Technical Data · Publication 440R-TD001 · Rockwell Automation
Guardmaster Minotaur Safety Relay (MSR) Specifications
Specifications, wiring, and selection data for the Allen-Bradley Guardmaster Minotaur safety relay (MSR) family on Bulletin 440R — monitoring relays for E-stop, safety gate, light-curtain, two-hand control, and expansion applications with mechanical safety contacts up to Cat. 4 PLe / SIL 3.
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Specifications
Safety Performance (per model)
| MSR5T Monitoring | Cat. 4 PLe per ISO 13849-1; SIL 3 per IEC 61508/62061; Stop Cat. 0; 3 N.O. safety + 1 N.C. aux |
|---|---|
| MSR117T Single-function | Cat. 4 PLe / SIL 3; PFHd < 2.53 × 10⁻⁹; MTTFd > 425 yr; 3 N.O. + 1 N.C. aux |
| MSR125H/HP Two-hand | Cat. 4 PLe / SIL 3 / Type IIIC per ISO 13851; PFHd < 1.44 × 10⁻⁹; MTTFd > 385 yr; 2 N.O. |
| MSR126R/T | Cat. 4 PLe / SIL 3; PFHd < 1.45 × 10⁻⁹; MTTFd > 398 yr; 2 N.O. safety; OSSD or dual-channel N.C. inputs |
| MSR127RP/TP | Cat. 4 PLe / SIL 3; PFHd < 1.45 × 10⁻⁹; MTTFd > 398 yr; 3 N.O. + 1 N.C. aux |
| MSR131RTP | Cat. 4 PLe / SIL 3; PFHd < 1.67 × 10⁻⁹; MTTFd > 389 yr; 3 N.O. safety + 2 N.C. + 2 SS aux |
| MSR132E / MSR132ED expansion | MSR132E: Cat. 4 PLe / SIL 3 (immediate) · MSR132ED: Cat. 3 PLd / SIL 2 (delayed); 4 N.O. safety + 2 N.C. aux |
| MSR138DP / MSR138.1DP delayed | Immediate outputs Cat. 4 PLe / SIL 3; delayed outputs Cat. 3 PLd / SIL 2; 0.15–30 s configurable delay |
| MSR142RTP | Cat. 4 PLe / SIL 3; PFHd < 1.92 × 10⁻⁹; MTTFd > 210 yr; 7 N.O. safety + 4 N.C. + 2 PNP aux |
| CU4 off-delay timer | Cat. 3 PLd / SIL 2; PFHd < 2.16 × 10⁻⁹; MTTFd > 345 yr; 2 N.O. timed + 1 N.C. aux; 0.15–30 s |
| Stop category | 0 for all (1 for MSR132ED, MSR138DP delayed outputs, CU4) |
Electrical
| Power supply variants | 24V AC/DC, 24V DC, 115V AC, 230V AC (model-dependent) |
|---|---|
| Power consumption | 2 W (MSR5T, MSR117T, MSR125H/HP, MSR127RP/TP) up to 5 W (MSR142RTP) |
| Input types accepted | Single-channel N.C., dual-channel 2 N.C., OSSD (solid-state from light curtain), 2 PNP, two-hand; Type IIIC per ISO 13851 on MSR125 |
| Input resistance, max | 25 Ω (MSR117T) – 200 Ω (MSR5T); cross-fault checking when wired with 2 N.C. |
| Reset modes | Automatic, Manual, or Monitored Manual (per model) |
| Response time | 15 ms (MSR117T/126R/126T/127/131/138/142) – 50 ms (MSR132E) – 90 ms (MSR5T dropout) |
| Thermal current Ith | 3 A to 7 A per contact path, model-dependent (e.g., MSR142RTP 7 × 4 A) |
| Utilization (UL) | B300 / R300 — 5 A @ 250V AC / 4 A @ 24V DC typical |
| Utilization (IEC 60947-5-1) | AC-15: 5–6 A @ 250V AC; DC-13: 3 A @ 24V DC |
| Rated impulse withstand | 2500V |
| Fuses, output | External 6 A slow-blow or 10 A fast-acting (MSR5T: 5 A quick-acting) |
Modular Architecture & Expansion
| Single-function base relays | MSR117T, MSR126R/T, MSR127RP/TP, MSR131RTP — feed up to 3 safety outputs directly |
|---|---|
| Expansion module | MSR132E (immediate) / MSR132ED (off-delayed 0.5–4 s fixed) — adds 4 N.O. safety outputs, driven by a host relay |
| Delayed-output base | MSR138DP — 3 N.O. delayed + 2 N.O. immediate · MSR138.1DP — 2 N.O. delayed + 2 N.O. immediate · delay 0.15–30 s depending on cat no. |
| Off-delay timer | CU4 — standalone or host-extension; 0.15–30 s depending on cat no.; used for Power-to-Lock guard-door hold (e.g., TLS2-GD2) |
| High-output monitoring base | MSR142RTP — 7 safety + 4 aux + 2 PNP solid-state in a single 67.5 mm housing |
| Two-hand control base | MSR125H (fixed terminals) / MSR125HP (removable) — 0.5 s input-simultaneity enforcement per ISO 13851 |
| Typical system | Base relay (MSR127/131/138) monitors E-stop or gate → feeds MSR132E/ED expansion → drives contactors M/K1/K2 with feedback loop |
Environmental & Physical
| Enclosure / terminal rating | IP40 enclosure (NEMA 1, DIN 0470) / IP20 terminals (DIN 0470) |
|---|---|
| Operating temperature | −5 to +55 °C (23 to 131 °F); MSR5T −10 to +55 °C |
| Humidity | 90% max non-condensing |
| Vibration | 10–55 Hz, 0.35 mm peak (0.75 mm on MSR5T) |
| Shock | 10 g, 16 ms half-sine, 100 shocks (30 g / 11 ms on MSR5T) |
| Mechanical life | 2,000,000 operations |
