An ODS (Ozone Depleting Substance) is a man-made chemical which, when released, destroys ozone molecules in the upper atmosphere. The ozone layer shields the surface of the planet from ultraviolet rays which are known to have negative effects on animal and plant life. Therefore it is generally accepted that depletion of the ozone layer represents a health threat and, to a lesser extent, a threat to agriculture.
Since 1996, governments and industry have made concerted efforts to limit the production and use of ODS’s. These efforts have taken the form of taxation, legislated production quotas, and legislation surrounding the handling of ODS’s. The result to users has been financial…equipment service contracts and ODS’s are becoming steadily more expensive. Up until now, all ODS’s have remained available for those willing to pay for them, so users have for the most part been able to continue using older ODS equipment.
For the residential building owner, the primary use of ODS substances is for refrigeration. The typical chemicals and applications are described briefly below, grouped by chemical families:
CFC family (highest Ozone Depletion Potential)
R11 - Mainly used in large chillers for air-conditioning. Many are still in use.
R12 - Used in domestic refrigerators and freezers built before 1994. Also used in other small hermetic systems such as retail display cases and icemakers.
Canadian Phase-Out Schedule, under the Ozone-depleting Substances Regulations, 1998:
Production has been phased out since 1996. Starting on January 1, 2005, owners have not officially been allowed to replace the refrigerant after a chiller overhaul, defined as the following:
|•||Maintenance requiring the replacement of any internal sealing devices;|
|•||Maintenance requiring the replacement of any internal mechanical parts, other than oil heaters, oil pumps, float assemblies, and vane assemblies in the case of chillers with single-stage compressors; or|
|•||Maintenance resulting from the failure of evaporator or condenser heater exchanger tubes.|
Because building owners have been very slow to respond to this deadline, an exemption to allow for the charging of a chiller and its continued operation with CFCs following an overhaul is available on the condition that the system is converted, replaced or removed from service no later than 12 months from the date of the charge. This exemption involves significant documentation, and it is our expectation that the 12 month grace period will be vigorously enforced.
So the R11 chiller owner can choose to wait until there is a significant failure before addressing the issue. However any investment in the repair at that point will probably be lost, because once an exemption has been granted, replacement of the machine or an expensive upgrade to change refrigerants will be the only options.
HCFC family (medium Ozone Depletion Potential)
R22 - Widely used in packaged air-conditioning systems such as those in rooftop HVAC units and most small residential air conditioning systems and heat pumps.
R123 - Introduced as an alternative for CFC 11 in large air-conditioning water chillers in response to CFC production phase out. I has been used in new machines built after 1995, and also as a replacement for R11 in older machines.
Canadian Phase-Out Schedule, under the Ozone-depleting Substances Regulations, 1998:
1996 freeze at 887 ODP tonnes annual production
2004 35% reduction to 577 ODP tonnes
2010 65% reduction to 310 ODP tonnes
2015 90% reduction to 89 ODP tonnes
2020 99.5% reduction to 5 ODP tonnes
2030 complete elimination of all production
As availability decreases, market forces will take effect.
HFC family (no Ozone Depletion Potential, but high Global Warming Potential)
R134a – Commonly used in new water chillers.
No Phase-Out Schedule
Progress on ODS Reduction
Since the signing of the Montreal Protocol in 1988, tremendous progress has been made in North America to reduce the production and use of ozone depleting substances (ODS). The substances of greatest concern (CFC’s) have been addressed effectively by government and industry. For example:
|•||All air conditioning in new cars is now CFC-free|
|•||Over 90% of foam blowing applications use alternatives to CFC's|
|•||Over 90% of cleaning agents that were CFC-based now use alternatives|
|•||All new chillers and direct expansion refrigeration systems are being produced with alternatives to CFC refrigerants|
|•||Production of CFC refrigerants was phased out completely at the end of 1996|
|•||Halons used in fire extinguishers are no longer manufactured|
|•||Refrigerant venting laws and increasing CFC pricing have made users much more careful in their handling of these chemicals|
That's the good part of the story. The downside is that a tremendous amount of CFC-using equipment is still in use. In the residential building industry, conversion has lagged far behind predictions...owners are reluctant to walk away from their investment in refrigeration plant equipment. So every year service contracts get more expensive.
Chillers in residential buildings are run only seasonally, meaning that they account for a smaller proportion of total energy costs than in most commercial buildings. Newer equipment is more energy-efficient, however energy cost savings from projects to address ODS concerns will almost never be enough to finance the project in a reasonable time. For that reason they are not considered energy conservation projects and should instead be though of as regulatory compliance projects (or environmental stewardship projects) with an energy savings side benefit.
So Why is There Still Confusion?
|•||Chiller manufacturers have not agreed upon one common alternative refrigerant.|
|•||Governments have not imposed strict guidelines, such as a complete ban on the use of CFC refrigerants.|
|•||Refrigerant manufacturers have not developed the perfect alternative refrigerant.|
|•||The technical issues are not easy for the lay person to understand, solutions are not obvious, and opinions vary quite widely among people in the industry.|
What To Do?
Wise facility owners are informing themselves on the issues and making a list of options. "Do nothing for now" is one option that should appear on that list, and it may well be the best option. But at some point, considering capital depreciation, energy costs, and maintenance costs, some other choice will be preferred.
