Fundamental Central Heating Requirements
Boiler Type and Size
There are three main types of high-efficiency condensing boiler- the combination or ‘Combi’, the Conventional (Open Vent Heat Only) and the System (Sealed). Each type delivers the benefits of high-efficiency technology, but is suitable for different types of homes.
Types of Boiler
Combination ‘Combi’ Boilers
Combi boilers are becoming increasingly popular within the UK as they remove the need for independent tanks, pumps and valves, as they are built in within the boiler. They heat your home and also provide instant hot water. The benefits are that everything is self-contained, thus reducing space, and parts repair. However, they do not provide stored water should the boiler ever breakdown, and if installed in an unsuitable type of property (ie one with 2 or more bathrooms), can lead to pressure problems should numerous services be run simultaneously.
Conventional Boilers
Conventional systems tend to be in older properties. These normally comprise of a heat only boiler, a copper cylinder which stores the hot water, a cold water storage tank and a Feed and Expansion tank. They mains water will supply both of these tanks and the kitchen sink cold tap, and usually no more. The advantage of these is that they do not suffer the pressure drops that combination set ups sometimes experience because the water is stored. However, the space required for all the aspects of this system can be quite extensive and also the running costs can be relatively large for only a one person household.
System Boilers
The System boiler set up is quite similar to that of a conventional one, but usually the cylinder is an Unvented Cylinder. (for example a Megaflow). Ie there are no cold water storage tanks or Feed and Expansion tanks. The cylinder is mains fed so the pressure at the hot tap will be similar to the mains cold feed entering the property. The advantages of this are the space savings that can be achieved by not having the tanks and greater flow rate at the hot tap. These cylinders can also be stored in garages and in attics. The disadvantage can be the cost of them and also a requirement of 22 litres per minute of mains water flow rate.
Here are a few considerations you might need to think about when deciding upon the most suitable condensing boiler for your needs.
| Property Consideration | Recommended boiler type | ||
| You want instantaneous hot water without heating it up | Combi | ||
| Your Bungalow or flat has limited space | Combi | ||
| Your wish to install Solar with a twin coil cylinder | System | ||
| You want to carry out a loft conversion | Combi, Conventional or System | ||
| To improve the energy efficiency of your system | Combi, Conventional or System | ||
| Your home has more than 2 bathrooms | Conventional or System | ||
| Your property has low water pressure | Conventional |
Size of Boiler
Calculating the size of the boiler is absolutely essential, and ideally should be carried out by a qualified engineer experienced in working out the property requirements. The calculation is based on upon such variables as room size and orientation (btu requirements), materials, insulation and flow rate* (for Combi’s)
The reason the size of the boiler is critical is because of the following:
Oversized – Can lead to the boiler not Condensing effectively, therefore not running at its optimum efficiency. It is possible for a knowledgeable engineer to range rate the boiler during the commissioning stage of installation, However, it is better to purchase the correct boiler at the outset.
Undersized – Here the size of the boiler (in Kilowatts) simply isn’t big enough for the property. The outcome will be that radiators will not become hot enough.
*Please note, if the property has two or more bathrooms, it is often prudent to increase the kilowatt boiler size to enable necessary hot water flow rate at the services.
All our engineers at Plumbing Wise are suitably trained at the quoting stage to correctly calculate the boiler size. Our calculations are based on the following calculator, which we have added on to our site, with a view to enabling you to calculate the boiler size should you wish.
We, at Plumbing Wise, welcome the opportunity to provide you with free impartial advise on the best type of install to suit your requirements. All our estimates are free of charge and will be provided to you in a quick and easy to read format.
Gas Rates for Boilers
In order to meet gas regulations and manufacturers’ warranty requirements it is imperitive that the gas supply to your boiler is sufficient. This is not always determinable if the existing boiler is not currently working and so therefore it might be necessary for your gas supply to be upgraded. As a general rule, if there is a 22mm gas supply to your boiler and the gas meter is not too far away then the supply should be good enough. However, if the supply of gas is insufficient, the following charges for re-running a gas line will apply. (Please note that these will ordinarily be included within the Fixed Quote that is provided, unless it is actually not possible to trace the gas supply from the meter to the boiler).
| Gas Rates | ||
| 0-2 m = No extra charge | ||
| 2-4 m = £50.00 | ||
| 4-6 m = £100.00 | ||
| 6-10 m = £165.00 |
FOR LONGER GAS RUNS A DETAILED SITE SURVEY WILL HAVE TO BE CARRIED OUT.
Condense Lines
All the boilers that are installed now have to be of the Condensing type. As mentioned, they are the most efficient boilers available. They recover as much of the waste heat which would escape from the flue of a conventional boiler.
The by-product of this is in an acidic water form and has to be taken away from the boiler to a drain or a soakway. Ideally, we will try to terminate this condense line to position internally within the property. However, this is not always possible and so sometimes will have to be run externally.
When this is the case, we will ensure that the condense pipe is properly lagged, securely clipped and run in 22mm Condense Line for no more than 2 metres. Longer runs will be increased in size to 1’ ¼” waste pipe. This will ensure no freezing of the condense line pipework which is becoming so prevalent of recent years.
Above Comprises of:
Automatic condensate tracing kit with thermostat, fully fitted and guaranteed
Magnetite and Sludge within the System.
Magnetite or sludge is made up of a combination of dirt, mites and corroded metals and can be found within any part of your central heating system.
It not only creates cold spots within your radiators, left untreated it can also create blockages, but more concerning, as it is corrosive, may well rot new aluminum heat exchanges that are common place within modern boilers.
This is why at Plumbing Wise, we recommend one or both of the following:
Installation of a Magnaclean – a magnetic device that attracts and filters magnetite before it enters the boiler.
A complete Powerflush of the system. Using recommended cleaning chemicals and neutralizing crystals, this aims to rid your existing system of sludge, thus extending the life of your new boiler and meeting manufacturers’ warranties.
As mentioned these are both optional, but are highly recommended.
For all your Plumbing Woes, call Plumbing Wise, for a free quote on 020 8362 1389
