Electric Furnace Notes

How does electric heat work? Having a basic understanding of what is happening greatly increases your ability to diagnose and repair these heaters. All of them basically work the same. Just as an air conditioner A-coil needs a certain amount of freon flowing through it, Air must be traveling over the heating coils at a certain rate or they will simply heat up and disentergrate in a very short time. But if the fan comes on straight away then only cold air will come out of the vent!. So how do they do it? The manufacturer installs a sequencer to bring on the heating coils in stages.
  Typical sequencer with 4 stages
 

This does 2 things. Pre warms the heater and keeps the breaker from tripping. A heating coil is first brought on to heat up the furnace and then 30 seconds later another one comes on 30 seconds later the fan and another one kicks in. Each coil is approximitly 5000 watts the typical furnace for a 3 bedroom. These coils will break individually and instead of 15000 watts you have 10000 or even 5000. Many times people would bring the heat strip to me with all 3 coils broken. Can you imagine that? The good news is each coil can be restrung

 
   typical restring kit
 
and the heater can be brought back up to normal. When restringing any element you must have the coils evenly spaced and you cannot have any gaps or they become weak spots and burn out. You must take care not to let the coil touch the heater chamber also.