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This valve provides mechanical modulating control of the gas outlet
GM-4_6_
pressure at a consistent ratio to the main air blower pressure. An example
(Dual On/Off
of a typical installation is shown in Figure 12. The burner control responds
with Gas/Air
to a higher demand for heat by increasing the amount of air being supplied
Ratio Control)
to the burner, resulting in an increased air pressure. With the air pressure
(P
the optimum outlet gas pressure according to the preset gas/air ratio.
The combustion chamber pressure (P
combustion quality in cases where the combustion chamber pressure is
significantly higher during operation than atmospheric pressure.
G as
L ine
The valve not only allows a gas/air ratio adjustment, but also an offset
adjustment (zero set), which allows for fine adjustment at lower ratios.
With these adjustments, the outlet valve pressure (P
P
P
G—GM-20/25 and GM-40/45 Series Dual-block Multi-function Gas Control Valves Technical Bulletin 15
All manuals and user guides at all-guides.com
) connected to the valve, the valve seat position is controlled to achieve
A
G M S erie s C om b inatio n C o n trol
O ptio na l
P re ssure
S w itch
M an ual
S h utoff
Valve
S o le noid
Filte r/
Valve
S trainer
A ir L ine
Figure 12: Typical Application Installation
= R • P
+ Z
G
A
- P
= R • (P
- P
) + Z
G
F
A
F
) can be connected to improve
F
S o le noid
Valve W o rking
w ith Con tro lle r
P
P
G
P
F
Gas/Air
Co ntroller
M
without combustion chamber pressure P
with combustion chamber pressure P
B o iler
A
) calculates to:
G
F
F
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