Vaillant Turbomax Plus 828/2e Hot water temp. and flow

[fletcher7751]

Good afternoon all, first post here
My seven year old boiler started giving DHW problems some time ago.
Took of DHW heat exchanger, de scaled - lightened it noticeably - then refitted. Improvement but not back to as new, intended to renew next time it happened..
Started playing up again ( luke warm showers) so fitted a new OE exchanger, but was disappointed with the result.
Took forty minutes to run a just warm bath.
Water temp touches 70 deg C indicated with cold water choked down a bit to a flow rate of 8 l/min., temp just OK for a shower but it won't reach the 80 degrees mentioned by others.
Diverter valve OK, no bleed over to heating side at all.
d.40 shows 67; d.41 shows - .
Thinking this might be DHW temp sensor, other than this, in heating mode runs sweet and is powerful.

All suggestions welcome and appreciated.

My speciality is brickwork, general construction, building regs and construction defects and inspections so look forward to replying to posts where appropriate elsewhere.

Best wishes

 

[Bunnyman]

The symptoms you describe point to a faulty shower thermostat mixer. This mixes cold water with the hot at EVERY hot tap you open not just the shower, in fact my grohe shower cartridge packed up last month causing poor hot water at all my hot water outlets. Try turning off the cold isolator under the boiler on the cold inlet. Then open a hot water tap and see if you have water still running

 

[chantelle]

 

[fletcher7751]

Thanks Bunnyman.
Tried that and not cross flow
I am concerned that the boiler indicates 68 to 70 at best when on DHW only and draw off reduced to 8l/min.
Still looking
Could it be hot water aquaflow valve?

Best wishes

 

[Bunnyman]

Probably a gas fault then an we can't help on that front, mods won't allow