How do the ZBZG156 and ZBZM156 lamp test blocks work?
1. What you need to know
A lamp test lets an operator light every pilot light on a panel at once from a single external push button, to check that no light source has failed. The ZBZG156 and ZBZM156 blocks feed the test voltage to each light block through diodes. The choice depends on the light block: ZBZG156 (one diode) for AC/DC LED blocks ZBVJx, ZBVBx and ZBVBGx; ZBZM156 (two diodes) for the 120 V and 230 V ACProtected LED blocks ZBVGx and ZBVMx. Used with ZBVGx or ZBVMx blocks, a ZBZG156 produces only a short light pulse, because of the coupling capacitor at the block input the test then proves nothing.
2. How the lamp test works
Each pilot light keeps it normal control contact. The lamp test adds a second, common supply path from a single test push button to every light block at once.
- Pressing the test button applies the test voltage to all the pilot lights simultaneously.
- The diodes in the ZBZ block route that voltage to each light block while keeping the pilot light circuits separated from one another.
- Releasing the button returns every pilot light to its normal state, so the test button should be a momentary (spring return) operator.
- The failure mode is silent: a ZBZG156 wired to ZBVGx or ZBVMx blocks does light them - briefly. An operator can read that flash as a passed test.
Wiring from the instruction sheet: ZBZG156 on the left, for AC/DC light blocks; ZBZM156 on the right, for 120 V / 230 V AC light blocks.
3. ZBZG156 vs ZBZM156
| ZBZG156 | ZBZM156 | |
|---|---|---|
| Construction | Single block - one diode | Double block - two diodes |
| Rated voltage | 12 and 24 V AC/DC, 24-120 V AC/DC | 48-230 V AC |
| Compatible light blocks | ZBVJ- (12 V AC/DC), ZBVBx (24 V AC/DC), ZBVBGx (24-120 V AC/DC), ZBV6x (BA 9s bulb holder) | ZBVGx (120 V AC) and ZBVMx (230 V AC), theProtected LED blocks |
| Result with ZBVG- / ZBVM- | A short light pulse only - not a valid lamp test | Continuous lighting for as long as the test button is held a valid lamp test |
| Why | The coupling capacitor at the input of ZBVGx / ZBVMx blocks limits the lighting time through a single diode | The two-diode arrangement is designed for these blocks |
| Wiring | Left-hand diagram of the instruction sheet | Right-hand diagram of the instruction sheet |
4. Schneider Electric references
| Function | Reference | Product description |
|---|---|---|
| Lamp test block - single | ZBZG156 | Single block for the lamp test function, 12 and 24 V AC/DC and 24-120 V AC/DC. One diode. |
| Lamp test block - double | ZBZM156 | Double block for the lamp test function, 48-230 V AC. Two diodes. Required for ZBVGx and ZBVMx light blocks. |
| LED light block, 12 V AC/DC | ZBVJ3 | Integral LED light block, green. The last digit sets the colour. Test with ZBZG156. |
| LED light block, 24 V AC/DC | ZBVB3 | Integral LED light block, green. Test with ZBZG156. |
| LED light block, 24-120 V AC/DC | ZBVBG3 | Integral LED light block, green, wide voltage range. Test with ZBZG156. |
| LED light block, 120 V AC | ZBVG3 | ""Protected LED" ight block, green, with input coupling capacitor. Test with ZBZM156 only. |
| LED light block, 230 V AC | ZBVM3 | "Protected LED" light block, green, with input coupling capacitor. Test with ZBZM156 only. |
| Bulb holder, BA 9s | ZBV6 | Light block for BA 9s bulb, listed on the instruction sheet as compatible with ZBZG156. |
The wiring instruction sheet "ZBZG156, ZBZM156 Wiring test pilot light" is available on both product pages on se.com. Contact Schneider Electric technical support to validate a lamp test circuit mixing several light block types.
Released for: Schneider Electric Macedonia
