High Lmit Switch


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Old 03-14-08, 03:48 PM
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High Lmit Switch

Im replacing my limit switch, need to know what it actually does? Definition. Thanks
 
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Old 03-14-08, 04:24 PM
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The high limit switch is attached to the heat exchanger and will trip if the temperature gets too high. A common cause for this trip is failure of the main blower. The burners are on but there is nothing to move the heat.
 
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Old 03-14-08, 07:38 PM
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Another reason is restricted airflow...5 possible causes for such:
1-very dirty air filter (replace)
2-a filter of too high an efficiency and hence too restrictive (increase blower speed or switch back to a cheaper filter)
3- return grilles that are closed (open them up)
4- insufficient returns in your duct system (lousy design, have a professional add return branches and grilles)
5- too high a temperature rise (increase blower speed)

Of course it could just be that the limit died of natural causes and none of the above apply to the situation at hand


Two definitions for a Limit Sitch:
- overtemperature protection device
- safety device, temperature sensitive, has a normally closed set of contacts that open-up if temperatures surrounding the sensing element are abnormally high.
 
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Old 03-15-08, 12:40 PM
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Limit

This is what it should look like once it arrives in the mail

 
 

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