Unvented Installation

“regardless of which unvented cylinder you choose, be sure the overall system is suitably designed…”

The design and installation of any Megaflo or Unvented hot water system is of paramount importance. Correctly sized pipes ensure optimum performance and efficiency in delivering high pressure hot and cold water to all outlets – get this wrong, and the whole system falls apart!

All unvented installations are subject to the legal requirements of Building regulation G3 and should only be installed by an “approved installer”. This requirement ensures the safe installation of a Megaflo or Unvented Cylinder, but does not regulate the quality, design or installation of the associated pipe work, fittings and components.

Apex Plumbing and Heating specify and design systems in-order to maximise the performance of an unvented hot water system. A poorly installed Megaflo system will under-perform a traditional vented system and will fail to offer any real benefits – don’t get this wrong!

With an unvented hot water system, it is essential that the cold water supply has adequate pressure and flow rate to meet the maximum flow demand for both hot and cold water outlets.

Pressure: the force of water delivered.

Flow rate: the volume of water carried in the pipework.

It is generally recommended that, as a minimum, the incoming mains is at least 25mm with pressure
of 1.5 bar and 20 l/m flow rate.

Is the Mains Water Supply Suitable?

Firstly, it is important to understand that with any mains fed system (i.e. without stored water), the performance is directly related to the incoming flow and pressure.

The higher the mains water pressure the faster the water will flow, however the size and length of pipe work is equally important. As water flows, pressure is lost through the pipes and fittings. Even with a high mains water pressure, the resistance in a length of small bore pipe will reduce the available pressure, resulting in reduced flow rates.

In existing properties, the water supply can be gauged by opening a tap connected directly to the mains supply. Typically, these are the outside tap or kitchen tap. As you open up more than one tap, the ability of each tap to maintain the flow rate is an indication of the water available. Your local water supplier should be able to assist in testing pressures and flow rates properly. We always test the flow and pressure when we carry out a survey.

If the mains supply pipe work is unable to provide the peak water requirements then there are various options available:

  • Accumulator Technology, if you have good pressure, but poor flow.
  • Accumulator and Booster, if you have poor pressure and poor flow.
  • Upgrade mains supply pipe. This may increase flow and dynamic pressure, but not static pressure.
  • Keep the cold water storage tank in the loft, and use pumps to boost pressure to taps and showers.
  • Break tank and pump set combination. Boosts pressure and flow.

That said, most properties have more than adequate water supplies, and mains fed hot water systems are an attractive and viable option.

Megaflo Location

As the Megaflo or Unvented system is pressurised, it can be sited virtually anywhere; it does not rely on a header tank to provide a head of pressure.

Common locations are within an airing cupboard, a downstairs cupboard, utility room, loft, garage or basement. However, consideration should be given to the requirement for a safety discharge pipe to run from the cylinder to either outside or to a soil and vent pipe.

Megaflo Installation Manual

The Megaflo Installation Manual should be left with the customer for future reference.
An example can be downloaded here Megaflo-Eco-installation-manual.

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