A Brief Guide to Megaflo Systems

Megaflo systems are one of the most popular heating devices in the UK.

But what are they exactly? And why are they so popular?

Read on to find out!

Megaflos: An Introduction

A Megaflo (also known as a Megaflo system or Megaflo unvented system) is a stainless steel unvented cylinder that stores hot water as part of a central heating system. 

It is not actually a type of boiler, but a hot water cylinder.

In some homes, you’ll have a switch by your cylinder for if/when your boiler fails. This will start the immersion coil within the cylinder to heat up the water without your boiler supplying it.

Note: The Megaflo is not to be confused with the manufacturer Baxi’s popular Megaflo system boiler range.

How Megaflos work

A Megaflo cylinder can be one of two types.

Direct Unvented

A direct unvented 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 temperature 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

The indirect unvented 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.

Integration with renewable energy

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.

Temperature controls

Unvented boiler systems use thermostatic controls to maintain the temperature of the water below 100 degrees Celsius (which can be especially dangerous).

The ideal temperature for a cylinder is usually between 60 to 65° Celsius. This tends to be the default setting for the controls.

This is also to mitigate the risk of Legionnaires Disease, which forms in water at lower temperatures.

If the water in the cylinder reaches a set temperature (often 85° Celsius, but this can vary by model), the cylinder’s 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. A situation where temperature and pressure are too high can be potentially explosive. 

To prevent this, the Temperature/Pressure Release Valve (TPRV) opens to ensure any excess pressure is released and reduces the cylinder water’s temperature.

Please note: it’s not advised to have your boiler and immersion switch on at the same time.

Megaflo warranties

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.

Pros and cons of Megaflos

Pros

Suit large households

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. 

In Combi boilers, by comparison, pressurised hot water from the boiler is split between outlets, leading to a drop in pressure. This in turn makes it difficult for more than one person to have a shower at the same time.

Saves space

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.

Easy and flexible install

Because you don’t need a cold water tank, you’ll have more flexibility over where your Megaflo cylinder can be installed.

Megaflo cylinders are easy to install. 

Less risk of contaminated water

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.

Strong water pressure

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.

Compatibility

If for whatever reason your boiler breaks down, or if an immersion heater is your only option, this system is compatible with solar thermal.

Safe

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.

Easy to maintain

With both types of Megaflos, parts are generally relatively easy to replace and maintain.

Cons of a Megaflo

Lack of backup

Using the mains water supply to power your system means there is no real backup storage of cold water. 

Reliance on mains water pressure

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.

Noise

The high velocity of water flowing through the pipework can create a lot of noise.

Safety qualifications around Megaflo installations and maintenance

Any cylinder, boiler, or component in your central heating system must be installed and maintained by a professional.

They must also hold their Unvented Hot Water qualification (also 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.

Conclusion

Megaflo systems are a space-saving alternative to regular boilers, especially if you want to remove a cold-water tank from your loft. 

They are a great fit for homes with high hot water demand. And they have a good warranty of 25 years for peace of mind. 

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.

If you’re looking for comprehensive, reliable boiler cover (which covers Megaflos and regular boilers), select a plan from Hometree today.