The Potterton Powermax HE
Despite sharing a name, the Potterton Powermax HE is about as
different from the old Range Powermax as it is possible to be (and
consequently suffers from a completely different set of problems). The
main differences are that HE is a now condensing boiler ('HE'
stands for 'high efficiency'), and is no longer a thermal store. Instead
it is a plain vanilla gas boiler and a small but conventional mains
pressure hot water cylinder all squeezed into a single box.
It's a shame that Potterton chose to keep the name 'Powermax' for
this appliance because it means owners still find difficulty in getting
a gas technician to attend because as soon as the word 'Powermax' enters
the conversation, the gas bod switches off and loses interest due to the
poor reputation of the preceding Range Powermax.
This appliance is actually quite a good piece of kit in my opinion.
Most of the problems they exhibit seem to be associated with system
pressure loss which is not always a fault in the boiler - leaking
pipework or radiators can just as easily be the cause. But not always!
Here are the problems I regularly encounter with the Potterton Powermax
1) A hard-to-find leak, causing water marks and/or dampness on the floor
or ceiling below. Early versions of HE has a rather thin aluminium
casting at the back of the heat exchanger to collect flue gases and
condensate. So thin in fact that the flue gas condensate tends to
corrode through it and leak out at the back of the boiler. This is
potentially very dangerous as flue gas leaks out through the same hole
into the house and it needs fixing immediately. It's a difficult repair
because the boiler part needs to be completely dismantled and the heat
exchanger removed to gain access to the failed casting. Potterton are
rumoured to come out and fix this fault free of charge even when the
appliance is long out of guarantee due to the potentially serious
consequences of this fault. when they hear of an instance of it. (Ok
it's not a rumour, an employee at Baxi-Potterton told me this!) Later
versions of the HE were built with a much thicker and more robust
2) An easy-to-find leak. It's probably the heating bypass valve, just
behind the front panel. It's adjustable. It's just 'there' at the front
and very tempting to both DIYers and gas technicians to idly adjust. BAD
MOVE, because once disturbed it will leak for ever more. The only fix it
to order and fit a new bypass valve. Of course a far easier fix is to
not touch it in the first place :-) Now you know, but probably too late
or you wouldn't be reading this.
3) User LED display is blank and the boiler is lifeless and won't start.
It's as though the mains electricity to the boiler is switched off but
you've checked and it isn't. This is typically control panel failure. A fiendishly
expensive part but replacement is necessary UNLESS one or both of the
surge protection fuses on the board happen to have blown - check them
first. New fuses 'could' save you a load of money! (Fuse info supplied
by James - many thanks James). Few merchants keep the control panel in stock
should the fuses be fine on your dead board so it usually has to be ordered directly from Baxi-Potterton. The
repair can then be complicated by the fact that the pressure sensor was
upgraded and old pressure sensor
may be incompatible with the new board and needs replacing too. Yes
you've guessed, it will have to be ordered as it's a special order component. Once you have obtained the
new, compatible sensor you will then find the connection cable is
different as well so it won't plug in, and a new cable also has to be
ordered as a special part from Baxi-Potterton. The whole process can
take up to a month. Can you guess how I know this? Fortunately my
customer had a second home to go to but the whole episode made me look
rather incompetent. Huh.
4) Boiler won't start, with error message A15 showing on the user
display. This is low system pressure. The immediate fix is to find the
filling loop and turn it on for a few seconds to raise the system
pressure back to the optimum range of 1 to 2 bar. Trouble with this fix
is that the fault will usually return after a few minutes/hours/days
because the reason for the original fall in pressure has not been found
and addressed. There will either be a leak on the radiator circuit OR
the water will be escaping through the pressure relief valve (PRV) in
the boiler. PRVs are notorious for letting water by. They do it when
crud (well-known technical term in the industry) gets stuck in the valve
seat. Crud only gets in the valve seat if the valve opens in the first
place. The valve only opens in the first place if the pressure in the
system gets too high. The system pressure gets too high if the expansion
vessel stops working. The expansion vessel stops working when it loses
the nitrogen charge it came with from the factory. This is supposed to
be checked each year during the annual service (you DID have it
serviced didn't you?) Even if you did, most service engineers don't
bother checking it because it is a faff to measure.... anyway I'm
stopping describing this fault now because I'm bored with it. I hope you
understand - you probably get my drift by now anyway... :-) Ok, fitting
a new PRV and re-charging the expansion vessel usually fixes this one.
Although half the time a new expansion vessel is needed on these...
5) User realises the boiler has stopped working and it has locked out
showing the A01 error message. Pressing the reset button makes it start
apparently normally but the cycle repeats an hour, a day or a week
later. No technician called to attend can ever find anything wrong.
Unfortunately I've yet to encounter this problem personally on a
Powermax HE so I have no experience of how to fix it but I DO however
get this exact problem from time to time on my Keston C25! I'm
reasonably certain both boilers use the same gas valve. The settings on
my Keston gas valve tend to drift out of adjustment over time, so the
first thing I'd try on a Powermax HE with this problem would be to check
the combustion settings using a combustion gas analyser and adjust if
necessary. The Powermax HE manual also suggests cleaning/replacing the
ionisation probe and lead.
6) Random lockouts with the boiler displaying the undocumented error
message A02. Irritatingly, the instruction manual does not list A02 as a possible
error message, so I called Potterton technical support this morning for
some information. It turns out this is an error message displayed on early
versions of the Powermax HE which have Version 1 control boards. It is caused by high resistance
or poor circulation in the radiator circuit. The most common cause of
this is all the TRVs closing down as the house approaches being warm on
a system with no bypass circuit having being fitted by the original
installers. A bypass circuit is needed to allow some water circulation
when all the TRVs (thermostatic radiator valves) are closed. I'm told board
versions 1A and 1B have different software and will not lock out the
boiler with error code A02 even if circulation is poor. The simple fix is to
leave one radiator permanently fully ON. If this makes no difference
then a new control board will be needed. Best to make sure its a v1A or v1B
control board. The version is marked on the board.
If you'd like me to fix your Powermax HE, click the 'Contact me' link
in the left hand column..
Mike Bryant, AKA Mike the Boilerman.
Page first published 30th December 2009
Last updated 7th January 2013
Copyright 2009 - 2013 Michael Bryant