Central Heating

Types of central-heating system

• As with cold and hot water systems there are many different types of central heating system out in the workplace.

• Some which could be decades old still working but in need of either refurbishment or maintenance

• Some systems need to be extended or have controls added to make them compliant with the latest Building Regulations

• Like TRV (Thermostatic Radiator Valves), mid position valves, programmers, cylinder and room thermostats for total control of heat and efficiency

The one pipe system

One pipe system

Two pipe system semi gravity

• This was a popular choice of system particularly in the 1970s. It is no longer permitted on new properties (other than with solid-fuel boilers) without additional controls being installed.

• Nor do they meet the requirements of the Building Regulations for extension or boiler replacements to existing oil- or gas-fired systems.

• In a two-pipe system, water is pumped around both the circuit and the radiators.

• This improves the speed with which radiators heat up. The system can easily be balanced by adjusting the lock shield valve on each radiator.

Building Regulations and central-heating

• The Building Regulations 2000 deals with the conservation of fuel and power

• Approved Document L1: Conservation of fuel and power.

• This document sets out the requirements for all central heating installations in domestic dwellings

Fully pumped systems Y - plan

Fully pumped systems

• In this system, the hot water and the heating circuits are operated completely by the pump.

• Installations are controlled by motorised valves.

• There are a number of system designs incorporating two-port zone valves or three-port valves (two-position and mid-position) that meet the requirements of the Building Regulations Approved Document L1.

S-plan ( zone valves )

Feed and expansion cistern

• As you have seen from the diagrams in this chapter, the feed and expansion (F&E) cistern is used on all open-vented central-heating systems.

• While the cistern allows the system to be filled up, its main purpose is to allow water in the system to expand. The water level should therefore be set low in the cistern when filling the system.

• The cold feed to the system in an average domestic property is usually 15 mm minimum, and this pipe should not include any valves.

• This is to ensure that, in the event of overheating, there is a constant supply of cooler water to the system to prevent the dangerous condition of boiling.

• The servicing valve to the system should be located on the cold-water inlet pipework to the cistern

Feed & Expansion cisterns

• The F&E cistern is located at the highest point in the system, and it must not be affected by the position and head of the circulating pump

Pump positions

Primary open safety vent

• In a fully pumped system, this should usually rise to a minimum height of 450 mm above the water level in the F&E cistern to allow for any pressure-surge effects created by the pump

Air separators• The purpose of the air

separator is to enable the cold feed and vent pipe to be joined closely together into a correct layout to serve the system.

• The grouping of the connections causes turbulence of water flow in the separator, which in turn removes air from the system.

• This reduces noise in the system and lowers the risk of corrosion

• Here is a common picture of a air separator

• The connections are normally

• to cold feed • to vent pipe • to boiler flow

Heat emitters

• Just another name for a radiator, well no there are many different heat emitters from fan assisted to your standard panel radiator here are just a few

• Kick space or plinth type

• The standard panel radiator which depending on manufacturer can have several different features as to sizing and shape

Some of the different types of radiator

• A traditional type towel rail with inset column radiator

• The radiator supplies a small amount of heat while the rail dries the towels

Modern type towel heaters

• A modern type towel may look decorative, but some rails are there only to dry towels.

• They hardly throw any background heat into the room, but are quite popular

How to fit them

• The standard radiator is fitted approx 150mm to 175mm from the floor, this is to allow for air flow around the radiator.

• However if required because of high skirting's or other obstacles they can be fitted higher

Radiator brackets• A number of brackets and

fixing• styles are available, and are

usually provided with the radiator.

• The bracket shown has deep hanging slots and corresponding lug positions.

• These provide greater stability. Plastic inserts are used to seat the radiator precisely and help to minimise expansion and contraction noises

Radiator valves

• There is a wide selection of valves available from manufacturers.

• Building Regulations require thermostatic radiator valves (TRVs) to be installed on new systems or for there to be some other means of controlling an individual room’s temperature

Wheel-head radiator valves

• These enable the occupier of the building to control the temperature of the radiator manually by turning it on or off.

• Rotating the plastic ‘wheel head’ anticlockwise will raise the spindle through the body of the valve, lifting the valve and opening the flow to the radiator.

Wheel-head radiator valves

• This is the inside of a radiator valve

• Most of them have similar internal workings , but some valves can withstand higher pressures, or are designed to fit the customers needs angled or straight or thermostatic

• Traditional boilers

• boilers with cast-iron, high-alloy steel, copper or aluminium heat exchangers

• system boilers.

