Radiant With A Solar Boost
Sol-Arte LTDAThe winner of the Best International radiant installation is Sol-Arte LTDA, of Bogotá, Colombia, for its solar-assisted heating and DHW system at Ancianato Hermanitas de los Pobres, a retirement home located roughly 8,700 ft. above sea level in the city of Zipaquirá.
Ancianato Hermanitas de los Pobres
Sol-Arte specializes in designing mixed natural gas networks and solar thermal energy systems. The 10-person company has 10 years and about 250,000-sq. ft. of experience installing radiant. The company won second place in last year's innovation category and routinely subcontracts work for the largest construction company in Bogotá.
There were many unique situations for Jaime Davila, the heating and plumbing designer, to contend with, but the most intriguing is that of the efficiency and reliability that were required at this job. The building is a retirement facility run by nuns who aren't exactly knowledgeable about complex heating systems. The equipment needed to function with little day-to-day maintenance. "The system must work by itself all year long with no problems," Davila says.
Another consideration that was somewhat unique was the population of the building. "The difficulty was to combine hot water for heating (140 degrees F) with low water temperature (104 degrees F) for elderly people. We used mixing or anti-scalding Giacomini valves in order to get the temperature required for each group of four showers," says Davila.
The entire system runs on a combination of a propane-fired Laars Trianco HWG-200 LP condensing boiler and approximately 1,400 sq. ft. of solar flat plate collectors. A 1,500-gallon storage tank for solar pre-heating and a 530-gallon storage tank to support the heating load are used with about 311 linear ft. of Slant Fin baseboard that heats an area of 3,900 sq. ft., in 16 independent heating zones -- each one controlled by a liquid thermostat. The brain of the operation is an "Easy" Moeller central programmer of functions with relays, protectors and a thermo differiential DeltaT control for solar energy.
The boiler capacity was calculated in order to support heating requirements as well as water production backup for the times when there is not enough solar radiation or the flow demand dramatically increases. The solar is active, automatic and programmed according to the needs of the users. The solar energy re-circulates the water between the collectors and the 1,500-gallon storage tank, using a Grundfos (ref UP S50-80/4) and a thermo differential DeltaT control with ohmic sensors. A Grundfos UP 26-99 circulating pump pushes the water from the large, 1,500-gallon tank to the smaller, 530-gallon tank, where the temperature is increased by about 36 degrees F by the 200,000 Btu/hr. boiler to get the 140-degree F temperature required by the baseboard.
The smaller tank feeds the three main DHW and heating networks of the building. The Moeller programmer controls the heating circulation pump and obeys a list of pre-programmed schedules as well as fallen internal or external temperatures. The Moeller programmer also controls the electro-diverting valves at the entrance of both tanks. If there is enough solar energy to provide the needed 140-degree F water to heat the baseboards, the programmer allows water to be circulated from the large tank. Otherwise, the water used in the heating system comes from the smaller, boiler-equipped tank.