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You are now in:>>Heating box
Propagation Box for Heating Cable
In order to make best use out of a heating cable it is advisable to construct a propagation box. The size of the box depend on the length of the cable. The following dimensions are recommended:
HK6 6m cable length - 50 watts 0.8m2 - 1.0 m2
HK10 - 10m cable length - 100 watts 1.6m2 - 2.0 m2
HK25 - 25m cable length - 320 watts 3.0m2 - 4.0 m2
The width/length of the box should be defined to take the maximum number of propagation trays.
Material required: Plywood 18mm ( e.g. 1 or 2 sheets 244cm x 122cm) , chipboard screws 4x40, Aeroboard 15mm to 25mm (or similar), strong plastic sheet to line the box, wheelbarrow of dry, course, washed sand.
Location of box:
In a tunnel or greenhouse or in an outbuilding, haybarn or similar (daylight required)
Position of box:
The box can be put on blocks on the ground or on a bench or table.
Construction:
Cut out plywood for base according to the required dimensions. The sides of the box should have a min. height of 30cm but could be as high as 60cm. Screw base and sides together. Place aeroboard on the bottom of the box. Glue/nail aeroboard pieces on the sides of the box. (Protection against heat losses). Now line the box with tunnel plastic or similar strong plastic. This protects the timber from the moisture of the sand. Put box in its final location.
Filling:
Fill a 2.5cm thick layer of dry sand into the box and level it . Drill a hole into the wall of the
box nearest to a socket. The hole should be big enough to feed the heating cable through.
Stick the complete cable from outside through the hole. Now run the cable over the sand in
such way that it is evenly distributed over the whole area. (The cable could be plugged in
immediately before this to make it soft and pliable).
Fill another 1 - 1.5cm of sand over the cable or as much is needed to cover the cable.
It should not be buried too deep. Level the sand carefully to achieve a smooth surface.
The cable can now be plugged in. The heat will be distributed through the sand.
When the propagator is in use keep the sand always moist (NOT WET)
Optional - Thermostat
To avoid overheating (e.g. additional heat due to sunshine) and electricity waste, a thermostat can be used to regulate the temperature.
To fit the plug of the heating cable into the Thermostat unplug the heating cable, loosen
Philips screw from black plug cover. Now pull out the ‘Euro 2 pin plug’ which is hidden under
the 3pin plug cover. Plug the 2 pin plug into the bottom of the Thermostat. Fix Thermostat
at/near propagation box. Stick stainless steel tip of sensor into the soil of one propagation
tray. Now you are ready to control the heating cable via the Thermostat . Set Thermostat
according to the manufacturers instructions.
Tip: It is highly recommended to install a light source directly over the propagation box. Often propagation takes place in short days where there are not enough natural light hours to achieve healthy plant growth. With the help of a light tube (ideally ‘Grow Light’ tubes or similar lights for plant growth) and a plug-in timer the plants can be exposed to additional light hours. This will reduce the danger of ‘legginess’.
Tip: In order to protect the plants in the propagator from night frost lids could be made up. Make several frames from 2cm x 2cm (or similar) timber - large enough to cover the box. Staple bubble film onto the frames. This leaves some light through but reduces the danger of frost damage.
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