The Saturn Service Center in White Bear Lake, Minnesota was able to increase energy efficiency and comfort with the installation of a custom REHAU radiant floor heating system.
Specific requirements of the project included compensation for heat lost through large garage doors and incorporation of the existing oil reclamation boiler, which could not be moved.
Spriggs Plumbing, Heating and Process Piping of St. Paul, the mechanical contractors for the project, worked in partnership with Harold Bruner, design engineer for Michel Sales Co., to finalize a design of the system.
“Since we were dealing with the dual demand for increased comfort and better efficiency of the heating system as a whole, we felt the quality and proven reliability of REHAU heating products would be the best choice for the job,” said Bruner. “We also knew from our own experience that REHAU would provide the support we needed in designing a custom and more cost-effective installation to handle the large distance between the boiler and the manifold locations.”
Goodin Company, plumbing and HVAC wholesaler, was also instrumental to the project’s success. “Kirk Moore, salesman for the St. Paul branch, managed the day-to-day coordination of material requirements to help accomplish the job in a timely and cost-efficient manner,” said Bruner.
Oil Reclamation Boiler
One of the main functions of the new Saturn service department is to provide customers with regular oil change services. As such, an oil reclamation boiler system was installed to dispose of used motor oil in an environmentally friendly manner while avoiding the additional cost of having it otherwise removed. With an output of more than 2,000 MBH, the system’s boiler could easily serve as the main heat source for the new radiant system, which requires less than 400 MBH. This provides an enhanced level of fuel efficiency—even greater than that typical of most radiant system installations.
In order to accommodate the oil reclamation boiler, the most cost-effective configuration was determined to be an innovative primary/secondary distribution system. The configuration called for the variable speed injection mixing of hot boiler water with colder return water from the floor panel at the manifold’s location instead of at the boiler itself. This meant that the system would need to move 180°F water at 8 gpm the 150 ft distance from the boiler to the manifolds, instead of the 114°F water at 38 gpm that a more traditional system would use.
The 8 gpm flow rate made it possible to use a smaller, 1 in. diameter RAUPEX pipe, instead of the conventional system that would require 2 in. distribution piping for this application. The installation of 1 in. RAUPEX was less expensive and much easier to install than 2 in. rigid steel or copper pipe.
To calculate water temperature and flow rates for the system, REHAU designed the system to ensure the floor could deliver the proper amount of heat.
A sophisticated outdoor reset system also plays a major role in determining the temperature of the water flowing through the radiant system. The system monitors outdoor temperature, thus creating an inverse relationship to the temperature of the radiant system itself (as the temperature outside increases, the outdoor reset alerts the radiant system to decrease its temperature setting). This results in greater energy savings and a more even, consistent temperature inside the space. Additionally, the system significantly decreases the stress on the ceramic tile floor above, as heat is increased intermittently and does not remain constant.
A circuit setter flow valve with flow gauge was also installed on the return injection riser so that the installer could easily set the system to the required injection flow rate of 8 gpm. “Usually there’s a bit of guesswork in adjusting the flow rate of the injection riser system, but with this gauge it was possible to read the results of adjustments as they were being made,” explained Lenahan. “This ensured the flow rate was correct, making it much easier during the injection riser system’s installation. Not only that, but installation also allows for any necessary fine tuning adjustments in the future.”
The system’s 3/4 in. RAUPEX heating pipe was installed in the center of a 4 in.concrete slab-on-grade, at 12 in. on-center spacing by attaching it to the structural wire mesh of the slab with nylon ties. A 3/4 in. pipe size was chosen instead of the 1/2 in. or 5/8 in. pipe usually used in the floor in order to accommodate installation of the longer loop lengths of 350 to 450 ft (107 to 137 m)
The system design employed a PRO-BALANCE manifold in each of the four individual zones, with flow gauges on each manifold circuit. The flow gauges eliminated the guesswork normally necessary when initially adjusting the system’s water flow, as PRO-BALANCE gauges make the rate easily visible and allow for it to be controlled and adjusted as necessary.
To ensure maximum comfort, the radiant system was designed in distinct controlled zones, allowing for a more targeted maintenance of temperature over the entire space. It was specifically divided into four heating zones, based on the location of the most significant heat loss—the two large lifting doors. Within each zone, the heat travels in the form of an electromagnetic wave that is emitted from the floor and provides warmth where needed.
“In much the same way as a beam of sunlight would make a person warm when it hits them, the electromagnetic wave brings targeted warmth to the technicians, the automobiles, or any other solid object in its path,” explained Bruner. “The result is a much more targeted supply of heat and heat recovery, especially compared to forced-air systems which heat an entire space at once.”
In addition to better and more efficient heat loss recovery, this type of zoning allows the radiant system to use the same water temperature at all manifolds, further reducing system costs by requiring only one of the usual four mixing controls. “The controllable zones really provided icing on the cake as far as reaching our goal in providing the technicians with a comfortable, warm workplace,” said Bruner.
“In the winter there’s obviously a lot of snow and moisture on the service center floor,” adds Griffith. “The radiant system not only keeps the general space warm, but it makes the muck and guck virtually disappear in no time. My staff is much happier—and much more efficient—with warmer, drier feet and floors.”
The Saturn dealership has experienced energy savings from both the radiant floor heating system itself and the system’s fresh air intake system, which tempers the air with a hot water coil system also fueled by the oil reclamation boiler. The system heats the fresh air before it enters the space, and as such does not present an additional heating load on the radiant system.
“Our heat savings has been noticeable, between the efficiency of the radiant system and the fact that we’re basically self-sustaining on waste use from oil changes,” said Griffith. “We really couldn’t have asked for more between the savings and the comfort this system provides.”
In addition to being a customer success, the overall project was recently recognized for its excellence by the Radiant Panel Association. REHAU received the 2003 System Showcase Award for best hydronic commercial design at the May awards presentation in Sacramento. The award competition included more than 60 entries in eight categories judged by a panel of experts in radiant heating.
|Project||Saturn Service Center in White Bear Lake, MN|
|Construction||Automotive service center renovation, 2002|
|Scope of Project||10,000 ft2 (930 m2)|
|Engineer||Michel Sales Company|
|Contractor||Spriggs Plumbing, Heating and Process Piping|
|REHAU Systems Used||Radiant heating (RAUPEX® pipe, PRO-BALANCE® manifolds)|