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Water leakage
The water pressure of the installation should be more than 1.0 bar and at a maximum of 8.0 bar in normal opera-
tion. When the water pressure drops below the minimum occasionally, there might be a water leak. Check the
water heater and the complete heating installation for any water leakages and have these repaired.
Flue gas & air supply
The flue gas pipes and the air supply pipes must be checked for gas tightness. Also check if the mounting of these
pipes is correct, safe and not damaged. Check the top side of the water heater housing for signs of water leakage
and traces of water coming from the air supply pipe, the air vent or any condensate coming from the flue gas
pipes.
Check to ensure the flow there are no obstructions for the exhaust venting or the intake combustion air venting.
Check that all intake and exhaust venting has been properly reassemble and sealed before leaving the job site
Gas supply & safeties
The gas pipes must be checked for gas tightness. Also check if the mounting of these pipes is correct, safe and not
damaged. Any built-in safeties should be checked for a correct functioning. Any gas pipe or fitting that have been
opened or adjusted should be checked for leaks.
Remove complete burner unit
The complete water heater burner unit consists of the fan, venturi, gas valve, the burner plate and the internal
burner. To make more space to dismantle the complete burner unit pull down the burner controller unit.
To remove the burner unit for an internal heat exchanger check: remove the six M6 nuts, the ignition cable and
the thermal fuse cables. Close the gas tap under the water heater and loosen the gas coupling by untighten the
swivel joint under the gas valve. Remove the plug from the gas valve. Remove the air intake pipe from the ven-
turi.
After this, take out the complete burner unit by moving it forward out of the water heater housing. It will be nec-
essary to tilt the assembly a little to the right to move the fan motor past the water pipe. Also mind the conden-
sate hose. NOTICE: Watch out not to damage the burner plate insulation during this operation.
While removing the complete burner unplug both of the electrical and controlling cables of the fan. After all this
dismantle the venturi on the suction side of the fan and check the blade wheel of the fan.
Checking Non-return Valve (NRV)
The non-return valve is placed directly after the fan and has to be replaced once every five years during mainte-
nance. For EFW 85, 105 and 125: Replace the non-return valve by removing the 4 nuts that are holding the fan.
All the parts included in the NRV maintenance kit must be replaced: the gaskets, NRV seat, lock nuts, and non-
return valve. Do not reuse any of the old parts.
Reassemble the Non-return valve to the burner unit be sure that the nuts are tightened again so no air/gas mix-
ture is leaking into the cabinet. Check during start-up of the boiler to ensure no gas mixture is leaking on these
gaskets near the non-return valve.
For the EFW 155 a separate NRV maintenance kit is available.
Required tools: Wrench 55, 10 and 8 mm, Hex key 5 mm
3
1
4
Always check gaskets on non-return valves for air/gas leakage.
120
2
E93.1804.014
1 = Seat check valve small
2 = Lock nut M5 DIN985
3 = Gasket gas air mixing
4 = Check valve small
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