Hydronic snowmelt systems

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Careful temperature control will prevent this concrete slab from being damaged by heat.

By Leah Den Hartogh

Snow is inevitable in Canada – whether you live in St. John’s, Nfld., Kamloops, B.C., Windsor, Ont., or Moose Jaw, Sask. There a few options on how to remove it once it’s here.

Commercially, snowmelt systems are a popular method of snow removal, especially when trying to avoid lawsuits. In residential applications, they are increasing in popularity.

There are two different basic types of snowmelt systems: hydronic and electric. For the point of this article, the focus will specifically be on hydronics.

These systems are usually compromised of PEX tubing, manifolds, a heat source – such as a boiler (non-condensing or condensing), controls, heat exchanger, insulation and mixing device (either variable speed injection or modulating valve).

A glycol mixture, separated from the boiler loop by a heat exchanger, is heated and circulated through the tubing which in turn warms the slab.

Controlling the system

Temperature control of the fluid is critical; too low and the snow won’t melt, but too high and the slab will be damaged by thermal shock if the difference in temperature between the glycol mix and the slab is too great.

There are three ways a snowmelt system can be managed: manually, semi-automatic and fully automatic. A manual system fully depends on human intervention to turn it on and off. This is rare and advisable only when the surface to heat is dirt or gravel, said Jean-Claude Remy, business development manager and trainer at Uponor Canada, Mississauga, Ont.

For hard surfaces like concrete, asphalt and paving stone assemblies, the need to avoid thermal shock precludes manual control. Semi-automatic systems maintain a certain amount of heat in the slab in idle mode. Human intervention is required to engage the melting cycle. If no one is home to “push the button” then you will find the driveway full of snow.

Careful planning and installation will result in an effective efficient snow melt system. (All photos courtesy of The Boiler Guys, Toronto)

A fully automatic system will always maintain the slab at a “ready” position and start the melting cycle when required. Sensors in the slab detect when there is snow falling and slowly ramp up the snowmelt system. It can take time before the snow begins to melt.

The benefit is that if you already had to slab pre-heated, so when the snow does fall it melts quicker, said Mike Miller, director of sales, commercial building services, Taco Canada, Mississauga, Ont. Sensor location is critical. Contractors need to consider vehicle traffic and parking or else “you are going to have a car sitting right on top of the snowmelt sensor,” explains Kevin Vieira, director of sales and marketing at HBX Control Systems, Calgary.

Freeze protection

To ensure that the pipes don’t freeze, the heating fluid is a glycol mixture. “How much glycol solution is needed depends on how cold it gets outside,” explains Miller. “In a place like Alberta where you get down to -40C outside, the glycol solution could be as high as 50 per cent. In other places like south-western Ontario, you may get away with 25 to 30 per cent.”

The glycol should be checked on a regular basis because glycol will deteriorate over time. If the glycol goes bad, this could cause the pipes to freeze or allow microbial growth in the pipes. This is where your water is going to start getting an odour or you may see black spots in the pipes, noted Michael Breault, senior technical instructor/senior instructional designer at Watts Water Canada.

Class system

There are three different classes of snowmelt systems: levels one, two, and three. Each level the Btu’s needed for proper system operation. For example, level one is usually a residential or warmer climate application requiring between 125 and 150 Btu’s per sq. ft. per hour. Installations in the Niagara Valley in Ontario or Okanagan Valley in B.C. are typically within this level.

Level two occurs in colder climates or larger residential applications. More demanding applications will range between 160 and 190 BTUs per sq. ft. per hour. Places like Calgary and Quebec City will commonly be found within the level two range.

From left, Alli Khan, Alexander Genzer, and Suhaib Shaikh of The Boiler Guys take a short break on a snowmelt job site.

Level three covers the most demanding heating needs. Critical areas that must be heated at all times like emergency entrances to hospitals, fire stations and helicopter pads fall within this category. In this class, between 200 and 220 BTUs per sq. ft. per hour is required.

Be careful what you promise!

Contractors need to gauge customer expectations. Sometimes only a flamethrower will do what they have in mind, warns Remy. “You’re going to sit down and have a conversation where you ask questions and talk 20 per cent of the time and listen 80 per cent of the time.” Don’t assume that you know what the customer is thinking.

As well, contractors need to do the math, stresses Breault. This includes a heat loss calculation to help determine supply fluid temperature, preliminary flow and pressure loss. As noted above, there are big differences from region to region.

It shouldn’t be forgotten that snowmelt system operation can be expensive. This means that contractors need to educate homeowners. Some homeowners may turn the system off and never turn it on again after the initial heating bill, warns Vieira.

“Homeowners that want snowmelt systems, want it to work and not cost them unnecessarily. Give your customers all their current options for system control and let them know how to use it. It will save you call-back time and keep them happy with their system,” suggested Vince Baggetta of Next Plumbing and Hydronics Supply, Toronto.

Specifications

Snowmelt tubing sizes vary from ½ to one-inch diameter depending on the installation. Pipe size affects loop lengths. Typically, they are kept as short as possible. A 3/4-inch pipe can see loop lengths around 300 ft., 5/8-inch will see should be between 200 and 250. “The bigger the pipe, the longer we can go with our loops,” remarked Alex Genzer, co-owner of The Boiler Guys, a Toronto based contractor.

When laying down the piping it is best to lay it down alternatively hot and cold, using a double serpentine, reverse-return or double spiral model. This will evenly distribute the heat; otherwise, only certain areas will melt and a “candy cane” scraping type effect can occur, said Breault.

Snowmelt systems can be installed with various slab materials including but not limited to asphalt, concrete and sand bed.

If asphalt is the material for the slab, the piping needs to be protected during paving. “Sometimes with asphalt, you have to run cold water through the system while they’re paving it and that’s just to keep the pipes from overheating when they put down hot asphalt,” explains Genzer.

Snowmelt projects vary from simple to complex. This custom home project required snow melting on several elevations.

Helium is often used to find leaks. The system is drained and filled with helium. “We then take a helium detector and we can pinpoint the leak within one foot because helium molecules are the smallest molecule and will go through concrete,” said Genzer.

The other key factor is drainage. The snowmelt water has to go somewhere to avoid a skating rink at the end of the driveway. “You are going to have the kids all playing hockey down there,” remarked Barry Cunningham, general manager at Triangle Supply, Red Deer, Alberta.

Set and leave

Once the system is commissioned, the last thing anyone wants is a callback. Smart controls allow contractors to receive error codes and may allow them to adjust the controls remotely.

As technology evolves, there are more opportunities for innovation. “I think a lot of systems will get away from in-slab sensor technology and just connect your system to the internet, which will run your system based on a forecast,” noted Vieira. In fact, that technology is already on the market, he added.

Hydronic heating contractors have the opportunity to expand their business with snowmelt systems. At the end of the day, it can be cheaper and less hassle for many customers than paying someone to scrape off the driveway.

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