Bulex Thema Condens AS 48-A, Руководство пользователя, Страница: 50 / 199

MAKSİCONDENSE 48-65
Notes
01/2018 44 Training 0020260859_00
Honeywell VK 8205V 48 kW section model
Honeywell VK 8205VE gas valve, source: Honeywell
Servo pressure control
The gas valves of the VK 8205VE/VK 8205V series contain a positive gas-servo system. This means
that the main gas valve is kept closed even during actuation (unit start) by means of spring force.
The spring force is only overcome by sufficient gas connection pressure and the main gas valve
opens. This ensures that the main gas valve is automatically closed in the case of insufficient gas
connection pressure (pressure drop) or a lack of electric actuation. At the heart of the system is the
servo pressure regulator, which comprises a relief valve integrated into an overlying control dia-
phragm.
If the gas expansion relief valve
1
(1st operator) and the second gas valve
2
(2nd operator, servo
operator) are now supplied with voltage, the servo gas flows into the servo system and into the gas
pressure regulator
3
via the opened second gas valve. This amount of servo gas then moves the
main gas valve
4
upwards, thereby opening the main gas route. As soon as the main gas valve is
open, the outlet pressure (burner pressure) is only monitored by the gas pressure regulator dia-
phragm, which occurs via the connection of a control channel.
If the gas pressure is higher than the pre-set spring pressure (gas pressure regulator adjusting
screw) at the gas pressure regulator and the current atmospheric air pressure to the diaphragm, the
gas pressure regulator opens and relieves the working pressure of the gas-servo system in a defined
way. This load relief reduces the gas pressure at the main gas valve and enables the main gas valve
to close proportionally. The main gas valve limits the burner/jet pressure to the pre-set value with
this function. As a result of the constant pressure regulation, the burner pressure remains constant
even if the gas flow pressure of the gas supply fluctuates.
After the burner is switched off, the gas-servo system is drained towards the gas valve assembly
outlet.
1 2
3
4