Quick Answer
A drainback system can work without glycol, but it requires a well-designed and properly insulated system that can maintain temperatures above the freezing point of water.
System Requirements
To operate a drainback system without glycol, the system must be able to maintain temperatures above 40°F (4°C) during the coldest months. This can be achieved by using a well-insulated tank, a large collector area, or a combination of both. A typical drainback system without glycol might include a 2,000-gallon tank with R-12 insulation and a 400-square-foot collector array.
Design Considerations
Drainback systems that operate without glycol require careful consideration of the system’s thermal performance and freeze risk. A general rule of thumb is to ensure that the collector area is at least 10-15% of the tank’s volume. In this example, a 2,000-gallon tank would require a minimum collector area of 200-300 square feet to maintain temperatures above freezing. Additionally, the system should be designed to drain quickly during freezing conditions, with a minimum flow rate of 20-30 gallons per minute.
System Operation
In a drainback system without glycol, the collector is filled with water during operation, and the tank is drained when the system is not in use. This requires a reliable drainback valve and a well-designed piping system to prevent water from freezing in the pipes. To ensure system operation during freezing conditions, the system should be equipped with a freeze protection system, such as a thermostatically controlled valve or a freeze sensor that can activate a backup heat source.
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