The Heat Pump – What it Is, What it Does, and What it May Do Someday

SINCE DECEMBER 1852, when Lord Kelvin presented before the Glasgow Philosophical Society a modest little paper, “On the Economy of the Heating or Cooling of Buildings by Means of Currents of Air,” the Heat Pump has been a prime target for technical writers. In fact, for most of the 96 years since Kelvin’s article, there have been more papers on the subject than there were heat pumps in operation. (A bibliography listing 160 references was published by the Southern Research Institute in 1946.) Recently, however, a number of experimenters and manufacturers have made efforts to equalize the disparity. In California, for instance, there are over 100 heat pumps now In use.

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NMD named 2015 Contractor of the Month by Contractor Magazine

Nelson Mechanical Design was honored by Contractor Magazine with their prestigious Contractor of the Month award for September 2015:

  1. What makes Nelson Mechanical Design unique when compared to other contractors?
    Nelson Mechanical Design is a one-stop shop:  We design, install, and service residential and commercial HVAC, plumbing, and water treatment systems and we offer both conventional (propane and electric) and green (solar hot water, air and geo heat pumps, composting toilets) approaches to our clients’ heating, cooling, and plumbing needs.

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Mansion Hotel Uses Displaced Heat to Warm Swimming Pool

Contractor Magazine, April 3, 2013


VINEYARD HAVEN, MASS. — Old can be perceived many different ways. For example, calling another person old, not so much a compliment. But when you take a hotel, for example, “old” suddenly becomes more interesting — it exudes character, charm, quaintness, stories and experiences. It could be the single reason you choose to stay at one hotel over another. A fire burned down the 200-year-old Tisbury Inn here, established in 1791. The owners decided to rebuild in 2003, making the new and improved Mansion House Hotel one of Vineyard Haven’s most desirable full-service inns. Transforming the old to new consists of adding comfort, adopting sustainable ideas, and saving some bucks along the way.
Fast forward nearly 10 years to 2012 when the hotel wanted to increase its energy efficiency and reduce energy consumption with a heating system. The Mansion House Hotel owners sought out the expertise and experience of Nelson Mechanical Design (NMD) to install an innovative heat exchanger that is projected to reduce the hotel’s fuel oil use by more than $13,000 annually. This savings is developed by a plate and frame heat exchanger that takes waste heat — essentially solar energy that has heated up guest rooms — and uses it to heat the swimming pool. The result is that the fuel oil-fired boilers will run much less, the pool will be heated indirectly by the sun, and the carbon footprint of the hotel will shrink dramatically.

“In December 2012, we installed a large plate and frame heat exchanger at the Mansion House Hotel to pull heat out of the building loop — generated at least 10 months of the year by all of the hotel’s heat pumps — to heat the swimming pool, displacing $13,000 annually in fuel oil cost at $3.80 gallon,” said Brian Nelson, principal of NMD.

TomNeadowNMDMansionHousePoolHXThe swimming pool is so deep that it is sitting in the aquifer. “An infrared Google Earth picture of the hotel would show a red streak running out of the hotel to the harbor as fuel oil is used to heat the pool — uninsulated — which then heats up the ground water as it runs under the pool,” said Nelson. This confirmed the suspicion that groundwater under the pool was constantly pulling heat out of the pool. Because the hotel’s basement is so deep, and the pool is in the basement level, the entire pool is essentially sitting in the groundwater that runs underneath the hotel.

The outside-the-box thinking that Nelson Mechanical is known for came through on the Mansion House project, in the money-saving heat exchanger application, and a newly installed heat pump configuration. The swimming pool was originally heated solely by oil-fired boilers through a flat plate heat exchanger. Based on Nelson’s analysis of the energy going through this small heat exchanger, he discovered that the heat loss for the pool was 180,000 Btuh, a lot higher than he would expect just for evaporative loss from the pool surface. Now, the pool heat uses geothermal ground water using a GEA plate and frame heat exchanger with Grundfos CRE series circulators — not through a heat pump. “This pool installation continues our coupling of the building’s heat load with the ground water by using the new heat exchanger to cool the building loop while it heats the pool,” said Nelson.

Nelson Mechanical installed hour meters on the existing pool heat exchanger circulator, the hot tub circulator, and the domestic hot water circulator in an effort to determine how fuel oil was used by the hotel. The analysis indicated that the pool was using about 8.6 gal./day of fuel oil or a bit over 3,000-gal./year.

“Fuel oil prices on the island have been fairly volatile, ranging from $3.80 to $5.00 per gallon. This meant that the hotel was spending up to $15,000 a year on pool heat,” said Nelson.

