NC-2009 EAc4: Enhanced Refrigerant Management

Background: The present equipment life assumptions are from Table 4, Page 36.3 of the 2007 ASHRAE Handbook - HVAC Applications. Justification: It is critical to understand that the median service life for these pieces of equipment is from statistical research by Akalin in 1976 under ASHRAE Research Project RP-186 which was tabulated and published in 1978. The footnote in the table states, "Note that data from Akalin (1978) for these categories may be outdated and not statistically relevant. Use these data with caution until enough updated data are accumulated in Abramson et al." Regarding the equipment service life estimates presented in the 1978 Akalin tabulation, ASHRAE makes the statement in the 2007 HVAC Applications Handbook that; "..changes in technology, materials, manufacturing technology, and maintenance practices now call into question the continued validity of the original estimates." It goes on to say that estimates of equipment service life not contained in ASHRAE\'s new equipment life survey (TRP-1237) now being conducted, that a service life estimate may be obtained from manufacturers, associations, consortia, or governmental agencies. Presently: * Rooftops of all sizes are designated as having a 15 year life for EAc calculations. * Chillers with scroll compressors are designated as having a 20 year life for EAc calculations. Rooftop units which had been replaced by the time of the 1976 survey and, therefore included in the statistical population, on average, would have been built in 1961. Equipment of that vintage was primarily small (less than 20 tons) packaged equipment the majority of which were used in residential or small unitary applications. Large air cooled chillers and large industrial duty packaged rooftop equipment were not readily available until the 1970\'s. By design these larger units have a longer expected service life. Due to its availability this larger equipment would not have been included in the sample population of the Akalin study. The basic design of that 1960\'s equipment used reciprocating compressors - with many more moving parts, and therefore higher failure rate than the scroll compressors available in today\'s equipment. Today both pieces of equipment (air cooled chillers and rooftop units) use scroll compression technology and in the case of an air-cooled chiller are subject to similar outdoor conditions. Therefore anecdotally, both equipment types should use the same equipment life, but it should be longer than equipment prior to 1978. Data: A program to replace less efficient rooftop equipment with newer, more efficient equipment was undertaken a number of years ago by one manufacturer (Trane) where part of the requirements for the program incentive was that statistical information had to be provided to that manufacturer. Five (5) years of data from this program is attached. While there may be some concern about the low minimum life, these are few and may have been replaced for some reason other than equipment failure (such as increased efficiency or insufficient capacity). Summary information * Sample Population: 808 units * Median life: 20 * Average life: 20.25 * Minimum life: 5 * Maximum life: 37 * Standard deviation: 4.24 Data does not vary significantly by manufacturer, although there are small data samples for all but one manufacturer. Request: Allow large rooftop equipment (20 tons or greater) using scroll compressors to use an equipment life of 20 years for Enhanced Refrigerant Management calculations.

In the calculation of EAc4, is it acceptable to count the quantitative cooling loads addressed directly by the direct/indirect evaporative cooling units, that would otherwise be met with chillers, so that the refrigerant in walk-in refrigerators is not given an unfair weight in the calculations?

The intent of Energy and Atmosphere Credit 4, Enhanced Refrigerant Management is to Reduce ozone depletion and support early compliance with the Montreal Protocol while minimizing direct contributions to global warming. Our project is a high-rise mixed use (mostly residential, but partly retail and commercial) building being built in a new section of Dubai and will be connected to a new District Cooling Plant using HFC-134a for all of its cooling demand. The project has no small HVAC or Refrigerant systems and plans to use in-ceiling sprinklers for fire suppression in corridors and occupied spaces in the building. Local code requires that the electronic building management equipment room (an area comprising less than 1% of GFA) for the building employ a different system for fire suppression utilizing the compound FM200. This is a chemical suppression system made by Dupont Chemical company. Upon our initial research, FM200 appeared to be noncompliant with Montreal Protocol Phase out efforts because a key ingredient in production of FM200 is HCFC-22. However, according to the manufacturer, the HCFC-22 is used and entirely consumed (except for trace quantities) in the production of FM200. In other words, the HCFC-22 is used in the chemical reaction required to create the fire suppression chemical, the reaction causes the HCFC to be changed to an HFC (HFC-227ea as listed on the manufacturer\'s MSDS at http://msds.dupont.com/msds/pdfs/EN/PEN_09004a358037d86b.pdf). As a result, by the time the product arrives packaged at our project site it is no longer an HCFC. In the event of release through leakage or a fire, this chemical will not contribute to ozone depletion. We believe that this product should not negate our capacity to achieve EA Credit 4 as the final use product is, in fact, an HFC. Please confirm that our approach to this credit is correct and will meet the intent and requirements of the credit.