• All boilers can be floor standing or wall-mounted, and are usually designed to fit in with kitchen unit installations.

• Gas-fi red back boilers are also available; these are concealed in a chimney opening at the back of a gas fire.

• Traditional or regular boilers supply hot water indirectly via a domestic hot-water storage cylinder, which is usually sited at first-floor level

Condensing boilers

• The condensing boiler has to include a fan to make the process work, and the heat exchanger is larger than that in non-condensing boilers.

• The boiler is able to extract more heat from the combustion process than traditional boilers, making it more efficient.

• As the flue gases are cooled, the water vapour they contain turns to liquid (condensates), which has to be drained from the boiler to a drain or soakaway.

• Condensing Combi boilers now are so efficient compared to old boilers, that from 2004 any new boiler fitted had to be condensing

Time switch

• A time switch is an electrical switch operated by a clock to control either space heating or hot water, or both together

• Some are programmer thermostat and have multi functional displays, and some are even wireless

Automatic bypass valves

• These are mechanical devices used to make sure water can flow through the boiler to maintain a minimum water-flow rate should a system using zone valves or TRVs become closed.

• Once set, the valve opens automatically as the TRVs or zone valves close and the system pressure goes over the pre-set limit.

• Use of the bypass valve reduces system noise and increases pump life by preventing it working against a ‘dead head

• An auto bypass open to stop damage to the pump on the system

• It can however become damaged with system debris which makes the valve vibrate and normally a high pitched buzz can be heard throughout the system

Automatic air vents• These are used on central-

heating systems in order to remove air from the system automatically.

• A vacuum break on the bottom of the valve prevents an air lock forming and encourages air to be released from the water.

• Vents should always be installed on the positive side of the system and positioned where air is likely to get trapped

Motorised valves

• Three-port diverter valve • This can only give hot

water or heating • The ports on the valve are • AB the inlet from the flow• A which is the out let to

the heating • B which is the outlet to

the hot water cylinder ( B for Bath )

Zone valve

• A motorised valve which opens and closes when told can be used any where on central heating required or for domestic hot water applications, usually though on larger building

Mid position three port valve

• This valve looks very similar to the three port valve, and it is.

• The difference is it can do central heating and hot water both at the same time, the valve goes to a mid position to do this

Junction box or Wiring centre• These provide the connections

between the electrical system components and the mains electricity supply.

• Most manufacturers supply their controls in packs, and these can include a wiring centre which is designed to simplify the wiring of a particular system pack.

• Packs include control valves, programmers and thermostats. All the terminal connections are clearly marked, and full instructions are included with the wiring centre

Soundness testing of central-heatingpipework systems

• visual inspections• Pressure testing • Cold flushing the system• final checks• Hot flushing of pipework• anti-corrosion procedures

Decommissioning of central-heating systems

• Isolate the system

• Make sure the electrical supply to the heating system is isolated. Turn off the boiler.

• Remove the fuse from the spur outlet to the wiring centre or junction box for the controls. Advise the customer of what you are doing and not to touch the controls.

• Only work on the system when the water has cooled.

• If you speak to the customer beforehand to arrange the job, it is a good idea to ask them to turn off the system so that it is cold when you get there

Close all outlets

• Turn off the service valve to the F&E cistern; close any automatic air vents.

• The open vent pipe and cold feed now need plugging – manufacturer devices are available, to carry this out

Draining down the radiator

• This is carried out by isolating both radiator valves and the loosening of the union nut on the radiator valve to be replaced.

• Catch the water from the radiator in a small bowl, and have a bucket handy to empty the bowl from time to time. Air needs to be let in to the radiator through its air vent to ensure that the water in the radiator fully drains out.

Filling a heating system

• There are a couple of different ways of filling a heating system

• With the open vent system the water fills its self, but air must be removed from radiators with a key

• However sometimes air locks can happen on poorly designed systems

Sealed systems

• With sealed systems such as combi’s most of the time this is done via a filling loop, it can be fitted external to the boiler, or inside of the boiler as per the manufacturer.

• The normal operating pressure of a sealed system is about 1 to 1.5 bar

• The rads are bled the same as before to remove any air, inside the boiler

• The radiators are bled the same as before to remove any air.

• inside the boiler an AAV ( automatic air vent ) removes the air from the boiler, then the pressure is checked on the gauge cold against manufacturers instructions

Finishing touches

• When the job is finished a fully fitted central heating system complete with boiler and all controls are complete, this should last the customer for years,

• At this point the instructions and how to use the system should be shown to the customer, and Benchmark left filled in by the installer for the customer

•Any Questions ?