A boiler which produces all your hot water on demand and gives you all the heating required to keep you warm all winter. All the controls and components (excluding the thermostat & programmer) are housed within the boiler. Other than the boiler this type of heating system does not require a hot water cylinder or cisterns in the loft, therefore is great for space saving
Flats, maisonettes and houses of a modest size. There are more powerful combi’s available for bigger houses but these do command a high price
All taps at mains water pressure
Space Saving- no hot water cylinder, no cisterns in the loft or connecting pipe work
Fresh mains water to your bathroom, not from a cistern in the loft
No pipes to freeze in your loft
Endless hot water, heated on demand, meaning …
There’s no hot water cylinder to run out to cold – as you don’t have one.
Internal corrosion (rust) to radiators and boiler, caused by air in the system, virtually eliminated
As the boiler does all the work you only have to maintain the boiler and not the cisterns in the loft - as you don’t have any.
If you’re having a shower and somebody runs a tap in the kitchen your shower will go cold whilst that tap is being run
Can’t have a power-shower
A 24Kw boiler with a hot water flow rate of 9 litres/ min will be quite slow to fill a bath, although will be fine for a shower
No warm airing cupboard
No stored hot water
Gas pipe work must be calculated to the correct size, usually larger than a traditional boiler- thus, you may need a new gas pipe run from the meter to boiler.
Can be bad in high top-floor flats, with poor water pressure.
TRADITIONAL OPEN VENTED OR HEAT ONLY SYSTEM
Boiler, floor standing or wall mounted
Hot Water Cylinder, often in an airing cupboard
A pump, motorised diverter valve(s) & wiring centre
2 x cisterns in the loft. One large the other small
Houses from 3/ 4 beds & upwards
Supply of hot water always available via cylinder
Great for homes with low pressure mains water
Reliable and understood technology
Hot water can be boosted with a pump, to give a Power-shower
Lots of hot water with a good flow rate per/ min. Often comes with a back up of an electric immersion heater/ element inserted inside your cylinder.
Older boilers, for this type of system, often very robust
Space Consumed by - a hot water cylinder, 2 x cisterns in the loft & connecting pipe work
Internal corrosion (rust) to radiators and boiler, caused by air in the system
Un-insulated pipes in your loft can freeze
Bathroom cold water is stored in a cistern in the loft giving potential hygiene problems.
Extreme worst case scenario - Legionnaires’ disease which develops in still water between 20 & 45ºC; leave a glass of water on a hot windowsill for a long time and watch what happens - green algae!
UN-VENTED SEALED SYSTEMS
Requires a boiler and an Un-Vented hot water cylinder - which is often referred to as a Megaflo – this is a makers name, like Hoover. Provides all your heating and hot water.
A sealed system of pipe work and components which are pressurised above atmospheric pressure. The system is fed directly from the mains water supply. With a Traditional Open Vented system (see previous entry) there are heating and hot water vent pipes terminating over the loft based cisterns; the un-vented system does away with such pipe work and cisterns. As a technology the un-vented system has been used in the rest of Europe for a lot longer than the UK.
Brilliant heating and hot water system for homes 2/ 3 beds and upwards. Highly recommended.
Gallons of hot water at mains pressure, giving fabulous showers
Cold water at mains pressure to all taps
Supply of hot water always available via un-vented cylinder
Has a back-up of an electric immersion heater/ element inserted inside the cylinder - great for topping up your hot water supply when there is a high demand of hot water.
Space saving in your loft - no cisterns in the loft or inter-connecting pipe work
Being a sealed system Internal corrosion (rust) to radiators and boiler, caused by air in the system is virtually eliminated
Risk of contamination from cold water storage eliminated - you have no cistern in the loft
Un-vented cylinders can be located in many places, even the loft
To operate successfully the water cylinder needs a good mains water pressure supply
To achieve a good mains water pressure supply you might need a new dedicated cold water supply pipe from your in-coming water main to the new hot water cylinder
In addition to the boiler, an un-vented cylinder requires an annual service
If choosing this excellent system to replace a combi boiler you will need a new boiler, hot water cylinder and associated controls (valves)
CENTRAL HEATING VARIATIONS – The Sealed System
Traditional, Open Vented Heat Only Systems with a cylinder in the airing cupboard and cisterns in the loft can be converted to what we call a Sealed System. The main benefit being that a sealed system virtually eliminates internal corrosion (rust) to radiators and boiler, caused by air in the system.
Ideal When: Up-grading a Traditional, Open Vented Heat Only Boiler and installing a new ‘System’ boiler. At a later date your traditional copper hot water cylinder could be exchanged for a more efficient Un-Vented cylinder, see enclosed notes on Un-Vented Sealed Systems.New Paragraph
For more information on different boiler types click the button below to ATAG's website. They also have a boiler finder tool to help you find the perfect boiler type for your home