In modern boilers up to 20% of the energy produced is lost to the atmosphere through the flue system. Condensing boilers are designed to capture part of this lost energy (latent heat) and can therefore maintain extemely high efficiency levels.

The Multipass was ahead of its time and is one of the most efficient non-condensing boilers available today. However, to achieve very high efficiencies - as in condensing boilers - it is neccessary to reduce flue gas temperatures to a point where they condense. As standard oil boilers are constructed of mild steel, corrosion would occur if they were continually operated at these lower flue gas temperatures.

The Grant Vortex condensing boiler has a high quality stainless steel heat exchanger incorporating 22 turbulator baffles. This unique design achieves exceptional efficiency levels of up to 100% nett (SEDBUK 'A' 94-95% gross).

Normally yes, but not in the case of the Grant Vortex, which on models up to 26kW have been designed to kitchen modular dimensions and will fit under a standard height worktop.

No! Plumbing and electrical connections are the same as standard boilers except for the addition of a condensate drain. This is generally run in 22mm [3/4"] plastic pipe to the household waste system, or run to a soak away. The only requirement is to maintain a fall as you would for a waste pipe from a sink, and to avoid any possibility of the condensate freezing and blocking the pipe.

Condensate occurs when the flue gas temperature of an appliance drops to below the Ôdew pointÕ and the steam present in the flue gases condenses and becomes a liquid. This liquid is slightly acidic but no more so than vinegar and can be run directly into the household waste system.

This is quite difficult to explain, however, in basic terms – Gross or Nett efficiencies refer to an efficiency calculated using either the gross or nett calorific values of the fuel. Gross Calorific Value is the maximum heat in the fuel, including the latent heat, released during the combustion process. Nett Calorific Value is the gross calorific value, less the latent heat produced. The latent heat converts the water produced during the combustion process into steam. This heat is normally lost with the combustion gasses through the flue system. An efficiency calculated ignoring the latent heat, ie. using the nett CV will always be greater than one where the latent heat is included, ie. using the gross CV. Therefore, the so called nett efficiency will be higher than the gross efficiency. All boiler tests in Europe use the nett efficiency method for calculating appliance operating efficiency!

Condensing boilers work at their most efficient when they condense, and this requires the return water temperature to the boiler to be 50°C or less. However, we do not recommend changing radiators for larger versions to achieve this as it is uneconomical, and for most of the year the radiators will be oversized anyway. The Grant Vortex Condensing boiler will operate efficiently on any system and even when not condensing will still be saving money against a standard boiler.

Grant Vortex Condensing boilers are no different from standard boilers, however, you also need to check that the condensate drain is working correctly as this is essential to the operation of the boiler.

Yes. Providing the system is cleansed thoroughly and updated to fully pumped operation (not gravity hot water).

As condensing boilers have Ôwet fluesÕ, it is important to follow GrantÕs guidelines for flue installations. Our range of EZ-Fit low level, high level and vertical balanced flues are suitable for condensing operation. When installing a condensing boiler on conventional flue, the Grant CF starter spigot must be used and only flue liners and components specified in GrantÕs installation manual used.
Note: If in doubt contact Grant first!

As flue gas temperatures are very low on condensing boilers, a plume of water vapour can often be seen at the terminal (similar to your breath on a cold day). This is the boilerÕs normal operating mode, but if this is likely to cause a nuisance to yourself or a neighbourÕs property, we recommend you install a high level or vertical flue system.

Yes, although we recommend the return temperature remains above 40°C. However, it is more usual to connect underfloor heating via a system of mixing valves or even a separate calorifier so that radiators which are normally heated to a higher temperature can be served as well.

The materials used to produce a condensing boiler are more expensive so generally the boiler costs more. However, in the case of the Grant Vortex Condensing boiler this additional cost will be paid back within 2-3 years against an older inefficient boiler. More information on running costs can be obtained from the GovernmentÕs SEDBUK database.

Any of the regularly used heating controls are suitable for use with these appliances, however, for even better control of the system you could choose to use a control package that incorporates inside and outside temperature sensor stats available from companies like Honeywell, Danfoss or Invensys.

As condensing boilers are much more efficient they burn significantly less fuel and consequently produce a smaller amount of harmful CO₂ than the equivalent sized standard boiler.