Vaillant Turbomax Pro DHW too hot

[Shabs]

When i got my boiler installed this winter, it was freezing and the dhw did not seem to get hot enough. when i told the installer he adjusted something at the bottom of the boiler with a screwdriver and the dhw was hotter.

Now in summer, even with the water control on full left, the water is too warm. Did he increase the gas flow? How do i get the setting back to the factory setting as i now realise i made a mistake by asking for hotter water. i have tried looking for some sort of screw but cannot find it.

Does anyone know what he tweeked, and how i get it back to the original setting?

Thanks in advance!

[Lee]

What's the hot water flow rate like? It's likely that he just throttled the cold water supply.

Have a look at where the mains cold water pipe goes into the boiler and see if there is a *water* valve that is not fully on. Not the filling loop obviously ;p

Lee

[Ed Sirett]

Yep the brass fitting contains both a 1/4 turn stop valve and flow rate control with hex flats. This latter needs to be opened up so as to give a better flow of water. You can of course turn down the HW temperature control knob but that will simply make a 'smaller' boiler and may lead to cycling of the output temperature.

[Shabs]

I had a look at the flow rate control and it was fully open, with no change. Is there anything else that could have been adjusted to give hotter dhw. He used a sparky's screwdriver to adjust something. Now the water is hot even with the heating control to the coolest position.

[Ed Sirett]

It is possible that the burner's gas rate was cranked up on the gas valve. That would have needed a small screwdriver.

IME an excessive gas rate does not make more HW it simply burns more gas and produces a hotter exhaust.

The procedure for checking the burner pressure is given in the service manual. However you will need a suitable manometer and the skills to use it. Also some leak detection spreay to check the gas test point has been correctly shut afterwards.

What's the kitchen sink tap CW flow rate like - I take it there is enough flow & pressure (15L/minute should be good enough). Also check there is no other unnecessary restrictions on the CW supply or HW outlet pipes.

Finally you may just have to turn the boiler down in the front panel.

[Shabs]

Ed when you say turn the boiler down in the front panel, do you mean turn the dhw setting to its coolest point or turn the boiler down in some other way. The DHW knob is turned fully to the left, ie the coolest point and it is still too warm. He did have the front panel open when adjusting something.

[Ed Sirett]

I'm really perplexed by you saying you've turned the DHW setting to minimum. At that setting the DHW should be around 50C. May be less. I would expect the burner to be have intermittent periods of rest when in DHW moded at that setting.

When you say too hot what do you mean? What does the LCD display say when the boiler is running? The NTC temp sensor is in the primary water as it emerges from the secondary heat exchanger so the displayed temp is the DHW temp when in DHW mode.