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What is a Megaflo Unvented boiler system?

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What is a Megaflo Unvented boiler system? What is a Megaflow Boiler?

A Megaflo (also known as a Megaflo system, Megaflo unvented system, or often misspelt as “Megaflow system” or “Megaflow boiler”) is a stainless steel unvented cylinder that stores hot water as part of a central heating system. The most important thing to note is that the Megaflo is not actually a boiler, but a hot water cylinder (not to be confused with Baxi’s popular Megaflo system boiler range).

A Megaflo cylinder can be either “indirect” or “direct”. The difference between direct and indirect Megaflo tanks is how the water is heated, either directly (by a built-in element) or indirectly (by a separate regular boiler or system boiler). In some homes, you’ll have a switch by your cylinder should your boiler fail. The switch will kick in the immersion coil within the cylinder to heat up the water without your boiler supplying the hot water. Please be aware that it’s not advised to have your boiler and immersion switch on at the same time.

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Who Manufactures Megaflo systems?

The Megaflo is manufactured by Heatrae Sadia, an expert in manufacturing hot water cylinders and storage water heaters among other products. The Megaflo hot water system is Heatrae Sadia's most popular and award-winning range. It fits with our modern-day lifestyles to use more hot water as we need powerful showers, baths, toasty radiators and more basins. Abundant hot water is seen as a pleasure and as a daily necessity. We also want a balance of efficiency and reliability on which Heatrae Sadia pride themselves with their Megaflo products.

How does a Megaflo work?

Direct Unvented Megaflo

An unvented direct Megaflo system uses mains cold water as its water supply. The immersion heater inside the cylinder heats the water using electricity until it reaches the temperate set by the cylinder’s thermostat. It’s recommended that the thermostat is set to 60 degrees to ensure that you will have hot water readily available for when you switch on an outlet. As this hot water exits the cylinder, the Megaflo system will replenish your cylinder's water supply with cold water from your mains water feed.

Indirect Unvented Megaflo

Unlike the unvented direct Megaflo system, the indirect version uses hot water supplied by an external source such as a traditional boiler. In this case, the coil within the cylinder simply maintains the temperature of the hot water so that it remains at the temperature set by the cylinder’s thermostat. As the hot water exits the unvented indirect Megaflo, the boiler will kick in to top up the hot water in the cylinder.

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Using renewable energy to heat your home?

Heatrae Sadia Megaflo hot water tanks are also compatible with solar thermal energy, which is great for the environment and makes use of renewable energy sources. If you have solar panels installed, this is a great backup heat source should your boiler ever break down.

What warranty can I expect with a Megaflo?

Long-lasting warranties and high-quality parts are particularly important in UK households with varying levels of water "hardness". Some regions have ‘soft water’ while some have ‘hard water’, which can lead to issues such as limescale in your kettle or pipes. The reliable and robust stainless-steel build of each Megaflo hot water cylinder ensures that you receive a 25-year warranty for your peace of mind. Please note that the rest of the components in an unvented boiler system may have shorter warranties.

Megaflo cylinders are perfectly suitable for large households with several outlets including multiple bathrooms. Due to the large volume of hot water being supplied by the Megaflo, you can expect enough hot water, and a steady level of water pressure even if multiple outlets are in use at once. This is a breath of fresh air in comparison to running hot water via a combi boiler, where pressurised hot water from the boiler is split between outlets, leading to a drop in pressure, which , in turn, makes it difficult for more than one person to have a shower at the same time.

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Pros and Cons of a Megaflo

Let’s weigh up the pros and cons of the Megaflo, if you are considering investing in this system for your home:

Pros of a Megaflo

Removing a cold water tank presents multiple benefits of an unvented system:

  • If you have a household with limited space, you won’t need space in your house for a sizeable loft-installed tank, in addition to a cylinder.
  • You'll have less risk of water becoming contaminated, as water sat in a cold water storage tank can run the risk of collecting sludge and dirt.
  • Because you don’t need a cold water tank, you'll have more flexibility over where your Megaflo cylinder can be installed.vers

In addition to the benefits of a lack of cold water tank:

  • The system uses mains pressure, which will significantly improve the performance of showers and baths, especially for those who prefer "power showers". The water pressure in your system will always remain consistent even if more than one outlet is being used at the same time, which is great for busy households.
  • Megaflo cylinders are easy to install, and parts are easier to replace and maintain.
  • They have 60mm of insulation.
  • If for whatever reason your boiler breaks down, or if an immersion heater is your only option, this system is compatible with solar PV.
  • The system also comes with several different safety features. The cylinder thermostat will shut the boiler down when it has reached the correct temperature. If it becomes too hot, the Temperature/Pressure Relief Valve (TPRV) would dump water out of the cylinder into a drain to reduce pressure.

Cons of a Megaflo

  • Using the mains water supply to power your system means there is no real backup storage of cold water. Even with a full Megaflo cylinder, the system needs water pressure from your mains water supply pushing through it to ensure it delivers hot water, or you may face a hot water shortage.
  • If your mains water supply is low in pressure, the pressure of the water reaching your outlets (showers and taps) will also be weak. A flow rate test has to be completed to gauge the pressure of your mains water supply and to determine whether a Megaflo is suitable for your home.
  • Pipework will need to be double checked to ensure that it can withstand the high pressure from the Megaflo. This may lead to having to replace pipework if it is not fit for purpose, which can be pricey.
  • The high velocity of water flowing through the pipework can create a lot of noise.

Safety Precautions of an Unvented Megaflo System:

Unvented boiler systems use thermostatic controls to maintain the temperature of the water so that it does not go above 100 degrees Celsius (which can be especially dangerous):

  • The ideal temperature for a cylinder is usually between 60 to 65° Celsius, which tends to be the default setting for the controls. This is also to mitigate the risk of Legionnaires Disease since anything lower than this temperature increases the risk of dangerous bacteria forming in the water.
  • If the temperature of the water within the cylinder reaches 85° Celsius, the cylinder thermostat cuts the boiler off to prevent the temperature from rising further.
  • Water expands when it is heated which increases the pressure within the cylinder. If the temperature and pressure are too high, which can be dangerous and potentially explosive, this forces the Temperature/Pressure Release Valve (TPRV) to open to ensure any excess pressure is released and reduce the temperature of the water in the cylinder.
  • Any cylinder, boiler, or component in your central heating system must be installed and maintained by a Gas Safe engineer. This engineer must also hold their Unvented Hot Water qualification (otherwise known as a G3 qualification) to install, maintain or inspect unvented cylinders. The Building Regulations Approved Document (section G3) requires an unvented hot water cylinder to be installed and maintained by a competent person.

In conclusion, the Megaflo unvented cylinder by Heatrae Sadia is a great choice for homeowners looking for a space-saving alternative to their old system, especially if they want to remove a cold-water tank from their loft. Megaflo cylinders are a great fit for homes with high hot water demand. There is a good warranty of 25 years for peace of mind, and the system as a whole pumps hot water efficiently to your hot water outlets - you won’t freeze in the shower if someone puts on the tap in another part of the house.

If you’re keen to swap out your old vented cylinder for an unvented cylinder, then look no further than the Megaflo, with fewer parts and components, and the perfect addition to any central heating system.

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