How do I install a SOC-E-IS smoke detector in a hazardous area?

Direct answer

Fit the SOC-E-IS only to the intrinsically safe base YBN-R/4IS (white version YBN-R/4IS(WHT)), and wire the zone through a certified shunt safety Zener diode barrier (30 V, 200 mA, 1 W or less) or one channel of a certified galvanic isolator such as the P&F KFD0-CS-Ex1.51P or KFD0-CS-Ex2.51P. Up to 20 detectors are permitted per channel. Non-I.S. bases such as the YBO-R/6RN must not be used, and the YBN-R/4IS base must not be fitted with any non-I.S. detector head.

Applies to

• Products / Models: SOC-E-IS, SOC-E-IS(WHT); base YBN-R/4IS, YBN-R/4IS(WHT) (also written YBN-R/4(IS) and YBN-R/4(WHT)-IS in older documents); the SOC-E-IS superseded the previous intrinsically safe photoelectric detector in 2020, so earlier installations may carry that detector
• Firmware / Version: Not applicable
• Region: UK / Europe
• Standards: BS EN 54-7 (point smoke detectors); BS EN 60079-11:2012 (intrinsic safety “i”); ATEX classification II 1 G Ex ia IIC T5, −20 °C ≤ Ta ≤ +55 °C, certificate BASEEFA19ATEX0143X; IECEx BAS 19.0122X. Suitable for Category 1, 2 or 3 hazardous atmospheres.

Key intrinsic-safety features and requirements

• The SOC-E-IS is an intrinsically safe conventional photoelectric smoke detector for hazardous areas (ATEX Category 1, 2 or 3). To bring it onto a Hochiki ESP addressable system, interface it through a CHQ-DZM(SCI)-IS dual zone module — up to 40 I.S. conventional detectors, 20 per zone — installed in the safe area. Where a zone uses a galvanic isolator and carries 10 or fewer detectors (call points do not count), fit an additional 27 kΩ resistor across the zone terminals of the CHQ-DZM(SCI)-IS itself, not at the end of the line, to prevent intermittent open-circuit fault signals.
• For intrinsically safe installations the SOC-E-IS must be mounted to an intrinsically safe detector base: YBN-R/4IS.
• The SOC-E-IS and its base must be used with either a certified shunt safety Zener diode barrier or one channel of a certified galvanic isolator, installed in the safe area in accordance with the system drawing in the product installation instructions (2-3-0-2853). There is no arrangement in which the detector is connected to a control panel without a barrier or isolator. For choosing the barrier or isolator, see Which intrinsic safety barrier can I use with the SOC-E-IS and YBN-R/4IS?
• Hochiki interface modules described as “I.S. compatible”, such as the CHQ-DZM(SCI)-IS and CHQ-ISM, are not themselves intrinsically safe and must be installed in the safe area with the barrier. I.S. sounders and beacons are driven through a CHQ-ISM, with only one I.S. sounder or beacon per barrier channel.

Compatible and incompatible bases

• Compatible base for I.S. use:
  • YBN-R/4IS — the intrinsically safe mounting base to be used with SOC-E-IS in hazardous areas.
• Incompatible base (do not use with SOC-E-IS in hazardous areas):
  • YBO-R/6RN — this is not an intrinsically safe base and must not be used for intrinsically safe installations.
• The YBN-R/4IS base may only be used with Hochiki intrinsically safe detector heads. Fitting any other detector head to it is expressly forbidden and may cause fire or explosion.

