Page 228 - Boiler_Operators_Handbook,_Second_Edition

Maintenance 213

than spare incandescent light bulbs. trips. Smaller GFCIs are also called personnel ground
Some operators are expected to perform normal fault protectors because their real purpose is to prevent
checks and maintenance of electrical equipment in addi- anyone that accidentally touches a hot electric wire or
tion to maintaining the boiler plant. I don’t expect you to any conductor (metal, wire, copper pipe, whatever that
pull wire or perform other functions that are appropri- will carry electricity) while in contact with a ground.
ately performed by an electrician but… in many cases it The concept of grounding needs some clarification.
won’t get done if you don’t do it. Changing light bulbs Grounds in electrical terms are conductors that are not
and performing the following maintenance functions supposed to carry electrical current but they can convey
can make you more valuable to your employer. It’s also it to the ground, the dirt below you. A concern in any
possible it will save you being called out in the middle installation is the lack of grounding, where a conductor
of the night to start up the boilers after an electrical mal- that’s not supposed to carry electricity is not connected
function. to the ground, it’s ungrounded. The concern with un-
Contrary to popular beliefs, electrical systems re- grounded conductors is they can become hot by coming
quire maintenance. You may think the systems in your in contact with a hot conductor.
house are so reliable you don’t have to worry about A hot conductor is anything in an electric circuit
them. I thought that way until I spent a cold Christmas that is designed to carry electric current and there is
Eve working on an outside receptacle (where you put a difference in voltage between it and ground. If you
the plug for Christmas lights and your electric hedge touch the ungrounded object and your feet are on the
trimmer) to restore power and lighting in all the bath- ground you can close an electrical circuit between the
rooms in the house. One wire had come loose from the hot conductor and ground. Electricity will flow through
receptacle and all the power to the bathrooms was rout- you and, if the current range is right, it will kill you
ed through it. The circuit breaker kept tripping because instantly. If it’s low voltage (less than 600 volts above
it was a ground fault interrupter and that complicated ground) it shouldn’t kill you but it can cause everything
finding the problem. I don’t expect you to fix a problem from a mild shock to severe burns.
or even find one but some regular maintenance activities Personnel GFCIs will sense the fact that the current
would have saved me freezing that night while relatives is going to ground (because of the difference between
were using candles to go to the bathroom. the currents in the two conductors) and trip before the
Those ground fault interruption devices, called current reaches a value that could give you a tickle.
GFCI for ground fault circuit interrupter, all have a Regular testing of those devices helps to shift dust and
test push-button on them. No, they’re not there for the debris that can settle in the mechanism and prevent its
electrician to use, they’re there for you to test the darn operation. Personnel GFCIs are very important in a boil-
things on a regular basis. Instructions for the smaller er plant because you have a lot of grounds around you.
units say to test them monthly. So, to protect yourself All receptacles in a plant should be fitted with personnel
from shocks, and both you and your employer from a GFCIs because everything around you is grounded (or
very expensive lawsuit, do it! Record the test in the log should be) and if an electric tool or trouble light you’re
though. Don’t use those little stickers that come with the holding has its hot conductor short to something you’re
breakers. holding you want that device to prevent you getting
Insert a test light or some other device that is obvi- shocked.
ously using power to determine if the device passed the Larger GFCIs (in current carrying capability) are
test for certain. When you’re confident that everything required because a current flowing through devices
powered by the circuit can be shut down, push the test not intended to carry current can overheat them to the
button. The test light should go out and then come back degree that they burn or explode. Look at the thickness
on when you push the reset button or reset the circuit of the metal in any large electrical panel compared to
breaker. the size of the wiring supplying it. If the current were
GFCI circuit breakers trip without shifting the to suddenly start flowing from the wiring through that
operating toggle all the way to the off position, just like thin panel to ground it would damage the thin metal in
a normal circuit breaker when it trips, so you have to that panel. Those devices should be tested regularly by
turn it off and back on. The GFCI has current detection an electrician and you should record it in the log.
devices in them to compare the current going out the Operating circuit breakers has the same effect as
hot conductor and the current coming back on the other GFCIs, you help ensure they will function when nec-
conductor; if the two currents don’t match precisely it essary by keeping them loose. It’s always a good idea