Vaillant 282 dhw water section.....how it controls heat?

[Flyingstu]

Hi

I have been working on a vaillant 282 and have replaced the dhw heat exchanger. This has improved the hot water temperature but I still think the water section needs replacing as the temperature setting wheel does not adjust water temperature.

I replaced this part about 2 years ago with a reconditioned part. Having looked inside it before I am not clear as to how the unit varies the output temperature of the hot water. Can someone explain this part of the device, I can see how the diaphragm works to switch the boiler on when demand is made but how does it reduce flow rate to control temperature?

Also the control wheel seems to,break very easily when the unit starts to get stiff with age, is there a fix for this? Buying a new valve every time is very expensive as the wheel is not sold as a separate part far as I can see.

Thanks for any info

Stu

 

[The831Bunny]

The temperature selector at the front of the water section regulates the flow rate through the water section from 7.5 L/Min (hottest water) to 10 L/Min (coolest water). This temperature selector is available separately, as is the control knob.

The water section also has a governor that coarsely adjusts the flow according to the incoming water pressure/flow. This can jam or break and requires the whole water section to be replaced if that's the case.

There are two water sections with temperature selectors. The older variation has a cross on the underside of the section, and the newer section (from 1995) sometimes has a brass top, not chrome, and has a governor that can be screwed out of the bottom (hex nut)

The part numbers are: old water section: Temperature Selector 012533. Newer water section: Temperature Selector 012554. Knob for either 125117

The hot water temperature requires the heat input and the flow of water to both be correct. if the temperature is still poor after changing the temperature selector then as you know a Gas Safe engineer needs to check the boiler is burning with the correct gas quantity.

Hope that helps

 

[Agile]

Stu....

Sh.... but you can get exactly the same effect by just not opening the hot taps as far!

 

[The831Bunny]

Stu....

Sh.... but you can get exactly the same effect by just not opening the hot taps as far!

Not quite Tony.

The temperature selector influences the venturi and the diaphragm movement. If a tap is turned down with a faulty temperature selector, the 'drop off' of the switch point can be as high as 5 L/Min. Showers won't then turn the boiler on...

 

[Flyingstu]

Thanks guys for the very useful info. I have already ordered a complete valve but in future I shall know how to get the control wheel only which is a massive saving. Interestingly we have been using the 'turn the hot flow rate down' method or leaving a cold tap on elsewhere to get an improved temperature when filling a bath. I shall do some flow rate tests and see how it improves after fitting the new valve section.

Another question came to mind regarding the replaced dhw heat xchanger. There was a sticker showing flow direction arrows for the primary and secondary water flows. These suggested that the flow should be in opposite directions for the primary and secondary. The pipe work though puts the flow in the opposite directions, is this a real problem or is the sticker on the wrong way round?

 

[Agile]

I dont remember ever going to one of these style boilers where the adjustment was not on max. Most were stuck too!