From: muratlanne@gmail.com   
      
   "Bob La Londe"  wrote in message news:v69l0s$3e65q$1@dont-email.me...   
      
   If I could get all the tiny little losses eliminated I'd be tempted to   
   use both tanks for air storage, and just periodically switch which   
   compressor fills them. Then even if a compressor failed it would carry   
   the air seals for hours.   
      
   I also considered some sort of auto backup.  The easy way would be to   
   set the backup compressor to switch on at a lower pressure, but there   
   are a number of small issues that could cause both compressors to run at   
   the same time.  That's power I do not always have.  ...   
   Bob La Londe   
      
   ----------------------------   
   The circuit in a Quick Recovery electric water heater does almost what you   
   want. The upper thermostat is double throw, when cold it selects the upper   
   element until the top part of the tank reaches the set temperature, then   
   switches power to the lower element and its on/off thermostat to heat the   
   whole tank. For two air compressors you would need a double throw pressure   
   switch for the lower setting.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)