Ideal Mini C24: Fix or replace?

It had to be a fix, really. Even if I had the money, I'm not paying a guy a grand for one day's work swapping a boiler over. Unfortunately I don't have the money so this was only ever going to be a fix.

Righty, my boiler is an Ideal Mini C24. It's a gas "combi" so delivers hot water on demand. There is no hot water tank. From various labels stuck on it, it seems to have been built in 2004 which means that it is getting on a bit. I don't know who fitted it but they could do with some lessons in pipework. There is literally a nest of pipes weaving in and out of each other under the boiler. But that is mainly aesthetics. My boiler had several issues which required attention:

• The central heating circuit would lose about one bar of pressure during the course of a week (but no visible leaks on the circuit)
  
• Running a hot tap would cause all the radiators to get warm
  
• Whether it was central heating or hot water, the boiler was noisy (not unlike the sound of a boiling kettle but perhaps a bit more rattly)

So, I did a bit of research. The first thing I looked at was whether I was allowed to work on my boiler at all. The Gas Safe Cartel... sorry... Gas Safe Register would evidently prefer it if I was legally barred from even thinking about working on my boiler. Alas, that is not what the law says and the GSR appears to accept that (without enthusiasm, evidently), in one of its downloadable leaflets. The true position seems to be this: where the law applies, a person working on the boiler needs to be competent. Moreover, it seems doubtful that even that legal requirement applies where the job does not involve interfering with or touching the gas side of things (the gas pipes and valves, any module which controls gas, and within the combustion chamber and flue). Lucky for me, then, my research suggested that all my boiler's issues were on the "wet side" of things. This is where I ended up:

• the pressure drop in the central heating circuit was likely to be a faulty or dirty pressure-release valve
  
• the issue with the hot tap and radiators was due to a faulty or jammed diverter valve
  
• the noise was due to a partially blocked secondary heat exchanger (which is where the mains-fed cold water is heated for the purposes of the hot tap)

Since I was still reeling at the prospect of laying out for a new boiler, I didn't mind spending a bit on some new parts (Ideal part number in brackets):

(172494) Pressure release valve

(172507) Diverter valve repair kit

(075460) HW Heat exchanger

(172525) Auto air pressure release valve

(172504) By-pass pipe

(075412) By-pass pipe o-ring (x2)

The last two items on the list were necessary because the original by-pass pipe (being push-fit and held in place by spring clips) had had a liberal dosing of "plumber's mate" or some such white stuff, during original fitment. I ended up wrecking the pipe when trying to remove it because it was stuck fast. Total bill for parts  was £110. Apart from the by-pass pipe, everything else came from ebay. I also bought a second-hand replacement temperature/pressure gauge as the one on my boiler had stopped working in both respects...

As far as the job goes, all in all it took a couple of hours. I'd never drained-down a boiler before so had to read up on that, and make preparations in my new kitchen for potential water spillage. Luckily, there was not too much mess. It also only occurred to me after starting that I would need to replace the fibre washers in various bits that I was disconnecting, so I had to nip out for those. I'm not doing a step-by-step because removing and replacing the parts is actually quite straightforward. In terms of tools, I used a couple of different sized wrenches, an allen key and a screw driver. Nothing special was required. 

Everything I removed was caked-up internally with gunge. The PRV was obviously leaking (draining down a pipe which led through my kitchen wall and into a garden). The air pressure release valve had failed in the "open" position so was presumably letting air into the system whenever the central heating was cooling down. The internals of the diverter valve had seized rendering the valve un-operational (hence the warm radiators whenever the hot tap was run). As far as the noise was concerned, the HW heat exchanger was likely partially blocked - certainly, with the new part fitted I now have pretty much mains pressure hot water which is actually very hot indeed! And the boiler runs so quietly! I'll let everything settle in and confirm no leaks. I'll then look to doing some sort of system flush and add some rust inhibitor.

Here are some pics of the old parts:

More soon, no doubt....

D