Solar Thermal in the Rockies

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Mention Colorado, and most folks think of the state’s unofficial soundtrack:  John Denver’s “Rocky Mountain High.”

What many Americans don’t know is that Colorado could compete with Florida for the moniker: the Sunshine State. The Centennial State gets its fair share of sun in a year.  Pueblo County, for instance, averages 260 sunny days each year – 50 more than the US average.

Mike Merryman (right) and Lance Harvey stand next to the tiny mechanical space in a 3,300-square-foot, super-efficient home in Southern Colorado.

While planning their retirement home, Nate and Amy Rye decided to trim their carbon footprint with a solar-thermal system. After purchasing Pueblo County property in 2005, they began gathering ideas for their next home.

The system Flow Right installed at the Rye’s Southwest-style home includes a 150 MBH, 95 AFUE Burnham Alpine boiler. Along with the home’s solar-thermal array, the boiler distributes heat to the home’s six in-floor radiant zones and domestic hot water supply.

They stumbled across Solstore — a solar retailer — while driving around Pueblo a few years ago. The Ryes went in looking for solar equipment, and learned that Solstore’s construction subsidiary, Harvestech, could build the home.

Five, four-foot by 10-foot AET (Alternate Energy Technologies, LLC) flat-panel collectors provide a minimum of 60 percent of the DHW need and 40 percent of the space heat.

Harvestech can provide comfortable homes with limited environmental impact, due in part to using the right sub-contractors. “If we’re building a house with radiant heat, we call Flow Right,” said Todd Tompkins, project manager at Harvestech, LLC.

Derrick McCabe, Senior Estimator/Project Manager for Flow Right, confirms the set point of the aqua stat that controls water circulation between the two storage tanks.

“Competition with other hydronic installers isn’t a challenge,” said Lance Harvey, owner of Flow Right Plumbing, Heating and Irrigation. “But selling against air-side equipment is. We install radiant in-floor systems exclusively, so we need homeowners to see the benefit of warm floors, while still buying ductwork for AC.”

A Taco circulator moves water from the storage tanks through the solar panels. Supply and return line gauges between the storage tanks and the panels provide accurate temperature readings.

Sunshine on my shoulders
Rye’s single story, 3,300-square-foot home — with flat-roof and Southwestern architecture – lends itself perfectly to the solar.  Five, four- by 10-foot AET (Alternate Energy Technologies) flat-panel collectors provide much of the DHW and space heat.

“Colorado winters would be problematic for a pressurized solar-thermal system,” said Mike Merryman, outside sales rep for McCoy Sales, in Littleton CO.  “But drainback systems only fill with water when’s they’re operating.”  At night, water flows into a drainback tank inside so there’s no risk of freezing.

Barb Satterfield, Lance Harvey, Derrick McCabe and Mike Merryman stand outside the new Pueblo, Colorado home before the exterior was colored.

Merryman and Harvey promised the Ryes that the solar array would handle 60 percent of the DHW load and 40 percent of the space heat. In reality, it does better, but they wanted to make sure the remainder of the load is supplied as efficiently as possible.

Supplemental heat comes from a wall-hung, 95 AFUE Burnham Alpine boiler. The 105 MBH modulating-condensing unit shares indirect water heaters with the solar array to distribute heat to the home’s six in-floor zones and DHW.

“Some jobsites used to give us altitude challenges,” said Harvey. “This home is at 6,000 feet. True to its name, the Alpine has no problems. Actually, we haven’t had a callback on a single Alpine since we started installing them, 40 boilers ago.”

Solar design
The indirect tanks are both 119-gallon Burnham Alliance units; one single-coil and a dual-coil. The coil in the first tank is part of the solar loop, using fluid from the array to heat well water as it comes into the home. An aquastat set at 120° allows pre-heated water to move to the dual-coil tank. The second tank has three purposes; bring in supplemental heat from the Alpine boiler via the upper coil, supply heat to the in-floor system via the lower coil, and provide DHW via the tank outlet.

Since the home is single story over crawlspace, the floor-plan sprawls a bit.  For the sake of efficiency and convenience, Flow Right installed a Taco SmartPlus domestic hot water recirculation system.

The outdoor design temp is 0°F — relatively low for a radiant system. But a robust design and the outdoor reset that comes standard on the Alpine boiler make it a non-issue.  Half-inch Uponor PEX is at eight-inch centers, while a layer of gypsum concrete over the tubing boosts thermal mass.  A Delta-T circulator provides flow to 4,300 lineal feet of PEX.

“Since we don’t install air-side equipment, retrofit work isn’t big for us,” said Harvey. “We do a number of boiler replacements, typically with Burnham ES2s. They’re not a hard sell, with a cast iron price tag and optional outdoor reset. It’s an easy install, with two venting options and a size range that fits most houses.”

The home was designed for an evaporative cooling system, but the altitude and tight construction make it unnecessary. Later this year, the Rye’s roof will also support a 6 kW photovoltaic array.

A team worth their salt
“The Burnham boiler and Alliance tanks, Taco circulators and AET collectors were delivered by Jimmy Rogers, president of Pueblo Winnelson.” said Harvey. “They’re the master stocking distributor of Burnham boilers for southern Colorado.”

“Rogers and Merryman make a good support team,” continued Harvey.  “They do more than sell equipment.  The solar-thermal design is Merryman’s brainchild, and he got us over the learning curve.”  McCoy has several solar packages, depending what the homeowner is looking to accomplish.

“Mike’s the main reason we switched to Burnham a few years ago,” said Harvey. “He helps us design and troubleshoot systems whenever we need him, but we’ve had zero issues with their line of boilers since we switched.”

Flow Right finished the system in June. The company now has experience with solar-thermal applications, and the homeowners will be singing Denver’s ’79 hit “Life Is So Good.”

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