Combi warm water NOT hot

[williamglossop]

I have a Valliant Combi fitted about 4 years ago. When I run the hot tap, it takes ages for the water to change from warm to what id call hot. Sometimes it just stays warm and never gets hot, on other occasions it gets hot eventually but takes a long long time - well over 3 minutes of running the tap.

Any ideas why this might happen? The target temp for DHW is set to max, which is 65 degrees.

 

[oldbuffer]

1. Is this a new phenomenon or has it always been like this.
2. How far is the tap from the boiler?
3. What sort of tap is it, mixer or individual hot?

 

[CBW]

Leave the heating off and allow to cool, or try this when cold. Run hot water and feel the flow pipe under the boiler, the big one on the left as you’re looking at it, if this gets hot whilst you’re running your tap, then you’ve found your issue and need to engage in a gas safe registered engineer to sort. Other thing it could be is a blockage - do you live in a hard water area?

 

[williamglossop]

Thanks.
Chris ...... do u mean the flow pipe for the central heating?

Old Buffer..... its been on and off like this for a few months i reckon. The boiler is close enough that they're are occasions when the water is really hot, and on other occasions it's just warm. The tap is a mixer tap in the kitchen, but the same thing happens in the bathroom too. Its like the boiler is heating the water up, just not enough. But the problem is intermittent...... which is infuriating.

 

[CBW]

Thanks.
Chris ...... do u mean the flow pipe for the central heating?

Yes I do.

 

[williamglossop]

I'll check it tonight when I get home.

 

[williamglossop]

Yeah.... as you suspected. The hot water pipe gets lukewarm, but the central heating flow pipe gets red hot. I'm guessing its the diverter valve. Its an EcoTec 832. It's under warranty, and hopefully that will be covered.

 

[CBW]

Yeah could be diverter (likely) or blocked plate heat exchanger - not too sure what’s covered with warranty’s.

 

[williamglossop]

Got this resolved in the end. Had boiler cover..... engineer came out and said either diverter or heat ex. He took a water sample and said the water was too black and wouldn't carry out work unless I had a powerflush. I couldn't afford that. So I did a mains flush of all the rads individually after running system cleaner through it for a week. I put two bottles of inhibitor and ran the heating for a couple weeks. Took a water sample after 2 weeks or so, and water was still clear. It did improve slightly with cleaner water in the system, but the central heating flow was still heating up when the hot tap was on. I bought a diverter valve service kit from buycombi and fitted it today. Problem solved now. Thanks for your help.

 

[williamglossop]

I did found that the metal shaft on the valve i removed was slightly corroded and really stiff to move in and out, but the replacement was a lot easier to move. I suspect this friction may have caused the diverter valve to stick/not fully open.