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Powermax Repairs by Mike the Boilerman - Gas Safe Registered technician covering areas within driving distance of Hungerford, Berkshire. Call or text me on: 07866 766364

Powermax flue:

The flue on a Powermax is the source of all manner of trouble, mainly because when the Powermax was first launched, builders thought it fine to conceal the flue tubes above ceilings and inaccessible building voids without realising one of the gas regulations requires flues to be inspected for integrity whenever the boiler is worked on. A concealed flue tube obviously cannot be inspected because it is, well, concealed. 

Here is a photo of a poorly installed Powermax flue I discovered in a loft in Maidenhead, Berkshire which illustrates the risk. This This boiler was discharging about 50% of its combustion gasses  out of this broken joint in the loft space over this top floor apartment, instead of discharging it all to outside. No-one was affected, fortunately. 

After a number of incidents where concealed flues had become disconnected like this and at least one fatality from flue gasses leaking into the living space, CORGI (who were the governing body back then) published a technical bulletin specifying how concealed flues could be made compliant by fitting inspection panels. Gas Safe Register took over from CORGI and re-published the bulletin as TB008, as follows:

Flues in voids:

Gas Safe Register Technical Bulletin 008 (Edition 3)

You probably won't have heard of Technical Bulletin 008 (TB008), but if you own a Powermax boiler installed in a flat then TB008 is likely to impact on you next time you have your boiler serviced or repaired if it hasn’t already. By 'impact', I mean it might hit you in the pocket and cause disruption in your home while the work demanded in TB008 is carried out.  

The 'work' comprises installation of access hatches in the ceilings to allow full visual inspection of the whole of the flue and air supply tubes, where the flue and air supply tubes are concealed in a ceiling or other building void. From 1st January 2013 we gas bods will not be allowed to leave a Powermax (or any other boiler) in operation if we cannot visually inspect the whole of the chimney system. This means installation of access hatches along the whole of the route from the boiler to the flue terminal outside.

After 1st January 2013 inspection access panels will have to be installed in accordance with TB008 before a gas technician can carry out ANY work on a Powermax with concealed chimney system. 

This will probably be the last straw for many Powermax owners and will prompt them to decide to replace their troublesome boilers that no-one will service or repair. The trouble here is that whatever new boiler is installed, a new chimney system will have to be fitted involving even MORE disruption and expense.  Any new boiler will mean abandoning the old Powermax flue and installation of a new flue compatible with the new boiler. Ceilings will have to be pulled down then reinstated with new access panels so the new flue can be inspected anyway!

The best thing to do is probably sell the flat and move....

Here are some links from those in authority explaining this in more detail. This link is the "Safety Notice" published on 10th December 2010 by the government's Health and Safety Executive: 


Next, a link to the document published by Gas Safe Register. This is titled "Boiler Flues in Ceiling Spaces. Important advice for consumers who have flues which run in ceiling spaces"


And another link to Gas Safe Register, this one being their list of FAQs on this subject of concealed chimney systems. A good list of pertinent questions answered with no punches pulled, so well worth reading:


And finally, in case you are wondering why I have not included a link to the original document all the stems from, TB008 (Edition 3) ends with a warning that it may NOT be reproduced in part or in whole without the permission of Gas Safe Register other than for personal reference only. I don't have that permission, and would not expect to get it should I ask, given that Gas Safe Register have decided to restrict distribution of TB008 to Registered Gas Installers only. A quick Google though should turn up plenty of links to the document by people willing to ignore the restriction.



Post Script:

A friend of mine has set up a business specifically to install access hatches for huge number of people with homes with concealed flues. His website is www.fluesinvoids.com should you be interested. He is well informed about the issues and offers a competent concealed flue inspection panel installation service in my personal opinion. He is based in Reading, Berkshire.

In the interests of transparency I am declaring my connection with fluesinvoids.com, but I would like to confirm I have no financial interest in the business, nor do I receive any commission, share of profits or any other financial benefit should you decide to follow the link.


***Update, 26th July 2013***

The latest guidance from Gas Safe Register allows use of a carbon monoxide detector to monitor the void space through which a flue runs, provided the CO detector is connected to a boiler interlock which shuts the boiler down if CO is detected. This saves cutting the access hatches.

Cost is likely to be similar to fitting access hatches but disruption will be much reduced, and the aesthetic integrity (!) of your ceilings can be (mostly) preserved.

The first company to market with such a device is Baxi, with their "NoCO" Carbon Monoxide Detection System. For more details see their website at www.no-co.co.uk.

***Update 6th August 2019***

It appears the NoCo has now been discontinued and is no longer available, so if you have one you will eventually need to remove it and fit inspection hatches anyway. The reason for this is the NoCo sensor/sender head is powered by internal non-replaceable batteries and when they go flat a new sensor head is required. New sensor/sender heads are no longer available according to Baxi. 


Powermax broken flue in loft in Maidenhead, Berkshire.
No-Co Co detector, the three components comprising the system
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Copyright MICHAEL BRYANT 2020

First created 21st July 2009

Last updated 10th May 2021

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