Thermal analysis

To find out how much heat was available in the building loop, Nelson looked at the trended data from the building automation system. This building loop is connected to the 48 guest room heat pumps, as well as 10 common area heat pumps. This inside building loop is connected to an outside 90-ton fluid cooler — with a groundwater geothermal spray system Nelson added previously — boosting cooling capacity to closer to 100 tons.

“If we used a plate and frame heat exchanger (instead of brazed flat plate), we could get close to a 2°F approach (the difference between the building loop temperature and the pool temperature), so if the loop was at 84°F, we could heat the pool to 82°F,” said Nelson. “The hotel’s goal for pool temp was 82°F and above, so we mapped out how many months per year the building loop was above 84°F.”

As it turns out, over eight months the hotel could reliably get 84°F building loop temperatures, meaning that it could heat the pool using just the plate and frame heat exchanger during those eight months.

MHPoolGeoHXPlateFrameHXDetail031313Further development of the building loop model data led Nelson Mechanical to propose a bypass valve for the building loop — normally all of the building loop water went outside to the fluid cooler and then back inside to the hotel. This meant that in the coldest months of the year, there was at least a 10-ton passive cooling effect on the building loop from the cold outside air cooling down the copper tube bundle in the fluid cooler. Installing a bypass valve in the building loop before the water left the building for the fluid cooler would keep the heat inside the building and would increase available heat for the pool heat exchanger.

“It turned out that we could add two more months of loop temperatures above 84°F to the heat available to the new heat exchanger, now over 10 months of the year, the loop would heat the pool instead of fuel oil,” said Nelson. “This boosted our projected savings to a bit over $13,000 per year.”

Building loop, pool loop

Using closely spaced tees, Nelson connected the building loop — flowing at 250-GPM — to the GEA plate and frame heat exchanger with StaRite (Pentair) pool-to-heat exchanger circulators, Webstone flanges and Apollo ball valves — flowing 75-GPM. Because the pool is salt water, the heat exchanger sheets are made of titanium. Poolside piping was Schedule 40 PVC pipe from Charlotte Pipe with Thomas Betts hanger struts.

At the pool loop connection, Nelson Mechanical installed two pairs of closely spaced tees due to the fact that water was continuously circulated from the pool through two filters and then back to the pool. The first set of tees sent water over to the new heat exchanger to heat it up to 82°F or higher. The second set of tees connected the pool water to the original brazed flat plate heat exchanger connected to the oil-fired boilers. A two-stage control looked at building loop temperature and turned on the new plate and frame geo circulator if the loop was 84°F and above and turned on the boiler heat exchanger circulator if the loop was below 84°F.Honeywell staging controls — for pool and boiler circulators — are used for both the geo heat exchanger and boiler heat exchanger.

The design that wasn’t

Initial plans called for the installation of a Mayakewa Eco Cute CO2 heat pump, which can actually replace oil boilers. Nelson and his crew worked tirelessly to develop a domestic hot water project based around the Eco Cute.

“The technical aspects are really interesting; to get the unbelievable COP of 5 and 197°F water, the incoming water to be heated had to be in the 70s or colder,” said Nelson. This meant that we had to engineer storage tanks versus multiple Eco Cute heat pump units to try to find the economic sweet spot for the hotel. We couldn’t make the economic side work out — basically because the Eco Cute is not yet available in a size larger than 300,000 Btuh — for the Mansion House, but it will be a homerun for the right load.”

Nelson Mechanical wanted to use the heat pump to heat domestic hot water and displace a significant amount of the fuel oil use at the hotel. “The 197°F output made us think that we could meet the temperature requirements for the hot water system,” said Nelson.

Because it uses carbon dioxide as a refrigerant, there are restrictions on inlet water temperatures if high efficiency is desired — cold inlet water is necessary to fully cool the CO2 refrigerant as part of the transcritical refrigerant cycle. As the CO2 passes through the transcritical phase, its thermal conductivity spikes and efficiency rises very quickly. Essentially, this is the sweet spot for this refrigerant. But cold inlet water is necessary to make this happen to the CO2 in the heat pump.

The heat pump is similar to a tankless water heater in that the water goes through in a single pass — heated from 50°F coming in to 197°F going out. It means that the inlet temperature has to be really low. In a typical boiler heat exchanger scenario, the hot water temperature rises in the storage tank based on how many boilers are on. A single pass approach to heating water (as dictated by this Eco Cute heat pump) would require a lot of hot water storage tanks to get the high efficiency possible with this technology.

