Solar thermal/condensing boiler project addresses multiple loads, earns energy offset

 

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In Eagle County, Colorado, local authorities not only promote energy sustainability, but insist on it. Any residential project that incorporates more than 200 square feet of snow melt, for example, must mitigate the load with an offset the draws upon a renewable energy source. So the county required owner to mitigate snowmelt energy draw with alternative energy or pay a hefty fee.

For Mustafa Aydin, president of American Plumbing Heating & Solar in Edwards, Colorado—an independent, family-owned plumbing and heating company that prides itself in personalized customer service—the county’s demand represented an opportunity for innovative energy planning. His client was gutting and rehabilitating a 7,000-square-foot home in the Red Sky neighborhood of Wolcott, Colo., completely redesigning its infrastructure to include radiant floor heating, 3,000 square feet of outdoor snowmelt, improved domestic hot water, and the comfort of a heated, year-round 1,500-gallon hot tub. The challenge for Aydin was to determine the loads for all the needs and design a system to support it.

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In addition to a clean install, American PH&S had an artist come in and paint an aerial view of a motorcycle on the mechanical room floor to add a personal touch.

 

Before Aydin had consolidated his design options, he knew immediately where he would source the core components: “I’m a Viessmann installer and have been for many years, I won’t install anything else.”

For design support, Aydin turned to Eric Anderson, a hydronics technical support specialist at Ferguson Hydronics in Denver. He was tasked with creating a system that would integrate solar thermal—the renewable energy resource—with condensing boilers to serve all four loads seamlessly and efficiently.

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The 7,000-square-foot home in the Red Sky neighborhood of Wolcott, Colo., completely redesigned its infrastructure to include radiant floor heating, 3,000 square feet of outdoor snowmelt, improved domestic hot water, and the comfort of a heated, year-round 1,500-gallon hot tub.

 

“At the highest level, we thought of the solar thermal contribution in two tiers,” says Anderson. “Its top priorities would be serving domestic hot water needs and the hot tub; at the secondary level, it would support the condensing boilers with the radiant heating and snowmelt loads.”

“When you have an involved project like this,” Anderson explains, “you start with a heat loss study to assess the loads. How much DHW do they use or need? What’s the load from the outdoor spa? Anderson ran a TSOL, a solar thermal computer simulation program that analyzes load within the context of the location’s climate and weather. The resulting analysis formed the basis for design that includes nine, 4’ x 8’ solar panels on the roof, and two Vitodens 200 wall-mounted condensing boilers. The solar system ties into two 120-gallon single-coil stainless steel tanks—one for DHW, the other to preheat water for the boilers (reducing their load)—a plate heat exchanger for the outdoor spa’s hot tub, and a 650-gallon stainless steel atmospheric tank that serves as a buffer for the solar thermal system, and as a contributing source of energy for the radiant heat and snowmelt loads.

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Vitodens 200 wall-mounted condensing boilers.

 

This installation utilized a Caleffi hydro separator, iSolar control, a diverting valve, Z-one valves, 6762 Series thermo-electric zone valves, 132 Series QuickSetter balancing valve and a 573 Series AutoFill combination valve with backflow preventer.

In addition to supplying the panels, boilers, and tanks, Viessmann provided the panel line set and the boiler controls. The line set—prefabricated from stainless steel and pre-insulated—include sensor lines in the insulation for easy integration into the controls, and, says Anderson, “really solid, high-temperature O-ring connections for the panels, which means there’s no need for us to do soldering on the roof.”

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Cascaded for maximum efficiency

A carefully planned mechanical room manages the flow of water, and allocation of energy, between the solar and boiler sources, using an integrated array of three-way valves and the intelligent application of the boilers’ controls. “We have the controller set for a cascading strategy that encourages the maximum amount of condensing,” says Anderson. The lead boiler usually fires at 25% to 30% of its peak modulation; when it exceeds 40% – 50%, the second boiler kicks in and the two modulate down again. “The whole goal,” Anderson says, “is to fire at the lowest rate for highest efficiency.”

While the system is complex, sourcing components from Viessmann made the project easier. “It’s the only boiler system I spec,” Anderson says. “Whether it’s solar, controls or boilers, everything’s thought out as a system. For me, that means peace of mind.”

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American PH&S had an artist come in and paint an aerial view of a motorcycle on the mechanical room floor. Discovering that the owners are big motorcycle fans during his initial bid process, Aydin surprised them with the motorcycle design. The color just happened to match the first motorcycle the owner ever bought. They were delighted with the attention to detail. “I like to add a personal touch when finishing a project like this.  In this case, the homeowner is a Harley Davidson fan, so we added the motorcycle image to the floor.  It was a surprise gift for the homeowner and he loved it!” said Aydin.

Ultimately, the homeowner was satisfied to have an alternative energy source for his home and a snowmelt system in his driveway.

Inside the Job

Boiler — Viessmann

Water heater — Viessmann

Pumps — Grundfos

Relays — Taco

Piping — Copper and flex

Solar Panels — Viessmann

Hot Water Storage — Viessmann

Separators — Caleffi

Expansion tanks — Caleffi

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5 thoughts on “Solar thermal/condensing boiler project addresses multiple loads, earns energy offset

  1. Excellent, excellent job. Modulating the firing rate of the boilers to accommodate the load is what we need more of. It still amazes me though that we stay incredibly focused on boiler modulation as though we had blinders on but completely loose sight of flow modulation through maintaining a fixed Delta T and the only way to do that is to use a Delta T Circ like the TACO VT 2218 which will adjust the flow base on the load/loss of the heat emitters which changes everyday. The use of these circs could compliment a system like this and increase energy savings in terms of using less fuel. It turns a “Rock Band” into a symphony performed by the NY Symphony. Ahh! I can hear the melody now.

  2. Unreal!! im fairly new too hyrdronic heating. I am a 4th year apprentice steamfitter from Sudbury, Ontario. Im more familiar with high pressure steam systems. Looking to get away from that and get into renewable energy systems. This is an awesome and professional looking project. Inspiring !

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