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What plumbing does a biomass boiler need?

Posted by Trish O'Flynn on 10 May 2017 at 2:33 pm

Thinking of installing a biomass boiler? Have you considered the plumbing involved with this? In the video below, SuperHomer Mark Brown shows us the plumbing and 500 litre buffer tank installed for his wood pellet boiler.

Mark chose this biomass boiler for the five bedroom house in South Buckinghamshire where he lives with wife Liya and their children. The house was built in the early 1980s and the boiler was installed in 2009. 

What does a buffer tank do?

Mark Brown has a pressurised system and the buffer tank acts as a heat store allowing for the most efficient operation of the boiler. The temperature of the water in the buffer tank water can be up to 95°C and there are pumped circuits for heating and hot water. The heating circuit directly feeds the radiators. The hot water circuit heats a cylinder for domestic hot water.

Do all biomass boilers need a buffer tank?

“In most cases only pellet boilers heating larger properties would require a buffer tank”, explains YouGen member installer Mark Howard of Sungift Solar.

“If a buffer tank is installed as part of a pressurised system, it does not need its own cold water tank. This is different to an open vented system which requires a header tank. A pressurised system is more efficient and less susceptible to corrosion. If your domestic hot water cylinder is vented, it can still work with a pressurised heating circuit and won’t need changing”.

“Log boiler systems operate differently to pellet boilers and would require an accumulator tank”.

Will I have to replace the central heating pipework and radiators if I install a biomass boiler?

The answer is No. Mark Howard explains “You can use the existing central heating pipework and hot water cylinder with a biomass boiler, provided they are in good working condition, as the requirements are no different to any other modern boiler. It can be a good time to upgrade your cylinder, radiators and pipework, if this is something you have been thinking about already”.

How much will the biomass boiler plumbing cost?

“The average £15,000 boiler installation should include all the plumbing costs, assuming the existing system is largely OK” says Mark Howard. “The type of things that might cost extra would be a long run of underground pipework, the addition of a bulk fuel store, or upgrades to radiators and hot water cylinders”.

Will the biomass boiler plumbing add to my water bill?

“On commissioning your heating system will require filling, treating and flushing out, so there would be some additional water use at the installation phase”, says Mark Howard. “In most instances this is not significant, however a log boiler with a large accumulator tank may require quite a lot of water to commission correctly.

“If you live in a hard water area, your system should be treated with a scale and corrosion inhibitor to reduce the build-up of scale”.

What back-up will I need in case of boiler breakdown or when it is switched off?

In the video, Mark Brown shows that he has a condensing gas boiler slave to the biomass boiler. It cuts in to heat the buffer tank if the boiler runs out of fuel or is switched off.

A good quality pellet boiler is very reliable and usually comes with a long warranty, so a back-up boiler is rarely fitted. If you have an existing boiler in good condition it makes sense to retain it as back up though.

Mark Howard adds that  “In the case of commercial customers, such as care homes, where guaranteed continuous operation is required either a dual biomass boiler or back up fossil fuel boiler set up is recommended”.

SuperHomers Mark and Liya Brown are committed to reducing their carbon footprint and have achieved a 90% carbon saving by investing in solar thermal and PV, insulation throughout the house and, of course, the biomass boiler.

For more information, see Mark and Liya’s SuperHome page.

 

Video credit: SuperHome 59 on YouTube

More information about Biomass Boilers and Energy Saving and Renewable Energy on YouGen.

Find a Biomass Boiler installer

You can find an up to date list of local wood fuel equipment and fuel suppliers on our Log Pile database.

About the author: Trish is a web content writer with the National Energy Foundation.

If you have a question about anything in the above blog, please ask it in the comments section below.

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