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Pump overrun and permanent live

A unique feature of Baxi heat only boilers (Baxi EcoBlue Heat, Baxi EcoBlue Advance Heat, Baxi 200 Heat and Baxi 400 Heat) is that they don't need a pump overrun or permanent live.

That means the installer does not need to run wires from the boiler to the pump, which often involves lifting carpet and floorboards before installing the boiler. This is good news for everyone as it is time consuming for the installer and inconvenient for the householder.

What is the pump overrun?

Older boilers were made of very different materials to the high efficiency models manufactured today. When they turned off, any residual heat left in the boiler could safely disperse through the casing and flue.

Today's boilers are much more energy efficient, but because they are lighter, they are less able to disperse any residual heat in the boiler, and there is a danger that the heat will cause the water in the heat exchanger to boil, causing extensive and costly damage to the heat exchanger.

Most other manufacturers overcome this risk by using a pump overrun. Typically,  boilers are designed so that the pump continues to run for a short period after the boiler has switched off, circulating the water so the heat is dissipated through the heating system and won't boil in the heat exchanger.

As the pump is usually installed in the airing cupboard next to the hot water storage cylinder, the installer needs to run a wire from the pump to the boiler, which is often situated in another part of the house. Wireless options are available, but they are costly and may not always be suitable.

Why don't Baxi heat only boilers need a pump overrun?

Baxi uses aluminium heat exchangers which we cast in our own foundry at our factory in Preston to our own design. This means that we can engineer every aspect of the heat exchanger design and have complete control over the manufacturing process.

Aluminium is a great conductor of heat, and holds less residual warmth. The heat exchangers for our heat only boilers have been carefully designed to be thinner and slimmer, so they react more rapidly when the boiler is turned off and the risk of boiling water is eliminated, as is the need for a pump overrun.

That means that with a Baxi Heat only boiler there is no need to run a wire from the pump to the boiler, no lifting carpets and floorboards - in fact less hassle and a quicker, neater job!

What is the permanent live?

The permanent live is a power supply to the boiler that is always live. It powers a screen or diagnostic/power light and runs the pump overrun when the boiler has switched off.

Many old boilers don't have a permanent live so the installer has to get it from a permanent power supply on the heating system; this can be more difficult than getting a wire from the boiler to the pump for the pump overrun!

Why don't Baxi boilers need a permanent live?

Baxi boilers don't have a pump overrun that needs power when the boiler switches off or a screen or power light that needs to be on when the controls have switched the boiler off.

This saves the installer the problem of getting a permanent power supply to the boiler and means less disruption for the householder as floorboards don't need to be lifted and made good.

Choosing a Baxi Heat Only boiler can you save you time, hassle and money when it comes to installation. Use our Find a Boiler tool to find the perfect Heat Only boiler for you!


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