types of heat emitters used in underfloor heating systems

Level 3 6035 Diploma in Plumbing Studies

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Types of heat emitters used in underfloor heating systems

Unit 306: Central heating



Heat emitters

Heat emitter come in various styles and sizes and are responsible for getting the heat in to the actual room or dwelling. The sizes, outputs and styles of emitters can be found in the manufacturers brochures. The more popular types available include:

•panel radiators

•column radiators

•towel rails

•fan convector

•skirting convector

•underfloor heating.

http://www.myson.co.uk/products/radiators.asp



Panel radiators

These are the modern radiators found in new build properties. Approximately 85% of the heat is convected via fins welded to the back of the radiator. They warm the cold air that passes through them, creating convection currents. Radiators that do not have fins rely heavily of radiated heat, which can result in cold areas in the room. These should be installed where obstructions will not interfere with the convection flow. Manufacturers recommend that they should be fitted at least 150mm from floor height, (depending on skirting height). Manufacturers supply many differing heights of radiators: 300–900mm They also supply varying lengths from 400mm (increasing by 100mm).



Low-surface temperature radiators LSTs, were originally designed for the NHS, where radiators couldn’t have a surface temperature above 43ºC. This was then accepted by nurseries, primary schools, homes for the elderly, disabled or infirm.

Low-surface temperature radiators



Column radiators

These are cast-iron emitters that have been used for many years, the more columns the greater the heat output. Now a days these are also made from steel and aluminium. Public buildings still use these and can be found in retro-fit properties.



Towel rails

These can come in a wide range of designs and colours, and can be used in a wet central heating system, or independently with an electrical element, for use during the summer when the heating system is not required. Towel rails can come with an inverted radiator, conventional tubular style or designer styles.



Fan convector

These work on a similar basis to the finned radiator. A copper heat exchanger mounted in the casing has lots of fins attached. This allows for additional surface area. Below this heat exchanger a low-volume electric fan is installed, which is operated by the heat exchanger warming up. These emitters can heat up large areas quickly.



Kick-space heater

These are designed for rooms with limited wall space to mount a radiator, eg kitchens, bathrooms or stairwells. They are installed under the kitchen unit or vanity unit and blow warm air into the room via a grill mounted on the kick plinth.



Skirting convector

This type of heater also has a finned copper heat exchanger but relies on natural convection only. It is installed around a room instead of skirting boards and tend to offer background heating. The main disadvantage with this type of emitter is that dust can block the fins and stalls the convection current.



Radiator valves

These are valves fitted to each end of the heat emitter. Normally, in the UK, these valves are installed in the bottom female tapings of the radiator (BBOE). Occasionally they are still found fitted to the top-bottom ends (TBOE).

http://www.screwfix.com/c/heating-plumbing/manual-valves/cat831018;jsessionid=jV9JQP7ZCQMtQJskzWyvfKlJMfGCM2Y2HhTBsfQNhhgDnpy9YkYx!1676769000



Thermostatic radiator valves (TRVs)

These valves are fitted instead of the wheel-head valve and allow temperature control of a single radiator. These are required under

Building Regulations Part L best practice.

http://www.draytoncontrols.co.uk/RadiatorValves.aspx

It has a special head fitted to the valve, which reacts to AMBIENT AIR temperature. Within the head there is a sensor containing a volatile liquid, which expands when heated. The warmer the room the greater the expansion, so it closes off the valve by pushing a pin down in the valve. As the room cools the liquid contracts, opening the valve allowing the radiator to heat up. One radiator in the circuit MUST be left without a TRV fitted. The Building Regulations state this should be the hallway radiator.



Underfloor heating

Underfloor heating, sometimes referred to as embedded pipe coils, is becoming more popular. It consists of pipework laid on a thermally insulated bed in a loop or coil formation around the floor of the room. This is then screeded over with concrete. The insulated bed prevents heat loss downwards and ensures that as much of the heat as possible is projected upwards into the room. Pipes are usually installed 150–225mm apart across the floor of the room. The pipework loops are fed back to a central pair of manifolds, one for the flow and one for the return. A special mixing valve regulates the water temperature to ensure that the floor does not reach too high a temperature. Each room is thermostatically regulated by its own room thermostat. With this system there are numerous benefits such as comfort, economy, flexibility and virtually maintenance free. Min 65ºC is required at the manifold which is then blended from the return to give approx 55ºC (40ºC can be used via a ground source.)



Principles of underfloor heating

The heat from the underfloor heating system conducts through the floor, warming the floor structure, making the floor surface a large storage heater, and the heat is then released into the room as radiated heat. Around 50–60% of the heat emission is in the form of radiation, providing a much more comfortable temperature at low room levels when compared to at traditional wet system with radiators.



