Varmax boiler
Varmax boiler
Varmax boiler

Floor standing, high output condensing boiler with a stainless steel heat exchanger.

New larger models added November 2020 - The range consists of 10 single boilers with outputs (at 50/30°C) of 127, 148, 191, 238, 290, 338, 415, 478, 558, 637kW. 

Efficiency 96 product icon
Fuel NG LPG product icon
Turndown 5 product icon
Warranty 5 heat exchanger product item
ErP Part L Compliant product icon
BIM objects icon

Product information

    • Improved efficiency on split temperature systems due to high and low temperature return connections.
    • Non-dependent on system flow allowing wide differential temperatures.
    • Easier installation with no requirement for dedicated primary circuit and no minimum flow rates.
    • Tolerant to a wide range of system water conditions with a corrosion resistant stainless steel heat exchanger.
    • Long life backed up by a 5-year heat exchanger warranty.
    • Well insulated for low standby losses.
    • NOx emissions comply with ErP legislation lower than 56mg/kWh.
    • Match heating system loads accurately with outputs up to 637kW from a single boiler and ability to cascade multiple boilers.
    • Simplified flue system design as the flue gas non-return valve is built in to provide effective protection from re-circulation of flue gases through non-firing boilers.
    • Built in boiler sequence controls capable of controlling up to 16 boiler modules, multiple heating circuits and a hot water circuit using the master/slave principle.
    • Quick release access panels for ease of service and maintenance.
    • BIM objects available to assist in design and management.

Technical data

Units 120
Building regulations Part L seasonal efficiency % gross 96.13
Boiler output - maximum 80/60°C, NG & LPG* kW 117
Boiler output - maximum 50/30°C, NG & LPG* kW 127
Boiler output - minimum 80/60°C, Nat Gas. kW 27.3
Boiler output - minimum 80/60°C, LPG kW 38
Boiler input (gross) - maximum, NG & LPG* kW 120
Boiler input (net) - maximum, NG & LPG* kW 108
Standby loss W 182
Water content litres 116
System design flow rate @ 30°C ΔT rise l/s 0.9
Water side pressure loss @ 30°C ΔT rise mbar 27
System design flow rate @ 20°C ΔT rise l/s 1.4
Water side pressure loss @ 20°C ΔT rise mbar 60
System design flow rate @ 11°C ΔT rise l/s 2.5
Water side pressure loss @ 11°C ΔT rise mbar 198
Minimum water pressure barg 1
Maximum water pressure barg 6
Minimum flow temperature setting °C 22
Maximum flow temperature setting °C 85
Gas flow rate, NG (G20) - maximum m³/hr 12.7
Maximum gas inlet pressure, Nat Gas mbar 25
Nominal inlet pressure, Nat Gas mbar 20
Minimum gas inlet pressure, Nat Gas mbar 17
Gas flow rate, LPG (G31) - maximum m³/hr 4.9
Nominal inlet pressure, LPG mbar 37
Maximum flue gas temperature @ 80/60°C Nat Gas °C 60.8
Pressure at boiler flue spigot @ 80/60°C Nat Gas B23P Pa 200
Maximum flue gas temperature @ 80/60°C LPG °C 60.3
Pressure at boiler flue spigot @ 80/60°C LPG B23P Pa 167
Dry NOx emission** mg/kWh 30
NOx Class 6
Electrical supply 230V, 1Ph, 50Hz
Power consumption - maximum boiler modulation W 204
Start current (per module) Amp 3.5
Run current (per module) Amp 0.89
Approx shipping weight kg 340
Noise emission @1m: @max. modulation dB (A) 65
*390kW, 450kW, 525kW and 600kW models Nat Gas only
**(0% excess oxygen, mg/kWh dry air free); NG/LPG


Varmax boiler brochure

Product brochures 5806 kb

500001305-B QAA73.210 Programmable Room Unit Guide.pdf

Installers guides 1783 kb

AGU 2.550 Kit instructions

Installers guides 445 kb

Navistem B3000 controller instruction manual

Installers guides 2177 kb

QAA55 room unit programming instructions

Installers guides 153 kb

QAA74 - Technical Manual

Installers guides 1640 kb

QAA74 Quick Reference Guide

Installers guides 178 kb

Siemens room operator units QAA55, QAA75, QAA78, AVS13, AVS14, AVS71

Installers guides 6621 kb

Varmax Boiler installation manual

Installers guides 11421 kb

Varmax accessory AVS75 installation manual

Installers guides 2767 kb

Volt Free Contact (VFC) and switch fitting instructions

Installers guides 1349 kb

Varmax scheme 1 - single boiler with split temperature heating and DHW

Hydraulic schematics 126 kb

Varmax scheme 2 - single boiler with multiple split temperature heating circuits and DHW

Hydraulic schematics 138 kb

Varmax scheme 3 - multiple boilers with multiple split temperature heating and DHW circuit

Hydraulic schematics 149 kb

Varmax scheme 4 - multiple boilers with low loss header

Hydraulic schematics 139 kb

Varmax boiler 120kW-140kW CAD

CAD 184 kb

Varmax boiler 180kW-225kW CAD

CAD 192 kb

Varmax boiler 275kW-320kW CAD

CAD 191 kb

Varmax boiler 390kW-450kW CAD

CAD 194 kb

Varmax boiler 525kW - 600kW CAD

CAD 1159 kb


We specified the Varmax based on resilience and life expectancy. Other than this, we find the pull-out step on this model and the integral light fitting to be very practical for commissioning and servicing the boiler.

Andy Cope, Mabey Francis

Ideal uses/applications

Optional extras

  • A large range of off the shelf flue options available
  • Room sealed and open flue solutions
  • Flue header kits

Single Boiler Controls

  • Outside air temperature sensor QAC34 (Part no. 533901457)
  • Domestic Hot Water sensor kit (sensor and pocket) QAZ36 (Part no. 563605674)
  • Mixing valve heating circuit control kit (AVS 75 control module, temperature sensor and pocket) for 1 zone (Part no. 059751)
  • Programmable room sensor QAA75 (Part no. 533901587)
  • Offset adjustable room sensor QAA55 (Part no. 533901589)

Multiple Boiler Controls

  • Outside air temperature sensor QAC34 (Part no. 533901457)
  • Heating circuit sensor kit (sensor and pocket) QAZ36 (Part no. 563605673)
  • Merley boiler sequence controller, wall mounted (Part no. 563605672)
  • LPB Bus communication module OCI345, one required per boiler module (Part no. 563605667)
  • Programmable room sensor QAA75 (Part no. 533901587)
  • Offset adjustable room sensor QAA55 (Part no. 533901589)

Often bought with

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Burstock expansion vessel

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Powerstock glass lined calorifier

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Merley boiler sequence controller

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Case studies

Bourne View care home in Poole

Bourne View Care Home

Sector: Care homes

Project: The prestigious local care home in Art Deco style was opened in April 2019 and looking for reliable boilers and water heaters to keep the future residents safe.

Building: New build care home

Application: Space heating 382kW, DHW 1,940 l/h l/h

Learn more