by Robert P. Mader of Contractor’s staff
Salt Lake City – Boiler manufacturers made a big splash down on the show floor at the Radiant Panel Association’s Radiant Expo here in mid-May, while upstairs in the seminar rooms water heater manufacturers had their say.
All the action took place at rpa’s "2001: A Heating Odyssey" conference. The convention drew the best in the heating industry, including Contractor columnists Mark Eatherton and Dave Yates, and often-quoted contractors such as Clay Thornton, Thornton Plumbing & Heating, Midvale, Utah; Jim Patterson, Orchard Valley Technologies, Haydenville, Mass.; and Robert "Hot Rod" Rohr, Maxrohr, Rogersville, Mo.
Burnham Corp. made the biggest splash, although the company did it with a "hydronic heat source," not with a boiler. The firm’s Opus G1 is 98% efficient but it’s not a pressure vessel so it’s not, technically, a boiler. The unit is fully condensing, made of stainless steel and vents with pvc pipe. It can provide supply water temperature anywhere between 70û F and 140û F. It’s available in 125,000- and 250,000-Btuh capacities. It comes standard with an Energy Management Control Center, which provides outdoor reset.
While a 98% efficient unit is a significant challenge to the German manufacturers who have dominated the high-efficiency market, the $8,000 price tag for the virtually hand-made device may put some contractors off.
Also making a splash was East Freetown, Mass.-based Heat Transfer Products with a 92% efficient boiler called the Munchkin that’s so small that it’s ups-able.
The fully modulating, low-mass boiler uses a stainless steel heat exchanger and a European-designed stainless steel burner with spark ignition and a Honeywell gas valve. Its control senses the set point temperature, supply water temperature and return water temperature and modulates the firing rate of the boiler accordingly. It can operate at low return temperatures without a bypass valve. The boiler, jacketed with abs plastic, costs about $2,200.
But while the boiler manufacturers were attracting a lot of attention on the show floor, they were getting beaten up in the seminar rooms, especially by consultant Tom Tesmar, Tesmar Applications Technology.
Tesmar is an advocate of water heaters for radiant heat. He told the contractors that homeowners should take the price difference between a water heater and a high-efficiency boiler and put the money into really good windows.
Radiant slab systems are hard to control because of solar gain and radiant ceiling systems are better, Tesmar said. If a slab cools down because of solar gain, it may take 42 Btuh/sq. ft. to "accelerate" the slab back up to temperature when the suns sets, he pointed out, but the total output capacity may be only 45 Btuh/sq. ft. The "accelerative load" is much greater than the steady state load, he said, and it can take hours to reheat the slab.
He said that radiant floors could be run at 70û F and radiant ceilings, which he called a lost opportunity for the industry, could handle temperature swings. A radiant ceiling can put out 60 Btuh/sq. ft. with 120û F water, he said.
Bill Clinton, Bay Hydronic, Sonoma, Calif., showed pictures of an installation he did with Polaris condensing water heaters in a dedicated (space heat only) system. The real efficiency of the high-mass, low-temperature system was in the 85% to 90% range with no concerns about condensing, Clinton said. He noted that there could be concerns about oxygen corrosion with water heater-based systems, especially those that handle both domestic hot water and radiant.
George Kusperer of Bock Water Heaters said boilers were invented 100 years ago to make steam, and water heaters are better suited to make hot water needed for radiant floor systems.
The debate highlighted the two schools of thought within RPA. One group of hydronics purists believes that contractors should take custom work and be well compensated for it. Another camp maintains that contractors should bring radiant to the masses.
"We’ve got to address the low-end market in order to grow," said Dave Springer of A/E firm Davis Energy Group, Davis, Calif., who moderated a panel discussion "Designing for Affordability." He added that he’s seen systems that are too complicated, such as one with four secondary loops.
Clinton brought along a brazed plate heat exchanger he uses for water heater systems that’s piped for a relief valve and an aquastat. A contractor in the audience said he had heard water heater manufacturers discourage using water heaters for both domestic hot water and space heat because of scalding problems, but Clinton replied that he installs a tempering valve for dhw.
Nevertheless, panelists had reservations about water heater-based systems that handle both heating and potable water, such as whether zone valves and manifolds can stand up to typical domestic water pressure and whether legionella bacteria would grow in the heating system over the summer. Hot chlorinated water could, over time, degrade anti-oxidants in pex pipe, Tesmar said.
Contractors in the audience were pragmatic about heat sources. Water heaters are great for small slab-on-grade houses, some noted. If a house, however, requires three water temperatures for radiant, radiators and domestic hot water, then a conventional cast iron boiler is called for.
Contractors swapped funny war stories in the session on "radiant nightmares," most of which consisted of bad jobs performed by other contractors.
For example, because pex pipe comes in 1,000-ft. rolls, one contractor encountered a job with a 1,000-ft. loop.
Another contractor found what looked like sand in the tubing. It turned out another contractor used automotive antifreeze in the pipe and the silicates precipitated out in what looked just like beach sand.
The contractors also told a number of nail-in-the-pipe stories, especially how a nail will self-seal, but when it rusts away five years later, the pipe leaks.
Contractors were warned on staple-up jobs that hot tubing could melt wax toilet rings, creating a predictable mess.
But perhaps the best story came from a contractor who was trying to figure out why one loop would not maintain pressure and heated inadequately. It turned out that an appliance installer had tapped into the glycol heating line for the icemaker. The homeowners blamed their well water for their ice cubes being red and tasting funny.
The next rex will be in May 2002 in Cincinnati.