“The end result is that if the heat pump was close to the size of the domestic hot water load, it could run continuously with a constant input of 50°F water and achieve a COP of 5 and deliver 197°F water,” said Nelson. “But we couldn’t make the economic side work out because the Mansion House domestic hot water load was about 900,000 Btuh and the Eco Cute is not yet available in a size larger than 300,000 Btuh.”

The GEA plate and frame heat exchanger has exceeded expectations. “It’s always a great thing when proposing a green solution to an energy problem,” said Nelson. “The hotel is surprisingly cooling dominant — high internal loads, lighting, guests, etc. — and we have had building loop temperatures in the high 80s when it is 35°F outside with all of the pool heat coming from the new heat exchanger.”
Because this project has been so successful and the thermal resource is so plentiful in the building loop, the hotel is considering Nelson’s next proposal: a plate and frame heat exchanger to tackle the pre-heat for the domestic hot water plant. “Our preliminary look at this project envisions a 1,000,000 Btuh heat exchanger saving almost 3,500 gal. of fuel a year!  Definitely another ‘green’ project that makes real economic sense,” said Nelson.

We’re Likin’ Daikin! Our Sales are up 100%!

Owners Brian Nelson and David Sprague have doubled their sales since becoming a Daikin AC dealer. The partners started out as a heating and plumbing contractor, but today 75% of their business is Daikin Altherma and Ductless split heat pumps from Daikin AC. “Daikin AC has allowed us to set our dealership apart as the ‘Green Experts’,” says Brian. To live up to their mission of offering customers only the best green solutions, NMD offers only the best products to complement their highly engineered applications. The results are efficient, cost-effective, easy-to-install Daikin AC systems that provide improved year-round comfort, and save their customers money.

See the Daikin ad here

Nelson Mechanical Design’s 7 Secrets of Success

Dave Sprague and Brian Nelson have seven great ideas to help other dealers accelerate their businesses.
“Set Your Dealership Apart.” Find a way to distinguish your dealership from your competitors. Think about the needs of homeowners and businesses in your area and then position yourself as the leader in that area. Or, identify a trend, like we did with the “green” approach, and use it to build a niche for your business. We believed so strongly that “green” was the best way to set our business apart, we added it to our web address:

See the full Daikin ad 

Presentation features new heat pump technology – Daikin Altherma

An innovative heat pump project that reduces fossil fuel use will be featured in a presentation hosted by Nelson Mechanical Design (NMD) and the Vineyard Energy Project (VEP) on June 29.  The event at 59 Hidden Valley Road in West Tisbury kicks off with a reception from 4-4:30 pm.

The focus of the presentation is a new Daikin AC Altherma air-to-water heat pump installed at the home of Ted Bayne and Lea Delacour.  It provides radiant heating and hot water, and significantly reduces the amount of propane used by the existing boiler….

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Daikin AC Blueprint – How to Integrate Daikin Altherma with boiler – West Tisbury

Retrofit Challenge: How to integrate Daikin Altherma with an existing fossil fuel boiler / radiant heating system while ensuring winter comfort with minimum operating cost.

Ted Bayne and Lea Delacour live on Martha’s Vineyard in a 3,000 square foot home heated by radiant floors and a Viessmann propane boiler. Their goal was threefold – to find a heating source that would make their existing 90% efficient heating system more economical to run, would not involve destroying their extensive gardens with a geothermal installation, and would use electricity to operate – making their home ready for the “all-electric” island that Martha’s Vineyard will become in the near future.

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Contractors Contribute to Environmental Activism

In the U.S. HVAC market, environmental activism doesn’t refer to anything too highly visible. There are no million-contractor marches planned for the National Mall, no protests, and no one throwing red paint on inefficient buildings. In our realm, the environmental activism taking place in 2010 centers on things like working through associations for legislative change, and focusing on the “act” part of activism in daily business activities.


Some contractors are taking activism as meaning “to act.” They are doing green things without them being mandated. “Every day we are thinking about how and what we are doing to be green,” said Brian Nelson, with Nelson Mechanical Design, Martha’s Vineyard, Mass.; “how we will reduce energy use for a client, how our proposal for an HVAC system will help the client save energy, and how our energy retrofit will save energy.

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Behind the Scenes Green: Mansion House on Martha’s Vineyard

For years, the leaky basement at Mansion House was proprietor Susan Goldstein’s annoying little secret. Even following a total rebuild, after fire destroyed the Martha’s Vineyard landmark in 2001, a daily 16,000 gallons of water had to be sump-pumped, thanks to a basement that was too deep into the groundwater. But Goldstein, who owns Mansion House together with her husband Sherman, recently decided to turn her dirty secret into a green one: by installing a geothermal system that relies on the groundwater to essentially store solar energy. Mansion House simply draws on the power as needed. A second phase to the project will ensure that the heat energy will be further used for the hotel’s pool and hot water needs.

