XB4BD21

What the range is

Harmony XB4 is Schneider Electric's range of metal 22 mm pushbuttons, selector switches, key switches, emergency stops and pilot lights, with a chromium-plated (or black) metal bezel. Older parts and many shops still use the Telemecanique name. The same functions exist as 30 mm flush-mounted versions (XB4F / ZB4F), and Harmony XB5 is the plastic, double-insulated twin of the range.

How the part numbers fit together

• Complete unit = body + head. XB4BA31 is the body with its contact (ZB4BZ101) plus the head (ZB4BA3). You can also buy the three loose parts: fixing collar ZB4BZ009, contact block ZBE101 and the head.
• One letter changes the mounting: ZB4B… is the standard 22 mm head, ZB4F… the 30 mm flush version (ZB4BA3 → ZB4FA3).
• Black metal bezel: add 7 to the head (ZB4BD2 → ZB4BD27).
• Push-in terminals: complete units ending in 5 use compact push-in contact blocks (XB4BD335 instead of XB4BD33).
• Selector heads: ZB4BD2 two positions stay put; ZB4BD4 two positions, spring return from right to left; ZB4BD3 three positions stay put; ZB4BD5 spring return to centre; ZB4BD7 / ZB4BD8 spring return from left / right to centre. J instead of D is the long handle (ZB4BJ3), G a key switch, K an illuminated selector.
• Pilot lights: the letter after BV is the voltage (B = 24 V, G = 110–120 V, M = 230–240 V); the last digit is the colour.

Bodies and contact blocks

Contact blocks clip on in up to three rows. Illuminated units take a Universal LED light block (ZBVB1 24 V, ZBVG1 110–120 V, ZBVM1 230–240 V, marked "UN"); one block works with every lens colour.

Ratings for the whole range (Schneider catalogue, January 2026)

• IP66, IP67, IP69, IP69K and UL Type 4X; impact IK06 (the plastic XB5: IK03)
• −40 to +70 °C; up to 10 million operations for pushbuttons
• 22 mm hole, with or without the anti-rotation notch; panel 1–6 mm
• IEC, UL, CSA, CCC, EAC, JIS; marine approvals (BV, Lloyd's Register, DNV)

Individual datasheets can differ from these range figures. The XB4BD33 selector, for example, is rated for 1 million cycles.

Installing

The head holds itself in the panel hole, so one person can fit it. The body clips on from behind and is clamped with its screw (0.8 N·m, max 1.2 N·m); there is no nut, unlike the plastic XB5, whose nut is tightened with tool ZB5AZ905. Terminals take 0.34–1.5 mm² (AWG 22–16), two wires per terminal, at 0.8–1.2 N·m. Schneider says the anti-loosening terminal screws need no periodic retightening. To remove a body, put a flat screwdriver into the black tab and pull it back.

Useful accessories

• Legend holder ZBZ32 (30 × 40 mm) with printed legends such as ZBY2385 "AUTO-O-HAND", ZBY2186 "I-O-II", ZBY2178 "O-I", ZBY2303 "START", ZBY2304 "STOP"; ZBY2101 is blank for engraving
• Guards: ZBZ2102 plastic guard for selectors and key switches; ZBZ1605 metal guard for emergency stops (padlockable)
• Blanking plug ZB4SZ3 (with collar ZB4BZ009) for an unused hole; liquid-spray washer ZB4BZ007 under the head
• 30 mm flush kits ZB4BZ021 (pushbuttons, pilot lights) and ZB4BZ022 (selectors, illuminated pushbuttons)

Metal XB4 or plastic XB5?

They do the same jobs and fit the same 22 mm hole. Choose metal for impact, vibration and heat (e.g. weld spatter), plastic for double insulation and a lower price; both come in high IP versions. Schneider China notes that there XB4 is import-only while XB5 is also made locally. Schneider's cheaper ranges are Easy Harmony XA2 (metal) and XB2 / XB7.

Buying notes

• Look-alikes: many marketplace listings use XB4 codes for unbranded copies, at factory prices around $1 a piece. A seller's video comparing a "high-quality counterfeit" with a genuine contact block shows the copy's NO contact cutting out on a continuity test. Buy from an authorised distributor and check the Schneider marking.
• IP66 vs IP67/IP69K: catalogue section headers quote IP66 for whole groups of products, while the datasheets of individual parts list IP67, IP69 and IP69K. Shops copy either figure.
• Discontinued and missing codes: some complete units are no longer made, e.g. XB4BD73 (January 2022). The heads are usually still sold, so the switch can be built from head + body.
• Problems in use: we found no recurring failure pattern for the range in the forums and reviews we could read; the complaints we found were about counterfeits and wrong listings.