VFD Applications in the Boiler Room – Tech Tip 8

Just as our industry is discovering electrical power savings through the application of variable frequency drives controlling motors on air handlers, circulating pumps, cooling tower fans and many others pieces of equipment, the boiler room is no exception. Two motors to better control are the fan motor on the burner and the boiler feed pump (on a steam boiler). Although small motors can be controlled by drives, the larger the motor, the more potential for savings. Steam boilers larger than 200 Boiler HP can be considered candidates. Special boiler control systems are necessary to generate signals which can be used by VFDs. (See Tech Tip #9) This is most easily added if a new boiler is being ordered or an existing boiler is being re-controlled.

Electrical savings from 5-50% can be expected! Savings depend on the application, but the more the boiler runs at part-load, the more the savings. If the combustion air and feed water can be controlled with a VFD rather than primarily a fan damper or water valve, there are savings.

Following are two examples of calculations of savings on larger boilers. TechStuff software is used in these examples.

Example 1 shows the calculations on a 30 HP blower motor on a burner.

Example 2 shows savings on a continuously run boiler feed pump. Let a sales professional at Federal help you survey your boiler room for possible savings.