How to specify a replacement Ex-rated fan motor

When an HVAC fan motor fails in a hazardous area, the replacement must match more than power and speed. It must also match the area classification and the protection concept of the original installation. A motor that is correct in every mechanical detail can still be wrong for the site.

This guide lists the information we ask for on every Ex motor request. If you send it with your first email, we can usually quote without further questions.

1. A clear photo of the nameplate

The nameplate tells us most of what we need: maker, type, frame size, power, voltage, frequency, speed, insulation class and the Ex marking. Take the photo straight on, in good light, and make sure the full marking string is readable.

If the nameplate is painted over or corroded, send the motor tag number and any data you have from the equipment register or the original datasheet.

2. The Ex marking and the area classification

The Ex marking on the motor shows how it is protected (for example Ex db for flameproof or Ex eb for increased safety), the gas group (IIA, IIB or IIC) and the temperature class (T1 to T6). The area classification drawing for the installation shows what the location requires.

Tell us both. If the original motor was over-specified for the area, a different protection concept may be available sooner or at lower cost. If the area classification has changed since the motor was installed, the replacement must meet the current classification.

3. Mounting and shaft details

A replacement motor must fit the existing fan and base. We need:

• Mounting arrangement (for example B3 foot, B5 flange, B35 foot and flange)
• Frame size and shaft diameter
• Terminal box position
• Any special features, such as anti-condensation heaters or thermistors

4. How the motor is driven

Tell us if the motor runs direct-on-line, through a soft starter or through a variable speed drive. A motor used on a drive in a hazardous area must be certified for that use, and the certificate may set conditions for the drive and the motor protection.

5. The documents you need

Most operators need a certificate of conformity, the IECEx or ATEX certificate for the motor type, and the maker’s instructions. Some also need a routine test report, a certificate of origin or material certificates. Tell us at the start, because some documents must be requested from the maker when the order is placed.

Common causes of delay

• Only the old part number is given. Many motor part numbers change when a model is updated. A nameplate photo removes the guesswork.
• The temperature class is missing. A T3 motor cannot replace a T4 motor.
• The drive arrangement is not known. This can change which motors are acceptable.
• Document needs arrive late. Adding test reports after dispatch can add weeks.

If you have a motor to replace, send us the nameplate photo and your area classification. We will confirm the correct replacement and the lead time.