| Mounting | 35 mm DIN rail; 22.5 mm wide (MSR5T/117T/125/127/CU4), 45 mm wide (MSR131/132/138/142) |
| Weight | 165 g (CU4) to 607 g (MSR142RTP, 115/230V) |
| Conductor size | 0.2–4 mm² (24–12 AWG); screw or spring-clamp terminals |
| Pollution degree | 3 (MSR5T, VDE 0110 Installation Group C) |
Catalog Number Format
How to read an Allen-Bradley 440R catalog number. Each position encodes a specific configuration attribute.
Position
Meaning
Example
440R
Bulletin prefix for Guardmaster safety relays
440R-B23020 → Bulletin 440R
-B / C / D / E / G / M / N / S
Series letter encodes the MSR model family
B = MSR5T, C = MSR131RTP, D = MSR125H/HP, E = MSR132E/ED, G = MSR142RTP, M = MSR138DP, N = MSR126R/T, S = CU4
23xxx / N23xxx / C23xxx / E23xxx / M23xxx / G23xxx / S23xxx
Feature + supply + terminal configuration within the series
440R-N23117 = MSR126T, 24V AC/DC, Auto/Manual reset; 440R-N23120 = MSR126.1R, 24V AC/DC, Monitored Manual
Terminal & reset suffix
Fixed vs removable (H vs HP) and Auto/Manual vs Monitored Manual reset embedded in catalog number
MSR125H = fixed terminals; MSR125HP = removable terminals (same safety function)
Typical catalog examples
Full catalog numbers assembled from model + supply + reset + terminals
440R-B23020 (MSR5T 24V AC/DC); 440R-D23166 (MSR125H 24V DC); 440R-C23139 (MSR131RTP 24V AC/DC); 440R-G23216 (MSR142RTP 24V AC/DC); 440R-S23173 (CU4 0.15–3 s)
Communication Protocols
Supported industrial networks and field buses for the products covered by this publication.
Hardwired safety circuit All MSR relays operate with hardwired inputs (N.C. contacts, OSSD, or PNP) — no fieldbus
Cross-fault monitoring Dual-channel N.C. inputs are cross-fault checked internally by the relay (MSR126, MSR127, MSR131, MSR138, MSR142)
OSSD input compatibility MSR126R, MSR127RP/TP, MSR131RTP, MSR138DP, MSR142RTP accept solid-state outputs from light curtains and safety scanners (external device performs cross-fault)
Relay chaining Host base relay drives MSR132E/ED expansion via monitored feedback loop to mirror contacts in a Cat. 4 PLe system
Guard-lock interface CU4 off-delay timer supports Power-to-Lock interlocks such as TLS2-GD2 for fixed-duration lock hold after stop
Certifications & Compliance
cULus Listed — UL 508 Industrial Control Equipment
CE Marked for all applicable EU directives
UKCA Marked for all applicable UK regulations
TÜV certified — ISO 13849-1 PLe Cat 4, IEC 61508 SIL 3, IEC 62061
ISO 13851 Type IIIC two-hand control (MSR125H/HP only)
C-Tick / RCM (Australia / New Zealand)
IEC 60664-1 — insulation coordination
Semi F47-0706 — voltage-sag ride-through (MSR5T)
Document Contents
Full PDF covers the following topics in detail:
- Why use Minotaur safety relays — fault detection, switching assurance, manual reset
- MSR5T Monitoring Safety Relay — 3 N.O. + 1 N.C., 24V AC/DC, Cat. 4 PLe
- MSR117T Single-function Safety Relay — 3 N.O. + 1 N.C., Auto/Manual or Monitored Manual reset
- MSR125H / MSR125HP Two-hand Control Safety Relay — 0.5 s simultaneity, Type IIIC per ISO 13851
- MSR126R / MSR126T / MSR126.1R / MSR126.1T Single-function relays — 2 N.O., OSSD or dual-channel inputs
- MSR127RP / MSR127TP Single-function Safety Relays — 3 N.O. + 1 N.C., OSSD-compatible
- MSR131RTP Single-function Safety Relay — 3 N.O. + 2 N.C. + 2 solid-state aux, versatile inputs
- MSR132E / MSR132ED Expansion Safety Relays — 4 N.O. + 2 N.C., immediate or 0.5–4 s off-delayed
- MSR138DP / MSR138.1DP delayed-output relays — 2 N.O. immediate + 3 (or 2) N.O. delayed, 0.15–30 s
- MSR142RTP Single-function Safety Relay — 7 N.O. + 4 N.C. + 2 PNP, high output count
- CU4 Off-delay Timing Relay — 2 N.O. timed + 1 N.C., 0.15–30 s, for Power-to-Lock / guard-door hold
- Typical wiring diagrams: single- and dual-channel E-stop, safety gate (auto/monitored reset), light curtain, two-hand control, contactor monitoring, expansion cascades
- Block diagrams and status indicator tables for each MSR model
- Approximate dimensions, terminal-block accessory kits (440R-A23209 screw, 440R-A23228 spring-clamp)
Frequently Asked Questions
Which Minotaur relay should I pick for a single-zone E-stop or safety-gate circuit?
