Ideal Isar hot water probs

[Benjibalz]

hi, have just changed diverter on Ideal Isar HE 30 thinking i would resolve intermittent hot water issue but no joy. The boiler has had this prob for over a year and im the 3rd engineer to have some fun with it.

Firstly, the DHW heat exchanger was replaced and a scale reducer installed a year ago. Seems sensible and it worked for a couple of months but then the problem came back. The 2nd engineer then made several visits, unstuck the pin on the diverter and installed a line strainer on the return.

Finally, I suggested changing the diverter valve as the return would heat up when the hot tap runs and it had been unstuck on a few occasions and this had resolved the issue. Still the the water runs hott(ish) then cold.

I only noticed after i had changed the valve that the boiler stopped firing every 20/30 secs for 4/5secs(the boiler is a long way from the nearest hot tap). Im wondering if there could be a blockage somewhere in the manifold that connects the DV,HE, pump etc that is causing the stat to to reach temp before water heats ups.

Before I strip the lot out to try and find a blockage has anyone had this prob or any ideas? Cheers.

 

[Master of None]

Mabe the HX is full of concrete I think this should be in Plumbing and central heating. The mods will probably move it.

Sorry I am not a heating engineer but I thought I would stick my head in. . I looked at this boiler last year when looking for a new combi primarily because of its small size. The only thing that put me off was the Aluminium HX. The manufactures state that you must use inhibiter in your heating system. Have you? Could the HX be badly corroded?

 

[Benjibalz]

Main HX should be fine boilers not that old.system is clean and protected. You may have something with the concrete theory though....

 

[Rob]

Generally the cause to your problem is a blockage in the plate HE. Might be worth an inspection.

Also measure the flow temp into the plate HE. Then the difference between Flow and Return temp just as it cuts out.

Check the Temp sensors are reading correct.

Gas rate. Boiler burning correctly?

Is there a by-pass? Could be blocked.

 

[Benjibalz]

Just in case this is of use to anyone in the future, I removed the DHX and pump to check for blockages and found they were a bit mucky. The main problem seem to be that the flexi pipe that connects the expansion vessel to the system was almost completely blocked with sludge. Strangely this didnt affect the system pressure as I would've expected.

I think the expansion in the system when heated, was being taken up via the return pipe as this is what was heating up first when hot water demand was made rather than the flow which would indicate a faulty diverter.

 

[shambolic]

Plate hex will be blocked with plateletts of solid sludge causing it to fail on dhw . If ok on ch thats the prob!