DraftMax Basic Spare Parts FAQs
Straight answers to the questions people ask most when finding and fitting spare parts for a downdraft extraction table.
Which parts of a downdraft table wear out or fail most often?
The parts that work hardest are the push buttons and switching elements, the relays and contactors, the fuses, and the fan motor with its fan wheel. Control components fail from heat, vibration, dust and repeated switching. Fuses blow when something else is wrong, such as a motor drawing too much current.
Mechanical items such as adjustable feet can also be damaged by moving the table. Keep a note of what has failed, because repeated failure of the same part usually points to an underlying cause.
What does a thermal relay do and how should it be set?
A thermal relay protects the motor. If the motor draws too much current for too long, for example because the fan is jammed or a phase has dropped out, the relay trips and stops it before the windings overheat.
It has an adjustable current range, and the setting should match the full-load current shown on the motor data plate. Setting it too high removes the protection, and too low causes nuisance tripping. Always choose a relay whose range covers the motor's rating, and leave the setting to a competent person.
Why does my table trip or blow fuses repeatedly?
A fuse is the weakest link by design, so repeated blowing means something is overloading the circuit. Common causes are a failing motor, a jammed or damaged fan wheel, a wiring fault, a failing relay or a transformer problem.
Do not fit a larger fuse to stop it happening, because that removes the protection and can start a fire. Use the rating and type specified for that position, and have a competent person find the cause before the table is used again.
What is the difference between normally open and normally closed switching elements?
A switching element is the contact block behind a push button. A normally open element completes the circuit only when the button is pressed, which is the usual arrangement for a start function. A normally closed element breaks the circuit when pressed, which is the usual arrangement for a stop function.
If you fit the wrong type, the button will do the opposite of what its label says. Check the existing element before you replace it, and test the stop function carefully.