Manifold Gas Pressure; Adjusting Gas/Air Flow - Bosch Greentherm T9800 SEC 199 Installation And Operating Instructions Manual

54 | Troubleshooting
2. Verify is gas pressure is within specified range (see
section 3.2).
If gas type is properly selected, gas pressure is within
range, the venting is according to specifications, and the
problem persists:
3. Perform the gas and air adjustment as described in
section 8.11.

8.10 Manifold gas pressure

The manifold gas pressure measurement is only carried out if it
is necessary to confirm the value from the rating plate. In case
of a high deviation between measured and stated values,
please proceed with Gas/air adjustment (see section 8.11).
▶ Turn Off the appliance.
▶ Remove the front cover of the appliance (see page 10).
Fig. 51 Pressure head points
[A] Air pressure head in the box
[B] Gas pressure head in the burner
[C] Tee (installer supplied)
▶ Loosen the set screw of the pressure head point [B].
▶ Connect the pressure gauge connection "+" to the test
point [B].
1) Manifold gas pressure from the rating plate is valid for sea
level operation with standard gas pressure and
composition. If operating conditions are different from
those, values from section 8.11 should prevail over
manifold gas pressure to assure a correct appliance tuning.
6 720 816 815 (2018/08)
▶ Connect the pressure gauge "-" to the pressure head point
[A] using the accessory [C].
▶ Turn On the appliance.
▶ Position the front cover near the appliance and make sure
the cable for the display is connected.
▶ Open all hot water taps to achieve a flow rate of at least 6
gallons per minute. (1 tub and 2 sinks should be sufficient).
If heater goes back to P2, open more hot water fixtures to
allow sufficient flow and access to P1 menu.
▶ Record the manifold gas pressure reading in table 22.
Manifold gas pressure refers to the relative pressure
between gas manifold nozzles inlet and outlet [A]-[B].
1)
Manifold gas
pressure
Table 22
▶ Turn Off the appliance.
▶ Disconnect the pressure gauges from the pressure heads
points [A] and [B].
▶ Tighten the shutter screws of the pressure heads points [A]
and [B].
▶ Reassemble the front cover onto he appliance.
▶ Turn ON the appliance to return to normal operation.

8.11 Adjusting Gas/Air flow

Appliance is pre-adjusted by default with
factory parameters.
Gas/Air adjustments are only required when;
• The appliance is converted to LPG and energy content is
more than 2820 BTU/cu ft( section 6.8).
• After installation, the appliance shows repeated
unresolved errors ( chapter 9).
• In Natural Gas installations where energy content is less
than 900 BTU/cu ft.
• After replacement of electronic control unit, fan or gas
valve.
Improper gas pressure will affect
combustion.
▶ Please see chapter 4.13 for more
information.
Access to CA menu is only possible after
accessing to AU Technical Settings menu
( section 6.6).
Value
Greentherm T9800 SE 160/199 | SEC 199
Date