Heatline c24 hot water problem

[Adam85]

Hi, I'm a proffesional gas safe plumbing & heating contractor with over 10 years experience, about 4 months ago I had a problem with the hot water flowing hot and cold on a Heatline c24. With the hot tap on fully you can see the burner go to full flame for about 20seconds then drop down to min flame for a couple seconds then shoot back to full flame, hence the water temp rising and falling. I changed the h/w ntc sensor and that solved the problem for about a week then the same problem but instead of the flame dropping to minimum it would shut off then re-light within a couple seconds. I had a spare new pcb, fitted that still no different so changed the hot water heat exchanger which was partially blocked with black iron oxide deposite. Fitted a magna clean on return to boiler, flushed system re-filled with inhibitor and all was fine for the last 4 months now it's doing the same thing again, I checked the magna filter and there were small deposits nothing to shout about, I'm baffled surely the plated heat exchanger can't be blocked again and the ntc is only 4months old. Any help would greatly appreciated.

 

[JAP&H]

I'm baffled surely the plated heat exchanger can't be blocked again and the ntc is only 4months old. Any help would greatly appreciated.

Hi Adam.

Have you been back on site and checked the plate hex and thermistor?

 

[Adam85]

No that's my next plan of action, I'm off on holiday for a week now, hence my post to see if could get some different surrgestion, I really can't imagine it being the hex again as the systems not that dirty (compared to some you see)

 

[grahamgas]

Plate hex or flow turbine sticking

 

[Adam85]

Plate hex or flow turbine sticking

I had flow turbine apart the first time it was happening and all seemed fine. It all seems to point to the plate hex again but just cant belive it would be after only a few months especially with the magna clean fitted

 

[Millsy 82]

Have a look at the flame rectification probe if the boiler overheats then the probe starts sagging

 

[pobsdad]

Plate hex could be scaled,not sludged?

 

[RoryD]

I had flow turbine apart the first time it was happening and all seemed fine. It all seems to point to the plate hex again but just cant belive it would be after only a few months especially with the magna clean fitted

Hi mate, did you ever get to the bottom of this problem, I have a similar one with a customers boiler at present

 

[Dotty]

Moved out of public view.