trouble with firemans switch for pool heater

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  #1  
Old 08-14-06, 08:46 AM
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trouble with firemans switch for pool heater

I just installed a firemans switch in a intermatic time control box to shut down a pool heater 20 min before the pump shuts down. The heater is run on millivolt, as generated by the thermocoupler. I ran 18/2 stranded copper from the heater to the timer which is a good 125 feet away. The heater will not run with this hookup. When I bypass this hookup in the heater it works fine. Is the distance too long for this to work? I am wondering if I used too small a wire.
Thanks,
Steve
 
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  #2  
Old 08-14-06, 09:29 AM
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To be clearer I am wondering if the 18/2 is causing too much resistance for the distance involved.

Any ideas?
 
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Old 08-14-06, 10:03 AM
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Usually the installation manual for the heater will have a chart for thermostat wire distance. I haven't done a ton of millivolt systems, but I seem to remember that 40-50' feet is the maximum for 18 gauge.
 
  #4  
Old 08-14-06, 10:33 AM
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I'll see if i can find the manual. Do you think a switch to 12/2 may do the trick?
 
  #5  
Old 08-14-06, 11:19 AM
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Check to see if you can even use regular wire and connectors. Many thermocouples require special wire/connectors, and switches, or they will not work.

I would also think that any length of wire added to a thermocouple will change its resistance. It would then need to be re-calibrated to work properly. My suggestion is that you break the circuit using some other part of the system, not the thermocouple.
 
  #6  
Old 08-14-06, 11:37 AM
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I am not using the thermocouple as an on/off switch. The firemans switch itself is breaking the circuit.
 
  #7  
Old 08-14-06, 11:55 AM
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It reads to me like you are breaking the wire going to the thermocouple in order to switch the heaters on and off.
 
  #8  
Old 08-14-06, 12:14 PM
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Sorry I know that sounds misleading. On the heater there is a wire that is labelled as the connection point for the firemans switch. it appears to come after the on/off switch on the heater. I understood the firemans switch as just adding another switch in the circuit. It does not appear to come from the thermocouple, but then again i don't know for sure.
 
  #9  
Old 08-14-06, 12:33 PM
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OH then I would say that the wire size is too small. I dont know enought about the heater to be sure what size you need.
 
  #10  
Old 08-14-06, 01:43 PM
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I have 12 gauge wire I can try, both in stranded and solid. Which would you use? i'm sure I can pull the solid through the pipe, just not as easy as the stranded.
 
  #11  
Old 08-15-06, 11:22 AM
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I would re check the mfg details on that heater. Specificly what it says about that firemans switch, beyond connect here. How much voltage is there, and how much amperage.

The trial and error method does not work well in the electrical field. Equipment blows up or people get hurt using that method.
 
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