Chain of Action
Types of Relays
There are two basic types of relays: the solid-state relay and the electromagnetic relay, with several sub-categories of relay in both. An electromagnetic relay sends electricity to trigger an electromagnet which causes a part of the electromagnetic relay, called the armature, to swing and trigger the relay in various ways, depending on the type of electromagnetic relay it is. An electromagnetic relay is the original type of relay, and is the cheapest and least common to use. Because of the risk of a spark being created by the moving parts, most boilers use a solid-state relay, which has no moving parts.
Solid State Relay
A solid state relay switch can also be called an SSR or semiconductor switch. In a solid state relay switch, the relay is usually triggered by an LED light that activates a light-sensitive component of the boiler. Older boilers, particularly oil burning boilers, used a protective device called a stack relay switch, which is no longer installed in new boilers.
Zone Heating
While some buildings with a large shared boiler have one thermostat and relay to trigger heat to the entire building, some buildings have individual thermostats for areas called "zones." Each zone is given heat from the boiler from its own relay setup which triggers the boiler to release heat through a pipe that goes straight to the room which needs heat.