WAT B5 Flange Electric Motor Replacement: Flange Dimensions

When renewing a B5 flange-mounted WAT electric motor, the real question is whether the new motor's flange will seat on the mating flange of the machine. Even with correct power and speed, a different spigot diameter, bolt circle or shaft end means the motor cannot be fitted or will run misaligned. This article covers which B5 flange dimensions to read and measure, what the WAT catalogue says about them and how to compare them with the DRG MOTOR B5 dimension table.

How to recognise B5 in the type code

The WAT type code gives the mounting arrangement in a separate letter group: FA means an A-type (large) flange, i.e. B5; PA is foot-and-flange B35. FB and FC are small-flange B14 versions, while PB and PC are their foot-mounted counterparts. If no flange letter appears, the motor is foot-mounted (B3). In a code beginning "Q3E-FA225M4…", for instance, FA indicates B5, 225M the frame and 4 the number of poles. Vertical arrangements such as V1 or V3 are also possible; in that case state the operating position separately.

Four key values to measure on the flange

IEC designates B5 flange dimensions by letters:

• P – flange outside diameter,
• N – spigot (pilot) diameter that centres the motor on the mating part,
• M – pitch circle diameter of the fixing holes,
• S – hole diameter and number of holes.

Spigot depth (T), flange thickness (LA), shaft diameter × length (D×E), key width (F) and overall motor length (L) also belong on the checklist. Even if the flange fits, a shaft that is too short will not seat the coupling or hub fully; one that is too long may hit the mating part.

WAT and DRG catalogue values side by side

The table shows the B5 flange examples given in the WAT catalogue next to the B5 values in the DRG catalogue by frame. Values are P/N/M/S in mm.

Matching catalogue values do not mean the installation will be trouble-free. For a cast iron WAT electric motor in frame 90, for example, the hole diameter is given as 13.5 mm, so bolts and holes need checking on site. Also, WAT compact types of the same output may sit one frame lower: if your old motor is frame 112 rather than 132, the row you compare against changes too. In short, the same kW and the same 1500 rpm class are not enough on their own; the flange row, shaft and length must be compared together.

For any dimension you are unsure about, measure the old flange with a caliper, photograph it and send it with the nameplate data to DRG MOTOR, so flange and shaft dimensions can be assessed against the DRG catalogue drawing. DRG dimension drawings are available on the technical drawings page.

DRG models with B5 flange that can be assessed

DRG Motor is a manufacturer, supplier and seller of electric motors; its range includes B3, B5 and B35 mounting. Specify the mounting when ordering. Example models in the DRG electric motor shop and their B5 dimensions:

• DRG-90L-4 – 1.5 kW, 4 poles, frame 90L; B5 flange 200/130/165/12, shaft 24×50 mm.
• DRG-112M-4 – 4 kW, 4 poles, frame 112M; B5 flange 250/180/215/14.5, shaft 28×60 mm.
• DRG-132S-4 – 5.5 kW, 4 poles, frame 132S; B5 flange 300/230/265/14.5, shaft 38×80 mm.

If your WAT motor is B14 (small flange, FB/FC), the situation differs: DRG offers a B14 option, but its dimensions are confirmed at order. For other aluminium-housing models, see aluminium housing electric motors.

Frequently asked questions

If the flange dimensions match, will the motor definitely fit?

No. Spigot depth, shaft length, key, motor length and terminal box position also affect installation. A firm decision is only possible after comparing each dimension.

My nameplate shows no flange data; what should I do?

Look for letters such as FA, FB, FC or PA in the type code. If the code is illegible, measure P, N, M and the number of holes directly on the flange and send them.

Can a B35 (foot-and-flange) WAT motor be replaced by a B5-only motor?

If the machine supports the motor by both feet and flange, the role of the feet must be assessed. This depends on the machine design and cannot be confirmed without seeing it.

Is extra information needed for a vertical B5 motor?

Yes. State whether the shaft points up or down and whether there is axial load on the shaft; the bearing arrangement is reviewed on that basis.

Information to send to DRG MOTOR

• Photo of the WAT nameplate and the full type code (including FA/PA/FB/FC letters)
• Flange dimensions: P, N, M, hole diameter S and number of holes
• Spigot depth and flange thickness (if measurable)
• Shaft diameter × length, key width
• Mounting position: horizontal, shaft down or shaft up
• kW, rated speed, voltage/frequency
• Driven machine and connecting element (coupling, hub, pump casing, etc.)

You can send the measurements and photos to our WhatsApp line, add them to the quote list, call +90 (542) 666 11 11 or e-mail info@drgmotor.com. The flange data you provide will be matched against DRG drawings to assess an option. Other channels: contact page.

See current prices of DRG MOTOR electric motors and order online in our storeSEE PRICES →

Technical Sources

• WAT Motor Sanayi ve Ticaret A.Ş. — Ürün Kataloğu (Product Catalogue, Turkish edition) — IM tr 24.0 — Motor type codes (Motor Tip Kodları) — printed page 16 (PDF page 18).
• WAT Motor Sanayi ve Ticaret A.Ş. — Ürün Kataloğu (Product Catalogue, Turkish edition) — IM tr 24.0 — Mounting arrangements, including the locating bearing note (Yapı Şekilleri) — printed page 12 (PDF page 14).
• WAT Motor Sanayi ve Ticaret A.Ş. — Ürün Kataloğu (Product Catalogue, Turkish edition) — IM tr 24.0 — IE3 three-phase aluminium motors, dimensions B3 — printed pages 43–44 (PDF pages 45–46).
• WAT Motor Sanayi ve Ticaret A.Ş. — Ürün Kataloğu (Product Catalogue, Turkish edition) — IM tr 24.0 — IE3 three-phase aluminium motors, dimensions B5, B35 — printed pages 47–49 (PDF pages 49–51).
• WAT Motor Sanayi ve Ticaret A.Ş. — Ürün Kataloğu (Product Catalogue, Turkish edition) — IM tr 24.0 — IE3 three-phase cast iron motors, dimensions B5, B35 — printed pages 77–78 (PDF pages 79–80).