Allen Bradley 800T/H 30mm Button Troubleshooting and Replacement Guide

Wiring changes: The terminal arrangement of the PentUFF contact block is the same as that of the standard block (1, 2 are NC; 3, 4 are NO; common terminal is shared). No need to change external wiring.

3.3 Replacement requirements in explosion-proof areas

When the equipment is installed in Class I Div. 2 hazardous areas, the replacement contact block must use explosion-proof certified models (800T-X... or 800H-X...). In addition:

The accompanying explosion-proof gasket and stop screw must be used.

Do not disassemble the button while it is live.

After replacement, leakage testing must be conducted in accordance with NEC 500 or local regulations (for sealed buttons).

Chapter 4: Special Considerations for Emergency Stop Buttons

4.1 Positive Opening Compliance

The normally closed contact of the emergency stop button for 800T/H (such as 800T-FX6A5S) adopts a positive open design: when the button is pressed, the operating shaft mechanically pushes open the contact, and even if the contact undergoes welding, it can be forcibly disconnected. This complies with the requirements of IEC 60947-5-5 and ISO 13850.

Common malfunction: After using for a period of time, the twist to release mechanism of the emergency stop button becomes stiff or cannot automatically pop up. This situation is usually caused by lubricant aging or foreign matter entering.

Exclusion method:

Try repeatedly rotating and pulling up the button head after power failure to see if it can be restored.

If it is ineffective, the entire emergency stop button head must be replaced. Do not attempt to disassemble and repair the rotating mechanism, as the internal spring and ratchet are not repairable.

When replacing, be sure to confirm the release method: push-pull or twist release. Incorrect selection can lead to the loss of safety features.

4.2 Testing cycle of emergency stop button

According to OSHA and ANSI standards, emergency stop buttons on industrial equipment should undergo functional testing once per shift. Test method: Press the button → Confirm that the machine stops → Rotate and reset → Confirm that the machine can be restarted. During testing, pay attention to observing whether the button head fully pops up and whether the contacts are reliably disconnected (which can be confirmed by PLC input status or circuit voltage).

Record: Test date, results, operator signature. Replace immediately upon discovering the malfunction.

Chapter 5: Selection and Replacement Guide - Correspondence between Old Models

Many factories still use the Allen Bradley 800T series buttons from decades ago, and some models have been discontinued. The following table lists the correspondence between common old models and current production models for easy replacement:

Old model (may be discontinued) Current recommended model description

800T-A1 (green, 1NO) 800T-A1D1 with the same configuration

800T-B6 (red with dust cover, 1NO) 800T-B6D1 dust cover material update

800H-R1A (plastic, red, 1NO+1NC) is still in production

800T-PTH16R (with light, 120V transformer, red) 800T-PTH16R can be directly replaced

800T-QH2R (Universal LED, Red, 1NO+1NC) 800T-QH2R Universal LED is more commonly used and can replace transformer type

Important: When replacing the illuminated button, pay attention to the voltage type. Universal LED (12-130V AC/DC) can directly replace multiple voltages, while transformer type (such as 120V AC) must be matched with the original power supply. Measure the existing power supply voltage with a multimeter before placing an order.

Chapter 6: Best Practices for Installation and Maintenance

6.1 Panel Opening and Sealing

The 800T/H button requires a circular hole with a diameter of 30.5mm (it is recommended to use a punch or hydraulic hole opener). Installation steps:

Clean the surface of the panel and remove burrs.

Insert the sealing gasket onto the button thread.

Insert the button from the front of the panel, install the mounting ring on the back, and tighten it by hand.

Use a wrench to tighten another 1/4 turn (do not over tighten to avoid fracturing the plastic panel).

Common mistake: Forgetting to install the gasket resulted in water seeping into the control cabinet from the opening. As long as the gasket is present and intact, the Type 4/13 rating can be achieved.

6.2 Wiring Techniques

The 800T/H contact block adopts a "self lifting saddle clamp" - when the screw is loosened, the pressing plate automatically rises without the need to remove the screw. Wiring steps:

The stripping length is about 8-10mm.

Insert the wire into the square hole and tighten the screwdriver to 0.5-0.6 N · m.

Gently pull the wire to confirm that it will not come out.

Prohibition: Twist the exposed part of the wire into a ball or tin it (tin plated wire will loosen at the crimping point). It is recommended to use copper stranded wire and cover it with a pre insulated terminal tube (ferrorule).

6.3 Cleaning and Maintenance

Regular cleaning: Use a lint free cloth dipped in isopropanol to wipe the surface of the button. Do not use strong solvents such as acetone and toluene, as they can corrode the plastic cap.

Check the seal: Check the diaphragm and gasket for cracks every year. If dust accumulation is found at the movable part of the button head, compressed air can be used to blow it (pressure ≤ 0.3 MPa).