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Posted: January 18, 2018


Boilers have come a long way in recent years. Up until 2005, boilers were what is known as standard efficiency. This meant that they had a maximum efficiency of around 80-85%. In monetary terms, this means that for every £1 of gas your boiler used, about 80-85p worth of the heat from the burner flame would be put into the water that heats your house. The other 15-20p would leave out of the flue and go to waste into the outside atmosphere.

Since 2005 it has been the law to install modern condensing boilers in almost all instances. These are also known as high efficiency boilers and they have a maximum efficiency of around 90%. So, in monetary terms, you get up to 90p worth of heat from £1 of gas used. However, in hot water mode combi boilers cannot hit peak efficiency due to instantaneous hot water production needing so much heat to be immediately produced, that it takes the boiler out of condensing mode, reducing their efficiency temporarily to standard efficiency levels.

From April this year, 2018, further measures to increase system efficiency will be legislated for, meaning one out of four additional requirements must be added to a system. One of these options is a combi boiler with flue gas heat recovery (FGHR) which pushes the 90% up a few more percentage points and means that combi boilers condense more in hot water mode so that they can perform at maximum levels of efficiency for more of their operation. It’s a great technology, and hopefully, FGHR will become standard over the next few years.

It’s fair to say that we are approaching maximum boiler efficiency levels. However, a boiler is only one part of a system. Inefficient systems are common place and I am often asked how a system can be made more efficient.

There are 3 main ways of increasing system efficiency;

  • Modern controls which auto adjust your boiler operating temperature depending on actual heating requirement, aka modulating / compensation controls.
  • Behaviour change, by using your heating and hot water at more appropriate times. Smart phone app controllable stats can help here.
  • Intelligent zoning of your heating system so that you only heat the areas of your property required.

Modern controls and behaviour change can have a massive impact, but most people can also benefit from zoning. Zoning is what we call it when we split your heating system up into sections. For example, let’s take a typical 2 storey 3 bedroom house with a conservatory;

Single Zone Thermostat Control

The standard set up for this house is to have a timer and thermostat that controls all of the heating in the house. Whenever the heating is turned on, every room will get heated. It’s standard to install thermostatic radiator valves throughout so you could set the upstairs bedrooms to a lower temperature than the rest of the house, but it’s still going to heat the whole house at the same time. Not very efficient when you spend the whole day downstairs in the kitchen and lounge.

This is obviously the cheapest option at the initial installation, but you’re throwing money away heating areas that don’t need heating, and adding all those extra miles on your boiler, inevitably shortening it’s life span. Expensive long term when you actually think about it.

– Cheaper installation
– Simpler to use

– Lack of area control
– Excessive boiler operation
– Unnecessary heating of unused areas
– Higher gas consumption – expensive to run

Multi Zone Thermostat Control

This is regulation, and standard practice for new build houses. It is typically split as upstairs zone and downstairs zone. You could even have the conservatory on it’s own zone too. This type of zoning requires a thermostat on the wall in each separate area, and typically a heating valve that stops the heating water being pumped to those areas when they are switched off.

This is easy to do when first installing a system with new pipework, but it’s usually not practical to retrofit. Once the pipework is in, it generally makes it’s way through the house feeding upstairs and downstairs radiators in a seemingly random order. If you’re lucky, you’ll have a separate downstairs pipe run and a separate upstairs pipe run, so they can be retrospectively split, but it’s unlikely. This is the type of zoning you do with a completely new installation.

– Cost effective multi zone solution
– Lower gas consumption – cheaper to run
– Minimise boiler operation
– Only heat areas in use

– Not usually practical to retrofit
– More expensive to install

Multi Zone Radiator Control

This method of zoning is relatively new to market, and is considered by some to be the holy grail of system control. Many controls manufacturers now have ranges available, from Honeywell Evohome and Tado, to Drayton Wiser and even boiler brand Vaillant. This gives you the greatest control of all zoning systems as every single radiator has a thermostat on it.

That might sound just like a regular thermostatic radiator valve, but it’s actually much more. Not only can it shut the heat off to your radiators, but it can also switch the boiler on and off, removing the need for a wall stat.

The main control centre, whether on the wall or on your phone, can control the temperature of every single radiator. You can group radiators together into rooms, so even if there’s 4 radiators in a lounge and kitchen area, you can have them all on the same circuit, controllable at the push of a button.

This type of zoning can also be retrofitted to any system, and there are options to adapt to underfloor heating manifolds and be combined with thermostat control systems.

– Most control
– Full flexibility to set and change zones
– Lower gas consumption – cheaper to run
– Minimise boiler operation
– Only heat areas in use

– Most expensive to install
– Slightly more complicated user functionality ie. Probably not good for my Nan

As with anything heating related, you should definitely seek expert advice, and seek it from an expert in these particular methods. Some of these products, particularly radiator zoning, are quite niche, and alien to a large amount of installers.

I highly recommend using an Eco Technician (ET) for this kind of work. Increasing system efficiency is a subject of particular interest to all ETs, and as the technology is still in it’s relative infancy, technical support is often seeked by installers having teething problems with setting up. ET provides a great community of support to one another, so no problem is unsolvable.

I hope this article has been both educational and interesting, and I hope that you paid attention and didn’t zone out…

This article was written by Michael Paini of option Energy Solutions

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