Original message
| Mooser
 |  "Sequence of operation"
, posted Sun 21 Dec 22:16  
I have a old electric furnace in the shop here. The only identifing marks are an ICG sticker on the outside and "EL-10, 15, 20 & 25" listed on the wiring diagram (inside the cover) showing the possible 10 through 25 kw configurations.
It is a 15 kw unit with 3 coils, two wire (heat only) thermostat, a manual / automatic fan switch and a low - high heat switch (I believe this to turn either 2 or 3 coils on)
When the thermostat turns on, there is a click noise, the middle coil turns on for a few seconds getting red-hot, then another click, the coil turns off, then the fan turns on, then the middle coil turns on, then the top coil turns on (have it set to low heat on the switch)
when the thermostat turns off, the fan and top coil turn off (hard to tell, maybe the coil then the fan) them middle coils stays on, glows red then click it turns off.
This pre-heating of the coil to prevent cold air being blown make some sense but I don't see why it stays on after the fan shuts off.
Can anyone tell me the correct sequence of on/off operations for an electric furnace?
Also, does anyone know what this furnace might be or where I can find information on it?
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Replies:
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| xenos
Webmaster 
| "Re(1):Sequence of operation" , posted Mon 22 Dec 08:04
Your furnace employs sequencers to stage the fan and heaters. These sequencers are time delays that both time on and off. The timing sequences between the first stage heating and the fan is normally quite fast since electric heat is almost instant heat.
Xenos.
The best way to escape a problem is to solve it.
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