17Installation and maintenance instructions ecoTEC 0020029172_035.4 Gas connectiond Danger!Danger of injury to persons and/or materialdamage due to improper installation!The Vaillant ecoTEC boiler may only beinstalled by a recognised skilled trade companywho also assumes the responsibility for properinstallation and initial start-up of the boiler.The legal directives and the local regulationsfor gas supply companies must be observed.a Caution!Ensure strainless assembly of the gas pipes toavoid leakages!h Note!Maintain the same gas pipe dimension all theway to the boiler and avoid reducing the dimen-sion downstream of the gas meter.a Caution!The gas valve may be damaged if the testpressure or operating pressure is exceeded!You must check the tightness of the gas valveonly using a maximum pressure of 110 mbar!1Fig. 5.8 Fitting the gas connectionThe boiler must be connected to your gas pipe via a gasisolation valve.• Screw the boiler‘s gas supply pipe (1) gas-tight withthe gas isolation valve (5, see Fig. 5.9). To do this, usethe R3/4 crimp connection supplied with the boiler.This is also suitable for the connection of a R3/4 gasisolation valve.• Inspect the gas connection for leakage.5.5 Heating connectiona Caution!Ensure strainless assembly of the supply linesto avoid leakages in the heating installation!The boiler is connected to the heating flow and returnvia service valves.23415Fig. 5.9 Heating connection• Fit the flow, return and gas isolation valves (3, 4, 5)including the seals onto the flow, return and gas pipes.Do not overtighten and ensure the joints are checkedfor leaks after fitting.a Caution!It is essential to use the combined filling andemptying valve (3, Fig. 5.10) in the return forfilling the boiler without fail, as otherwise thebleeding of the boiler cannot be ensured.h Note!We recommend the use of seals made of a fibre-based material similar to cardboard instead ofmaterials similar to rubber as the latter canplastically deform and cause pressure losses.Installation 5