If a heater is installed in the radiator, remove the plug from the socket or turn off the appropriate fuse in the distribution box. Make sure the ladder radiator is completely free of water or other liquid. If it is filled with water, drain the water from the radiator.

Radiator connected to C.O.
In the case of installing a heater in a radiator working in a central heating system, and when it is possible to cut off the supply and return using existing valves, close them. This will avoid draining water from the entire central heating system.

Open (unscrew) the air vent (photo of the radiator with the air vent) to equalize the pressure in the radiator. Note: water may splash. Then empty the radiator of water by gently unscrewing the plug in the lower part of the radiator (manifold). The amount of water in the radiator depends on its size. Remember to prepare a container of appropriate size.

If a heater is installed in the radiator, unscrew it.

In the case of installation with a T-piece (allows connecting an electric heater when the radiator is connected to the central heating system), screw the connecting T-piece into the radiator, being careful not to damage the surface. Adjust the position of the T-piece to the location of the connecting elements on the system side.
NOTE: The T-piece is not standard equipment for the heater.

Install the heater in a vertical position, with the heating element pointing upwards, in the lower part of the radiator on the left or right side. Screw the heater gently (with feel) into the radiator or into the T-piece (in the case of installation with a T-piece), using a 22 mm open-end wrench, being careful not to damage the surface.
It is forbidden to tighten the heater by turning the thermostat casing.

GL01 and GL02 heaters are equipped with heads that are not rotatable. To ensure the correct position of the head (knob facing the room), screw the heater in completely and check if the position of the head is favorable. If the orientation does not correspond to the preferred position for use, gently unscrew the heater until the head is in the correct place. If the unscrewing of the heater is significant (over 90 degrees), unscrew the heater and additionally insulate the plug thread with teflon tape or an additional gasket. After unscrewing the heater and applying additional sealing (teflon tape, hemp, gasket, etc.), do not tighten the heater completely, but stop at the last and established correct position.

After installing the heater, fill the radiator with system water while simultaneously venting the system.

Radiator connected to C.O.
In the case of a radiator connected to central heating, first open the return valve, then the supply valve, and gradually fill the radiator with water. After the radiator is completely filled with system water, close the air vent and the supply valve. Leave the return valve (if installed) open. Check the tightness of the connections. To prevent heated water (by the heater) from entering the central heating system during heater operation, the radiator must be cut off by closing the valve. If the radiator is connected to the central heating system via two valves (on the inlet and outlet), one of them must be completely open during heater operation, because an increase in temperature causes an increase in water volume.

In the case of a radiator that is not connected to central heating, fill the radiator with system water while simultaneously venting. Leave 8% free space because water increases its volume under the influence of increased temperature.
Then close the air vent and check the tightness of the connections. Do not allow water to drip down the heater casing. Make sure that the radiator in which the heater is installed is filled with the heating medium (water) and the entire heating element is immersed in it. Never turn on the heater if the heating element is not completely immersed in water – this risks its overheating and permanent damage.