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Author Topic: Experiences of Dunsley Neutralisers (or non-branded varieties)  (Read 1843 times)
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« on: May 05, 2020, 04:02:36 PM »


For some time now I have had an interest in linking up a solid fuel system with a gas one. After a bit of research regarding dunsley neutralisers I am broadly interested in how they function and how people have found their performance. I have read on here that people have found them to not work, or not perform as expected. As far as I can tell, the neutraliser is essentially a small cylinder which allows the hot water from multiple sources to 'mix' and 'stratify' and then be diverted to the DHW cylinder or radiators. Is this about right, and what is it about them that means sometimes they don't work?

As for the system we have at present, it is a mixed bag. We live in a small terraced house in Cardiff and when we moved in the hot water was heated by an open fire in the kitchen with a solid-copper block-back boiler to a combination cylinder in the bathroom above (or electric immersion). We were surprised at how well it functioned, and so when we removed the kitchen chimneybreast, I kept the parts from it and re-installed it in the dining room (with a Victorian surround rather than a 1950s beige one!). I did do quite a bit of research into back-boilers and their performance, efficiency and so on (our boiler gives between 2 and 3 KWH at about 50% efficiency with the damper open. The brickwork of the chimney gives about 15-20% heat gain too). I installed a new indirect cylinder in the bathroom, and connected the backboiler directly with essex flanges to the top and bottom of the cylinder. This left the coil for the gas system which we installed later.

Since the laying-on of gas, the back boiler is clearly redundant, but when I go to West Wales to visit my parents I can fill the boot with logs and heat the domestic hot water with the fire, which is nice. What I would like to do is also heat the radiator in the front room with the back boiler (and perhaps a bedroom).

I am hoping that I won't garner too much criticism for the blatant inefficiencies of my heating system. I know I could put a log stove in with a modern back boiler, but there was an attractive simplicity to re-using something I already had, and that had been here since the bathroom was installed in 1947. I also quite enjoy groping up the chimney with a poker to move the damper. What I did not enjoy, I will admit, was the 4 degrees Celsius that our bedroom fell to prior to the gas central heating. 

Do you think it would be worth installing a neutraliser under the cylinder in the airing cupboard for the occasional fire? Would the neutraliser have an adverse impact of the re-heat time of the cylinder or the central heating performance generally when it is running off gas?

I should also note that the central heating is S plan vented system.

Many thank,


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« Reply #1 on: May 05, 2020, 06:36:13 PM »

We have had a Dunsley Neutraliser installed in our "other" house for about 15 years. Feeds are gas boiler and Hunter stove. Supplies DHW and 8 Radiators in an end terrace.
Never had a single problem with it and the Hunter would be sufficient for all but the colder periods. Also proved "tenant proof".
Think I put some more details in an old thread on here and would need to jog the old memory a bit for more details now.

Off grid AC coupled, 6kW Proven, 2.8kW PV, SMA SI/SB/WB Inverters, 4x576ah Rolls batteries @ 24v, 25kW Biomass Boiler, Wood Stoves, Spring/Well water. Sorry planet - I did try.
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