Vaillant Turbomax 837E hot water not hot enough

[Searcher2]

Perhaps foolishly last weekend I drained my CH system and fitted a Magnaclean thinking that I would get the pipework and radiators clean in case I had to have a condensing boiler fitted if the Vaillant 837E packs up.

I added an extra drain valve at a lower point in the system too, put in Fernox F3 cleaner and filled the system. When I checked my new drain valve for leaks I discovered it was open so I don't know if I lost all of the F3 cleaner.

Anyway - all seemed well. After a couple of days I checked the Magnaclean and there was quite a bit of gunk in it which I cleaned out.

Today I have had a shower and the water was only just warm enough even with the shower turned to full heat. I checked the hot water tap in the bathroom too and that was the same. I then turned the boiler hot water dial up to maximum and felt the hot water outlet - it still was only warm.

Looking at some posts on this forum it looks like I could have blocked my heat exchanger. Given that I don't know if I have any F3 cleaner still in the system could putting another dose in possibly unblock the heat exchanger (if that's what is wrong)? Or is it a matter of getting someone out to take it out and try to clean it?

Thanks.

 

[Bunnyman]

Take it out an clean it, make sure u clamp it when u put it back, they have a habit of jumping off if the clips not on right

 

[Searcher2]

Thanks for the reply. As an update - as mentioned above I turned the hot water dial up to maximum to see how hot the water would get. I didn't realise that this would activate the 'warmstart' feature on the boiler and I woke up at 4am because I could hear the boiler running when it shouldn't have been as there is no call for heating overnight. I eventually worked out what I had done but prior to this I had checked the radiators and they were warm.

Should the radiators get warm when the warmstart function is on? If not then I wonder if it's actually the diverter valve which is stuck. (EDIT : Having said that I've just run some hot water and it has come out piping hot! I'll see what happens tonight at shower time)

 

[Bunnyman]

Yes if its hot now it cant be a blocked plate, its either a sticking diverter or u have a shower passing

 

[Searcher2]

Thanks again. I'd been looking at videos on blocked Vaillant heat exchangers and if I understood correctly a blocked heat exchanger could result in hot water temperature being reduced whilst running because the boiler temperature itself reaches its safe level and stops burning.

The difference last night was that the heating was on and this morning it wasn't so I was wondering if the hot water temperature drop was because of the boiler hitting this safe level (and therefore thinking again that it is the exchanger that could be blocked).

Just out of interest there are new, compatible exchangers on Ebay which are reasonably priced (about £60). Are they likely to be okay? Anyone used them?

 

[Bunnyman]

Just read the theead above mate forget the plate

 

[Searcher2]

Bunnyman - thanks for the replies. I bought a genuine Vaillant diverter valve for under £50 and fitted it. It's been in over a week now and all is well. Cheers!