Wiring and enclosure considerations

• Power and interface:
  • The detector’s supply, the zone wiring and any remote indicator wiring (base terminal 4; LED only, 20 mA maximum, with an LED body surface area of 230 mm² or more) must be routed through a certified Zener diode barrier or galvanic isolator, so that circuits in the hazardous area remain within the allowed I.S. energy limits.
• Use of mounting enclosures and cable entry:
  • The SOC-E-IS is rated IP42 and is for indoor use only. Where armoured cable, glands or a junction box are needed, the arrangement must be assessed against the certification: any additional cable length counts towards the interconnecting-cable capacitance and inductance limits, and any enclosure used in the hazardous area needs its own certification for that area. Confirm the arrangement with the barrier or isolator manufacturer and with Hochiki technical support before installing. Ensure the selected mounting base is the designated intrinsically safe base (YBN-R/4IS) when installing in a hazardous area.
• Do not substitute a non-I.S. base for the intrinsically safe base even if mechanical fit appears compatible. Using a non-I.S. base renders the installation unsuitable for hazardous areas.

Limits set by the certification

• Up to 20 SOC-E-IS detectors with YBN-R/4IS bases per certified channel, plus up to 20 certified simple-apparatus devices such as CCP-E-IS call points.
• Zener barrier: 30 V or less, 200 mA or less, 1 W or less. The barrier earth needs a high-integrity connection equivalent to a 4 mm² insulated copper conductor, with less than 1 ohm to the main power system earth.
• Galvanic isolator: one channel of a certified isolator; the barrier earthing requirement above does not apply.
• Interconnecting cable maxima — group IIC: 0.07 µF, 0.62 mH, 36 µH/ohm; IIB: 0.56 µF, 1.86 mH, 1456 µH/ohm; IIA: 1.82 µF, 4.96 mH, 286 µH/ohm.
• End-of-line resistor: body surface area 230 mm² or more.
• Cable screen, if used: earthed only within the safe area, isolated from the circuit, and able to withstand 500 V AC for one minute.
• The hazardous-area circuit must withstand an a.c. test voltage of 500 V to earth, or to the equipment frame, for one minute without breakdown.
• A durable label identifying the certified system must be fitted on or next to the principal item of electrical apparatus, or at the interface between the intrinsically safe and non-intrinsically safe circuits. The marking must include the word SYST or SYSTEM, for example “System No. BAS Ex 98D2264”.
• The installation must also comply with national requirements.

The exact figures and the system drawing are in the product installation instructions (2-3-0-2853); always work from the current issue.

Practical steps for hazardous-area installations

1. Select the SOC-E-IS detector for the hazardous area detection point.
2. Use the YBN-R/4IS mounting base for hazardous-area installations.
3. Route the detector supply, zone wiring and any remote indicator wiring through a certified Zener diode barrier or one channel of a certified galvanic isolator; there is no arrangement that connects the detector to a control panel without a barrier or isolator.
4. If armoured cable, glands or a junction box are needed, confirm the arrangement with the barrier or isolator manufacturer and with Hochiki technical support before installing — any additional cable length or enclosure must be assessed against the certification limits.
5. Do not use non-I.S. bases such as YBO-R/6RN in hazardous areas.
6. Fit the durable system identification label and carry out the 500 V a.c. test to earth before handing the circuit over.

When to contact technical support

• You are not sure whether your Zener diode barrier or galvanic isolator model meets the certified parameters above.
• You want to design a circuit with more than 20 SOC-E-IS detectors, or more than 20 simple-apparatus devices, on one channel.
• You need to use armoured cable, cable glands or a junction box and want the arrangement checked against the certification.

Safety note

This article is general guidance for Hochiki Europe products. Design, installation, commissioning, maintenance and modification of fire detection and alarm systems should be carried out by, or under the responsibility of, a competent person in accordance with the applicable standards (for example BS 5839-1 in the UK). Statutory requirements imposed by the relevant enforcing authority also apply. Always refer to the current product manual and data sheet for the exact model before carrying out any work.

References

• SOC-E-IS Installation Instructions, 2-3-0-2853 (ISS1, January 2020)
• SOC-E-IS Specification (ISS6, September 2025)
• YBN-R/4IS Specification (ISS4, March 2026)
• CHQ-ISM Installation Instructions, 2-3-0-1469 (ISS7)

Last reviewed: 2026-10-23 — Reviewed by: Hochiki Europe Technical Support