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Technical Specs

Kelford's Range

Model: KESB 75

Nominal Capacity:=75KW
Steam Output:[@75KW] 100KgHr¯¹ @ 10 Bar G / 184°C
Design Pressure:12 Bar G.
Design Code:PD500: 2021 CAT 3
Electrical Supply:440V 3-Phase + Neutral + Earth.
Current Required:130A per phase for 75KW output.
Boiler Control:PLC Based.

Model: KESB 150

Nominal Capacity:=150KW
Steam Output:[@150KW] 210KgHr¯¹ @ 10 Bar G / 184°C
Design Pressure:12 Bar G.
Design Code:PD500: 2021 CAT 3
Electrical Supply:440V 3-Phase + Neutral + Earth.
Current Required:220A per phase for 150KW output.
Boiler Control:PLC Based.

Model: KESB 300

Nominal Capacity:=300KW
Steam Output:[@300KW] 420KgHr¯¹ @ 10 Bar G / 184°C
Design Pressure:12 Bar G.
Design Code:PD500: 2021 CAT 3
Electrical Supply:440V 3-Phase + Neutral + Earth.
Current Required:520A per phase for 300KW output.
Boiler Control:PLC Based.

Model: KESB 600

Nominal Capacity:=600KW
Steam Output:[@600KW] 840KgHr¯¹ @ 10 Bar G / 184°C
Design Pressure:12 Bar G.
Design Code:PD500: 2021 CAT 3
Electrical Supply:440V 3-Phase + Neutral + Earth.
Current Required:1040A per phase for 600KW output.
Boiler Control:PLC Based.

specifications common to all sizes

DimensionsFrame approximately 1800W x 1700H x 900D self-contained unit
Frame materialStainless steel
Exterior panels2mm Aluminium
Floor fastening4 x M16 anchors
Water connectionDN15 Minimum available flow 0.5m3hr¯¹ @ 4 Bar G minimum [for
300KW output]
Blow-down dischargeDN50 Maximum discharge [intermittent] 0.4m3hr¯¹ @ 90°C minimum
[for 300KW output]
Vent dischargeDN100 Stainless dairy tube < 100°C [combined blow down and safety
valve vent]
DrainsFloor drained recommended for maintenance / cleaning purposes
Steam main stop valveDN25 PN16 flanged
Condensate returnDN15 Screwed connection
Water treatmentSite specific, however water softener recommended

construction details

boiler description

Our boilers operate on the electrode boiler principle. Water is pumped from a stainless feed-water tank mounted inside the frame into the boiler drum where it makes contact with three pairs of cast iron electrodes, each pair connected to a different phase from a 440V supply.

The water completes the circuit between the electrodes and the heat generated causes the water to boil and produce steam. The electrical current and thus steam produced is directly proportional to the level of water in contact with the electrodes. At maximum boiler output, the whole length of electrode is covered with water and maximum current is drawn. When the boiler is idling, and no steam as being drawn off, the water level sits below the end of the electrodes.

A steam pressure transducer connected to the boiler drum tells a small PLC in the electrical cabinet if the steam is above or below a preset steam pressure set-point and either starts the water pump to raise the water level to match an increase of load or opens a solenoid valve to drop the level of water in the drum for a decrease in load. The water blowing out of the drum for decreasing load is piped back to the feed-tank thus saving the expelled hot boiling water for reuse in the boiler.

The above method of load control through steam pressure makes the boiler fully modulating over it’s output range, stuff a constant steam load will result in a steady water level and constant electrical current across each phase.

boiler design

The pressure vessel and seismic control components of our boilers been designed to comply with all New Zealand codes of practice and regulations. The boiler drum itself has been designed to meet the requirements of PD:5500 2015 Category 3.

A third-party engineering consultancy has peer reviewed our design and it has received design verification from an approved inspection body in accordance with New Zealand Pressure Equipment, Cranes and Passenger Ropeways [PECPR] Regulations.

In the actual design we have tried to embody improved features not previously seen on designs of element an electrode boilers such as:

  • Incorporation of feed-water and blow-down tanks into the boiler frame making the boiler a complete ‘packaged’ unit, only a suitable water supply, trade waste connection for the blow-down discharge and an electrical supply are required to make steam
  • Stainless construction of frame, tanks and pipe-work where appropriate, making the boiler infinitely more suitable for clean or food-grade environments
  • Modern PLC control and electrical system with common components that are readily available and replaceable
  • Water level limiting to prevent flooding of the boiler drum at high loads and reduce carryover of water into the steam range

documentation provided

All our boilers are supplied with the following documentation

  • Design verification certificate
  • Hydrostatic test certificate for boiler drum
  • Electrical compliance certificate for the control panel
  • Basic electrical drawings
  • Basic boiler drawings showing frame dimensions and locations of connections
  • Boiler safety valve test certificate
  • Commissioning test certificate as tested in our workshop prior to despatch
  • A short operating manual and compass and daily operation, compliance with relevant codes and letlet legislation, common boiler faults and basic maintenance


The maintenance requirements for our boilers are divided into two categories

  1. Operational maintenance
  2. Annual inspection (survey)

In general, there will be little operation on maintenance required on a day-to-day basis. Of the oil level in the pump and for any steam or water leaks is recommended and quarterly replacement of the boiler sight glass is advisable.

Once installed and commissioned, an annual boiler inspection by a third-party inspection agency must be undertaken for compliance with New Zealand pressure vessel regulations and re-certification. This generally involves stripping the pressure valve apart for cleaning and third party inspection, of any worn or rejected components, servicing of all boiler valves and fittings back to serviceable condition and re-certification of the boiler upon a successful steam test witnessed by the third party inspector. Annual surveys of boilers typically take a single day given reasonable planning.

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