My apologies if this is just too naive...

I am trying to explain to a collegue why there are so many cautions against 
"mixing" water with electricity. He is not the type to accept "common sense" as 
an answer. This is what I have reasoned so far...

MAL-OPERATION
Water is generally conductive. If it enters the area of a chassis that houses 
control elements such as relays or switches, it can short circuit the control 
elements and cause the affected device to "operate" unexpectedly, and sometimes 
in unexpected ways. 

ENERGIZING SURFACES
Water is generally conductive. If it enters a chassis containing hazardous 
voltages it is possible it may act as a conductor of the voltage to an 
otherwise un-energized conductive surface. If the conductive surface, for 
whatever reason, is itself not sufficiently grounded, it can carry hazardous 
voltage potentials. 

INCREASED LEAKAGE CURRENTS
Water is generally conductive. If you are working on a chassis and accidentally 
touch an energized contact, you may not experience any shock because there is 
no current path between you and the voltage source supplying the contact. Let 
us assume the contact is energized by a local AC mains. There is always SOME 
leakage current possible from where you are standing back to a grounded point. 
Usually it is a very small leakage. However, if you are standing in water, the 
leakage current is likely to be much higher, and you may experience a serious 
electric shock from your accidental touching of a contact. 

AVALANCHE EFFECT
Water is generally conductive. If it enters a chassis with high power 
electrical components, it can instigate an avalanche of failure that results in 
the release of a lot of energy. For example, the water can provide a short 
circuit between two potentials. As it carries current, the water may heat up 
quite rapidly, in doing so it creates steam. The effects of the heat and steam 
may then provide an even lower resistance path for additional current 
flow...and so an avalanche of conductivity (from less conductive to more 
conductive) is started...

I welcome any comments and additional "generic" scenarios.

Regards, 

Jason Mallory
Product Safety Consultant. 
 
-- 




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