What is a boiler bypass valve?

A boiler bypass valve is a type of valve that is used in hydronic heating systems to regulate the flow of water through the boiler. It is typically installed on the return side of the boiler and is used to maintain a constant flow rate through the boiler, regardless of the demand from the heating system. In this article, we will explore the purpose and function of a boiler bypass valve, as well as the different types of valves available and how they are installed.

Purpose of a Boiler Bypass Valve

The purpose of a boiler bypass valve is to regulate the flow of water through the boiler in order to maintain a constant temperature differential across the heat exchanger. When the heating system demands heat, water is drawn from the boiler and circulated through the heating system. As the water in the heating system cools, it is returned to the boiler for reheating.

If the flow rate through the boiler is too low, the temperature differential across the heat exchanger will be too high, which can cause damage to the heat exchanger and other components of the boiler. If the flow rate through the boiler is too high, the temperature differential across the heat exchanger will be too low, which will reduce the efficiency of the heating system and can cause the boiler to cycle on and off unnecessarily.

By regulating the flow rate through the boiler, a boiler bypass valve ensures that the temperature differential across the heat exchanger is within a safe range, which maximizes the efficiency of the heating system and extends the life of the boiler.

Types of Boiler Bypass Valves

There are several different types of boiler bypass valves available, each with its own advantages and disadvantages. The most common types of boiler bypass valves are thermostatic radiator valves, flow control valves, and automatic bypass valves.

Thermostatic Radiator Valves

Thermostatic radiator valves are typically installed on the radiators in a heating system and are used to control the temperature in each room. They work by sensing the temperature in the room and adjusting the flow of water through the radiator to maintain a constant temperature. In addition to controlling the temperature in the room, thermostatic radiator valves can also be used to regulate the flow of water through the boiler.

Flow Control Valves

Flow control valves are typically installed on the return side of the heating system and are used to regulate the flow of water through the system. They work by adjusting the resistance in the flow path to maintain a constant flow rate. Flow control valves are often used in combination with a differential pressure controller to ensure that the flow rate through the boiler remains constant, regardless of the demand from the heating system.

Automatic Bypass Valves

Automatic bypass valves are typically installed on the return side of the heating system and are designed to open and close automatically to maintain a constant flow rate through the boiler. They work by sensing the pressure differential across the valve and adjusting the resistance in the flow path to maintain a constant flow rate. Automatic bypass valves are often used in combination with a differential pressure controller to ensure that the flow rate through the boiler remains constant, regardless of the demand from the heating system.

Installation of a Boiler Bypass Valve

The installation of a boiler bypass valve is a relatively simple process that can be completed by a qualified plumber or heating engineer. The valve is typically installed on the return side of the boiler, between the boiler and the heating system. The valve should be installed so that the flow of water through the valve is in the same direction as the flow of water through the boiler.

Once the valve is installed, it should be set to maintain a constant flow rate through the boiler. This can be done by adjusting the resistance in the flow path, either by adjusting the valve itself or by using a differential pressure controller. The flow rate through the valve should be adjusted so that the temperature differential across