Outer Casing design

Overview

The outer casing is the external enclosure of the electric water heater. It combines protection, structure, insulation containment, and product aesthetics.

It works together with PU (polyurethane) foam insulation to form a rigid system around the inner tank.

Main Functions

• Protect internal components

• Provide structural strength

• Contain insulation

• Define product appearance

Main Components

1 — Top Cover

Material: Metal (powder-coated steel thickness 0.5 mm ) or ABS (flame-retardant)

Function:

• Closes the upper side

• Provides aesthetic finish

• Interfaces with the body

2 — Body (Main Shell)

Material: Metal (powder-coated steel thickness 0.5 mm )

Function:

• Main structural part

• Contains insulation space

• Connects all covers

3 — Lower Cover

Material: Metal (powder-coated steel thickness 0.5 mm ) or ABS (flame-retardant)

Function:

• Covers bottom area

• Allows maintenance access

• Protects electrical components

4 — Electric Cover (Internal)

Material: Flame-retardant ABS plastic

Function:

• Covers live electrical parts

• Provides safety insulation

• Organizes wiring

5 — EWH External Holder

Material:

• DC04 steel sheet

• Thickness: 2 mm

• Surface: Electrostatic powder coating

Function:

• Supports and fixes the internal tank assembly

• Transfers load from tank to outer casing structure

• Provides mounting interface for installation (wall fixing)

• Enhances overall structural rigidity of the heater

Top Cover / Body Fitting Types

Type (1) — Plastic Snap Over Edge

Description:

• Plastic cover snaps over metal body edge

Advantages:

• The casing body is longer , So the electric water heater looks longer overall

• Fast assembly

• Low cost

• Easy removal

Limitations:

• Lower strength

• No sealing

Use: Basic models

Type (2) — Plastic Snap with Sealing

Description:

• Snap fit with added sealing (foam/rubber)

Advantages:

• Dust & moisture protection

• Reduced vibration

• Better quality feel

Limitations:

• Higher cost

Use: Mid / high-end models

Type (3) — Metal Hook (Rolled Seam)

Description:

• Metal cover locks into body using hook joint

Advantages:

• Very strong

• Clean appearance

Limitations:

• Not easily removable

Use: Premium designs but this is classic design fitting

PU Foam – Function & Process

Process

1. Place inner tank inside body

2. Close casing

3. Inject PU liquid

4. Foam expands

5. Foam cures into rigid insulation

Functions

Thermal Insulation

• Reduces heat loss

Structural Bonding

• Bonds tank to casing

Rigidity

• Strengthens thin metal

Vibration Damping

• Prevents internal movement

Engineering Insight

Tank + PU Foam + Outer Casing = One Solid Unit

Design Guidelines

• Body thickness: 0.5 mm

• Plastic thickness: 2 – 3 mm

Summary

The outer casing is a structural system, not just a cover. Proper joint design and PU integration ensure strength, efficiency, and durability.