Product Description
WEG RW27-2D3-U040 Thermal Overload Relay — 25–40A, Class 10
The WEG RW27-2D3-U040 is a 3-pole bimetallic thermal overload relay with an adjustable current range of 25.0–40.0 Amps and Class 10 trip characteristics. It includes phase loss protection, current unbalance protection, and built-in 1 NO + 1 NC auxiliary contacts. The RW27-2D3-U040 direct-mounts to WEG CWB40, CWB50, CWB65, CWB80, and CWBN2 contactors. It is the largest range in the RW27-2D3 series — for higher current applications on CWB40 and above, the next series is the RW67-5D3.
⚠ Note on Current Range
The RW27-2D3-U040 is adjustable from 25.0 to 40.0 Amps per the WEG catalog. Set the dial to your motor’s nameplate full-load amperage (FLA). Do not select this range if your motor FLA is below 25A — use the RW27-2D3-U032 (22–32A) for motors in that range.
Quick Specifications
- Part Number: RW27-2D3-U040
- Current Range: 25.0–40.0A (adjustable dial)
- Poles: 3-pole (three-phase applications)
- Trip Class: Class 10 (trips in ≤10 seconds at locked rotor current)
- Phase Loss Protection: Yes — 4th bimetal strip detects phase loss
- Current Unbalance Protection: Yes
- Aux Contacts: 1 NO + 1 NC (built-in)
- Reset: Manual or automatic (selectable)
- Compatible Contactors: CWB40, CWB50, CWB65, CWB80, CWBN2 (direct mount)
- Frequency: 50/60 Hz rated; operable to 400 Hz (see VFD note below)
- Series: RW27-2D (CWB contactor series overload)
- Certifications: UL, CSA, IEC/EN 60947-4-1, CE
RW27-2D3 Series — Full Range Selection Guide
Select the range that covers your motor’s nameplate full-load amperage (FLA). Set the adjustment dial to the motor’s exact FLA. The RW27-2D3-U040 is the largest range in the RW27-2D3 series.
| Part Number | Current Range (A) | Compatible Contactors |
|---|---|---|
| RW27-2D3-D004 | 0.28–0.40 | CWB9–CWB38 |
| RW27-2D3-D008 | 0.56–0.80 | CWB9–CWB38 |
| RW27-2D3-D012 | 0.80–1.20 | CWB9–CWB38 |
| RW27-2D3-D018 | 1.20–1.80 | CWB9–CWB38 |
| RW27-2D3-D028 | 1.80–2.80 | CWB9–CWB40 |
| RW27-2D3-U004 | 2.8–4.0 | CWB9–CWB40 |
| RW27-2D3-D063 | 4.0–6.30 | CWB9–CWB40 |
| RW27-2D3-U008 | 5.6–8.0 | CWB9–CWB40 |
| RW27-2D3-U010 | 7.0–10.0 | CWB9–CWB40 |
| RW27-2D3-D125 | 8.0–12.5 | CWB9–CWB40 |
| RW27-2D3-U015 | 10.0–15.0 | CWB12–CWB40 |
| RW27-2D3-U017 | 11.0–17.0 | CWB12–CWB40 |
| RW27-2D3-U023 | 15.0–23.0 | CWB18–CWB40 |
| RW27-2D3-U032 | 22.0–32.0 | CWB32–CWB40 |
| RW27-2D3-U040 (this item) | 25.0–40.0 | CWB40–CWB80, CWBN2 |
WEG RW Series — Overload Family for CWB Contactors
The RW27-2D3 is the entry-level overload series for WEG CWB contactors. Larger CWB contactors require the next overload series up. Note that these are CWB-series overloads (RW27-2D3) and are not interchangeable with the older CWM-series overloads (RW27-1D3).
| Overload Series | Current Coverage | Compatible Contactors |
|---|---|---|
| RW27-1D3 | 0.28–50A | CWM9–CWM40 (legacy CWM series) |
| RW27-2D3 | 0.28–40A | CWB9–CWB80, CWBN0–CWBN2 (CWB series) |
| RW67-5D3 | 25–80A | CWB40–CWB80, CWBN2 (larger frame) |
| RW117-3D3 | 63–140A | CWB95–CWB125, CWBN3 |
Product Features
- 25.0–40.0A Adjustable Range: The RW27-2D3-U040 covers motors with a full-load amperage from 25.0 to 40.0 Amps. Set the adjustment dial to the motor’s nameplate FLA. This is the top range of the RW27-2D3 series. For FLA values below 25A, use the RW27-2D3-U032 (22–32A).
