SOLFEX Unvented Direct Solar Cylinders

Last Updated: March 16, 2017 12:44

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Product Details

SOLFEX's unvented cylinders were specifically designed with solar applications in mind, therefore providing an efficient way of providing domestic hot water. Each model features a dedicated high performance solar coil, transferring the maximum amount of heat from the solar circuit to the stored water.

The direct cylinders are electrically heated cylinders, using the 3kW immersion heater supplied with the unit, with a high performance solar coil. They are capable of meeting the requirements of Building regulations, provided that it is matched to the panels and the hot water requirement correctly.

Features & Benefits

Duplex Stainless Steel

Using the latest high specification Duplex stainless steel to resist all forms of corrosion including crevice and stress whilst its high mechanical strength gives it durability.

The very latest automated welding procedures along with full post weld treatments guarantee welds that are as strong as the metal.

All cylinders are factory pressure tested to a full 12 bar which is four times the normal working pressure.

Corrugated Stainless Steel Coil

The high heat transfer corrugated tube heat exchanger to gives a 20% faster recovery than plain tube heat exchangers, it is also lighter & stronger than plain tube making the storage cylinder the lightest and easiest to handle on site.

Maximum Capacity

An inbuilt diffuser reduces turbulence when cold water enters the storage by baffling the flow, the end result is that the hot water output is equal to the capacity, a 180 litre cylinder will produce 180 litres of hot water!

Heat Loss

Manufactured using the latest HCFC free Enviro-foam insulation, tests show that 50mm of Enviro-foam injected into the case and covering both domes achieves astonishingly low levels of heat loss which ensures it fully complies with the 2010 Part L requirements for both new build and replacement cylinders.

Quality Standard

All SOLFEX unvented stainless cylinders are manufactured in accordance with BS EN 12897 the specification for unvented water storage vessels. The cylinders have been tested by Kiwa which is a member of the European Organisation for Technical Approvals and comply with current UK Building Regulations G3 and Water Regulations, in performance it complies with the requirements of BS 6700 and meets the NHBC criteria for domestic properties.

Cylinders are supplied with:

  • Immersion heater(s)

  • Inlet control set

  • Expansion vessel kit

  • Temperature and pressure relief valve

  • Control thermostat and drain valve

  • Tundish

  • Installation manual & benchmark log book

Technical Specification

DescriptionSOL 180dSOL 210dSOL 250dSOL 300dSOL 400d
Height (mm)12951483173320202040
Diameter (mm)550550550550630
Weight empty (kg)2630343949
Weight full (kg)206240284339449
Capacity (l)180210250300400
Pressure regulator (bar)33333
Expansion vessel size (l)182424352 x 24
kW rating of primary coiln/an/an/an/an/a
Recovery time after 70% draw off (min)90115139187260
Standing losses (kWhr/24hr)1.401.601.751.933.33
Surface area of solar coil (m² )0.6800.6800.9700.9701.270
Dedicated solar volume (l)607084100150

Model Selection Guide

Maximum hot water demandMaximum solar panel area (m²)BedroomsModel
1 shower room2.4BedsitSOL180d
1 bathroom2.81-3SOL210d
1 bathroom & separate shower room3.361-3SOL250d
1 bathroom & 2 separate shower rooms4.02-4SOL300d
2 bathrooms & separate shower room6.04-5SOL400d


  1. Recovery time is based on primary coil/immersion heater duty (ie. assumes the boiler outputt is adequate)
  2. All connections are supplied with compression fittings for direct connection to copper pipework
  3. The model sizes shown are based on a typical days hot water use assuming an Economy 7 tariff is provided. A reduction of one model size can normally be made with an Economy 10 tariff
  4. When using the Direct model for high specification developments, an increase of one model size should be considered
  5. When selecting a solar model, it is important to check the dedicated solar volume is suitable for either the total floor area of the dwelling or the total net area of the solar panel to ensure compliance with Building Regulations
  6. Maximum solar panel area is calculated based on 25l/m² of net solar panel area

Specification & Product Codes



939982 - SOLFEX 180l Cased Direct Solar Unvented Cylinder

939986 - SOLFEX 210l Cased Direct Solar Unvented Cylinder

163715 - SOLFEX 250l Cased Direct Solar Unvented Cylinder

163722 - SOLFEX 300l Cased Direct Solar Unvented Cylinder

163737 - SOLFEX 400l Cased Direct Solar Unvented Cylinder