Our project is connected to a district energy system which provides both heating and cooling for the building; no additional building-level cooling systems are installed. The district system draws heavily on deep lake cooling with a complement of refrigerant-based cooling. We also have walk-in refrigerators on the premises. We are not permitted to count the deep lake cooling with a refrigerant factor of zero, so because the walk-in refrigerators use refrigerants with a high impact (according to the LEED calculation), we exceed the impact limit of 100 for the credit even though the project?s cooling capacity is largely provided by refrigerant-free sources.
We propose a calculation methodology that demonstrates a design case reduction of the total refrigerant impact as compared to the baseline case:
• The baseline case is calculated by factoring the total cooling capacity of the building?s baseline case and a refrigerant impact of 100 per ton. The demand (during the simulated year) is 1496 kW for the baseline case and 1704 (483,9 tons) installed capacity, as per the EAp2 form and the EA Section 1.4 Tables respectively.
o total design case cooling capacity = 483.9 tons
o total refrigerant impact = 483.9 x 100 = 48390
• The design case factors the labeled capacity on the district energy system?s heat exchanger (district cooling exchanger) and the walk-in refrigerator equipment, and their respective refrigerants.
o total design case cooling capacity = 393.7 tons
o total refrigerant impact = 393.7 x 86 = 33798
• Total reduction in cooling demand = 393.7 / 483.9 = 81.36 (18.64% reduction)
• Total reduction in refrigerant impact = 33798 / 48390 = 69.85 (30.15% reduction)
The calculation confirms that the refrigerant impact reduction is in excess of that associated with the reduced cooling capacity. We would like this to be an ACP.

EA Credit 4 has been restructured between LEED-NC 2.1 & 2.2 to take into account the global warming impacts of HVAC equipment. The premise is that HFC refrigerants, preferred for their low ozone depletion potential, are less efficient than their CFC and HCFC counterparts, and thus cause more emissions from electricity generation. The formula developed guides applicants to utilize systems and refrigerants that optimize global warming and ozone depletion reductions, and uses the ratio of refrigerant to cooling capacity as a measure. We believe that refrigerant charge is a good indicator of Ozone Depletion Potential, but not of Global Warming Potential. Our experience with numerous projects, including supermarket and school projects, all of which use packaged rooftop units and ductless split systems, has created confusion and conflicting rewards in the goal of using less refrigerant. Case in point, the Trane 5-ton standard efficiency packaged rooftop unit has a refrigerant charge of 1.88 lbs/ton (meets the criteria of the credit as written) and uses 1.05 kW/ton, while the Trane 5-ton High Efficiency has a refrigerant charge of 2.5 lbs/ton (does NOT meet the criteria of the credit) and uses 0.95 kW/ton. The high-efficiency unit uses 10% less electricity, but still does not meet the credit despite a reduction in emissions due to less electricity used. This example is typical of major HVAC manufacturers of packaged rooftop units, and not simply an anomaly. Furthermore, supermarkets are heavy users of refrigeration equipment, and almost always utilize remote condensers and heat rejecters to prevent excess heat loads within the sales area. The refrigerated cases and freezers are connected to the condensers through refrigerant lines, typically using the HFC refrigerant R404a. The constraints of the building type and the distance between the heat rejection equipment and the cases necessitates using large amounts of refrigerant, sometimes up to 6 lbs/ton, and cannot possibly meet the criteria of the credit. The mere existence of this equipment precludes supermarket buildings from receiving this credit, despite the use of environmentally friendly refrigerants and waste heat recovery technology to assist in dehumidification and hot water heating. Similarly, the credit does not directly address the use of ductless split systems. This type of unit is most effective for conditioning spaces that are difficult to reach with traditional ductwork, and by nature must use refrigerant to connect the condensing unit to the fan coil unit. The quantity of refrigerant is indicative of the distance between the two and not necessarily of the efficiency of the unit. In the context of the supermarket building type: 1) Should we specify less efficient HVAC equipment that meets the credit instead of pursuing increased energy efficiency? Does that meet the intent of the credit? 2) Can we exclude the refrigeration equipment from this calculation? If not, what is the best practice recommended to achieve this credit, as the current criteria are unreachable? 3) Can the limit for ductless split systems be raised, or does achievement of this credit create a de facto requirement to eliminate use of these types of systems? Please contact Andrew Ellsworth at andrew@evolveea.com or 412.362.2100 to obtain supporting documentation for this CIR in the form of charts, graphs and cut sheets. This information is critical to understanding the issue being raised.