Vaillant Ecotec Pro 28 - tepid hot water?

[Chuckles1066]

Hello,

Apologies if this is a stupid question, there's a bit of a story to this.

So, back in April I noticed that our hot water was temperamental, you could draw some at 10a.m and it would be fine, at 11a.m it would heat up briefly before running cold. I looked at the LCD display when this happened and it was flashing "0.7 bar".

The boiler was due a service so we got our usual guy out. He explained what was wrong with the pressure and even showed me how to add water to the system in future if needed.

After he'd gone, everything was good although whenever the central heating kicked in I noticed the LCD display would flash "3.1 bar". Maybe he added too much water to the system, I don't know?

So summer came, we didn't need the heating and the hot water behaved perfectly.

Yesterday we fired the central heating up for the first time in about four months and today we are only getting tepid water from the hot taps. There is nothing flashing on the LCD display.

I'm trying to get my head around the boiler behaviour and I'd appreciate your words of wisdom.

I've attached a picture the boiler "at rest", i.e no hot water being drawn and the central heating off. The 34C I assume is the temperature of the water in the system? If I turn the hot tap on, that 34C slowly increments upto 49C, sometimes 50C, and then doesn't go any higher. The water coming out of the taps is tepid / lukewarm at best.

I know that the boiler is set to 60C for hot water.......so something is stopping it going beyond 49C / 50C.

I have bled one radiator but only about an egg cup full (bit scared to take too much out).

Any thoughts greatly appreciated and I thank you for your time.

 

[picasso]

The expansion vessel needs recharging, it should have been done on the annual service, with the boiler cold run the hot tap and see if the far left 22mm pipe starts to get hot, if it does the diverter valve needs replacing.

 

[DP]

I know that the boiler is set to 60C for hot water.......so something is stopping it going beyond 49C / 50C.

Have you checked hot water at other taps?
Does not have to be the boiler if it shows 50 degree of hot water temperature. Cold water will be at lower than 15 degrees at the moment ( getting colder as winter sets in)
When was the boiler serviced last
Based on what you have written, service is either well overdue or not carried out correctly.

 

[Chuckles1066]

Thank you both for your time, much appreciated.

None of the taps are providing "hot" water, just tepid and the boiler was serviced in April.

I don't know if this is relevant but we had the mixer taps in the kitchen replaced about a week ago which necessitated turning off the water at the mains? Just a coincidence I assume?

 

[picasso]

Turn the cold to the new tap off and see if it makes a difference.

 

[Chuckles1066]

The expansion vessel needs recharging, it should have been done on the annual service, with the boiler cold run the hot tap and see if the far left 22mm pipe starts to get hot, if it does the diverter valve needs replacing.

Ok, everything at rest, wife turned the hot tap on in the bathroom and the far left pipe gets hot quite quickly - so we have a knackered diverter valve?

I'm a layman, what does the diverter valve do? (Lesson 1 for me in basic plumbing)

EDIT: is there a test I can do? If I turn the heating off completely, would that mean we'd then start getting hot water at the taps? Sorry if that's a stupid question!

 

[picasso]

Your boiler can do either heating or hot water. it cannot do both, the diverter valve sends primary water round the rads or through a plate heat exchanger, your diverter is stuck half way so needs replacing.