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Greening Martha : Mansion House uses geothermal technology to green its business

Published by the Martha’s Vineyard Times
August 12, 2010

A geothermal heat pump system, run by the stored solar energy found in the abundant groundwater below the Mansion House, along with a sophisticated energy control system, now make the hotel one of the greenest hotels in Massachusetts, according to a press statement released this week by Susan Goldstein, the owner with her husband, Sherm, of the Vineyard Haven business.

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Energy Excellence in Martha’s Vineyard

Nelson Mechanical Design (NMD) has a long‐standing reputation for being a green contractor, and it goes beyond the steps many HVAC contractors are taking now, well intentioned though they may be. That’s because NMD has been a trailblazer, pushed in part by the progressive customers on Martha’s Vineyard. We already introduced one of them in the article that ran in the May 5 NEWS: The Doug Rothmann home on the Vineyard is a net‐zero energy, LEED for Homes building powered by a wind turbine. The horizontal, 6‐ton, direct‐exchange geothermal system serves radiant space‐ heating loads. A heat pump uses R‐407. It’s only one of several geothermal projects the company has designed and installed. The system’s zoned control adds considerably to its functionality and convenience to the homeowner.

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Contractors Leading Green by Example

While contractors across the country are hitching onto the green bandwagon, a few have been leading the parade. These are the HVAC contractors, both commercial and residential, who are actively using green technologies and principles in their businesses. These are the contractors that we call “green by example.” By using technologies and business practices that make ecological as well as economic sense, these companies are representative of those leading the way in the application of green business practices. These practices (which can be as diverse as basic recycling, installing very‐high‐efficiency mechanical systems, offering financial counseling, and using green service vehicles) offer numerous benefits. Not only can they help reduce overhead costs and demonstrate the viability of green technologies, they can also be used to promote the companies as good environmental stewards. Over the next few weeks, we will be examining these HVAC companies and their green projects in more detail. Here is an introduction to three contractors who are setting their own high standards for green practices: Hill York, Nelson Mechanical Design, and A‐1 Guaranteed Heating & Air Inc.

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The Power of Two – Green Mechanical Contractor

Alex Boyle speaks passionately about what he thinks should be a national imperative: to shift to renewable energy sources. “We need to move beyond the barriers that are impeding our progress,” he says. “We have to get serious about this. We can continue to burn fossil fuels, pollute the atmosphere and threaten our national security, or we can use the wind and geothermal energy right within our reach.” Alex and his wife Betty had a home built on Martha’s Vineyard last year. The 5,000-sq.ft. timber frame net-zero house is powered by a 10kW wind turbine. Annually, the output of the wind turbine will be greater than the power used by the house and its geothermal system. Nelson Mechanical Design, Vineyard Haven, Mass., won a 2009 Green Mechanical Contractor (GMC) award for the project in the “Most Innovative” category.

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In Business: Vineyard Energy Project energy trial set for Spring

If you need a new appliance – or several – and don’t mind being part of an energy conservation experiment for two years, now is the time to buy. The non-profit Vineyard Energy Project (VEP) which received a $787,250 grant from the US Department of Energy in October, still has funds to help 15 to 20 households participate in the program. Specifically, a household could purchase any number of General Electric appliances (including refrigerator, range, dishwasher, washer, dryer or heat pump water heater) at a GE discount averaging 22 percent. Then the VEP, using the DoE funds, will also reimburse 50 percent of all the purchase costs including the price, shipping and installation.

…..Medeiros Appliance of Vineyard Haven has been selected as the vendor for the GE appliances, and Nelson Mechanical Design Inc., also of Vineyard Haven, will do the installation and hook up of the HEM units, according to Mr. Bayne.

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Vineyard Energy Project Load balancing technology tested with NMD

VEP energy trial set for spring Load balancing technology to be tested in 50 households….
……The VEP is interested in learning how the residents of the Island might better control energy costs. And, the federal government wants to learn as much as it can about the potential of energy savings, using a combination of highly efficient appliances and this process of load balancing. Medeiros Appliance of Vineyard Haven has been selected as the vendor for the GE appliances, and Nelson Mechanical Design Inc., also of Vineyard Haven, will do the installation and hook up of the HEM units, according to Mr. Bayne…..

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