18
DOMITOP HF 24 - 30 E
FERELLA GOLD HF 24 - 30 MEL
Version - 09.2002
25+/-50V DC
COMMON
80+/-110V DC
B
Gas valve
It supplies gas to the nozzles between a minimum and maximum pressure. For
the valve to work correctly, it is necessary for the pressure upstream from it to
be stable and suited to the type of gas being used, while the valve will supply
a regular pressure to the nozzles. The gas valve contains two operators. The
function of the first one is to open or close, while the task of the second one is
to modulate the capacity according to the systems requirements. The signal
comes from the card (X6-1/2/3/4) and is in the form of continuous voltage. The
first operator receives fixed voltage that may be between 80 and 110V DC, for
the second operator the voltage will vary between 25 and 54V DC according
to the need of the main card.
Checks
If the valve doesnt work:
Check there is gas, and that gas comes out of the valve by means of screw
B.
If there is no gas, you must check there is voltage at the operators. This
makes it possible to understand whether the problem lies with the valve
(there is voltage at the operators) or with the card (there is no voltage at
the contacts X6-1/2/3/4).
Modulation
The control system governs its boiler capacity so as to keep the delivery temperature constant in accordance
with the settings on the control panel. The nozzle gas pressure is modulated by the valve and specifically
via the 2nd operator. The card provides a change in continuous voltage (between 25 and 54 V DC) according
to the difference between the delivery temperature and the set point.
Checks
Modulation can be checked in three ways:
Visually, by checking the flame.
Using a pressure gauge to check the gas pressure downstream from the valve.
Checking the voltage of the second operator on the card (X6, 1/2). This is the most effective method
in some situations. With this test, it is possible to understand whether the problem lies with the valve
or with the card.
Note that with very low pressure upstream from the valve, opening the valve may be slow and the
boiler could shut down due to failed ignition.
Supplied by HeatingSpares247.com
