Vaillant mains interference problem

[mdurkin]

Hi All,
I have a strange problem on my ecomax 8 year old boiler (824e). It seems sensitive to other electrical appliances. If I have the microwave, dishwasher, washing machine, or fridge running, the display showing temperature starts changing rapidly (I'd say 6 times a second) and sometimes this results in an F.64 error and the boiler stopping.
If I turn all the other appliances off, it works fine all the time.

I've had 2 different companies round to have a look (I had replace the temperature sensor, cleaner out the heat exchanger, and have replaced the diverter valve for a different fault about a year ago). On both occasions I couldn't recreate the fault, and just worked out that it is other appliances that are causing the problem.

Anyway - does anyone have any idea how to fix the problem. I'd rather not replace the whole circuit board - I'm assuming there must be some interference cancelling circuitry on it somewhere that's not working properly.

Anyway - anyone come across this before / have any suggestions?

Thanks,
Matt

 

[Agile]

The Vaillant has little supression on the PCB apart from a VDR to supress high voltage spikes.

Apart from Ideal, few boiler PCB have much interference supression at all on the latest models.

Its much more likely to be a supply/wiring problem.

I have no problem dealing with diagnosing these problems but then I came to the industry from an electronics background. I have yet to come across anyone else in the industry who has much of a clue on anything like this.

The first think you might be able to check is with a well calibrated volt meter to see what the input voltage is.

Tony

 

[bengasman]

First port of call is to check the powersupply and the earth on the feed for the boiler, and the earth and bonding for the house.

 

[The831Bunny]

Sounds like a live to Earth fault affecting the NTCs. If you are competent, check the voltage at the boiler between Earth and Neutral with your various appliances on. Anything over 4VAC will cause voltage on the frame (Earth) of the boiler to influence the NTC sensors. Also watch the digital temperature display, you will find it flicks quickly between two or three figures.

If you find this is correct, then not a boiler problem. Contact an electrician to check your wiring/appliances. Worst culprits are Showers, Kettles, Ovens, Tumble driers etc. Have you got an earth trip?

Bunny

 

[mdurkin]

All,
I know this post is old, but I just wanted to confirm that this was an earth fault. We had no bonding between the house earth and pipes. They're all bonded and the problem has gone.
Thanks so much for your help,
Matt

 

[bengasman]

The problem may have gone, but it is a clear sign your electrical installation in itself is more than a bit suspect; bonding to gaspipe or waterpipe should have no influence on the working of the boiler. I strongly recommend you get a reliable electrician to check the wiring in your house.

 

[mdurkin]

Hi Bengasman,
That's exactly what I did - I had all the wiring checked out, RCD/MCBs fitted to replace the fusebox, and the earth bonding between water and gas done.
I was assuming that because the only point the water, gas and electric earth met was through the boiler, that this could be causing the problem due to (normal) variations in the static voltage floating on earth. Now they're all bonded together, there will still be a static voltage, but it will be the same across water pipes, gas pipes, the main earth, and ground - so no weird currents flowing through the boiler.

All the above is assumed as I didn't specifically test for currents running through the boiler, but really the boiler is not designed to be the common earth point so I could imagine how this could cause problems.

All circuits were earth tested, correctly fused etc so it's all sound now.
Thanks,
Matt