For a small machine with two or three safety contactors to drop, an MSR126T (dual-channel N.C. with automatic reset) or MSR117T (3 N.O. + 1 N.C. aux with monitored manual reset) covers most cases at Cat. 4 PLe / SIL 3. If you also need light-curtain OSSD input support, move up to an MSR127RP/TP (three safety contacts + aux, OSSD-compatible). Use an MSR131RTP when you want two solid-state aux outputs for PLC status feedback in addition to the mechanical contacts. Two-hand control is a different rubric — see MSR125H/HP.
When do I need an expansion module vs. a larger single-function relay?
If the base relay's 2–3 safety outputs aren't enough to drop all your contactors directly, add an MSR132E (4 more immediate N.O.) or MSR132ED (4 off-delayed N.O., 0.5/1/2/3/4 s fixed) — the expansion mirrors the host's state through a monitored feedback loop and keeps the whole chain at Cat. 4 PLe. Alternatively, use a single MSR142RTP which provides 7 N.O. safety + 4 N.C. aux in one unit, eliminating the expansion module. Expansion is the right choice when you need delayed drop-out (e.g., motor stop before guard-lock release); single-unit is cleaner when you just need more contacts.
When would I use a CU4 off-delay timer instead of an MSR138DP?
Both produce delayed outputs for Power-to-Lock guard-door interlocks and motor-stop sequencing. The MSR138DP is a complete safety relay — it monitors the E-stop/gate input and directly produces both immediate and delayed outputs, Cat. 4 PLe on the immediate channel and Cat. 3 PLd on the delayed channel. The CU4 is a pure timing extension (Cat. 3 PLd) that is driven by a separate host relay (typically an MSR124RT) — use CU4 when you want to keep the timing logic independent from the primary safety relay or add delay to an existing Cat. 3 installation.
Are Minotaur MSR relays OSSD-compatible?
The outputs are always mechanical relay contacts (2 to 7 N.O., model-dependent) — not solid-state OSSDs. On the input side, several models (MSR126R, MSR127RP/TP, MSR131RTP, MSR138DP, MSR142RTP) explicitly accept OSSD signals from light curtains or safety scanners; in those cases, the connected device must perform its own cross-fault detection because the MSR doesn't pulse-test OSSD inputs. For mechanical N.C. dual-channel inputs, the MSR performs cross-fault checking internally. If you need OSSD outputs from the safety controller itself, step up to the MSR200/MSR300 modular family or GSR series (separate publications) — this document covers only the legacy Minotaur mechanical-output relays.
What's the difference between MSR126R and MSR126T (and the 126.1R / 126.1T variants)?
MSR126R / 126.1R use Monitored Manual reset (requires a momentary N.O. switch to re-enable outputs after the inputs are restored) — appropriate for E-stop and safety-gate circuits where a deliberate human reset is required. MSR126T / 126.1T use Auto/Manual reset (can be jumpered automatic or configured manual). The .1 variants accept dual-channel 2 N.C. inputs (with cross-fault monitoring); the non-.1 variants accept OSSD or single-channel N.C. All four share the same 2 N.O. safety-output architecture at Cat. 4 PLe / SIL 3.
Can I control a TLS-series guard-locking switch with a Minotaur relay?
Yes — the typical topology is a base MSR (e.g., MSR131RTP or MSR124RT) monitoring the E-stop / machine stop, driving both the main contactors and a CU4 off-delay timer. The CU4 holds the TLS2-GD2 solenoid energized (Power-to-Lock) for a configurable 0.15–30 s after the stop command, ensuring hazardous motion has fully ceased before the guard can be unlocked. See Figure 34 in the publication for the dual-channel wiring example and Figure 35 for single-channel. The 700S safety contactors and SK-series accessories referenced in broader Guardmaster literature are covered in separate publications (440R-SG001 selection guide, SAFETY-TD001).
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