Honeywell L4008E1255 High Limit Water Temperature Controller

L4008: Honeywell basic series of water temperature controllers, used for liquid temperature limiting and regulation in boilers, storage tanks and other equipment, equipped with remote temperature bulb.

E: Series function code, stands for High Limit type, Réinitialisation manuelle, Breaks on Temperature Rise.

1255: Code de configuration, defining key parameters such as temperature range, temperature bulb length and mounting method.

2. Core Basic Parameters

3. Principales fonctionnalités
4. Remote Sensing Design: The temperature bulb is separated from the controller body, allowing installation far away from the sensing point.
5. Safety Lockout Function: Automatically trips and locks when temperature reaches the set limit; manual reset is required to resume operation to prevent equipment overheating damage.
6. Réponse rapide: Adopts fully enclosed Micro Switch™ snap-action switch for rapid tripping at set temperature.
7. Intuitive Adjustment: Equipped with visible temperature scale and external adjustment screw for easy on-site setting.
8. Flexible Mounting: Supports horizontal or vertical installation; sensing bulb can be directly immersed in liquid or installed via thermowell.
9. Durable & Fiable: Industrial-grade construction suitable for harsh operating environments.
10. Compatible Replacement Models
11. Same Brand Replacement:

L4008E1305: Same temperature range (100–240°F), manual reset, different bulb length

L4008E1040: Temperature range 130–270°F, manual reset, 66-inch bulb

L4008E1313: Temperature range 100–200°F, manual reset, remote bulb type

2. Modèles compatibles entre marques:

Johnson Controls A19ABC-1C: High limit aquastat, 100–240°F, manual reset

Siemens RWD62: Universal temperature controller, configurable for high limit mode, supports remote sensor

5. Application Guidelines
6. Remarque sur l'installation: The temperature bulb shall be fully immersed in measured liquid, avoid contact with tank walls or heating elements to ensure accurate measurement.
7. Opération de réinitialisation: After system shutdown, confirm temperature drops to safe range first, then press the red reset button to restart.
8. Wiring Standard: Strictly wire according to electrical ratings; avoid overload operation.
9. Setting Recommendation: Set high limit temperature per boiler or equipment manufacturer’s specification; shall not exceed the maximum withstand temperature of the equipment.
10. Entretien: Regularly inspect bulb insulation and terminal connections to prevent corrosion and loose contacts.
11. Safety Tip: When used as a high limit cutout, it is recommended to cooperate with other safety protection devices to enhance system safety.

Complete Installation Guide for Honeywell L4008E1255 High Limit Aquastat Controller

1. Préparation avant l'installation & Consignes de sécurité

1.1 Required Tools & Accessoires

1.2 Précautions de sécurité

Fonctionnement hors tension: Disconnect system power before installation to avoid electric shock hazard.

System Draining: Drain liquid inside boiler / tank below the connection port before bulb installation to prevent water spillage.

Temperature Check: Ensure system cools down to safe temperature (<50°C) to avoid scalding.

Professional Qualification: Installation and commissioning recommended by qualified HVAC technicians.

Rating Matching: Verify controller electrical ratings (120V AC @8A; 240V AC @5.1A) match system load.

2. Controller Main Unit Mounting Methods

L4008E1255 supports two main mounting options according to site space:

2.1 Wall / Montage par vis sur panneau (Recommandé)

1. Positionnement & Marquage

Select vertical wall or control cabinet panel with dry, ventilated and vibration-free environment.

Use three mounting holes on controller rear as template to mark screw positions with pencil.

Hole spacing: environ. 76mm horizontal, 51mm vertical (standard mounting dimension).

2. Drilling & Fixation

Drill with 3/16 inch (environ. 4.8mm) bit for drywall / wood.

Install plastic wall anchors for wall mounting.

Fasten controller to wall / panel with 8 ou 10 self-tapping screws, ensure firm installation without looseness.

2.2 Pipe Surface Mounting (Facultatif)

1. Accessory Preparation: Use dedicated Honeywell pipe mounting bracket (included in some models).
2. Bracket Fixing: Secure bracket to pipe with diameter ≥2 inch using pipe clamp, ensure tight clamping.
3. Controller Installation: Fix controller onto bracket; either vertical or horizontal orientation is acceptable.

2.3 Mounting Orientation Requirements

Vertical Mounting: Most recommended for internal component heat dissipation and mechanical stability.

Horizontal Mounting: Allowed; ensure capillary hangs naturally without sharp bending.

Inverted Mounting Prohibited: Do not install upside down, otherwise internal switch operation accuracy may be affected.

