In the January issue we asked for suggestions for imbedding electrical wire in concrete without using metal conduit. This was for a reader involved in the development of a low-cost concrete housing system.
Larsen Products Corporation suggests that after the cable has been installed in accordance with the instructions of the manufacturer the entire wall or ceiling surface be coated with a thin, continuous film of their plaster bonding agent. The material may be applied by brush, roller or spray. The temperature should be at least 50 degrees Fahrenheit. When the film is dry to the touch (usually in 30 minutes to an hour). apply a 3/16-inch brown coat in the direction of the cable. This will avoid damage to the insulation. It is important that sand aggregate be used, since lightweight materials would impair heating efficiency. A 1/16-inch finish coat is applied after the brown coat is firm and hard, but not dry (usually after 24 hours). The plaster must be thoroughly dry before the heating system is turned on, and the lowest possible thermostat setting should be used at first. The thermostat setting may be increased by 5-degree increments every 24 hours until a 70-degree setting is reached.