The thermowell in my new boiler had two sensors in it.  I think I can fit a third.  Is thermal grease the only way to assure good thermal contact, or is there a less gloppy way?  Maybe a homemade copper shim or copper wire to apply sideways pressure?  There was no thermal grease when I looked at it and no cap on the well.
	
		
			
		
		
	
				
			 
	 
	 
 
		 
 
		 
 
		 
 
		