The Castair TD100M is a 230-volt time delay relay designed for use with single-phase air compressor motor starters. If your compressor is tripping breakers or blowing fuses on startup — particularly on 230V circuits — a properly spec'd time delay relay is often the fix. This component gives the motor a brief delay window before the unloading valve closes, allowing the motor to reach full speed before accepting load. That protects the motor, protects your wiring, and prevents nuisance trips that interrupt shop workflow.
What a Time Delay Relay Does for Your Compressor
On 230-volt compressor installations, the motor draws significantly higher inrush current at startup — often 6 to 8 times the running amperage. Without a time delay, the full load hits immediately at the moment of startup. Over time, this hammers motor windings, stresses contactors, and can damage pressure switches. The TD100M introduces a brief, controlled delay so the motor comes up to speed unloaded before the system pressurizes.
Key Functions
- Startup Protection: Delays load engagement to reduce inrush current stress on 230V motors
- Breaker Trip Prevention: Prevents nuisance trips caused by high startup amperage
- Motor Winding Protection: Reduces thermal and mechanical stress during the most vulnerable phase of operation
- OEM Castair Specification: Designed to integrate with Castair 230-volt compressor motor starter configurations
- Direct Replacement: Replaces failed or worn time delay components in existing Castair 230V installations
Who Needs This Part
If you're running a Castair compressor on a 230-volt circuit and experiencing any of the following, a time delay relay is the first thing to check:
- Breaker trips on startup, especially in cold weather when motor resistance is higher
- Motor starter contactors showing signs of arcing or pitting on the contact faces
- Compressor that previously ran fine but has started having startup issues after years of service
- New installation where the circuit is correctly sized but startup loads are causing breaker sensitivity issues
- Replacement of a failed or burned-out time delay relay in the motor starter panel
This is a maintenance and repair part, not an upgrade component. If your existing time delay relay has failed or your compressor was installed without one, the TD100M is the Castair-specified component for 230-volt systems.
Installation Notes
- Voltage: 230V applications
- Location: Mounts in the motor starter panel or control box
- Wiring: Follow Castair wiring diagram for your specific compressor model — verify terminal assignments before connecting
- Professional Installation Recommended: 230V electrical work should be performed by a qualified electrician or technician familiar with compressor motor starters
- Compatibility: Confirm your compressor model and existing starter configuration match before ordering
What's in the Box
- 1x Castair TD100M Time Delay Relay (230V)
Note: Manufacturer product page data was not available at time of writing. Specifications are based on product name, part number, and category data on file. Contact us to confirm compatibility with your specific Castair model before ordering.
When Does a Shop Need This vs. Other Options
The TD100M is the Castair OEM time delay relay for 230-volt systems. If you're running a 115-volt compressor, this is not the right part — voltage rating on time delay relays must match your system exactly. If you're not sure whether your compressor uses a time delay relay or what voltage your system runs, check the motor starter label or call us before ordering. Ordering the wrong relay wastes time and money.
If the motor starter itself has failed (not just the time delay component), you'll need to evaluate whether replacing the full starter assembly is more cost-effective than replacing individual components. Call us and we'll walk through it with you.
Technical Specifications
- Part Number: TD100M
- Manufacturer: Cast Air / Castair
- Voltage: 230V
- Function: Time delay relay for compressor motor starter
- Application: Single-phase 230V air compressor motor starter circuits
Additional specifications including delay time range, amperage rating, and contact configuration were not available from manufacturer data at time of writing. Contact us for full spec sheet.
Why Buy From Air Compressor Factory Direct?
- Castair Parts Specialist: We stock Castair electrical components and can help identify the right part for your specific compressor model and wiring configuration
- Free Shipping: On qualifying orders to the contiguous US
- Free Tech Support: Call 866-217-0063 and talk to someone who understands compressor electrical systems — not a general customer service rep
- Full Manufacturer Warranty: All Castair parts carry the standard manufacturer warranty
- Honest Guidance: We'll tell you if this part is right for your application — or point you to what actually is, even if it means a different part number
Call 866-217-0063 for quick answers and help!
