Hydronic Radiant Floor Heat 101 - Part 2February 2012
By Les Graham
When it comes to what type of tubing to use in the concrete, the choice is either Pex-Al-Pex or a Pex tubing. Let’s look at the differences between the two options. (The word Pex in both types of tubing is an abbreviation for cross linked polyethylene.)
Pex-Al-Pex or Pex-Aluminum-Pex features: (This style of tubing has an aluminum sleeve centered between two layers of Pex.)
- 100-percent oxygen barrier (the aluminum sleeve).
- The oxygen barrier is protected (centered between the layers of Pex).
- Better heat transfer because of the aluminum sleeve.
- Ratings: European quality 145 psi at 203 degrees or Asian quality 125 psi at 180 degrees.
- Ease of layout, bends like soft copper, stays put.
- Less fasteners needed.
- Have all advantages of both plastic and metal tubing.
- The best coefficient of linear thermal expansion.
- Kinked tubing: if severe, replace roll or splice.
- Price is middle of the road.
Pex with an oxygen barrier features:
- 98-percent oxygen barrier.
- The barrier is usually located on the outside of the tubing; the oxygen barrier is not protected from sun, water, and abrasion.
- Ratings: 100 psi at 180 degrees.
- Ease of layout; Pex has memory, it will try to recoil.
- Additional fasteners needed.
- Coefficient of linear thermal expansion is poor compared to Pex-Al-Pex.
- Kinked tubing: depends on the brand of Pex; replace roll or splice, and others need to heat up to a certain temperature to go back to its original form.
- Price varies; note that some Pex is sold that has no oxygen barrier.
THE OXYGEN BARRIER
An oxygen barrier prevents oxygen from penetrating through the wall of the plastic tubing and entering into the boiler solution. Oxygen can penetrate the wall even with a pressurized boiler system. Boilers are designed to be closed and sealed off from oxygen, and if not, rust and sludge can start to build up in the boiler system.
HYDRONIC TUBING OR ELECTRIC MATS
When it comes to radiant floor heating, both hydronic tubing or electric mats may be used. There are indications that hydronic tubing is the better choice. The reasons why are outlined below:
- With hydronic tubing, multiple heat sources can be used: natural gas, L.P. gas, fuel oil, ground source, electric boilers, biomass burners, wood boilers, corn boilers, solar, etc.
- Electric mats require a commitment to the electric company.
- The track record for tubing in concrete is better than for electric mats.
The two most common sizes are 1/2-inch and 5/8-inch. Many times, this decision comes down to someone’s opinion. Most people assume 5/8-inch does a lot better job compared to 1/2-inch. The truth of the matter is that there is very little difference between the two sizes. In fact, it is common to install both sizes using the same on center spacing. Some installers prefer to use one size over the other. There are times when the layout of trench drains and manifold locations force the designer into the 5/8-inch tubing. With 5/8-inch, the maximum is 450 foot loops; 1/2-inch is 330 foot loops max.
STARTING THE PROJECT
To start a project, the design needs to be done by someone who is in that business. Listed below are what a designer will need to get started:
- Dimensions of building: 60 ft x 80 ft x 20 ft.
- What is the purpose of the building: farm shop, body shop, etc.
- Any obstructions: division walls, trench drains, hoist, mechanics pit, etc.
- How many concrete pours?
- Type of fasteners: zip ties, staples, screw clips.
- Heat Loss: R-values, door sizes, window sizes, inside temperature, etc.
With the above information, the designer can suggest loop layout, on center spacing, loop lengths, pump sizing, boiler sizing, etc.
CONCRETE CONTRACTORS CAN INSTALL
Yes, concrete contractors are able to install the radiant heat floor tubing once the proper design work is completed. About 99 percent of the brain work is finished at the designer’s desk. There are several advantages for the concrete contractor to get involved and do the installation:
- Taking control of the time frame of the concrete pour; no need to wait for the plumber to arrive.
- Sell the radiant floor as part of the concrete package.
- Create a new profit center making money selling the product; install the product and keep the project schedule.
ISSUES WITH RADIANT FLOOR HEAT
Installation problems are rare; however, there can be design problems. Some of the design problems that could be encountered are:
- Loop lengths too long.
- Pumps or heat source are too small.
- On center spacing incorrect on the loops.
- Layout patterns not matching the building.
- Pour quality products.
- Cutting and drilling into loops by mistake; fix by carefully chiseling concrete away and adding a coupler.
Hydronic Radiant Floor heat is here to stay and has many benefits over conventional heating systems. It is pretty simple when starting a project, just consider insulation under and around the perimeter, choose to use Pex-Al-Pex or regular Pex, and have a design person involved.
The importance of the oxygen barrier tubing and why hydronic floor tubing is a better option than electric mats has been explained. Hydronic radiant floor heat is simple to install once a designer has done their job correctly. Concrete contractors are getting more involved with hydronic radiant floor heat. This information should equip you with the confidence to talk radiant floor heat with your customers and add additional profit to your bottom line. ■
About the Author:
Les Graham is the president and owner of Radiant Outfitters based out of New London, Minnesota. Graham has 24 years of experience in radiant floor heating and is certified with the Radiant Panel Association. Radiant Outfitters, a wholesale distributor, offers complete design service and product, partnering with all types of contractors that install radiant floor tubing. For more information, call 877.855.2537, or visit www.radiantoutfitters.com.
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