Vaillant "Warmstart" function (EcoTEC Plus 831) an

26 Jan 2011
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United Kingdom
Operating my new EcoTEC Plus 831 combination boiler in conjunction with VRC430f results in one oddity. Although the Warmstart function (preheating of the DHW heat-exchanger) can be switched on at the boiler, with appearance of "C" on LCD display, the preheating does not work.

On the VRC430f controller, as set up by the installer, the HC1 registrations appear on the LCD display, but no DHW settings appear. In other words, all the DHW registrations and screens are blanked out. [This blanking out does not seem to be documented.]

I have reported the Warmstart issue to the installer, who has gone away to think about it.

Does anyone please know if this is correct --- is there a way to get the Warmstart to work in conjunction with VRC430f? Or is there an undocumented restriction?

[Otherwise the new setup seems to be working well --- in particular, the optimum start and carefully targeted CH flow temperatures. In my property, heating curve 1.5 seems to be about right.]
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you cannot see any dhw setting as you dont have a cylinder installed. it is disabled in the instalation assistant screen.

how can you tell the warm start isnt working? have you looked at the S. codes?
Thank you for your response.

Evidence for non-operation of Warmstart is threefold. (i) DHW is taking a time to get up to temperature; (ii) even though the 'C' appears in the boiler LCD, indicating that warmstart is switched on, the 'C' never flashes (to indicate preheating of DHW heat-exchanger is in operation); (iii) the boiler diagnostic codes are typically showing a difference of over 30 degrees between warmstart temperature target value [d7] and current temperature for warmstart sensor [d4].

I cannot see anything in the documentation to suggest that warmstart should not work when the VRC430f is connected. What I do know is that warmstart was working before the VRC430f was connected.
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As I now have a solution to the above DHW warm start problem, I should record details here.

There had been an error by the installer in setting up the VRC430f controller settings. On installation screen A2 [System configuration] the 'Cylinder' registration had been set as inactive. For the "warm start" function to work, the correct setting is active. Changing this setting allowed access to various DHW screens, and allowed the setting of timer details [screen #4 --- Domestic hot water time programme].

The use of the term 'Cylinder' for a function that includes not only heating of water in a storage tank, but also preheating of DHW heat-exchanger in a combi, is perhaps confusing for any installer. After the 'Cylinder' function has been activated, it is possible [screen #14] to rename the function, and to avoid confusion I have called it 'HW PREHEAT'.

In the event, the installer had no interest in providing a remedy for what was an installation error, and regarded it as Vaillant's responsibility. Ultimately, Vaillant UK were very helpful in getting this sorted. My thanks to Vaillant.

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