Underfloor heating

Make the right manifold choice

Chris Ingram, founder of Continal Underfloor Heating, reveals what gas engineers should look for when they choose an underfloor heating manifold

The manifold is at the very heart of every underfloor heating (UFH) system. It connects hundreds of metres of pipework to the heat source and controls the distribution of hot water to each zone in the system so that it is always at the correct temperature and flow rate.

Not all manifolds are created equal, however, and UFH installers should make sure they know exactly what each component does, and how it works, to make sure they choose the best-quality product.

Each manifold has a flow and return side, with fill and drain loops on the ends. They can be made from different materials but we would always recommend avoiding welded manifolds, which have more stress points that could shorten their working life.

The fill and drain loops each contain a bleed point, where a radiator key can be used to open up the valve if air needs bleeding from the system. You can also connect a hose to the loops if the system needs draining down completely.

When you’re choosing a manifold, make sure the fill and drain loops are bolted on rather than moulded – again, moulded versions are at greater risk of leaks. Some manifolds feature automatic air vents, but these can leak over time, so we would advise using manual versions.

Choosing a manifold with fill and drain loops that are bolted to the end rather than inside the manifold also helps to futureproof the system. If your customer’s plans change over time and you get called back to add more underfloor heating to an extension, for example, then you can simply unbolt the fill and drain loops, and join an extension

manifold to it.

The flow gauges are critical to setting the flow of water through the system. These should be nice and clear, with printing that will stay readable even over time. Flow rates can be adjusted easily on most systems: look for actuators that enable you to turn each zone on and off using thermostats in each room.

When installing UFH in a larger building, you may need more than one manifold: each manifold can only control up to 12 zones. Your chosen manufacturer should be able to provide you with all the advice you need.

The British and European standard for underfloor heating, BS EN 1264, requires that you must be able to shut off an UFH zone on both the flow and return side of the manifold, but a lot of cheaper manifolds that you can buy online don’t have this feature, so we would advise checking this carefully before you buy.

Mix it up

The mixer is responsible for taking the hot water from the boiler or other heat source to the pipes, after having blended the water to achieve the correct temperature. It then returns cooler water to the heat source once it has travelled around the system.

The mixer has a temperature gauge next to it, so that engineers can see that the water is at the correct temperature level, and a circulating pump comes as part of the mixer unit.

Mixers also provide a simple fail-safe overtemp protection. If you’re connecting the UFH to a heat pump, a mixer may not be necessary.

Some manifolds are easier to assemble than others. Look for components that bolt together securely, with no need to use jointing tape or welding tools, both of which can increase the risk of leaks.

With so much choice of UFH, it can be difficult to decide whether to invest in a more expensive manifold that offers lots of additional features, or whether a basic mode will do the job. Researching and understanding how the different manifold components work, and what you need them for, means you you can make an educated decision on which type of manifold is best suited to the job at hand. ■

www.ufh.co.uk

Continal’s stainless steel HeatMax manifolds are individually pressure tested

“Look for components that bolt together securely, with no need to use jointing tape or welding tools, both of which can increase the risk of leaks.”