Ojo Caliente:

A health spa with ingenious mechanical systems

By John Mesenbrink
Chief Editor, Phc News

Tucked away in the desert mountains just north of Santa Fe, New Mexico is one of the oldest health resorts in North America -- Ojo Caliente Mineral Springs. And if you say “O-ho ca-lee-en-tay,” you’ve got it right. In Spanish, it simply means, “hot springs.”

Phc News took a road trip to this remarkable resort this summer, but not -- mind you -- to bask in warm mineral pools under a copper sun. We went to explore the facility’s remarkable heating and cooling system. But before we offer those insights, we’ll give you a glimpse into magic of this place.

Ojo was once considered sacred by the ancestors of the present day Tewa pueblo Indians who still today -- thousands of years after the first settlements -- inhabit the mesas and valleys surrounding these waters. Their ancient relatives built an extensive Pueblo community overlooking the springs. Called Posi or Poseuinge, the “village at the place of the green bubbling hot springs,” was once home to thousands of people.

Ojo Caliente is the only natural hot springs in the world with the combination of four different types of geothermal mineral waters: iron, arsenic, lithia and soda, each with unique healing and restorative properties ideal for the symptoms of chronic pain, arthritis, skin conditions and digestive problems, just to name a few.

Today, more than 100,000 gallons of emerald green water still streams to the surface each day from a subterranean volcanic aquifer, just as it has for centuries. Those same waters -- which come from ground at temperatures ranging from 80 F to 109 F -- are also being cleverly harnessed as a source of the energy for heating and cooling the health spa’s many facilities. “We’re in the unique situation of having a natural resource amazingly suitable for geothermal heating and cooling,” said John Young, Ojo Caliente facility manager.

Situated on 1,100 acres and at an elevation of 6,292 feet, Ojo Caliente today features a relaxing spa with mineral spring baths and many well-appointed cottages and a hotel, a superb restaurant and staff facilities.

Business has been good at Ojo, and under new management, they’ve committed to a $5.6 million construction project, adding new facilities and greatly improving those they’ve had for some time, all the while maintaining the ambience of the stetting that generations of locals and global travelers alike have come to enjoy.

One of the most intriguing facets for those of us in the plumbing and mechanical business is that they’ve so smartly harnessed the earth’s thermal energy to heat and cool the cottages, restaurant and hotel, and to provide abundant heat for all domestic water and laundry facility needs. Today, their mechanical systems are saving them thousands of dollars each month, with system pay-back calculated at about two years.

What they’ve done can be described as one of the most ingenious solutions to heating -- and one of the oldest. It’s what makes the mudpots bubble, the fumaroles steam and Old Faithful rumble. Geothermal heating takes advantage of the abundant thermal energy stored within the earth. And behind the scenes of this relaxing hot-spot is hard work, dedication and a 21/2-year commitment to energy efficient solutions.

“Here at Ojo, our ideal [geothermal] setting matches-up perfectly with the needs we have for centralized heating and cooling, and high-volume domestic water,” said Nick Wimett, primary subcontractor on the project.

Jason Valdez, Ojo Caliente plumbing and electrician, completes the installation of a three-speed Grundfos circulator in one of the north cottage mechanical rooms.

But before they tapped the earth’s bubblin’ brew, they went to another resource, one of the country’s leading experts on geothermal technology, Jay Maze, heating & cooling specialist for Dahl Santa Fe, wholesale plumbing distributors. Maze’s vision and expertise in geothermal systems was just what Young was seeking when contemplating an efficient, practical and smart energy design for the mechanical systems there. With help and counsel of Maze, and Helen Gates, also at Dahl, Young and Wimett moved confidently into making their mechanical dream, a reality.

Today, the ingenious system includes plentiful use of geothermal energy for space heating and domestic hot water, geothermal cooling, solar heat, extensive hydronic heat, and radiant heat, all masterfully planned out and installed.

 

Taking the heating tour
With Young and Wimett as our tour guides, we embarked on a facility tour. Our first stop would be the North Cottages and mechanical rooms. According to Wimett, the north mechanical room, or “North Geo,” serves eight cottages, a large commercial laundry facility, 16-unit hotel and the hotel restaurant. At this facility is one 30-ton, EW series commercial water-to-water geothermal heat pump by WaterFurnace. It provides domestic hot water, heating water and cooling water.

Also in the north mechanical room are three Laars custom storage tanks, each of which stores 335 gallons of domestic hot water, heating water and chilled water. The heat source for this plant is a heat exchanger in a 130 F well.

“Each north cottage is individually comfort-controlled,” said Wimett. “We operate seasonally through the same circulation system from the North Geo plant. Summer operation moves heat via a heat pump from the Laars ‘source’ and ‘heat’ tanks. Fluid is circulated from the heat tank through a 200,000-Btu heat exchanger, and on the other side of the heat exchanger, circulates through the other Laars tank for domestic hot water storage for the laundry facility. This tank also serves as the pre-heated water supply for the two storage tanks that serve the north cottage units.”