The available solution depends on the type of equipment in question. Centrifugal water chillers found in many buildings have traditionally been built as low pressure machines, for CFC-11. CFC-11 has a very high Ozone Depletion Potential (ODP). Several years ago, Trane promoted the use of the low pressure alternative HCFC-123 as a replacement, but that option was still quite expensive. HCFC-123 is more chemically reactive than CFC-11, and unfortunately it will break down the materials used in the seals and motor windings of many existing chillers. A refrigerant replacement job, where it is possible at all, involves tearing down and rebuilding the chiller.
Additionally, there has been some debate about the carcinogenic properties of HCFC-123, and some service organizations initially refused to work with it. HCFC-123 has a smaller ODP than CFC-11, but it is still scheduled to be phased out of production by 2020.
From the start, Carrier has promoted replacement of existing low pressure centrifugal R-11 chillers with medium pressure units using HFC-134a which has no ODP and therefore no planned phase-out date. But HFC-134a has it's own drawbacks:
|•||the theoretical energy efficiency is not as good|
|•||though it has no ODP, the Global Warming Potential (GWP) is very high|
Other manufacturers like York and McQuay waited out the debate, developing a broad product range to cover all the bases.
Other compressor technologies (reciprocating, screw, scroll) have made inroads into the retrofit market, particularly to overcome site-specific problems with access to the chiller room. These machines most commonly use the high pressure refrigerant HCFC-22, which itself has a significant ODP and is scheduled to be phased out of production by 2010.
This refrigerant is in widespread use in rooftop air handlers and split systems prevalent in smaller buildings. A tremendous amount of HCFC-22 equipment is still being produced despite the fact that the refrigerant is scheduled for phase-out. The purchase of HCFC-22 rooftop or split sytems (direct expansion) is not too much of a risk at this point, since that equipment only lasts 25 to 30 years at the most...there should be plenty of it around to last the lifetime of equipment being sold today. But water chillers are a different story...there are many 40 year old CFC-11 machines still in use, so a HCFC-22 chiller could be forced into obsolescence before its time. Refrigerant manufacturers are working on development of "drop-in" HCFC-22 replacements, but they have been working on the problem for many years now. There is no assurance that a viable replacement will ever arrive.
Other Things to Think About
When you upgrade a chiller plant, you will very likely be obliged to comply with newer more stringent building code requirements. These could be:
|•||Structural separation of the chiller room from the boiler room|
|•||Installation of a refrigerant monitoring and alarm system|
|•||Installation of a high efficiency purge to minimize refrigerant venting|
|•||Formal chiller room ventilation system (exhaust and makeup)|
|•||Provide breathing apparatus for emergency service|
Short Term Measures
There are several less complicated things that a building owner can do to cut operating costs and extend the useful life of the chiller plant. These initiatives don't eliminate the problem, just delay addressing it.
|1.||Refrigerant Leak Testing - Refrigerants will last essentially forever, so if you don't lose any you don't need to buy any more. 60% of all refrigerant loss is due to leaks. Make sure your service contractor is performing a full leak test every year during winter shutdown.|
|2.||High-Efficiency Purge - In theory if we could find all the leaks in a refrigerant system there would be no need for a purge unit. However the design of low pressure chillers is such that they do leak. Low pressure units using CFC-11 or HCFC-123 operate at a slight vacuum, meaning that leaks allow air to be drawn in with the refrigerant. A purge unit evacuates the air. Older purge units discharge as much as 10 lbs. of refrigerant for every lb. of air. The industry standard today is less than one lb. of refrigerant per lb. of air. A modern purge unit will cost between $6000 and $9000 installed.|
|3.||Purge Capture Cannister - Installed after the high-efficiency purge, this device will reduce refrigerant emissions to virtually zero. It also serves as a purge problem or leak indicator when it fills up too fast. A small cannister costs $1,000 to $2,000.|
|4.||Minimize the Effect of Pressure Relief Activation - Low pressure chillers have a device designed to relieve pressure in the vessel when it exceeds 15 psi. On most chillers, this is a carbon disk designed to shatter at that pressure. Although this would be a rare occurrence, the results can be catastrophic. First, the entire refrigerant charge is lost and can cost over $12,000 to replace. Second, the internal parts are exposed to air and moisture. If left inside, the moisture will mix with the new refrigerant, creating an acid which will eat away at chiller components. Third, many older mechanical rooms have boilers and chillers close together. If a boiler should fire during the refrigerant leak, deadly phosgene gas will be produced at the burner. Aside from presenting a safety hazard, the gas will destroy the heat exchanger and may reduce the boiler to scrap. There are ways to address the risk (and cost) of such an event:|
|•||Install a recovery tank to capture the refrigerant in case of pressure relief activation; $10,000 to $15,000.|
|•||Install a spring activated re-seating pressure relief valve that closes when pressure drops below 15 psi; $3,000 to $6,000.|
The choice to convert, replace, or wait should be revisited regularly, and particularly when an existing R-11 machine is in need of major service. Keep in mind that there are considerations weighing in favour of replacement:
|•||Energy Costs - Newer chillers are much more energy efficient, at about 0.55kW per ton cooling. Chillers 15 years and older are rated around 0.9kW per ton. Also, chillers are notoriously inefficient at part load operation where they spend most of their time. Where an existing plant is oversized, a new system can be designed for improved efficiency over a wider range of operating loads.|
|•||Maintenance Costs - New machines require less maintenance than older ones.|
Keep in mind that each manufacturer or installation contractor will have a preferred approach. Where possible, get more than one opinion, and get the opinion of an independent outside specialist with no vested interest in the equipment or the approach taken.