Skip to content
English - United Kingdom
Contact us
  • There are no suggestions because the search field is empty.

Which Hochiki CHQ zone monitor do I need - CHQ-SZM2(SCI) or CHQ-DZM(SCI)?

Compare zone count, EOL options and power needs before choosing CHQ-SZM2(SCI) or CHQ-DZM(SCI).

Direct answer

Use a CHQ-SZM2(SCI) for a single small conventional zone (up to six smoke or heat detectors of the types limited to six, any number of conventional call points, or one beam detector); it is loop powered and takes one loop address. Use a CHQ-DZM(SCI) for two independent conventional zones (up to 30 limited-type detectors per zone, 60 in total, or three beam detectors; call points have no limit); it also takes one loop address but requires an auxiliary 24 V DC supply. Both are addressed with DIL switches before installation, both need an end-of-line device on every zone, and both provide a remote indication output rather than a switched relay contact.

Applies to

  • Products / Models: CHQ-SZM2(SCI), CHQ-SZM2/DIN(SCI), CHQ-DZM(SCI), CHQ-DZM/DIN(SCI)
  • Firmware / Version: Not applicable
  • Region: Not applicable
  • Standards: BS EN 54-18 (input/output devices); BS EN 54-17 (short-circuit isolators, all (SCI) variants). Note that BS EN 54-18 does not prescribe detailed functions; it requires the manufacturer to specify them, so the product data sheet is the controlling document for zone capacity, output ratings and supply requirements.
Resolution / Steps

Key features

  • Zones: the CHQ-SZM2(SCI) provides one conventional zone input; the CHQ-DZM(SCI) provides two independent conventional zone inputs.
  • Remote indication output: the CHQ-DZM(SCI) provides an auxiliary output for local alarm indication, rated 24 V DC at 8.5 mA. The CHQ-SZM2(SCI) provides a remote LED output. Neither is a relay contact and neither is intended to switch plant or ancillary equipment - for switched outputs use a CHQ-DRC2(SCI) dual relay controller or a CHQ-MRC2(SCI) mains relay controller (see Which Hochiki CHQ output module should I use — DRC2, MRC2, DSC2 or PCM?).
  • Auxiliary monitored input: the CHQ-DZM(SCI) provides one general-purpose monitored input in addition to its two zones. On the CHQ-SZM2(SCI) the single fully monitored input is the conventional zone itself; there is no separate auxiliary input.
  • Auxiliary supply: the CHQ-DZM(SCI) is an externally powered module and requires an auxiliary 24 V DC supply. Allow 2 mA quiescent and 70 mA with both zones in fire when sizing that supply and its standby batteries. The CHQ-SZM2(SCI) is loop powered and needs no auxiliary supply. Neither module is a distribution point for powering other equipment.
  • Zone terminals take conventional detectors and call points wired as a conventional circuit. They are not for connecting ESP addressable devices - those go on the addressable loop.
  • Environment: the module is IP21 as supplied. Fit the CHQ-BACKBOX (with suitable glands, not supplied) where IP65 is required. Operating range is -10 °C to +50 °C, 95% RH non-condensing at 40 °C.

Detector quantity limits per zone

The number of detectors allowed on each conventional zone depends on the detector type. Always confirm against the Quantity per zone (CHQ-DZM(SCI)) or Detectors per zone (CHQ-SZM2(SCI)) table in the relevant data sheet before designing a zone.

Detector type CHQ-DZM(SCI), per zone CHQ-SZM2(SCI), per zone
DCA, DFB, DFE No limit No limit
SLG, SLK, SLR, SIF, SIH, SIJ, DCC, DCD, DFJ 30 max 6 max
SPB-ET, SPC-ET, SRA-ET 3 max Only one, and no other detectors
HF-24 Only one, and no other detectors Only one, and no other detectors
DRD-E 15 max 3 max
CCP-E No limit No limit

Typical use cases and configuration rationale

  • Address space mitigation: zone monitors are used when there are insufficient addresses available on an addressable loop. Fitting a zone monitor allows conventional zones (multiple devices on a conventional circuit) to be represented on the loop without using addresses for each conventional device.
  • Avoiding loop overload: installers use zone monitors to prevent exceeding recommended device counts on a single loop.

Wiring and wiring points (practical notes)

  • Connect conventional zone cabling to the zone inputs on the module (one zone on the CHQ-SZM2(SCI), two zones on the CHQ-DZM(SCI)).
  • On the CHQ-DZM(SCI), use the auxiliary monitored input for any required supervised local input function.
  • Connect the auxiliary 24 V DC supply to the module's input terminals, from a supply monitored in accordance with the system design.

End-of-line devices

  • Each conventional zone needs an end-of-line device. On the CHQ-DZM(SCI) choose one of three options with the 2-bit DIL switch: a TE-RH-E Zener EOL (supplied), an LCMU (6K8) (not supplied) active EOL with a 47 µF capacitor, or a 6K8 ± 5% 0.4 W resistor (supplied). The CHQ-SZM2(SCI) uses the TE-RH-E, which is polarity conscious.
  • The CHQ-DZM(SCI) auxiliary monitored input needs its own 10 kΩ ± 5% 0.4 W end-of-line resistor.
  • The CHQ-SZM2(SCI) zone does not support any line continuity option at all, so any call points on it must be wired at the beginning of the zone. On the CHQ-DZM(SCI) the same restriction applies whenever the Zener (TE-RH-E) EOL option is selected; the active (LCMU) and resistive (6K8) options do support line continuity.

Setting the address

CHQ modules are addressed with the first seven switches of the 8-bit DIL switch, set before installation. Note that the switch sense is reversed between the standard and DIN versions: on a standard CHQ module, switch up is ON; on a DIN module, switch up is OFF. These modules are not addressed with a hand-held programmer.

Operational guidance (field practice)

  • Use zone monitors when loop addressing limits would otherwise be exceeded; this is a standard field approach to add conventional zones without consuming multiple loop addresses.
  • Ensure the correct mapping of conventional zone wiring to the module's zone inputs (one on the CHQ-SZM2(SCI), two on the CHQ-DZM(SCI)) so each conventional circuit is represented correctly on the addressable loop.
When to contact technical support

Contact Hochiki Europe Technical Support if you need the exact model number, terminal layout or wiring diagram for a specific zone monitor, or if loop address usage or zone mapping does not behave as described in this article.

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

Last reviewed: 2026-10-12 — Reviewed by: Hochiki Europe Technical Support