During the design stage, the pipe coils are fixed at specific centres depending on the heat requirement of the room and the heat emission (in watts) per metre of pipe.

Quite often underfloor heating is used in conjunction with traditional wet radiators. The higher temperatures required for radiators do not present a problem because the flow water is an important aspect for underfloor heating. Some floor coverings create a high thermal resistivity making it difficult for the heat to permeate through. Carpet underlays and some carpets have particularly poor thermal transmittance, which means the heat is kept in and not released. The underfloor system is blended with the return water via a thermostatic blending valve.



The manifold is at the centre of an underfloor heating system. It is the distribution point where water from the heat source is distributed to all of the individual room circuits and, as such, should be positioned as centrally in the property as possible. Room temperature is maintained via thermostatically motorised actuators on the return manifold while the correct flow rate through each coil is balanced via the flow meters on the flow manifold.

Both the flow and return manifolds contain an automatic air valve to prevent air locks and a temperature gauge, so that the return temperature can be monitored. Most manifolds contain a circulating pump and a thermostatic mixing valve, often called a blending valve.



Pipework arrangements

There are many variations of pipe patterns based upon two mainpattern types. Which are:•the series pattern•the snail pattern.

The flow pipe runs in ever decreasing circles until the centre of theroom is reached, it then reverses direction and returns with parallelruns back to the starting point.

The flow pipe must be directed towards any windows or the coldest part of the room before returning backwards and forwards acrossthe room at the defined pipe-spacing centres.



Commissioning, testing and fault-finding

The testing and commissioning of central heating systems is probably the most important aspect of any heating installation, as it is here that we see if the system we have installed is leak free and performs according to the requirements of the design. Correct commissioning procedures are laid down by industry standards and manufacturer’s instructions. The correct commissioning procedures must be adopted if problems are to be avoided. There are documents that must be consulted which include:

•the Water Supply (water fittings) Regulations 1999

•British Standard BSEN12828, BSEN12831, BSEN14336 and BS7593

•The Building Regulations Approved Document L1A and L1B

•The Domestic Building Services Compliance Guide

•The manufacturer’s instructions of any equipment and appliances.



Full commissioning should include:

Soundness test

Cold tlush

Cleanse system(BS7593)

Hot flush

Fill system (inhibitor)

System check



Soundness test

The initial system fill is always conducted at the normal operating pressure of the system. Again, the British Standard BSEN14336 is very clear:

‘The heating system shall be water tight and tested for leakage . . . This test may be an independent test or combined test for water tightness and pressure verification.’

The system must be filled with fluid category 1 water direct from the water undertaker’s mains cold water supply. It is usual to conduct the fill in stages so that the filling process can be managed comfortably.



Soundness test

Cold flushing – After the system has been filled with water and checked for leakage, the system should be drained and completely emptied. This will remove much of the debris left over from the installation process

Hot flushing – A hot flush is conducted to remove any excessjointing compounds, flux residues and oils that may be present after the installation has been completed. The hot water separates these from the pipework and components.



British Standard BSEN14336 makes recommendations regarding chemicalcleaning. It states that:

a. chemical cleaning should be preceded by flushing with frequent sample testing as necessary;

b. the system shall be completely flushed and water filled with or without inhibitor, in accordance with the specification;

c. where the whole system is not being chemically cleaned at the same time, it is recommended that the isolating valves be locked in order to avoid pollution from untreated sections.

The cleanser should then be circulated around the system for a period of one hour with the boiler on, after which the system should be drained down and then flushed to remove thecleanser until the water runs clear.



Power flushing

When replacing boilers, or dealing with blocked pipework or radiators, a power flush may be required to remove any sludge within the system. In most cases, where a new boiler is being installed, a power flush is required as part of the warranty. Manufacturer’s warranties are void if this is not carried out.



When identifying faults that have occurred on hot cold water systems, the customer can prove an invaluable source of information as they can often describe when and how the fault first manifested itself and any characteristics that the fault has shown.

Verbal discussion with the customer often results in a successful repair without the need for extensive diagnostic tests.



When attempting to identify faults with hot water systems, the most important document that can be consulted is the manufacturer’s instructions. In most cases these will contain a section on fault-findingthat will prove an invaluable source of information.

A replacement parts list will also be present for those components that can be replaced. When ordering parts, it is advisable to use the model number of the equipment and the parts number from thereplacement parts list. This will ensure that the correct part is purchased.



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types of heat emitters used in underfloor heating systems

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