Help needed to solve Valliant hot water issue!

hulkiebear

Hi,

I have a valliant combi boiler(turbo max) and whilst the CH works just fine, the hot water goes hot, cold, hot, cold continously. Now, I replaced the heat exchange (over £100) and the diverter valve(again about £100), but the problem still remains and it makes for very annoying showers! I have watched the boiler temp gauge whilst the HW runs and it seems to switch on and heat the water rapidly, then gets too hot, cuts out and cools down, then the process starts over again! THe only thing I can think is that the boiler part is blocked slighty by sludge or lime scale build up.

Does anyone have any suggestions about why or how I can solve this problem? Do I keep throwing money at it or bit the bullet and get a new boiler(which I really don't want to do!)

Many thanks
HB

EliteHeat

Which heat exchanger did you replace?

hulkiebear

Hi, thanks for the speedy reply!

The heat exchange I replaced was the secondary heat exchange(that is the only writting on the box it came in) Basically its the one that is about 8-10 inchs long and 3-4 inchs wide, with 4 inlets/outlets. It sits just behind the control panel.

any ideas?

cheers
HB

EliteHeat

Well temperature sensor and flow switch would be obvious choices. Flow switch less likely.

hulkiebear

Cheers, I'n not too sure exactly what those bits look like? Anyone know if I can get hold of an exploded diagram of the boiler on line?

hulkiebear

Whilst running a bath I had to turn the bath hot tap on until it went cold then turn the sink hot tap on and the bath off until the water ran hot again then switch back to the bath, so on and so forth.

During this process I had several Fault 22's (Low water, no water in appliance, or possible pump problem) which involved resetting the boiler, whilst doing this I check that the pump would run on the lower setting and the higher(by way of the amount of noise it was making).

Also, I realised that if I ran the hot tap not full tilt, maybe 25% open, then the problem was better, in that it would only go from hot to warm then back to hot.

So, i'm thinking two things, if the temp gauge is not working properly or very slowly, then by me reducing the flow(25% tap open) then it has enough time to instruct the diverter valve to operate. Or, the pump is not working properly and the hot water in the CH side needed to be pumuped to the secondery heat exchange is not enough to keep the water hot.

I will start with the temp gauge as yu suggested HE, as that seems the most likely.

Cheers (more of a blog this one, rather than a question!)
HB

hulkiebear

Right, now that christmas is out of the way, I'm going to try and get this boiler situation sorted.
It has got worse aswell. The HW doesn't work properly at all now. The CH works quite well though, so, I'm going to take apart the water side of the boiler(following manufactors instructions for various bits). I have no intention of touching the gas side, but will turn it off whilst working on the boiler.

My thinking is to replace the temp sensors and try to check the rest of the system for blockages.

Apart from the obvious of getting a plumber in to do it,(which I've already tried)
has anyone got any advice or suggestions to help me with this?

Cheers
HB