Attention to detail is paramount for snow melt systems. As winter looms, homeowners and businesses scout for effective solutions to maintain ice-free driveways and pathways. Yet, even seasoned engineers and contractors can attest to the intricacies of crafting an effective snow melt system. Even experts falter, primarily due to rapidly evolving technology. Many people, myself included, have been tutored through a mentor-mentee method, and although this approach is invaluable, it only works if the mentor has kept pace with contemporary techniques.
My mentor showed me how a properly designed snow melt system can offer an economically viable and highly effective means of ensuring a safe and snow-free environment during winter. However, it’s crucial to acknowledge that terms like “snow melt” and “cost-effective” don’t always go hand in hand.
Brains of the operation
There’s a variety of snow melt controls available, and numerous strategies to deploy this technology. Options range from basic on/off switches to aerial sensors, or the highly recommended snow/ice puck sensor. The latter is superior but is occasionally overlooked due to perceived initial costs, overshadowing the potential operational savings of this option.
The on/off approach is straightforward — a switch triggers a pump to activate the snow melt. However, an immediate challenge arises when users forget to switch it off.
Aerial snow melt systems use different sensor technology to detect snowfall, low- temperature conditions, and moisture. They typically monitor the ambient temperature and engage the snow melt system during snowfalls. These are typically chosen for retrofit projects where installing a puck sensor isn’t feasible or the snow melt is added to a project as an afterthought.
Puck sensors directly monitor the driveway, ensuring peak efficiency. However, their placement is crucial. Unfortunately, many still install sensors in suboptimal locations, hindering both system performance and operational costs. Instances include placing sensors under parked cars or too close to the snow melt apron’s edge causing misreadings. The potential consequences can mean overheated slabs and non-stop systems.
Proper heat conduction
For pavers, ensuring proper heat conduction to the sensor is essential. A useful tip is to sidestep silicone, which hinders heat transfer. Instead, grout ensures the sensor receives precise readings, optimizing system efficiency. It is equally important that we understand the operation of the snow melt control.
A hybrid fuel approach might be the answer, but it always means planning and foresight.For instance, if you were to choose a Tekmar snow melt control, choosing manual over auto mode can be advantageous, provided one knows its implications. Ignorance here can foster inefficiencies and disgruntled customers. In Tekmar’s context, if you use the manual mode for six hours, the control adheres to that and melts for only six hours, overlooking auto configurations. This can lead to either unfinished tasks or excessive heating, with users often misunderstanding the difference between manual and auto.
Oversizing and undersizing boilers are also a recurring issue in snow melt systems. Typically, the culprit in a snow melt system isn’t capacity but a mishmash of control settings, operational methods, or tubing layouts. A common misstep is mistakenly believing the same tubing layout.
The result is the system performs poorly due to incorrect flows and high-pressure drops. “When we stray from best practices, we encounter difficulties. We might opt for a 125 BTU per sq. ft. ratio to economize on the boiler, or use half-inch pipe to reduce tubing costs, among other shortcuts,” explains Matthew Pottins from Laylan Hydronics. “However, what tends to slip our minds is that homeowners have invested in a high-end system; therefore, it’s only fair to provide them with an installation that matches that luxury standard.”
Exceeding costs
In terms of temperature, ideally, 36 F to 38 F will suffice for most slabs, barring specific areas like helipads or hospitals. Exceeding this only escalates operational costs. A snow melt system’s efficacy hinges on its seamless communication with the boiler. Historical setups relied on simple communication methods between the snow melt control and the boiler, often by a boiler supply sensor. However, issues arise when manual mixing valves are controlling water temperatures downstream from the boiler.
We’ve encountered situations where, even though the snow melt control signalled the boiler, the mixing valve restricted the water temperature going out to the slab. Consequently, despite the boiler’s continuous operation and the absence of snow on the driveway, the desired slab temperature wasn’t achieved. The sensor necessitates two conditions for optimal functionality: reaching the target slab temperature and detecting an absence of snow or moisture. In this scenario, due to the mixing valve’s limitation, the slab couldn’t attain the set temperature resulting in an inefficient system.
Such oversights can cripple system efficiency. Modern condensing boilers permit direct modulating signals. Having the boiler communicate with a variable speed pump using a 0-10V signal to regulate both the boiler and system pump allows the snow melt system to perform better, generating more heat when it is needed and resulting in lower return water temperatures.
These setups are more complicated and may add to the installation cost, but they are notably economical in the long run. “To enhance system efficiency, I would suggest incorporating boiler controls. There’s no need to shy away from pushing the boiler’s limits,” explains Pottins. “For instance, NTI boilers can comfortably operate with a 45 F Delta T, and it’s common knowledge that maximum efficiency is achieved by manipulating return water temperature. So, how do we go about achieving this efficiency?”
A common misstep is believing the same tubing layout used for radiant heating will suffice for a snow melt system.Complexities
Heat pumps, whether a water-to-water or air-to-water, undeniably present certain advantages. However, when it comes to snow melt systems, they aren’t without their challenges. A glance at the manufacturer’s specifications might suggest that delivering water at 130 degrees is within its capability, leading one to assume it’s a good choice for snow melt systems. While this is technically accurate, the full picture reveals more complexities.
It’s important to understand that hydronic heat pumps typically can only elevate the water temperature by about 8 degrees. This can become problematic when designing snow melt systems that might require a temperature differential of up to 30 degrees.
The capacity of residential hydronic heat pumps shouldn’t be overestimated. They don’t pack the same punch as their counterpart, the condensing boiler. For perspective, if a residential hydronic heat pump’s capacity is capped at five tons, its snow melting capabilities are somewhat limited. Given that snow melting demands 130 to 150 BTU per sq. ft, the area it can effectively cover is not that large.
When considering a residential air-to-water heat pump during the intense cold of winter, one must consider its true operational capacity. While hydronic heat pumps have their merits and can indeed be integrated into snow melt systems, it’s essential to approach their application with a deep understanding of its operation. At times, a hybrid fuel approach might be the answer, but it always necessitates thoughtful planning and foresight. “Heat pumps excel at sustaining consistent temperatures. However, when it comes to handling domestic hot water and snow melt requirements, the situation differs,” said Matt Irvine, geothermal sales manager at Eden Energy Equipment Ltd.
Designing a snow melt system is not a simple process and it necessitates a harmonious blend of material choice, control, understanding, and system integration. While the path is riddled with challenges, a well-informed and meticulous approach can yield a robust and efficient system. Just because you have done something a certain way doesn’t mean it is always the best or right way.