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Boiler Terms & Definitions

Boiler Books imageBoiler BooksHydronic Heating:Heated water or steam that is transferred through a closed system of piping. There are several different types of radiant heat components (terminals) that can be connected to the piping. A few examples are radiant floor heat, radiators, convectors and forced air water coils.
Boiler Control imageBoiler ControlsAquastat:A control used on boilers to regulate the temperature of the water used for heating and domestic water. The control has a low (on) and high (off) limit and a differential range setting. The differential setting determines the range of the low limit. The differential is set higher when the boiler is used for both heating and domestic water use and lower for heat only use.
Boiler Electrical imageBoiler Electrical GuidesContinuity Test:Checking an electrical circuit to see if it complete (closed) or interrupted (open). In HVAC service, this is performed with an Ohm meter that checks for continuity and resistance. Electrical resistance is a measurement in ohms and shows the reduction in electrical current flowing through a part or wire.
Gas Boiler Equipment imageGas Boiler UnitsDirect Vent:Also known as power venting, this is a term for venting a boiler where a chimney may be nonexistent or impractical. Commonly piped in schedule 40 PVC pipe or steel tubing to exterior of building. Check with local building codes and manufacturer's specifications for clearances and materials.
Oil Boiler Equipment imageOil Boiler UnitsOil Pump Filter:A filter inside an oil burner's pump assembly that removes particles from entering the pump and nozzle assembly. Not to be confused with an in-line oil fuel filter. Tech Note: If the in-line fuel filter is seriously clogged; the pump filter most likely needs to be cleaned or replaced.
Boiler Parts imageBoiler Replacement PartsFlame Sensor:Also know as a flame rod or detector on a flame rectification system. A device on a gas-fired boiler that proves "verifies" that a flame is present before the igniton control is powered to open the gas valve. Not to be confused with a thermocouple that senses a flame through a lit pilot that controls the gas valve.
Boiler Software imageBoiler Software ProgramsPipe Sizing Program:Software program used for determining the correct componets and size of supply and return piping used in the design of hydronic systems. Correct pipe sizing is crutial for determining different types of radiant heaters and number of zones and loops in a system.
Boiler Supplies imageBoiler AccessoriesDiverting Tee:An in-line pipe fitting used on a one-pipe hydronic system to overcome the problem of circulating hot water flowing directly back to the boiler without diverting to a terminal (e.g. baseboard heater, etc.,).
Boiler Technical imageBoiler Technical ManualsTwo-Pipe System:Boiler term for the design of a single supply and a single return. Each terminal (e.g. radiator, etc.,) is connected by a supply and return branch to its main. This designs allows separate control to each terminal. A two-pipe system can be used for any properly sized application.
Boiler Repair imageBoiler Troubleshooting GuidesExpansion Tank:A tank which compensates for the normal expansion of water pressures and temperatures in a boiler (hydronic) system. Some older tanks need to be drained annually. Modern tanks contain a rubber diaphragm, charged with air, that expands and contracts with fluctuating water conditions.
Boiler Thermostat imageBoiler ThermostatsDigital Thermostat:A thermostat that provides a digital temperature reading instead of a manual dial or lever. Not to be confused with a programmable thermostat.