Camus Hydronics ADVANTUS AVH 1000, Installation, Operation And Service Manual

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Figure 10: AV1000
– 4000: 1:1 Air/Gas Ratio Control Valve
3.5 OPERATION OF NEGATIVE PRESSURE AND DIFFERENTIAL PRESSURE VALVES

Advantus models 500 & 600 both operate on the principle of negative pressure. As the fan varies in speed it generates a varying
negative pressure at the fan suction which draws in a corresponding amount of gas.

Advantus 800 utilizes two negative pressure gas valves. As the fan varies in speed it generates a varying negative pressure at
the fan suction which draws in a corresponding amount of gas.

Advantus models 1000 - 4000 utilize both a negative pressure gas valve and a 1:1 air/gas ratio control valve. At the low end
these models operate on the principle of negative pressure and at the high end they operate on the principle of differential
pressure.

The differential air pressure measurement is made between the high and low pressure taps across the fan discharge and the
fan static discharge. There are two pressure taps at the fan discharge and care must be taken to tee into the correct line. The
correct line may be identified by tracing it back to the ratio control valve where the identification of the tapping is stamped into
the die cast actuator.

The differential gas pressure measurement is made between the high and low pressure taps across the inline metering gas
orifice. Check this value to confirm that it matches the differential air pressure while the appliance is firing.

The controls on this appliance may fire the burner from 4.0% up to 100% of rated input.

Differential manifold gas pressure will be reduced as burner input is reduced.

All reference gas pressure measurements must be made at 100% of rated burner input.

The differential gas manifold pressure is preset at the factory through the ratio gas valve. Adjustment of manifold pressure is
not normally required for proper operation. It may be necessary to adjust the low fire adjustment screw located on the ratio
control valve actuator in order to achieve acceptable light off under field conditions.

Always check settings posted on boiler test label.
3.6 GAS MANIFOLD DIFFERENTIAL PRESSURE ADJUSTMENT (AV1000-AV4000)
Tampering with gas valve adjustments after startup and commissioning will void the warranty on the gas valve assembly and the burner.
The appliance’s manifold gas pressure
IS NOT field adjustable after startup and commissioning. The gas valve pressure ratios have
been factory set with an internal bias adjustment to ensure a 1:1 air/gas ratio on operation. Tampering with this adjustment will void the
warranty on the gas valve assembly and the burner. An appliance supplied with a properly sized gas line, properly sized meter and a
minimum gas supply pressure (see table 7 for minimum allowable inlet gas supply pressure) while firing at full rate will ensure full burner
input. The manifold pressure supplied to the burner is a differential pressure. This pressure is the result of the difference in two gas
pressure measurements. A differential manifold gas pressure measurement should not be made until you have measured the gas supply
pressure. Gas supply pressure must be at least at minimum allowed with all appliances on the gas line firing at full rate before a manifold
pressure measurement is made. Use the following procedure to check gas supply pressure with a manometer connected to the inlet
pressure tap on the gas line connection at the rear of the appliance.
Lift top cover to access high fire air/gas
ratio adjustment
(use 3mm allen key for adjustment,
counter-clockwise increases CO
2
)
Low fire air/gas ratio adjustment
(use T-40 for adjustment,
clockwise increases CO
2
)
Gas Inlet
Figure 9: AV500
– 1600 1:1 Negative Pressure Air Gas Ratio Control Valve