A second sensor located externally of the vessel and within a coupling in fluid communication with the vessel serves as {HEAD ~ a backup safety device} and is connected to a second relay coil also having contacts interrupting the flow of electrical energy to the heating element when {TAIL ~ the water level} is below the outside sensor 
A second sensor located externally of the vessel and within a coupling in fluid communication with the vessel serves as { HEAD ~ a backup safety device } and is connected to a second relay coil also having contacts interrupting the flow of electrical energy to the heating element when { TAIL ~ the water level } is below the outside sensor
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH