Sanden CO2 Refrigerant Heat Pump Water Heater at FutureFit Home
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Residential heat pump domestic water heating systems (HPDWH) use synthetic refrigerants with high global warming potential (GWP). In the 1990s, Japanese engineers developed an alternative HPDWH technology known as "Eco-Cute" that uses CO2 for refrigerant, a naturally occurring gas with global warming potential (GWP) 2,000 times less than synthetic. Oregon’s plumbing code requires hot water heating systems to be tested and listed by an approved agency (such as Underwriters Laboratories UL). Although it is not yet UL listed, the City of Portland allowed us to install the CO2 HPDHW system as an alternate material through its Alternative Technology Advisory Committee process.
|Code Requirement||Compliance Path|
|2011 ORSC section M1302.1 Requires appliances to be listed and labeled by an approved agency (e.g. UL)||
City of Portland building code appeal based on ATAC’s recommendation (see below); administrative ruling by City staff, followed by written, online approval.
|2011 ORSC section R104.11 allows alternative materials, design and methods of construction and equipment when the material or work offered is equivalent
||Written application to City’s ATAC, ATAC in -person hearing, and ATAC’s written recommendation to approve..|
Even after futurefitting our home (remodeling for the future) to the super-efficient Passive House Standard in 2009, we still needed a small amount of space heating. And futurefitting did not change our need for domestic hot water. An "active" heating system like HPDHW fit well with our plan: efficient, affordable, and electric to make use of renewable energy and avoid combustion of fossil fuels. When installed, it will satisfy both our space heating and hot water needs.
The specific Eco-Cute equipment we want to install is not UL listed but it is environmentally superior, so we made an application to the City of Portland Alternative Technology Advisory Committee (ATAC). ATAC heard remote and in-person oral testimony and reviewed written materials we submitted. ATAC recommended approval, and the Bureau of Development Services approved our code appeal based on the ATAC's recommendation.
|Oregon Residential Specialty Code||Oregon Plumbing Specialty Code||Laboratory Assessment of Sanden GAU
Heat Pump Water Heater Lab
|Oregon Mechanical Specialty Code||Oregon Reach Code||WSU Case Study on C02 Refrigerant HPDHWs|
In 2009, there were heat pump “combi” space and water heating systems on the market, but they were costly. Worse, they use synthetic refrigerants with high global warming potential (GWP). Although no one intends the refrigerants escape into the atmosphere and cause warming, some will escape notwithstanding our best efforts. Typically, refrigerants leak into the atmosphere both very slowly during normal heat pump operation and quickly either upon an accidental release (during charging or equipment damage) or at the end of the equipment’s use if the refrigerant is not carefully captured and either reused or destroyed. There are government refrigerant capture requirements, but I am not optimistic about refrigerant capture, especially in countries with less robust environmental safeguards, regulations, and enforcement.
In the 1990s, Japanese engineers perfected high-pressure CO2 refrigerant heat pump technology (known as “Eco-Cute”). Available in Japan since 2001, this technology has spread to Australia and Europe, but to date, it has not been available for North American homes. Now, thanks to the City of Portland’s accessible ATAC process that approved its use for mine and also for future projects, Sanden is importing its Eco-Cute system to Portland, Oregon.
Sanden's Eco-Cute heat pump domestic water heater combines highest-in-class heating efficiency and adequate hot water capacity even in subfreezing weather. Sanden's system includes an 84-gallon DHW tank with sufficient heat storage for both residential hot water and space heating for high-performance homes. It's environmentally better because it uses CO2 refrigerant instead of synthetic refrigerants which contribute to global warming if/when released into atmosphere. CO2 has a GWP of one, far below the GWP of conventional, synthetic refrigerants (1,000 or 2,000).
We believe this technology will also help us come within the primary energy consumption limit of the Passivhaus Institut’s Passive House Standard for new buildings and EnerPHit Standard for remodeled buildings. Also, this all-in-one electric heating system's electrical load matches residential-size roof-top solar PV output for not just annual Net Zero Energy homes but "real-time" NZE operation.
Design / Build Process
We are working closely with our electrical and plumbing subcontractors and the manufacturer’s representatives to design and install our system.
Cost / Benefit
In 2009 when we sealed and super-insulated our home, we removed our gas furnace and installed a 2.5kw electric resistance heating system within our ventilation air supply ducts. This space heater was inexpensive, easy to install, and avoided onsite fossil fuel combustion. There were heat pumps like mini-splits available at the time, but we did not expect to use much space heating energy.
Over the last few years, we appear to consume almost 3,000 kwh of electricity per year for space heating. That's more than I expected. And it is $300/year at current prices. This is far less than most houses, but still, we’d like to reduce our consumption further. In our climate, Sanden's Eco-Cute system should produce about 2.5 to 3.5 units of heat for each unit of electricity in our winter conditions. That’s far greater efficiency than our electric resistance heater which produces one unit of heat for each unit of electricity. We estimate that this technology will reduce our electrical consumption for space heating by 60%.
And it will replace our natural gas DHW system. We already support the transition to renewable energy by participating in our utility's 100% wind electricity purchase program. By switching to electrical water heating, we'll speed the transition away from fossil fuel combustion.
We hope the total cost to install a Sanden Eco-Cute HPDHW system providing both water and space heating will cost approximately $5,000 after Oregon Residential Energy Tax Credits and incentives from the Energy Trust of Oregon. For space heating alone, the financial payback period is long (25 years) if electricity prices stay low. At current low natural gas prices, including fuel-switching for our DHW, the financial payback period is even longer.
However, if the financial payback analysis includes the cost of global warming (accelerated by conventional refrigerants leaking into the atmosphere), Sanden's Eco-Cute's benefits outweigh its costs.
|Owner: Tad Everhart, Certified Passive House Consultant Tad Everhart Energy Advisor LLC 503 239 8961||Other: Maho Ito, CO2 Product Line Manager Sanden International (USA) 734-207-3532||Subcontractor: Mike Elrod, Owner Gresham Electric|
|Subcontractor: Jonathan Cohen, Owner Imagine Energy 503 477 9585|