expansion relief cartridge
Isolate the cold supply and open a ground floor
cold tap. unscrew blue expansion relief headwork
from valve body. Clean valve seat face and seating
- do not scratch or damage either seat face or seat-
ing. Refit in reverse order. Do not overtighten.
6.6.4 Temperature and Pressure relief valve
Ensure that Temperature & Pressure Relief valve
works by manually opening to discharge water to
tundish.
6.6.5 Internal inspection
The immersion heater can be removed to provide
visual inspection access to the cylinder.
Summary of Contents for Delta Twincoil DTC 200
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