First of all, thanks for visiting istor Repairs.

Just by way of introduction, I'm Mike Bryant, also known as Mike the Boilerman. I specialise in repairing central heating boilers. In particular, I like repairing the old, the awkward and the unusual ones that most technicians announce cannot be repaired and tell you must be therefore be replaced. Always treat such advice with skepticism ;-)

Anyway back to the subject. The Ideal istor (a name which grates with me for being spelled in all lower-case characters by the manufacturer, Ideal) is a combined gas boiler and mains pressure unvented hot water cylinder all jammed into in one large box. It suffers from a number of expensive faults. In addition, the instruction book is spectacularly unhelpful in tracing and diagnosing many of the problems an istor suffers from. Ideal have abandoned the fault-tracing flow-chart that most boiler manufacturers publish in favour of a chart of 'fault codes'. The fault codes are incomplete and no help at all if you have a failed istor with, say, the common problem of a completely blank display screen. (The fault code chart does not mention what to do if the fault code screen is blank!) Ok, I'll stop ranting about it now and write some stuff covering the more common, undocumented, faults :-)

I've written this site mainly as an aide-memoire for myself but I see no reason not to publish it. Anyone is welcome to use it. Make sure you are competent within the meaning of the Gas Safety (Installation and Use) Regulations 1998 if you attempt to sort out your own boiler though. Gas accidents kill a dozen or two people every year and the cause is usually over-confident and under-competent technicians working without a full understanding of the appliance, or complete lack of service or safety-checking of the appliance, ever.

But back on topic again, here are the problems I usually encounter when I attend a broken istor (in no particular order):

1) Fault code alternating L & 9 displaying:

This is the "dry fire thermistor", according to the fault section in the book. What they don't actually explain is the dry fire thermistor is a heat sensor attached to the top of the heat exchanger which shuts off the boiler if the temperature of the heat exchanger rises about about 90 degrees C. So if you have error code L9 you have to figure out WHY the heat exchanger is getting so hot. Usually a jammed pump. They are horribly prone to sticking. Un-jamming it will work for a while but the problem will return. Fit a new pump. Sometimes the pump appears to be running correctly when actually it is not. The istor pump is noted for failing but continuing to run unsuitably slowly. This can fox even the most experienced repair technician! A new pump to replace the apparently working existing pump will often fix the L9 fault code.

2) Blank screen, no codes or anything displaying:

This is usually control board failure. Fit a new one. Be warned, they are EXPENSIVE. Prove the diagnosis by checking there is mains power passing through the On/Off switch. If the On/Off switch is supplying power, this is main control board failure. If not, then it is failure of the user display board. But the On/Off switch is always supplying power, in my experience....

3) Water dribbling continuously from the copper overflow pipe (or "safety discharge pipe" to give it it's correct title):

This is another fault not listed in the fault code chart. One or more of the three safety valves is operating. These are all complex faults. The investigating technician first needs to investigate which of the three relief valves is letting by. The three valves are the central heating pressure relief valve, the hot water cylinder pressure relief valve, and the hot water cylinder temperature and expansion relief valve. So now you know ;-)

The CH PRV letting by is usually associated with failure of the CH expansion vessel and, perhaps, the central heating filling loop being left turned permanently on as a stop-gap measure to maintain heating system pressure. This is seriously bad news as by the time the problem has penetrated the consciousness of the user, serious corrosion of the radiator system has usually occurred and the system will be contaminated with black muddy stuff (known in the trade as 'sludge'). The short-term fix is just to replace the expansion vessel and the CH PRV, and ignore the sludge problem. If the customer wants things 'just so', then an expensive powerflush will usually be necessary too.

The discharge from the copper overflow pipe is just as likely though to be coming from the pressure relief valve on the hot water cylinder. This is usually caused by loss of air pressure in the hot water cylinder expansion vessel. This should be checked during the annual service but few users actually get istors serviced properly every year, if at all! Even if they get them serviced, the servicing technician rarely reads the service schedule and checks the air pressure in the hot water cylinder expansion vessel. The fix is to re-pressurise the expansion vessel and fit a new HW PRV. 

The third valve, the temperature and expansion relief valve, only discharges if the EV has lost it's air charge and the HWC PRV has stuck shut, in which case the T&ERV does the job instead. i.e. opens to relieve the excess pressure. (Please excuse all the abbreviations but my fingers are tired and I expect you can figure out what they all mean!)

4) The boiler runs for an hour or two, or three, or six, then shuts down for no apparent reason with an alternating 'L' and 'F' showing on the display panel. Pressing the re-set button gets rid of the L and F and the boiler lights again and runs happily for a further random period of a few hours then the lockout repeats. You'll be disappointed to hear I have no answer for this one yet beyond checking the condensate trap for blockage. This is not a five minute job by the way, as to check it, one has first to remove it. The location of the condensate trap is between the boiler section and the hot water tank, right at the back and behind several pipes which are normally VERY HOT. So you need arms of asbestos and the size of knitting needles with three elbows in each to get to it off, unless all the hot water in the tank is first drained off, in which case one's arms only need to be like multi-elbowed knitting needles. (Can you tell I don't like this boiler?)

That's it for now. I'll be back and add all the faults I've forgotten about today, next time I encounter them :-)

If you'd like me to come and fix your istor then please feel free to get in touch. I'd better point out that I live in Reading, Berkshire. Most of my work is in Berkshire, Hampshire, south Oxfordshire, Surrey and west London but if you are outside this area then I'm perfectly happy to visit. In fact I'll go anywhere! The only trouble with this is, from your point of view, is that I charge for all the time I spend repairing a boiler, including the time spent travelling to and from site. This means the further you live from Reading the less economically viable it is to get me to visit. 

Alternatively I'm happy to give email advice to anyone wanting it, but not telephone advice. I had to stop that years ago when the weight of calls grew too great.

For my main site, check out www.miketheboilerman.com

Once again, thanks for visiting.

Mike Bryant, AKA Mike the Boilerman. 

First published 6th May 2011
Last updated 6th April 2012