Page 230 - Boiler_Operators_Handbook,_Second_Edition

Maintenance 215

connections with an infra-red thermometer to find any out and into the electrical appliance to become a conduc-
hot spots. On a five-year interval you should open all tor between hot and ground you could get stung but a
peckerheads at motors to check the motor connections damp rag can’t do that.
and open rear covers on motor control centers to check Transformers are frequently allowed to die for
the bus bars, make that two years if they’re aluminum. lack of maintenance and it’s a shame that so many of
You don’t even have to check connections in your home, them are neglected because they not only represent a
shut down the circuit and tighten them, there aren’t that significant repair or replacement cost; there’s the matter
many. You may find that regular annual tightening of of the downtime associated with their failure and the
aluminum conductors is required, my kitchen stove and very large and very real additional cost of power that’s
heat pump have aluminum wiring and I check them an- wasted when the transformer is operating inefficiently.
nually. Whenever a transformer can be taken out of service you
High temperatures are the worst enemy of electri- should use the opportunity to maintain it. Opening the
cal systems. There is a rule of thumb that claims the life enclosure and removing accumulated dust and dirt then
of electrical equipment is halved for every ten degree inspecting it for apparent hot spots and tightening all
increase in temperature. It’s important that you do what the connections is the minimum you should do.
you can to limit the temperature of the electrical equip- Samples of oil from oil filled transformers should
ment you operate even if you don’t maintain it. It’s a be drawn and sent to a qualified testing lab at least every
simple matter of keeping cooling passages clean and five years; the lab should provide you with sampling
unobstructed. kits. Refer to the manufacturer’s instructions because
Don’t let painters lay their drop clothes over op- there are a variety and forms of transformers with dif-
erating pumps or electrical enclosures so they block the ferent requirements. You also have to be careful with
flow of cooling air. I’ve noticed a fresh coat of paint on some real old transformers that may still contain PCBs,
and around electric devices that failed is very common. a known carcinogen.
In one case the coat of paint actually froze a motor bear- During the operation of the transformers a regular
ing on its shaft. Regular cleaning of vent screens, lou- cleaning of any external fins should be scheduled based
vers, and the like will prevent blockages that could kill on an observed difference between metal temperature
your equipment. Always use a vacuum to clean them, and ambient air. Also make sure you maintain the ven-
blowing air and brushing simply loosen the dirt and al- tilation equipment for any electrical enclosure, it’s a
low it to flow into the equipment, not keep it out. Use a lot easier to replace a hundred dollar exhaust fan than
damp rag for removing dust from the top of motors and several thousand dollars worth of transformers. If you
electrical enclosures so you pick it up instead of brush- do no more than walk through the room containing a
ing it off and into the vents. transformer while noting temperatures you will still
Okay, somebody jumped on it. A wet rag! I don’t improve their reliability.
want to get electrocuted! First of all, let me dispel one Newer transformers can produce dramatic savings
myth that’s always perpetuated by Hollywood. If you’re in energy cost because they’re so much more efficient.
in a bathtub full of water and someone drops an electric Add to that the problem with many transformers op-
appliance in the water you are not automatically elec- erating at very low loads (where the losses are more
trocuted. You can only suffer harm if the current passes significant) to be aware that replacements should be
through you and the only way the current can do that is considered on a regular basis.
if you are in the circuit between the electrical appliance
and the water which serves as a grounding conductor.
You have to touch the electrical device and the current VOLTAGE AND CURRENT IMBALANCE
has to flow from you to the water to do you any harm.
The concern in bathrooms and kitchens is that Changes in electrical loads in facilities can create
the water is there, contacting drain piping, etc. and is a voltage and current imbalance that can generate seri-
ground which you can contact at the same time as a hot ous problems with alternating current motors and other
conductor. Re-read the above on GFCIs; that’s why all equipment. One significant contribution to changes in
new bathrooms have to have them. Electrical enclosures facilities includes the conversion to more efficient light-
and motor housings should be grounded, not hot, so a ing. If that’s not done with some attention to the share
little scrubbing with a damp rag can’t cause a problem. each phase of a three phase power supply is altered you
If you’re using a soaking wet rag that’s squeezing water will start having strange situations with motors and