EHC Comet 12/16/20/24kW 3 Phase System Electric Boiler | EHC.CS24KW | 400V

Description

The EHC Comet 12/16/20/24kW System Electric Boiler (EHC.CS24KW) is the highest-output model in the Comet Standard System range, built on over 21 years of EHC electric heating expertise. It is intended for larger domestic properties and light-commercial systems where a 3-phase electrical supply is available, delivering central heating and domestic hot water via an S-Plan configuration from a single wall-mounted unit.

This model runs on a 3-phase 400V supply with four selectable output settings — 12kW, 16kW, 20kW or 24kW — configured on-site to match the property’s heat loss and balance load evenly across all three phases. The pump, expansion vessel, automatic air vent, auto-bypass and high-current thermal cut-out are all factory-fitted inside the casing, removing the need for external plumbing or pipework.

12–24 kW

Selectable Output

400V 3N~

3-Phase Supply

41 dB

Quiet Operation

20.5 kg

Boiler Weight

20–85°C

Flow Temperature

5 Years

Manufacturer Warranty

Important Safety Information

This boiler must be installed by a qualified electrician in accordance with BS 7671 Wiring Regulations. A 30mA RCD, dedicated local isolation and an in-line magnetic filter are all mandatory — failure to fit a magnetic filter to this boiler will invalidate the manufacturer’s warranty.

Please Note

This model requires a 3-phase 400V electrical supply — it is not compatible with a standard single-phase domestic supply. Confirm 3-phase availability and carry out a full load check before specifying this boiler. At the 24kW setting, load current reaches 3 x 34.6A and requires a 40A MCB per phase.

Key Features

Flexible Multi-Output Technology

Four selectable outputs (12, 16, 20 or 24kW) let installers range-rate the boiler on site to match the exact heat loss of larger properties.

Six-Stage Modulation

A stainless steel heat exchanger with six-stage heating modulates output in real time, reducing electricity consumption and running costs.

Balanced 3-Phase Loading

Output is spread evenly across all three phases, helping avoid overloading any single phase on larger installations.

Virtually Silent Operation

Rated at just 41dB, the Comet Standard operates quietly enough for plant rooms, kitchens and utility spaces.

Underfloor Heating Compatible

Adjustable flow temperature from 20–85°C makes it equally suited to underfloor heating and traditional radiator systems.

Compact Wall-Mounted Design

All core components — pump, expansion vessel, auto-air vent and auto-bypass — are built into a single 716 x 316 x 235mm casing for a one-person lift and install.

Specification

Performance

Rated Power Output

12 / 16 / 20 / 24 kW

Rated Voltage

400V 3N~ (3-phase)

Outlet Flow Temperature Range

20–85°C

Maximum Temperature

100°C

Sound Level

41 dB

Minimum System Flow Rate

4.5 l/min

Electrical Data

MCB Rating

20 / 32 / 32 / 40 A

Load Current

3x17.4 / 3x23.1 / 3x28.8 / 3x34.6 A

Minimum Supply Cable Cross-Section*

5x2.5 / 5x4 / 5x6 mm²

Maximum Supply Cable Cross-Section

5x16 mm²

Maximum Allowed Network Impedance

0.27 / 0.13 Ω

Hydraulics & Build

Boiler Connections

G 3/4" (internal thread)

Maximum System Pressure

0.3 MPa (3 bar)

Minimum System Pressure

0.05 MPa (0.5 bar)

Built-In Expansion Vessel

5 litres, 1.5 bar precharge

Safety Class (Ingress Protection)

IP 22

Heat Exchanger

Stainless steel

Dimensions & Warranty

Dimensions (H x W x D)

716 x 316 x 235 mm

Weight

~20.5 kg

Manufacturer Warranty

5 years (registration required, T&Cs apply)

Good to Know

*Minimum cable cross-sections are the manufacturer’s stated minimums only, given per phase across a 5-core cable. The cable size for your installation must be calculated separately by a qualified electrician in accordance with BS 7671, accounting for cable type, routing and supply voltage deviation.

Frequently Asked Questions

Does this boiler need a 3-phase supply?

Yes. The EHC.CS24KW is a 3-phase 400V model and is not compatible with a standard single-phase domestic supply. If only single-phase power is available, the 2/4/6/8kW or 7.2/9.6/12/14.4kW Comet Standard models are the correct choice instead.

What electrical supply capacity do I need for the 24kW setting?

At the top 24kW output, load current reaches 3 x 34.6A and requires a 40A MCB per phase. A full load check of the property’s 3-phase supply by a qualified electrician is essential before installation.

Can this boiler provide hot water as well as heating?

Yes. The EHC.CS24KW can be installed for heating only, or for combined heating and domestic hot water when wired in an ‘S’ Plan configuration alongside a compatible hot water cylinder and twin-channel control.

Do I need to choose one fixed output, or can it be changed later?

The boiler ships with all four output settings available. The installer configures the required output (12, 16, 20 or 24kW) during commissioning via the DIP switches and control panel software — it is not locked to a single kW rating at the factory.

Is a magnetic filter really mandatory?

Yes. A magnetic filter must be fitted to the return of this boiler. This is a manufacturer warranty condition, not just best practice — installing without one will void the warranty regardless of any other fault.

Is this boiler suitable for larger commercial-style installations?

The 3-phase design and up to 24kW output make it suitable for larger domestic properties and light-commercial systems. For higher demand still, EHC also offers dedicated 3-phase commercial boiler ranges and cascade-linked multi-boiler setups.

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Room Dimensions

Length (in m):

Width (in m):

Height (in m):

Room Type

Living Room

Bedroom

Kitchen

Bathroom

Conservatory

Hallway

Glazing Type

Single Glazed

Double Glazed

Triple Glazed

External Walls

0 Wall

1 Wall

2 Walls

3 Walls

4 Walls

Insulation Level

Poor

Average

Good (New Build)

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