Re-evaluating Standard Practices For Hydronic Piping
Some of the advances in technology that have made radiant floors cutting edge are also making traditional installations of baseboard convection heaters and radiators easier, faster, more cost-effective, and more reliable. To take advantage of the newer technology, though, contractors need to re-examine how they have traditionally installed traditional hydronics.
Clarence Cleer, Highlander Energy Products Inc., in Kane, Pa., is one contractor who is well aware of the changes occurring in the hydronic heating industry. Highlander performs a lot of retrofit and custom work in and around Erie, Pa. According to Cleer, creating effective zones is the keystone to integrating the old with the new.
"Whether you're doing a retrofit or new construction, the more zones you can create, the more effective, efficient, and comfortable the building will be," Cleer says.
The use of PEX tubing is one big reason multiple zones are easier to install. Oxygen-barrier PEX protects the ferrous elements of a heating system from oxidation. And PEX is available in sizes that range from 1 inch - for primary supply and return lines - down to 1/4 inch for short-run, single-element distribution branches.
"We do a lot of low-flow systems, using pipes as small as 1/4 inch," Cleer says. Smaller pipes are more efficient and cost less per linear foot than larger pipes, and they are easier to handle on the job than larger diameters.
Copper and PEX both have their place in the installation of hydronic systems. Copper has a long track record of successful installations in baseboard systems, and the main element for baseboard is made from a copper pipe. The four factors that contribute most to pressure loss through a baseboard system are the fluid properties, inside diameter, surface roughness and the number of fittings in the distribution piping. The interior roughness of copper and PEX are very similar with plastic being a little smoother. With a PEX pipe installation, less fittings are required. All these factors can sometimes allow a smaller pump to be used. It is not uncommon to use copper pipe to go from the baseboard to just below the floor, transition to PEX, then connect back to copper in the boiler room.
Combating NoiseOne problem PEX can't overcome is the noise associated with baseboard heat. "The typical copper baseboard with aluminum elements is noisy because of basic physics," Cleer says. "The cold element gets hit with hot water from the boiler. The copper and aluminum expand and contract with the changes in temperature, causing the familiar 'pings' and sliding noises every time the pump cycles."
Cleer uses two main tactics to control noise in their installations: outdoor reset controls and careful zoning with heat injection to baseboards.
Outdoor reset controls regulate the boiler temperature based on the ambient temperature outside the building. On a mild day, the boiler might maintain 130 degrees F, for example, while a cold day demands the full output of 180-degree F water. Resetting the water temperature based on the outdoor temperature lets the system run nearly all the time, which dramatically reduces the affect of thermal shock and nearly eliminates noise.
This can increase operating cost for the pumps, but, with careful pipe sizing, the impact is minimal. In addition, the boiler is much more efficient at lower temperatures so energy-cost savings will easily cover the cost differential. And, Cleer notes, the increased comfort of a silent system is an added benefit.
Careful consideration of distribution methods for baseboard zones will also help combat noise. PEX enables contractors to set up multiple zones with all of the controls at a central location such as the boiler room. Using zone valves and injecting heat only into zones that need it (based on outdoor and indoor reset controls) will keep water temperatures (and baseboard temperatures) more constant, reducing noise and increasing comfort.
The simplest method for avoiding noise, though, is to install a boiler bypass to temper the water temperature for the baseboard system.
Regardless of the type of installation, Cleer believes many contractors are oversizing their systems because they rely too heavily on rules of thumb. Even contractors who follow traditional heat-loss methods religiously can run into problems, especially on retrofit projects.
"When we go out to bid on a church or social club retrofit, traditional heat-loss calculations are of little value," Cleer says. "The time it takes to measure and count windows, find and measure cracks, and guess about the R-values of 100-year-old walls can be better spent figuring out exactly how much heat the building really needs."
Cleer uses software that the company developed to calculate the actual energy usage in the building over the past two years. Additional analysis allows them to calculate the heat loss and estimate the size of the boiler and radiators or baseboards they'll need to install. Because they're more concerned with accuracy than making a "conservative" estimate, Cleer says, they can often win bids because their specifications call for smaller boilers and less-extensive in-room heat exchangers.
"We get accused of low-balling quotes," Cleer says, "but our estimates are very accurate. In fact, we tell our customer that if they're not comfortable once the system is installed - if there's not enough heat in the rooms - we'll come back and put in a bigger boiler or re-size the radiators or baseboards for free."