By Michael Zales, Containment Products Marketing Manager, Carrier Commercial Applied Equipment & Services.
With the Clean Air Act of 1990's phase out deadline for domestic
CFC production behind us, the question of what to do with the
estimated 60,000 negative-pressure chillers using chlorine-based
refrigerant CFC-11 in the United States weighs more heavily with
each passing day. If you operate one of these chillers, you
face a decision that will have a profound impact on your operation
and budget for years to come.
While the issues are complex, the alternatives are well-defined:
contain the refrigerant in your existing chiller using specialized
containment devices; replace your chiller; or convert
your existing chiller to use an alternate refrigerant.
Determining which option is the most cost-effective requires a
careful examination of your individual situation. Such analysis
typically begins with a consideration of the age and condition
of the chiller in question.
It is further estimated that half of the negative-pressure chillers
in the United States -- approximately 30,000 chillers -- are less
than 15 years old. With the life span of the average chiller
at 30 years, these chillers have many years of useful life remaining.
Understandably, many chiller owners are not ready to accept the
expense of replacing equipment that is performing well.
While the decision to replace an aging, inefficient chiller is
fairly clean-cut, the dilemma with a younger chiller is typically
whether to convert to an alternate refrigerant such as HCFC-123
or to responsibly contain the CFC-11 currently used, as outlined
in the Clean Air Act, Title VI, Section 608, and in conjunction
with specialized containment products and improved service practices.
For most negative-pressure chillers, conversion to HCFC-123 is
costly. Typically, all original gaskets and seals, and other
major components (such as the motor stator), must be replaced
with HCFC-123 compatible materials. Often it is necessary to
install a new impeller wheel to minimize capacity and efficiency
losses.
The implications go beyond the upfront costs of converting. Since
exposure limits are much lower for HCFC-123 than for other common
refrigerants, consideration of a refrigerant monitor, self-contained
breathing apparatus and ventilation system improvements should
accompany any refrigerant change, per ASHRAE 15-1994 standards.
Moreover, because HCFC-123 contains chlorine, refrigerant containment
devices are required even after conversion.
In total, converting a typical, 500-ton chiller to HCFC-123 is
likely to cost as much as $88,000, or approximately 60 percent
the cost of complete replacement. And that figure does not include
the hidden expense of higher operating costs due to efficiency
and capacity losses, or the cost of the same containment devices
required of CFC-11 chillers.
The efficiency loss is not something to gloss over. If we convert
our 500-ton example, chiller efficiency will drop a minimum of
three percent, significantly decreasing system performance while
increasing operating costs. Consider, for example, a 15 year-old,
500-ton chiller with a full load efficiency of .75 kW/ton operating
3,000 hours per year. A drop in efficiency to .77 kW/ton would
add at least $3,000 annually in energy costs (500 tons x .02 kW/ton
x 3,000 hrs. x $.10/kWh). Multiplied over the remaining life
of a converted chiller, that is an additional cost of $30,000
to $45,000. When the multi-year cost of chiller efficiency loss
is added to the initial conversion costs, the lifetime cost of
a CFC chiller conversion is nearly as high as the one-time cost
of a replacement chiller.
For chillers less than 15 years old, a cost analysis of conversion
versus containment proves that containment is by far the more
economical solution, in the first year and well beyond. For the
same 500-ton chiller, the installed cost of a complete containment
package is currently estimated at $29,500, one-third the upfront
cost of conversion. Additionally, many chillers require only
selected containment devices, making the actual containment cost
substantially less.
The reduced need of expensive refrigerant replacement can quickly
offset the initial cost. The U.S. Environmental Protection Agency
currently allows a 15 percent annual leakage rate for commercial
applications and a 35 percent leakage rate for industrial installations.
Yet with today's new technologies and improved service practices,
annual refrigerant emission rates of two percent or less are achievable.
What does this mean in the long run? ASHRAE 15-1994 allows a
maximum of 330 lbs of refrigerant to be stored in a mechanical
room. At a two percent leakage rate, a 500-ton chiller could
continue to operate for more than 13 years on that initial supply.
A refrigerant containment strategy is an economical and responsible
way to add years to the life of a CFC chiller in good working
order. Containment is the first and least expensive option compared
to conversion or replacement. While a refrigerant containment
program improves the operation, maintenance and servicing of negative-pressure
centrifugal chillers, it also saves money by capturing the refrigerant
lost to the atmosphere during normal use and servicing.
In addition to reducing CFC emissions, a refrigerant containment program also extends the useful life of an existing chiller, providing the you ample time to plan a clear migration path to a chlorine-free future for your facility.
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