The hot water for the north cottage units are “finished” with solar. The source-side tank is what they circulate through the heating/cooling system during the cooling season.

“Basically,” added Young, “we remove heat from our housing units and put that heat in our laundry and domestic hot water supply. Today, the laundry facility requires 3,000 gallons of 180-degree water per day, and the new system delivers it free of charge.

“Heating water for the laundry water is a huge benefit,” continued Young. “It consistently takes about a million Btus to bring the water from 55 F to 120 F -- all supplied by the geo system. From there, we take it up to 180 F with propane.”

During the summer, the closed-loop system extracts heat taken from the cottages and hotel, cooling them, and transfers that into the laundry hot water, and pre-heat for domestic hot water in the hotel, the kitchen and the north cottages. They purposefully restrain the max temp going into the heat pump to about 90 F (now, there’s a new twist) so as not to over-heat the unit; this is accomplished with a buffer on the input side.

From the buffer tank, they circulate water through a Water Furnace heat pump at 80 gpm, and as the temp swings in the tank, they can add a bit of heat to maintain the 90 F input temp during winter operation. Heat moves to the ‘source tank’ through a 200,000-Btu plate-to-plate heat exchanger from a 130-degree well.

All told, heating and cooling for the eight remodeled north cottages -- with four, two-unit buildings (330 sq. ft. per living unit) -- requires just over 105,000 btu./hr. Wimett explained that pre-heated water from the North Geo plant (at 118 F) provides domestic hot water for the living units. The hot water is held in a heat-exchanger storage tank.

“We also have two, roof-mounted solar panel systems for the north cottages,” added Wimett. “When the solar temperature control senses a 10º F differential between the temp of the collector output, and the bottom of the tank, a Viessmann Divicon manifold pump turns on. Two fan coil units are wall-mounted in each unit, along with one kick space heater under the vanity in the bathroom. The convection units are connected to Grundfos SuperBrute, 3-speed circulators.

“The kick-space heater fan responds when circulation through it reaches 110 F,” he continued. “The convectors and the feed and return piping are also used for cooling. We have a switch-over date when we go from heating to cooling. We’re now in the process of adding more solar panels and another Laars storage tank for thermal storage for the north cabins.”

About 100 yards from the north mechanical facility is the south mechanical room, which is still in the early stages of construction. It provides heat for three 2,000-gallon pools, radiantly-heated concrete slabs around them, the bath house with individual massage rooms, and 12 new suites, each about 800 sq. ft. in size, and each with a private spa. Here, there are two 30-ton commercial water-to-water geothermal heat pumps by WaterFurnace and three, 335-gallon Laars custom storage tanks to hold domestic hot water, heating water and cooling.

The primary function of the water-to-water heat pump system is to remove the energy from the wastewater geothermal water, tapping it as heat for domestic water, heating water and a dump for cooling. “We’ve set it up to create a mix that’s the optimum temperature for the source-side of the heat pump. Also, if we are in a bind, we can run 101 F water through the exchangers and get a decent in-slab radiant temp just from that. Also served are south cottages, administration building and a 60,000-gallon swimming pool. Domestic water is from the pre-heated geo source but, here too, solar panels are set up for 12 new living units and the existing south cottages.

An advantage for the south mechanical room is that the mechanical systems receive 90-100 F water flow from the mineral pools at a rate of 100 gpm. Prior to the installation of the new geothermal systems there, they used propane-fired furnaces to maintain the temp in three new pools.

“These have been a big problem for us,” said Wimett, “because of excessive mineralization in our waters, and the high delta T across the heat exchanger. Once a week we have to drill out the heat tubes. Ultimately, we’ll use these just as a backup system.”

He explained that regulations call for each pool to have its own distinct ‘circulatory’ system. “We’re confident that the new Water Furnace heat pumps we're putting in will amply heat the pools with less maintenance,” continued Wimett. “But these things take time. And we’re doing it with sufficient care so that the mechanical makeover is done right the first time.”

A geothermal oddity
Wimett and Young explained that, situated where they are on this hotbed of geothermal activity, with a plentiful supply of warm water so readily available, they have the “odd reality” of too much heat, and that this had to be dealt with in the geo-exchange process.

“If the source water is much above 70 F,” said Wimett, “the head pressure can be problematic. So, we need to temper the source-side to get constant source temperature. The load is so variable that it affords us flexibility in taking from ‘here’ and dumping ‘there.’ For example, we have the 6,000-gallon swimming pool to heat during the winter months, and to temper-down during the summer months. And we have the laundry facility that uses a large volume of hot water. So, if the cooling load far exceeds the heating load, we can dump heat into the pool during certain hours and schedule heaviest use of the laundry equipment when it makes best sense.”

Yet with varying source water temperatures, wild swings in outdoor temperatures year-round, and many demands placed upon complex mechanical systems, Ojo Caliente’s geothermal team is bringing it all together. The spa’s customers get all the comfort.