- Phase Loss Protection via 4th Bimetal Strip: The RW27-2D3 series includes a 4th bimetallic strip in addition to the three current-sensing strips. This 4th strip detects single-phasing (phase loss) and trips the relay to prevent motor winding damage from unbalanced or single-phase operation. Phase loss is one of the leading causes of motor burnout in three-phase applications.
- Class 10 Trip Characteristic: Class 10 means the relay trips in 10 seconds or less at locked rotor current (approximately 6× FLA). Class 10 is standard for general-purpose NEMA Design B motors. Class 20 would be used for high-inertia loads with longer start times — this relay is Class 10 only.
- Direct Mount to CWB40–CWB80: The RW27-2D3-U040 snaps directly onto the T1-T2-T3 load terminals of the CWB40, CWB50, CWB65, CWB80, and CWBN2 contactors without additional wiring or mounting hardware. This reduces panel wiring and ensures reliable contact between the overload and the contactor.
- Manual or Automatic Reset: The reset mode is field-selectable. Manual reset requires an operator to press the reset button after a trip, preventing automatic restart — preferred for safety-critical machinery. Automatic reset restores power after the relay cools, useful for remote or unattended equipment. The reset button is accessible on the front of the relay.
- 1 NO + 1 NC Auxiliary Contacts: Built-in auxiliary contacts are available for wiring to a control circuit. The NO contact (normally open) is typically wired to a run indicator or PLC input. The NC contact (normally closed) is wired in series with the contactor coil circuit to drop out the contactor on trip.
- VFD Applications — Setting Adjustment Required: The RW27-2D3 relays are rated to 400 Hz, but when used downstream of a variable frequency drive, the current settings should be set higher than the motor nameplate FLA. VFD output waveforms generate harmonic currents that cause additional heating in the bimetal strips beyond the fundamental (rms) current. Consult the WEG RW27-2D technical manual for derating guidance.
- RW27-2D vs RW27-1D — CWB vs CWM: The RW27-2D3 is designed for the current-generation WEG CWB contactor series. The older RW27-1D3 was designed for the WEG CWM contactor series. The two series are not directly interchangeable due to different direct-mount footprints. If you are replacing an overload on a CWM contactor, use the RW27-1D3 series.
In Stock at Kent Electrical Supply — Emmaus, PA — Same-Day Shipping on Orders Before 4:00 PM EST.
Frequently Asked Questions
What is the actual current range of the RW27-2D3-U040?
The RW27-2D3-U040 is adjustable from 25.0 to 40.0 Amps per the WEG product catalog. Set the dial to your motor’s nameplate full-load amperage (FLA). If your motor FLA is below 25A, select the RW27-2D3-U032 (22–32A range) instead. If your motor FLA is above 40A, step up to the RW67-5D3 series.
Which WEG contactors is the RW27-2D3-U040 compatible with?
The RW27-2D3-U040 direct-mounts to the following WEG contactors: CWB40, CWB50, CWB65, CWB80, and CWBN2. It does not fit the smaller CWB contactors (CWB9 through CWB38) due to the terminal spacing of the 25–40A range. It also does not fit the CWM contactor series (those require the RW27-1D3).
What is the difference between the RW27-2D3 and the RW27-1D3?
The RW27-2D3 is designed for the WEG CWB contactor series (current generation). The RW27-1D3 was designed for the WEG CWM contactor series (legacy generation). The direct-mount footprint differs between the two — they are not interchangeable. If you have a CWM contactor (CWM9, CWM18, CWM25, CWM32, CWM40, etc.), use the RW27-1D3 series. If you have a CWB contactor, use the RW27-2D3 series.
How does phase loss protection work on the RW27-2D3?
The RW27-2D3 series uses a 4th bimetallic strip in addition to the three current-carrying strips. This 4th strip is connected differentially and responds to current unbalance. When one phase is lost entirely, the current in the remaining phases rises (to maintain motor load), creating a temperature differential in the bimetal assembly that trips the relay within seconds. This protects the motor from the overheating that occurs during single-phase operation of a three-phase motor.
Should I use manual or automatic reset for my application?
Manual reset is recommended for most motor applications and is required by many safety standards for machinery where an unexpected restart would be hazardous. After a trip, an operator must physically press the reset button, confirm the fault condition is cleared, and then restart. Automatic reset is appropriate for remote pumping stations, HVAC equipment, or other unattended applications where an immediate restart is acceptable and safe after the relay cools. The reset mode is selectable on the relay itself.
Does the RW27-2D3-U040 qualify for same-day shipping?
Yes — the RW27-2D3-U040 is stocked at Kent Electrical Supply’s warehouse in Emmaus, PA and ships same business day when ordered before 4:00 PM EST. For other ranges in the RW27-2D3 series, the RW67-5D3 series, or bulk orders, call us at 1-800-222-5129 or text your RFQ to 484-425-0652.
