2. How to verify the recirculation flow. Close all water taps,
access to information menu, P4 information > Operation
Data, choose the option Flow.
The value should be above 1 GPM (4 l/min).
3. If the appliance doesn't make the recirculation. Confirm if
recirculation mode is active, inspect the recirculation
circuit and water filter for any obstructions, ensure that the
recirculation circuit is fill with water, verify if the
recirculation circuit is below the maximum pipe length, see
8.11 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
▶ Turn Off the appliance.
▶ Remove the front cover of the appliance (see page 12).
Pressure head points
[A] Air pressure head in the box
[B] Gas pressure head in the burner
[C] Tee (installer supplied)
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 8.12 should prevail over
manifold gas pressure to assure a correct appliance tuning.
Greentherm T9900 SE/i – 6 720 813 635 (2019/03)
▶ Loosen the set screw of the pressure head point [B].
▶ Connect the pressure gauge connection "+" to the test
▶ 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 24.
Manifold gas pressure refers to the relative pressure
between gas manifold nozzles inlet and outlet [A]-[B].
▶ 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]
▶ Reassemble the front cover onto he appliance.
▶ Turn ON the appliance to return to normal operation.
8.12 Gas and Air Adjustment
Appliance is pre-adjusted from factory.
Gas/Air adjustments are only required when;
The appliance is converted to LPG ( section 6.8).
The appliance shows repeated unresolved errors (
After the replacement of the electronic control unit, fan or
The gas and air adjustment can be completed in two ways:
Automatic <UC - Auto Adjust> ( section 8.12.1).
Manually <MA - Manual Adjust> ( section 8.12.2).
Improper gas pressure will affect combustion.
▶ Please see chapter 4.13 for more information.