Radiant Snow Melt and Basement Heat in Toronto
Another hydronic radiant snow melt and floor heating project for Pure Building Group in Toronto. The owner of this house does not like to shovel snow in -30C. Weird I know. You can see the 3/4″ Oxygen Barrier Sharkbite tubing on HotRock panel insulation installed, the porch was completed a month or so ago. You can then see the loops pressurized with air to instantly realize if the integrity of the pipes gets compromised while pouring the concrete.
The Boiler Room
We have since finished this job and installed the Laars Mascot Combi Boiler alongside a Schuller Hydraulic Separator and an Axiom glycol feeder. When it comes to snow melt there are a few things you don’t want to skimp on. If you do, the radiant heating system may even limp along for a while. Or damage components, lower the performance and send efficiency to hell. At worst the snow wont melt on colder days at all. We design our boiler rooms not only to be functional but also clean and aesthetically pleasing.
Critical considerations in radiant snow melt systems
The following list has a few important things listed that you do not want to either leave out or under size. Considerable savings can be made which many unscrupulous installers take an advantage of. They will leave the home owner paying through the nose for his gas bill, or leave him unhappy with a constantly breaking down and under-performing radiant heating system. If you want to save money try installing a less fancy kitchen instead cutting corners in the boiler room.
Size your boiler right
When it comes to snow melt we recommend 150 BTU/h/sq’ heat to be accounted for. Heating Canada in -28C Requires a lot of energy. Under-sizing your boiler will result in the snow melt taking forever or on the coldest days not happening at all. The boiler has to be able to meet the demand or you will just burn gas forever with little or no results. Over-sizing however is not a good idea either as it may lead to short cycling.
Use a glycol feeder
The circulated medium in a closed loop hydronic radiant heating system needs replenishing from time to time due to loss through evaporation and bubble forming and venting through air vents and eliminators. If there is no make up system in place the pressure in the system will drop below the minimum that boilers require to operate. When that happens the system will shut down requiring a service visit for a manual refill. This can happen 1-3 times a heating season depending on the size of the system among others. We always use a glycol feeder which will not only make adding glycol to the system an easy task but also will give visual clues to any excess glycol consumption through the level of glycol in the reserve tank.
Use a Hydraulic Separator (low loss header)
Hydraulic Separator Tanks serve several functions. They are air vents to purge the system of bubbles and air that would damage the circulating pumps and degrade heat transfer. Hydraulic tanks also equalize pressure differentials between the supply and return legs of the radiant circuit. The hydraulic separator also tamps down the temperature difference (ΔT) between the intake and output ends of the boiler’s heat exchanger keeping it from cracking. On the bottom of the tanks rust and dirt can settle and be drained keeping preventing pumps from getting damaged and heat exchangers in the boiler to be clogged.
Use 3/4″ tubing
Using 3/4″ tubing to melt snow results in faster melt and run times. While installing them is more difficult and cost more than the smaller diameter 5/8″ tubing some people use, the hassle is well worth it.
The more insulation the better. If the heat goes into the ground and to the sides instead of to the surface of the driveway you will spend more time and energy to melt the snow. We use HotRock Panel insulation rated to R10 under the slab. This insulation will not absorb water like foam insulation and has a built in vapor barrier on its surface. Of course tying down pipes to a wire mesh and pouring concrete over it is cheaper but not for long.
During heating the circulated liquids in radiant floor heating setups expand in volume. When the heat goes off the liquids cool down and contract. The thermal expansion tank which needs to be sized right absorbs this constant volume change. If you leave these tanks out during heating the water or glycol will expand, the pressure in the system will go up and if one is installed ( a must by code) the pressure relief valve in the boiler will let go spraying hot liquids onto the floor. If such a valve is stuck however due to calcium build up then the boiler and pipes will crack. Once the liquid is cooled down there will be a vacuum in the system sucking in fresh water or glycol. If you leave out an expansion tank or you buy a too small one then radiant floor heating becomes no fun pretty fast.
We use a 50% glycol/water mix in our snow melt systems which remains liquid down to -45C. Some installers dilute the glycol further saving on the cost of the install. This will result in the glycol in the radiant loops in the driveway turn into slush or even solidify resulting in burst tubing, pipes and a non functioning system on the coldest days.