Heating Controls

 

(1) Thermostat - Is a switch that opperates according to temperature. 

      Old type - bi-metalic strip opperates contact  

      New type - electronic

 

(2) Timer - 24hour clock

 

(3) Programmer - Complex electronic (digital) Controller.

Multiple functions (multiple output) (multiple input)

 

Input - Thermostats, temperature sensors, input controls, frost sensor

Output - boiler, motorised valve, circulation pump. 

 

 

 

 

 

For any electrical load. 

We have effiency  -   useful energy out

                                    ---------------------------

                                        total energy in

 

Example

electric motor

 

             |-----600w useful mechanic power

1kw in

             |-----400w heat (waste) 

 

                         600w

efficiency =     --------  = 0.6w

                         1000

 

                   total light output (lumens)

Efficacy =  -------------------------------------- 

                         power in (watts)

 

(1)

Luminous flux (f)   Lumens (Lm)

Total light output in the visable range in all directions. 

 

(2) Luminous intensity (L) Candela (cd) 

light emited in a particular direction. 

 

(3) Illuminance (e)  LUX (lux)

Light falling on a surface at a given distance

 

 

 

Inverse sqaure law

E=I

   ---

   d2

________

|E(lux)|

|I(cd)  |

----------