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Pneumatic
Control Repair or Replacement
What are pneumatic
controls? Pneumatic
controls are temperature control devices, thermostats, that use low pressure air
to control the temperature in spaces served by heating and air conditioning
equipment. As the air temperature
in the space varies, the thermostat varies the controlling air pressure.
The controlling air pressure then signals the heating and air
conditioning equipment of the needed heating or cooling. Why
were pneumatic controls used? Years
ago, only pneumatic controls could be used in certain heating and air
conditioning applications. Today,
many other types of controls can be used instead of pneumatic controls.
However, some architects/engineers will still specify pneumatic controls
because of their personal preference or installation cost considerations. Why
do pneumatic controls fail? The
pneumatic controls contain a series of small orifices and passages.
Eventually, the orifices and passages become contaminated with oil and
water. This contamination causes
the controls to become un-calibrated or “stick” and eventually completely
fail. How
do I know that the pneumatic controls are contaminated? Your
building will have uncomfortable areas. The
annual utility heating and air conditioning repair cost will be higher than
normal. What
is the source of the contaminating oil and water? Pneumatic
controls operate on low pressure air. This
air is supplied by an air compressor. The air compressor is lubricated with oil and some oil is
discharged with the compressed air. Also
when air is compressed and then cooled, water forms in the compressed air.
Both the oil and water will move with the compresses air throughout the
control system. My pneumatic control
system has cleaning devices to remove the contaminating oil and water, why is my
temperature control system contaminated? Various
air cleaning devices are installed in the compressed air piping to remove the
oil and water. These include
various types of water/oil separators and refrigerated air dryers.
These cleaning devices require continuing maintenance.
Even with proper maintenance, some oil or water will migrate into the
pneumatic control system and contaminate it.
When a cleaning device fails, massive amounts of oil and water will
contaminate the control piping. When
my pneumatic controls become contaminated, what must be done to restore them to
proper operation? The
complete control system including all controllers, actuators and thermostats
must be rebuilt and the air piping must be disassembled and cleaned.
The clean up must be complete. If
any portion of the control system is not replaced, rebuilt or completely
cleaned, the contamination that remains will eventually invade and contaminate
the entire control system. What will it cost to
clean up my pneumatic control system? The
cost of the clean up varies, but a good budget amount is $250.00 per control
point. A control point is any
sensor or control actuator. Therefore,
a temperature control zone or space thermostat will usually represent three
points, the thermostat cooling actuator, and heat actuator.
This means that you could count the number of thermostats and multiply
the sum by three control points and $250.00.
This budget amount should include the cost of the labor and materials to
flush the contamination from the piping installed in the facility.
For example, if your building is equipped with fifty variable air volume
fan terminal units with terminal reheat you can budget clean up as follows: 50
thermostats X 3 control points/thermostat X $250.00 = $37,500.00 Can the clean up be done
at a lower cost? No,
although many repair companies will quote you a lower price, it does not include
a complete clean up. Unless the
clean up is complete, residual oil and water will quickly contaminate the
recently cleaned components. This
means that you wasted the money that you spent on the initial clean up. If I spend the
money for a complete clean up, how long will the clean up last before it must be
done again? The
clean up was necessary because your pneumatic system was contaminated with oil
and water. If a problem develops
with either the air compressor or the air cleaning devices, the pneumatic system
will become contaminated again. Then
the clean up must be done again. This
could happen in one week or five years. If the contamination of
the pneumatic system cannot be avoided what can be done to minimize the clean up
expense? Our
Computerized Temperature Control (CTC) system can replace all the pneumatic
hardware, except the actuators. Or
“CTC” system is not subject to contamination and the actuators that will
remain are not affected by the contamination.
This eliminates the future clean up cost. Why is the “CTC”
system not subject to contamination? The
“CTC” system will harmlessly pass the oil and water that normally
contaminates conventional pneumatic controls.
In the future when your pneumatic system becomes contaminated, the
controlling “CTC” system will not be affected. What
is the cost of the “CTC” system? The
“CTC” system costs approximately the same as a complete clean up of the
pneumatic system. What
other benefits does the “CTC” system offer? The
“CTC” system will substantially reduce the annual utility cost.
Often, the reduction in utility cost will return the total “CTC”
installation cost in less than four years.
Not only do you eliminate the future clean up cost, but you are
installing the “CTC” system free because you would have spent the same
amount performing a proper clean up. What
is the annual maintenance cost of the “CTC” system? The
“CTC” system is virtually maintenance free.
One of our largest customers, who has over sixty “CTC” systems
installed, states that their annual “CTC” maintenance cost is less than 0.3%
of the original “CTC” installation cost. |
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