Vaillant firing when no call for heat

[Harry Bloomfield]

Some months ago, I had a new Vaillant ECOfit Pure 18Kw installed as a replacement boiler, in a special cupboard for the purpose, in the kitchen. Since when - during the day, with the timeclock set to allow heating, but with no demand for heating, I would occasionally catch the boiler firing up briefly or maybe doing a purge. It is set to bring the HW tank up to temperature once per day, or on a push a button demand.

I emailed Vaillant to ask if it was maybe designed to do this - no reply, so last week I rang them. They expressed no opinion whether it should or shouldn't, but suggested catching the boiler when I heard it running and pressing certain buttons to produce its reason for firing code.

Since then and trying to do that, I have had the cupboard door open to better hear it fire, but not once have I heard it fire :/

I can force it to fire up briefly at anytime, by pressing the 'on' button on the boiler. The resulting brief run, seems similar to the ghost firing I am complaining about.

[Brian Gaff]

So are you suggesting that its got a sensor that does not like to be in a sealed enclosure? are there not any ventilation holes in it? Brian

[Harry Bloomfield]

Brian Gaff wrote on 21/07/2018 :

No, I am not suggesting that - the cupboard is purely cosmetic, open top and bottom, plenty of space at the sides and front. I built it to accept a much larger boiler, long ago.

My original thoughts were, that the boiler would run a purge every so often just to exercise itself - pumps etc., if it hadn't been called for a while. That was the sort of brief cycling I was witnessing.

[John Rumm]

Many of the Vaillant boilers seem to have similar facilities - basically to exercise fans, pumps, valves etc to make sure they don't seize during periods of low use.

[Harry Bloomfield]

John Rumm used his keyboard to write :

The Vaillant help desk tec didn't seem to suggest, or realise it had such a facility. It seemed to be once per day, but at no particular timing. HW is triggered once per day at 16:20.

[Jethro_uk]

My Vaillant has a feature designed to minimise the delay between calling for hot water, and delivering it. It tries to keep the internal temperature around 60-70C. So will fire every so often.

It can be enabled/disabled from the front panel where the DHW temperature is set.

[Harry Bloomfield]

I have an open vented HW and heating circuits by choice. So this is just being used as a simple boiler system.

[John Rumm]

I have a feeling, its mentioned somewhere in the documentation for mine...

[John Rumm]

That's usually on the 800 series combi boilers.

[dennis]

The person that fitted my Valliant forgot to remove the 24V link when using mains ON. This causes the boiler to cycle. I had quite a hard time explaining the mistake to the "engineer" that came to investigate the problem after I spotted the link still being in place. It would have been easier for me to have opened it up and looked myself in the first place.

[Graham.]

Does the system have a wireless thermostat?

[Harry Bloomfield]

John Rumm laid this down on his screen :

If it is in my documentation, I have been unable to spot it.

To be fair, I would be surprised if it didn't exercise things regularly.

[Harry Bloomfield]

Graham. used his keyboard to write :

A wireless room stat., yes..

[Graham.]

Consider the possibility that the receiver is picking up an ON command occasionly from another device nearby.

My radiators came on mysteriously in the night on two occasions during the recent heat wave The pairing was done via 8 bit DIP switches in the stat and receiver, since I changed the code it seems to be OK. The original setting was not the manufacturer default (all OFF) I thought that would be asking for trouble.