What pipe should i use for central heating

There are a few main materials used in the construction of heating pipework, each boasting their own unique properties, advantages and disadvantages. Stainless steel and carbon fibre are the most popular pipework manufacturing materials on the whole. However, there are a whole host of other non-metallic, plastic and lined piping options available too, including concrete, copper, fiberglass and aluminium.

An overview of each type will follow later in this article, but as a basic starting point, any decision on material should take into account the array of conditions the pipework will encounter. In particular, the shifts in material strength in environments with enhanced temperatures.

Given that fluid flow can cause erosion or corrosion in pipework over time, it is a sound idea to choose a material that will corrode slowly at a rate that is known. Essentially, three main arrangements are typically in place to connect the boiler to your home radiators or heated towel rails.

These come in the form of a single pipe loop, feed and return pipes, and a micro bore. In most cases, the heating pipework will be installed beneath the radiator. It can be fitted underneath the floorboards in rooms with suspended timber flooring, with risers used to connect the pipes to the radiators.

Usually, these types of pipework fittings will feature high level feed pipes connecting to adjacent or single domestic radiators. For spaces with suspended ceilings, the piping will typically be installed between the joists of the ceiling from overhead, but that might not be viable if each floor is a dwelling of its own.

Another option is to set the pipes to travel around the top of the wall slightly beneath the ceiling using fall pipes. In such instances, the pipes would have to be wound around the door frame or buried underneath the floor, which might be a touch too invasive for your taste. In the event that high level feed pipes require installation in an attic or loft space, the pipework will need to be insulated. And in instances where the circulating pipework is positioned higher than the radiators or other connected heating devices, the pips will have to feature bleed valves to release any air trapped within the system.

As the moniker suggests, single pipe loop systems feature a lone pipework loop which runs from and returns to the boiler. All radiators involved are positioned upon the pipe with each radiator connection leading to the same pipe. As heated water from the boiler travels along the pipe, convection occurs, leading the heated water to elevate into the radiator, sending cooler water back to the pipe. One of the major drawbacks of this sort of pipe arrangement is that the first radiator will heat up to a greater extent than the second and third one and so forth.

As such, the final radiator in the system will be significantly cooler as it will have transmitted the majority of its heat to the initial radiators on the pipe run. Theoretically, an unlimited amount of domestic radiators can be installed on a single pipe loop. But, the more radiators that are fitted, the more apparent will be the cooling between the first and final radiators. Single pipe loop systems are more regularly found in industrial settings in which the loop pipe could be immensely large, as opposed to residential buildings.

Modern domestic pipework installations are highly unlikely to follow the single loop line, and instead focus on a more efficient pipe fitting arrangement. Feed and return pipe arrangements operate in a more efficient manner than single pipe loop systems. As a result, the temperature of the water infiltrating each domestic radiator is practically the same, so a very similar heat output should be emitted from each heating device. An automatic bypass valve, or pressure relief valve, connects the feed and return pipes, enabling the pump to transport boiler water should all the radiators be shut off at any one time.

On account of the flow restriction dictated by the radiators, the amount of radiators required is generally limited by the scope of the circulating pump. A standard pump for domestic feed and return pipework installations will typically offer an adequate supply for up to 12 radiators or heated towel rails.

The size of the piping can prove another limitation to the number of radiators fitted too. In most instances, the main pipes entering and exiting the boiler are significantly sized at over 22mm, with smaller pipework 15mm or less tailing off to feed a few radiators or alternate heating components.

Just how many residential radiators can be fed through these smaller pipes will be dependent on the length of the 15mm pipe runs. The longer the length of the pipe run, the less radiators will be needed. Heating professionals would tend to recommend no more than three radiators are run along a single 15mm pipe branch. This more modernized setup, sometimes referred to as a two-pipe system, is far more likely to be found in contemporary homes, and is typically better suited to serve domestic needs in residential properties.

Micro bore piping arrangements make use of standard pipework for the feed from the boiler to manifolds, and from manifolds back to the boiler on the flip side, or the return to speak a touch more technically. Small pipework typically 8mm stems from each manifold, connecting to several radiators. The piping between each manifold and the radiators usually measures five metres or shorter.