3. Temperature Bulb Installation (Core Procedure)

L4008E1255 is equipped with 20 ft (environ. 6.1 m) remote temperature bulb, installation quality directly affects temperature control accuracy.

3.1 Mounting Method Selection

3.2 Thermowell Mounting (Standard Procedure)

1. System Preparation

Cut off system power and drain liquid below connection port.

Clean boiler / tank thread port to remove dirt and impurities.

2. Thermowell Installation

Adopt standard 1/2″ NPT threaded thermowell (usually supplied with product).

Wrap 3–5 layers of PTFE tape on thread and apply proper sealant.

Screw thermowell into port with pipe wrench; torque controlled at 20–25N·m, avoid over-tightening thread damage.

3. Bulb Installation

Remove bulb protective cover and inspect bulb for damage.

Insert bulb fully to the bottom of thermowell for full liquid contact.

Fix bulb wiring to prevent capillary pulling or sharp bending (minimum bend radius ≥50mm).

3.3 Direct Immersion Mounting (Simplified Procedure)

1. Ensure tank opening diameter ≥25mm for easy bulb insertion.
2. Fully immerse bulb into liquid with depth ≥100mm; avoid contact with tank wall or heating elements.
3. Fix bulb cable with matched clamp to prevent displacement affecting measurement accuracy.

3.4 Key Bulb Installation Points

Position Selection: Install in well-flowing liquid area, away from stagnant zones and heating elements.

Capillary Protection: Avoid excessive bending, squeezing or stretching to prevent internal fluid leakage.

Waterproof Sealing: Apply waterproof sealing at cable entry to prevent moisture entering controller interior.

Regular Fixing: Fasten cable every 1–1.5m to reduce vibration impact.

4. Electrical Wiring Procedure

4.1 Définition du terminal

4.2 Wiring Operation Steps

1. Remove Terminal Cover: Unscrew front terminal cover screw and open wiring compartment.
2. Wire Preparation: Use 14–18AWG (2.5–0.75mm²) copper wire, stripping length 6–8mm.
3. Power Wiring: Connect L1 to live wire, L2 to neutral wire, ensure firm connection.
4. Load Wiring: Connect T1 to load live wire, T2 to load control wire; load other end connects to neutral.
5. Ground Connection: Fasten yellow-green ground wire to ground terminal, ensure grounding resistance <4Oh.
6. Terminal Inspection: Gently pull each wire to confirm no looseness; check no exposed conductor to avoid short circuit.
7. Reinstall Cover: Close and fasten terminal cover to prevent dust and moisture ingress.
8. Mise en service & Test Procedure

5.1 Temperature Adjustment

1. Default Setting: Factory preset high limit 240°F (115.6°C), adjustable per equipment requirement.
2. Adjust Method:

Rotate front adjustment screw with flat screwdriver: clockwise for higher temperature, counterclockwise for lower.

Set target temperature referring to scale dial (adjustable range 100°F~240°F).

Recommended setting 10–15°F lower than equipment maximum withstand temperature for safety margin.

5.2 Functional Test Steps

1. Opération de réinitialisation: Press red reset button to release safety lockout before first power-on (factory locked state).
2. Power-On Test: Switch on power and check indicator light (si équipé) operates normally.
3. Temperature Rise Test: Start system and verify controller automatically trips output when temperature reaches set point.
4. Reset Verification: After temperature drops to safe range (set point −10°F below), press reset button and confirm system resumes operation.
5. Repeat Test: Repeat 2–3 cycles to ensure reliable tripping and normal reset performance.
6. Installation Prohibitions & Directives d'entretien

6.1 Installation Prohibitions

❌ Do not install controller in humid, dusty or corrosive gas environment.

❌ Prevent direct contact between bulb and high-temperature surface (>250°F) to avoid damage.

❌ Do not use AC24V or DC power supply; only 120V/240V AC is permitted.

❌ Do not overload output contacts; shall not exceed rated current (8A@120V, 5.1A@240V).

6.2 Recommandation d'entretien

6.3 Common Installation Troubleshooting

7. Installation Summary

Installation of Honeywell L4008E1255 shall follow the principle of Safety First & Standard Operation, core steps as below:

1. Power off preparation to ensure system safety.
2. Mount controller main unit on wall or pipe in vertical or horizontal orientation.
3. Install temperature bulb via thermowell or direct immersion for accurate sensing.
4. Standard electrical wiring matching power supply and load rating.
5. Complete commissioning and testing to verify temperature control and reset function.

Après l'installation, record installation date, set temperature and test results for future maintenance and troubleshooting reference.