How many contact blocks can be stacked on a Harmony ZB4 or ZB5 22 mm operator ?
1. What you need to know
A standard non-illuminated 22 mm Harmony pushbutton accepts up to 9 single contact blocks — 3 side by side, 3 rows deep. The maximum drops with more complex heads: up to 6 behind selector switches and illuminated push-buttons, 4 behind illuminated selector switches and emergency stop buttons, 3 behind push-push buttons and 2 when those are illuminated.
2. How contact block stacking works
Contact blocks mount at the back of the button head on a fixing collar. The number of possible contact blocks behind a button depends on its head type and if it is illuminated or not. The contact blocks are designed for direct stacking, with no extra accessories required.
- A single contact block (1 NO or 1 NC) occupies 1 row; a double contact block occupies 2 rows.
- Full-capacity layout for spring return pushbutton : 3 rows of 3 single contacts (9 contacts), or 1 row of 3 double contacts + 1 row of 3 single contacts.
- When a light block is installed, it is not possible to add any contact block on its column.
3. Maximum number of contact blocks by operator type
Respect of the following specifications will ensure compliance with the catalog specifications.
| Harmony operator type | Maximum single contact blocks | Stacking | Sample reference |
| Spring return Triple-headed spring return | 9 | Spring return : ZB4BA3 | |
| Illuminated spring return Illuminated double-headed spring return | 6 | Spring return : ZB4BW343 | |
| Double-headed pushbutton | 6 | ZB4BL7341 | |
| Selector switch | 4 to 6 – depends on contact block organization | ZB4BD3 | |
| Illuminated selector switch Illuminated push-pull mushroom head | 4 | Selector switch : ZB4BK1213 | |
| Push-pull / turn to release mushroom head Emergency stop or switching off head | 4 (3 on first row, and 1 on second row in any position) | Push-pull : ZB4BT2 Emergency stop : ZB4BS844 | |
| Push-push | 3 | ZB4BH06 | |
| Illuminated push-push | 2 | ZB4BH053 |
4. Related references
| Type | Reference | Description |
| Spring return head | Push button head, metal, flush, green, Ø22, spring return, unmarked | |
| Illuminated Spring return head | Illuminated push button head, Harmony XB4, metal, red flush, 22mm, universal LED, spring return, plan lens, unmarked | |
| Spring return double-headed | Green flush/red flush illuminated double-headed pushbutton head Ø22 with marking | |
| Selector switch | Black selector switch head, metal, Ø22, 3 positions, stay put | |
| Illuminated selector switch | Illuminated selector switch head, Harmony XB4, metal, white handle, 22mm, universal LED, 2 positions, stay put | |
| Push-pull head | Black Ø40 mushroom pushbutton head Ø22 latching push-pull | |
| Emergency stop head | Emergency stop head, switching off, metal, red mushroom Ø40, Ø22, trigger turn to release | |
| Push-push head | Blue flush pushbutton head Ø22 push-push unmarked | |
| Illuminated push-push head | Illuminated push button head, Harmony XB4, metal, orange flush, 22mm, universal LED, push-push, unmarked | |
| Single NO contact block screw clamp or compact push-in terminals | Single NO contact block screw clamp or compact push-in terminals | |
| Single NC contact block screw clamp or compact push-in terminals | Single NC contact block screw clamp or compact push-in terminals | |
| LED light block | Integrated LED light block, white, 24 V — reduces available rows | |
| Fixing collar | Metal fixing collar |
Note : Those products are also available in plastic versions through XB5 range.
Launch Product Selector on se.com to configure a Harmony pushbutton according to your requirements or contact Schneider Electric Technical Support to check a configuration against your control scheme.