It could be that special radiator installation techniques are utilised to ensure both the feed and return micro bore pipes are attached to the same end of each radiator. Contrastingly, the pipework could be fed into the opposite ends of the accompanying radiators.

Also i havnt bought a boiler yet so would the first option need a larger output btu to compensate? Simon F Plumber. Gas Engineer. Messages 2, If the boiler is not sized correctly it will not be working to the best efficiency. Last edited by a moderator: Dec 28, AWheating Plumber.

Messages 9, Thanks for your response.. I intend to do the reverse return plumbing method as this is a self -balancing system and have done all the other calculations.

I just couldnt find any info on pipe sizing. I'im not going to do any illegal work , as a few seem to be worried about just doing as much as i can then getting it checked and connected to gas by an engineer. Bit over kill doing a reverse return on a domestic house but whatever floats your boat. Hi im trying to get some help here, thats why im on a forrum, just trying to read up on what to do ,if its over kill ill think again. Generally it's a 22mm pipe forming a flow from the boiler to create a heating circuit and returning to return in the boiler.

Off this you'll have 15mm preferably or 10mm. One pipe attaches to flow and goes to trv and other pipe comes from lockshield to return. Bear in mind that there are a multitude of variances on this theme and I'm blown if I'm going to go through them all!! Howsie Plumber. This is due to the fact that the water will arrive hot in the first radiator, but by the time it reaches the furthest radiator, most of the heat will have dissipated, causing the radiator temperatures to be uneven around the house.

In theory, unlike the feed and return system, it is possible to fit as many radiators as you like to this installation, however there will always be the issue of the last radiator being colder than the first. In general, although this system can be found in old buildings and industrial premises, the single pipe loop is considered inefficient and antiquated, and is no longer used on new builds. Microbore Pipework This system utilises regular pipework to feed the water from the boiler to manifolds and then from the manifolds to the boiler on the return side.

As with the feed and return system, there is a pressure relief valve between the boiler and the return pipes in the event the rads are all shut off. The main benefit of the microbore system is that because the pipes are smaller. The smaller pipes are also easy to bend and reshape whilst they are being installed making the more versatile and decreasing the amount of joints needed. These are available in wired or wireless versions.

The problem with a room stat is that it doesn't accommodate local temperature variations, perhaps caused by the sun shining through windows or by an open fire in a living room. You can reduce the heat output of your individual radiators by closing a manual valve. But it's much more efficient to install thermostatic valves, which do this automatically for you and then open again when the room temperature drops.

Even better are programmable thermostatic radiator valves, which maintain the desired temperature of individual radiators at set times of the day.

Radiators and towel warmers needn't just be functional heat providers. These days there are lots of stylish options to complement every interior. A simple time switch will turn the system on and off at pre-set times, but a programmer lets you operate your heating and hot water circuits independently at different times of the day.

A controller gives you even more flexibility. This operates the system at set times and also responds to temperature fluctuations, while a boiler manager ensures that the boiler only runs when necessary by sensing a variety of conditions - including outdoor temperature. When the temperature in the cylinder reaches the set limit, the thermostat operates a motorised valve and shuts off the flow to its heat exchanger.

When the water temperature drops, the valve opens again. Motorised valves known as 'zone' or 'mid-position valves' can also be used to shut off parts of the system at specific times of the day when heating isn't needed in some rooms. This can be useful in a large house, where you might not want to heat all the bedrooms on upper floors during the day. It's a requirement in systems heating more than m2. Introduction In a central heating system, heat is produced from a single source usually a boiler and distributed through the house as either hot water or hot air.

Pipework The radiator circuits in most modern wet central heating systems are made from standard 15mm copper pipe, while the pipes that link the boiler, pump and points where the circuits split off will be 22mm or 28mm in diameter. Two-pipe and single-pipe systems More modern systems have a two-pipe layout, where hot water is carried from the pump to the inlet valve of each radiator by a flow pipe, which terminates at the last radiator on the circuit.