Heating Freezer Floors
Radiant under-floor heating and commercial freezers may not seem like a natural fit, but to food companies that keep a lot of frozen inventory, the combination can solve a big problem and save them thousands of dollars.
Even though the concrete floors in these freezers have insulation, the insulation doesn’t stop condensation, says Jeff Jannetto, hydronics manager at Lino Lakes, Minn.-based Northern Radiant Floors, a division of Northern Wholesale Supply (www.northernwholesale.com). When a bare concrete slab gets cold, the moisture in the soil below will start to gravitate toward that cold spot and turn to ice. Over a few years, a large ice ball begins to form under the floor. As the ice expands, it will crack or push the floor up.
“Those ice balls can lift the footings off the building,” he says. “I’ve seen them go as high as four feet. It can cost a food distributor thousands a day to get the product out of there because it can’t be removed with fork lifts. Then refrigerated trucks need to be rented to store the food while the floor is being fixed.”
Jannetto started working on frost-proofing projects in 1998. Before he became a radiant heat specialist, he worked in the refrigeration field, so he knows how these big freezer systems work. On his first frost-proofing job, Jannetto was called in on a system that had broken down. He reviewed the existing system and applied his radiant heating knowledge to improve the design.
“I didn’t invent the frost-proofing system, I just took it to a new level by adding controls,” he explains. “It’s fun to do something different with radiant.”
His designs have evolved as radiant technology has evolved. Today, he uses an injection system with tekmar controls to regulate the temperature of water going into the floor - about 95 degrees F. The purpose is to eliminate the humidity from under the floor so it is dry, he says, not to raise the temperature of the freezer floor itself. That would add to the refrigeration load and cost more money to run.
“We control the amount of heat we put into the floor and we control the return temperature, which is related to the temperature under the slab,” Jannetto explains. “That’s what turns the system on and off.”
Hot Job In Puerto RicoA recent job in Puerto Rico involved contractor Bruce Wikstrom, owner of Siren, Wis.-based Earth Energy Systems (www.earthenergywi.com). The project was planned about two years before work started. Eurgel Berry, president of Blain, Minn.-based Thermal Construction Specialists (www.tcscold.com), approached Jannetto about designing a frost-proof system for a big food distributor in Puerto Rico.
“When Eurgel bids a freezer job, he calls me to bid the frost-proofing system,” Jannetto explains. “He knows how important it is that the floor doesn’t freeze and bust up. He includes our work in his scope of work and he warranties the vapor barrier around the freezer, which is critical to a freezer application.”
“That layer of insulation under the slab keeps the dirt warm,” Wikstrom says. “Heat drives the moisture away so it keeps the soil dry and maintains the integrity of the slab.”
Once Berry’s team started putting the freezer wall panels in and completed the prep work, he called Jannetto and gave him the general contractor’s schedule. After a few delays, Jannetto, Wikstrom and Jim Johnson, also of Earth Energy Systems, started the radiant floor portion of the job this past March. Johnson is a sheet metal fabricator, but he wanted to check out the tubing side of Earth Energy’s business.
The radiant team had shipped all their tools and equipment (including uncoilers and twist-tie tools) to the island about two months before; they had figured on an earlier start, Wikstrom explains. It took them about nine to 10 days to complete the job, working with and around the other trades.
“You’ve got to be pretty flexible,” Wikstrom says. “Every day we were putting down tubing or piping boilers or something else, while dealing with the heat and humidity at the same time.”
The main problem on the project was the language barrier and trying to coordinate with the other trades on the jobsite. The first day, after a safety meeting, Jannetto and Wikstrom went to check the site where they were supposed to start tying down the radiant tubing. “None of the final grade had been done on the freezer and none of the mesh had been laid, so we couldn’t get going,” Wikstrom recalls. “There were numerous holes that had to be drilled through a 6-inch concrete footing, so we started drilling the holes for something to do.”
They laid out 23,000 feet of private-label 3/4-inch tubing between two buildings totalling about 50,000 square feet. The Thermolec electric boiler was wall-mounted on the outside of the building.
Jannetto handles about a dozen of these projects a year, while Wikstrom has about 20 projects under his belt. The size of the job is always different, but they are usually for manufacturers or large food distributors.
“I’m providing a foolproof, state-of-the-art radiant system so the food manufacturers or distributors don’t have to worry about their food,” Jannetto says. “Basically, these types of radiant systems are big dehumidifiers. As long as the freezer floor is a few degrees warmer than the dirt on the outside of the freezer, the moisture won’t go there and the floors will be fine. I don’t want to have to go back to Puerto Rico to fix a broken system!”