Vaillant ECOfit 418 purge cycle

[Harry Bloomfield]

Last summer, when there was no call I was aware of for the boiler to start up, I heard it a number of times run what I guess is the 'purge cycle'. When it is called normally, the fan starts up, runs for a few seconds, all goes quiet, then the fan and ignition sequence begins. That few seconds of run, is what I have supposed is a 'purge cycle' - making sure there is no unburned gas in the combustion chamber, before lighting up.

The purge seemed to happen at any hour of the day, quite randomly and as I'm not constantly by the boiler, no doubt I would miss some. Curious as to what it was supposed to be doing, I asked Vaillant's Tech, who seemed unaware it might do this and suggested I check the fault log for a fault number - no faults have ever been logged, either during the mystery purges or later.

It was operating on a none Vaillant timeclock and mechanical stats last summer, providing a regular cylinder of HW once per day. I have since converted to a full VRC 470F controls.

Has anyone noticed this action or have an explanation? I can understand it occasionally running the circulation pump to prevent seizure, if unused for weeks on end, but why run the fan so often?

 

[Mottie]

I know when I had my EcoTec Plus 418 fitted with non Vaillant controls, they forgot to remove a 24v link and the boiler/pump/valves were acting strange until the link was removed. Did you refit that link when fitting Vaillant controls as I believe they run on 24 volts?

 

[Harry Bloomfield]

There was a red wire link removed when it was installed, the lower right - 24v RT. Boiler was powered, called and grounded via a four core. I refitted that LINK, when I swapped to Vaillant controls (I think).

The new Vaillant system uses ebus power to power the VR65 control module, ebus or plugged directly into boiler for radio receiver, wireless solar powered VR61 weather sensor, then wireless (battery powered) for the VRC 470F.

EDITED TO ADD THE WORK LINK to first paragraph to make it clearer.

 

[ScottishGasMan]

Does it do it still on the vaillant controls?

 

[Harry Bloomfield]

Does it do it still on the vaillant controls?

Impossible to tell. Because it is winter it is frequently firing. It was only noticeable last summer, because there was obviously no calls for heat at all, apart from the hour I set it to come on to provide HW in time for washing up after dinner.

 

[ScottishGasMan]

Most Vaillants I think have a 24hour anti seize feature, so they would only run fan/pump/diverter once per day, more than that and its something wrong.

Reason I ask about the new controls, if you find this summer its stopped doing it, then chances are it was one of the zone valve micro switches was faulty causing it to get a signal to run or a stray voltage on the same wire, with the new controls you wont have anything wired to the switched live and the end switches in the zone valves are not used so if it is the case then it wont happen any more.

Only other thing can be the frost protection mechanism which is set quite high on these boilers (12*c) but being that it was doing it during summer and during the day at that, it wont be this in your case,

 

[Harry Bloomfield]

Not the zone valve(s), I have a mid position three port and I was playing about with three different valves during the summer and the 'purge cycle occurred with them all. The boiler was new in March, so I was keen to find something more reliable than the Sunvic 2701 spring return actuators which have given me constant grief in the decades since the heating system was installed in 1985. I had fitted a brand new 2701 with the new boiler, then found the 1901 momo, so in mid summer I changed valve and actuator over to that and bought a second spare just in case. So I was doing quite a bit of swapping and testing of the valves and actuators.

I was so despondent with the 2701, I was even thinking I could design something more reliable myself, perhaps using stepper motors and a pic.

I had sort of decided it might have an anti-seize feature, but it didn't do the 'purge' at the same times of day and ignored the fact that it was run at least once per day anyway. Ringing Vaillant, they didn't seem to own up to it having an anti-seize facility - hence my OP on here. I will see what it does in the summer, in a few months, with the Vaillant controls in place.

 

[ianmcd]

if the boiler was new in March then it is still under warranty so just get Vaillant out

 

[Harry Bloomfield]

if the boiler was new in March then it is still under warranty so just get Vaillant out

Pointless getting Vaillant out, if the purge is a feature or some issue with my system. I don't think I have caught it doing it more than once per day, or even actually caught it doing it every day. It was just a matter of hearing it whilst in the kitchen and wondering why it might be about to fire up when there shouldn't be a call for it.

 

[Kent212]

I'm having the same problem with my Vaillant eco TEC plus 418 fitted last month. It comes on briefly for about 10 seconds outside the timed periods and then switches off. This happens every 23 hours. This doesn't matter during the day but is a nuisance at night as it is waking me up so this week it's been coming on at 4.10 am, 3.10am, 2.10 am etc so by the end of the week it will be evening. My plumber had never come across this before. The Vaillant technical helpline said there's nothing we can do as it's the anti-seize. On my original post a reply said it's a fault as it should only come on if it hasn't come on in the previous 24 hours. And it's not showing a fault code. Is yours still the same?

Read more: https://www.diynot.com/diy/threads/...-on-outside-timed-hours.551292/#ixzz6W2tgnzhP

 

[Harry Bloomfield]

I'm having the same problem with my Vaillant eco TEC plus 418 fitted last month. It comes on briefly for about 10 seconds outside the timed periods and then switches off. This happens every 23 hours. This doesn't matter during the day but is a nuisance at night as it is waking me up so this week it's been coming on at 4.10 am, 3.10am, 2.10 am etc so by the end of the week it will be evening. My plumber had never come across this before. The Vaillant technical helpline said there's nothing we can do as it's the anti-seize. On my original post a reply said it's a fault as it should only come on if it hasn't come on in the previous 24 hours. And it's not showing a fault code. Is yours still the same?

Read more: https://www.diynot.com/diy/threads/...-on-outside-timed-hours.551292/#ixzz6W2tgnzhP

Too be honest, I have not noticed it now for a long time - It doesn't mean it is not happening, I am just paying less attention to it. It is in a cupboard in the kitchen which hides the noise quite well, so never obvious - its just that I gave it more of my attention when I first had it installed. I will suggest it seems not to happen as much in the summer, as in the heating season, which is rather at odds with their suggestion that it is an 'anti-seize' feature.

 

[Harry Bloomfield]

Can I draw everyone's attention to this thread - https://www.diynot.com/diy/threads/vaillant-eco-tec-plus-418-coming-on-outside-timed-hours.551292/

It seems it is a built in feature, which is not mentioned in either manual and Vaillant technical are not even aware of it. A once per day run of the fan, in addition to which it will run the pump if the pump has not run for 24 hours or longer (they suggest in the thread).

An anti-seize feature after all, so not some weird issue with my boiler or its controls.