Brian Nelson - Nelson Mechanical Design

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"Hi - Brian Nelson of Nelson Mechanical Design from Martha's Vineyard here. Air to water heat pumps will make combustion obsolete - probably within five years. I am a master plumber and mechanical engineer (MSME) - my firm is a pioneer in the green mechanical market on our island.

In addition to plumbing and conventional heating systems, we design and install geothermal (direct exchange with copper tubing and closed loop), air to air heat pumps, solar hot water, and digital control systems to optimize these installations. We designed and installed the mechanical systems for the Vineyard's first two net zero houses (geothermal radiant and fan coils powered by wind turbines).

We are currently designing and installing mechanicals for the first two LEED for Homes houses on the Vineyard. One of them is 10 tons of horizontal closed loop geothermal operating Florida heat pumps (water to air and water to water) - fan coils and radiant. The other LEED home is Daikin air to air and probably Buderus wall hung boiler heating the radiant. The only reason to state the above is to perhaps lend validity to my opening remark - air to water heat pumps will take over the boiler market in five years.

We have done our research and have followed the history of heat pumps (US utilities were pioneers in 1930s through 1960s in air to water, water to water, water to air, even solar heat pump hybrids - but our research and development was doomed by low fossil fuel prices). Japan and Europe picked up where we left off (sounds familiar) in the 1970s and made a multitude of refinements in heat pump technology.

We have watched with interest how Daikin and Mitsubishi refined the air to air heat pump using a variable speed compressor to optimize energy use. The efficiency of these units (and the Maine based Hallowell units) is rapidly approaching geothermal efficiencies at half the installed cost. We also watched Viessmann and Buderus migrate towards air to water heat pumps in Europe - we reckon that they don't bring them to the US because that would demolish their American boiler market. Our experience is that the operating cost of these air to air and air to water heat pumps is close to half that of a condensing boiler or furnace

We seen the Japanese (Daikin, Sanyo, and Mitsubishi) develop their own versions of the air to water heat pumps, test and sell them in Japan (over a million installed!) and recently introduce them to Europe. Their inverter drive compressors (variable refrigerant flow) are more efficient than the Viessmann and Buderus one or two speed compressors and have better performance (these units are designed to deliver 135 F water using 5 F outside air!). The latest unit from Daikin (Altherma) is the complete package - air to water heat pump, with a control system ready for solar integration, that makes hot and cold water for radiant and higher temp - around 140F - for domestic hot water.

Visit daikinuk - the British Daikin website. This unit will revolutionize the American radiant market - a Daikin sales engineer told me it would be out this fall here in the US. Half the operating cost of a condensing boiler at about the same price. Because geothermal is so expensive, we always offer our clients alternatives - mostly air to air heat pumps as systems with similar efficiencies and operating costs. But if the client wants radiant, we have to either go geothermal or back to combustion... now we will have a real air to water alternative. The COP of the Daikin will be higher than the Aquaproducts unit or the Unico Unichiller.

I predict that when Daikin brings this Altherma unit to the US in the fall, Viessmann and Buderus will have to introduce their air to water units too - at the expense of their boiler business.

If this wasn't exciting enough, all of the above is antiquated technology! Once again, our low fossil fuel prices have hobbled our innovation... All of the above units use an HFC refrigerant (R410a) which has a well established upper limit of temperature and performance. The real deal is the Eco-cute heat pumps coming out of Japan - they use CO2 (carbon dioxide) as the refrigerant (last used in the 1920s on refrigerated ocean vessels for shipping fruit) - much much higher pressures (around 1300 psi instead of 400 psi for R410a) but much higher temperatures. Over a million of these units are in place in Japan - they are subsidized up to 80% to boost market share. Now that the Japanese are ready, they are exporting these CO2 air to water heat pumps to Europe. Sanyo unveiled their version of the Eco cute heat pump - 180F water, domestic hot water and radiant - at better efficiencies than geothermal!!!!! For more indepth info on these air to water heat pumps, visit for all the technical details. We are in the stone ages here!!! And I get to tell my clients about these developments they can't have!

My website is link title - I haven't updated it with our most current projects but it may be of interest. thanks Brian Nelson