Russell Haskins

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Honest and reliable service for all your plumbing needs


What is a condensing boiler?

Condensing boilers are the most energy-efficient boilers on the market today. They use less fuel and have lower running costs than other boilers. They achieve this high level of efficiency by extracting heat contained in the combustion gases, which would otherwise be lost to the atmosphere. Old, conventional boilers have an efficiency rate up to 60%, which means that they convert 60% or less of their fuel into heat, while the efficiency of new condensing boilers can be above 90% (A-rated). This means huge energy savings and significant cuts on your CO2 emissions and gas bills.

There are 2 types of high-efficiency condensing boiler:

  • System boiler: heats your hot water through a hot water cylinder
  • Combination (combi) boiler: gives you instant hot water without the need for a cylinder

Each type delivers all the benefits of high-efficiency technology.

Here are a few examples and guidelines to help you identify the type of condensing boiler most likely suited to your needs:

Most suitable boiler
I live in a flat or bungalow with little or no roof spaceCOMBI BOILER
I want to convert my loftSYSTEM BOILER
My home has more than 2 bathroomsSYSTEM BOILER
My main water pressure is lowSYSTEM BOILER
I need to have hot water available on demand without waiting for it to heat upCOMBI BOILER
I want to install a MegafloSYSTEM BOILER

What is a combi boiler?

The high efficiency condensing combi or combination boiler combines both a conventional boiler for radiators and an independent water heater in one compact unit, eliminating the need for a hot water cylinder and cold water storage cistern. With a combi boiler hot water is always available instantly and for as long as you need it.

Additional benefits of having a combi boiler include significant saving on your gas bills and the fact that your hot water comes from the mains pressure so you can enjoy showering without needing a noisy pump.

What is a system boiler?

A system boiler works on the principle of stored hot water. It provides heat for your heating system while being able to heat a hot water cylinder (like a Megaflo). This guarantees simultaneous supply of hot water to all outlets. These type of boilers work with both vented and unvented how water cylinders.

System boilers operate on a sealed system like the combination boiler. As the system is not affected by mains water pressure, they can operate in areas where combi boilers cannot (like lofts). System boilers are usually compact as all the major components like the pump and the diverter valve are built into the boiler.

A system boiler is a great choice for a larger home or family with hot water needs that can’t be met by a combi boiler. You will need a tank in the airing cupboard, though.

Which boiler manufacturer do you recommend?

We can supply and install any type of boilers. We will assess your individual needs and advise on a suitable boiler. There are several very good central heating boiler manufacturers in the market. We usually recommend Which? Best Buy rated boilers like Vaillant and Worcester Bosch, however as we are independent installers our advice is based on your individual needs and budget.

What is Gas Safe Register™?

Gas Safe Register™ is the official Great Britain and Isle of Man registration scheme for installers and maintenance engineers dealing with natural gas appliances. By law, anyone carrying out work on gas installations and appliances in your home must be on the Gas Safe Register™. Russell Haskins Heating & Plumbing are registered Gas Safe Register™ installers.

What is an unvented hot water (Megaflo) system?

An unvented hot water system is a cylinder where hot water is stored at mains pressure and therefore hot water flow rates are much better than traditional open vented systems. Megaflo is a market leading name for unvented cylinders and is manufactured by Heatrae Sadia.

How do I know if I have a low pressure (or unvented) system?

If you have a cold water storage cistern in the loft and a hot water cylinder in an airing cupboard, then you have a typical gravity fed system in your property. Your water pressure is determined by the height of your cold water storage cistern in relation to the appliance outlet. For example, a weak shower could be due to low water pressure, but in an ideal world this could be solved by raising the height of the storage cistern. However, this isn’t always possible and pumps can be used to boost the pressure.

What are thermostatic radiator valves (TRVs)?

Thermostatic radiator valves control the temperature of an individual room or area. They are fitted to your radiators and have an internal thermostat to enable temperature control to individual rooms in your home.

What is a programmable room thermostat and how does it work?

Programmable room thermostats switch the heating system on and off automatically several times a day, or night, to suit regular household needs. It works by sensing the air temperature, switching on the heating when the air temperature falls below the thermostat setting, and switching it off once this set temperature has been reached.

Programmable room thermostats are wireless and can be programmed to suit your lifestyle needs.

Why is my radiator cold at the top and hot at the bottom?

This usually means there is air trapped at the top of your radiator and it is stopping any more hot water filling the radiator. To resolve this problem you can bleed the radiator to release the air by opening the bleed nipple (a small square peg at the top of the radiator, usually protected by a round cast in the radiator body) and allowing the air to hiss out.  Hold a cloth close to the bleed nipple and when water starts to come out the air should have gone. If this does not help or the problem reoccurs we suggest that you have your central heating checked by a heating engineer in case there are any underlying system problems.

Why is my radiator hotter at the top than at the bottom?

Assuming the radiator has reached operating temperature, this usually means there is a build up of sludge and rust at the bottom of your radiator and this displaces any water leaving the bottom of the radiator cold. In this case we advise that you have your heating system power flushed.

Why are my radiators hot downstairs and cold upstairs?

This usually means that the feed and expansion tank in your loft has run dry which can indicate a problem with the ball valve. This needs addressing quickly and can be resolved by replacing the ball valve.

Why are my radiators cold downstairs and hot upstairs?

This could indicate a faulty central heating pump which should be checked by a heating engineer.

What is power flushing?

Power flushing is a process by which heating systems are cleansed from sludge using chemicals with a power flushing pump. The process makes no mess and causes minimal disturbance to your property as no radiators need to be removed. At the end of the power flushing process, the system contains fresh clean water.

What is an immersion heater?

An immersion heater is an electric element which screws into the hot water tank. It is wired to the mains electrical supply via an isolating switch, a thermostat to control the temperature, and sometimes a timer which enables you set the times you wish to have the water heated. Using a timer, together with a well insulated tank, it is possible to heat the water during the night, when electricity rates are cheaper, and use it during the day.