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Brian, HVAC Technician
Category: HVAC
Satisfied Customers: 818
Experience:  OFTEC registered oil heating engineer and plumber.
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My boiler is an ECO TEC Plus 831 saying: F.22 Safety switch

Customer Question

My boiler is an ECO TEC Plus 831 saying:

Safety switch off
Water Shortage

0,3 bar

I therefore have no heating or hot water - what do I do?
Submitted: 3 years ago.
Category: HVAC
Expert:  BillyHvac replied 3 years ago.

Do you have good water supply to the unit?

Has the water been turned off lately?

Customer: replied 3 years ago.

Yes good water supply

No the water has not been turned off recently.

Expert:  BillyHvac replied 3 years ago.
Thank you,

Then you likely have a water sensor issue.

F.22 Dry fire Too little water in the appliance, water pressure sensor defective,
cable to pump or water sensor defective, pump blocked or defective,
pump output too low.

If the pressure is good it eliminates the supply/output or blockages.

You will want to check the cable and/or wiring associated with it.

These are technical units so if not familiar with them I recommend to call for service.


Customer: replied 3 years ago.

I'm not sure that telling me to get expert advice is worth £22. I have tried to contact Vaillant but their helpline is closed. So I came to you for help which amounted to what I did earlier.


I assume therefore that I shall not be charged the full amount.

Expert:  BillyHvac replied 3 years ago.
I am willing to continue with repair internally. Do you have a voltmeter with a resistance setting available?

This is a satisfaction site. Plus...did you read this

What To Do Now?

If the answer supplied was helpful, please rate the answer. If the answer is not satisfactory, do not rate but use reply for further information.

Customer: replied 3 years ago.

No I do not have a voltmeter

Expert:  BillyHvac replied 3 years ago.

I really do not mean this to sound negative at all....I am trying to help.

You came here with a question about the code you have on your heater.

I tell you what the issue are looking for a more detailed answer and list a "Poor Service" response.

I am willing to go into the technical troubleshooting to raise the "poor to an ok".

But you have no voltmeter to do this. I do not know your comfort level with the mechanics of this unit so I start simple...

But what is it you were expecting for me to do with the info supplied and no meter to test?

I can understand if the answer is not what you wanted...but there is no magic button or resets on these units to make this go away.

I apologize you felt the service was Poor, but I really do not know what you would expect given we have no test equipment on your end.

Can you get a meter or borrow one and do you know how to use it?

Customer: replied 3 years ago.

Why do we need a volt meter. My understanding is that all that is needed is to fill the heating system via the filling cock. I have no idea where this is or how to fill the system even if I did. I thought that you,as an expert, would. If you don't then please do not waste my money and your time.

Expert:  BillyHvac replied 3 years ago.


Your expert has opted out and is no longer available to view your question.


Customer stated code failure. Was advised of code. Cust rated poor, offer to begin technical troubleshooting of sensor offered. Customer has no equip. States then it could be filled but stated earlier all water pressures were fine.


Tried to help and advise customer. Customer ended with rude response after offer to help.

Recommend another expert or close question. Customer not mechanical.
Expert:  Brian replied 3 years ago.
Hi 0.3 bar pressure means you will need to fill the system check out this video fill to approx 1.2 bar, it should work fine after that.
Customer: replied 3 years ago.

Video gave the correct information that I needed to resolve the problem.

Expert:  Brian replied 3 years ago.
Brilliant glad it helped you out

Merry Christmas