Maintaining Heating Systems
Electrical Troubleshooting Quiz
Replacing HVAC Blower Motors
NEC at the Facility
Answer to Electrical Troubleshooting Quiz
North Texas Facilities Expo
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MRO Insider addresses topics such
Working with management and supervision
National Electrical Code® on the production floor
Safety procedures and programs
Equipment maintenance and testing tips
Managing motors and generators
Trends in training and education
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The designations "National Electrical Code” and “NEC” refer to the
National Electrical Code®, which is a registered trademark of the
National Fire Protection Association.
Maintaining Heating Systems
Do you have a formal HVAC maintenance program, or will
you simply react to failures while production workers complain about
bitter cold indoors this coming winter?
HVAC manufacturers specify maintenance practices, but few owners
follow them. Among those that employ the recommended maintenance
practices, there's a tendency to treat suggested schedules as maximums.
This can cause unnecessary expense and preventable discomfort to
Some things to consider:
- Perform insulation resistance tests on the blower motors
For two-speed motors, check both sets of windings. When a blower fails
in the summer, the condenser may ice up and not thaw for several hours.
A winter blower failure may go undetected until the occupants finally
complain. By the time you troubleshoot and obtain a replacement, the
heat loss may be significant and result in extended indoor cold.
- Use infrared or ultrasound regularly to nearly eliminate "surprise"
motor bearing failures. Bearing failures typically result from
maintenance failures -- such as improper lubrication and inadequate
- Understand that the recommended filter change interval is based on
"typical" application, not necessarily your application. You can
inspect filters frequently, or you can automate detection by installing
d/p instruments (delta pressure) across the filters.
- When the cooling season has ended, cover condenser units so they
don't accumulate winter grime. Schedule time in early spring or late
winter to clean and comb the condenser fins.
- Have a qualified person conduct the full battery of heating system
inspections, if these inspections were not performed during the
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During several periods of deep chill last winter, the
offices stayed frigid until late afternoon -- about the time people
started going home. This problem first arose last year, and the system
has been in service for many years. So your boss naturally concluded
this must be an "electrical problem." Spring came, and other priorities
Now with cold weather approaching, the plant manager remarked that
maybe the plant should issue gloves and mittens with the company logo
all office personnel -- not a good sign.
The system uses a modern furnace with heat pump, and you can hear
furnace kick in during high demand. Is this really an electrical
problem? What should you do?
The answer to this question appears at the end of this
Replacing HVAC Blower
The primary modes of blower motor failures are:
If your blower motor is relatively new, have a motor shop do a
post-mortem on it to determine the cause of failure. Yes, this motor is
probably only a few hundred dollars, so a replacement is not a big
budget item. But that's not the point. The point is to identify
that may cause the remaining blower motors to fail. If you have several
HVAC units, consider this step mandatory.
- Bearing loss. This is typically due to overloading from
- Phase on phase shorting. Manufacturing defects (insulation
deficiencies) or power quality issues in your plant are the probable
- Open conductors or connectors. Manufacturing defects or
severe power disturbances are the likely culprits.
If your blower motor has been in service for a long time, it's not
likely you have a preventable cause of failure. But it is likely that
other motors installed at about the same time will fail soon. Have
replacements on hand. If there's an accessibility problem or extreme
temperatures are forecast, don't wait for failure to happen. Do a
post-mortem on the failed motor and then check the remaining motors for
signs of a similar failure.
For example, the motor shop tells you the insulation failed. Do an
insulation resistance check on the remaining blower motors, and replace
the ones that appear marginal.
Beware - Arc
Pin and sleeve plugs & receptacles can be dangerous if operated under
load. To prevent accidents install Decontactor Series switch rated
and receptacles. They are a UL rated plug, receptacle and disconnect
switch in one device. 100 kA short circuit ratings protect users in
fault conditions. Inquire about our free trial program.
Meltric Corporation, call 800-433-7642, www.Meltric.com
NEC at the Facility
Check your enclosures for openings, such as those left
by unused knockouts. Plug any that exist. [312.5(A)].
Smart safety directors know there's a difference
fulfilling a "check off the box" corporate mandate and truly
communicating the safety message. Make sure your safety performance
reflects this same knowledge.
Managers, take note. The goal isn't to protect your company from
fines. It's to protect your workers from unsafe conditions and unsafe
acts. Go beyond formal activities, and engage people on safety in the
field. Ask an electrician to stop working for a moment, then ask about
the safety issues involved in whatever task is at hand. Ask how that
person is addressing each of those issues.
This practice gets people "thinking safety" outside of safety
training sessions. It makes it far less likely OSHA will have a reason
to fine your company. But more importantly, people are less likely to
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exclusive displayed numeric value (0-99) and variable tone/pitch
maximizes the ease-of-use when identifying breakers, tracing wires and
finding opens/shorts. For more information on our circuit tracer kits,
here to download a PDF.
Answer to Electrical
Multi-stage heating systems improve energy efficiency.
When the temperature differential is minor, the system uses only one
stage and maintains the desired temperature. If your system has a heat
pump, you might think the heat pump is stage one and the furnace is
stage two. But that's not the case -- the furnace operates in a
multi-stage mode (typically, two stages).
The programmable controller or setback thermostat in your system
allows the nighttime temperature to drop below what's needed for
comfort. In the morning, the system tries to close a large gap between
actual and desired temperatures. If it has only the heat pump and the
first stage available to it, this won't happen. Most systems have an
"Emergency heat" control, and you can use this to test whether the
blower and furnace are getting the control signal to boost into second
You should probably get an HVAC service call authorized and have a
specialist examine the system. Otherwise, you may spend time digesting
the schematics and manual, only to discover you need a proprietary
Now, here's where the electrical part often gets overlooked. The
likely cause of a controller failure is an unbonded grounding electrode
(or connection to a discontinuous water pipe). Your system doesn't need
to be grounded -- it needs to be bonded. See Art. 100
the NEC for definitions of these key words.
Proper bonding prevents the high potential that can produce an
electronics-destroying flashover. The technician will be back for the
same problem, unless you correctly bond everything.
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meets hazard risk category four. All Carhartt FR can be home or
industrial laundered and is guaranteed to be flame-resistant for the
life of the garment. www.carharttFR.com
Show & Events
North Texas Facilities Expo
The North Texas Facilities Expo will take place from
Oct. 31 to Nov. 1 at Dallas Market Hall in Dallas. Seminars at this
year's event include "2005 NEC Requirements for Concrete-Encased
Electrodes and Other Grounding Electrodes," "Infrared Technology for
Electrical Applications and Beyond," and "Who Is a Qualified Electrical
Worker?" For more information, a full list of exhibitors, and to
register, visit the expo's Web site.
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