F23 error Vaillant EcoTec Plus

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I know that this thread is over 5 years old and hopefully all F23 problems on Ecotecs have now been resolved!
Unfortunately not mine. F23 started appearing 10 months ago on my 4 year old boiler and so for the last 6 months I have spent most of my time in the airing cupboard monitoring flow / return temps etc, etc, etc. My wife even bought me a stool to sit in there.
After 3 months I was told by the Vaillant engineer who serviced my boiler that no external bypass was required and it was my single pipe 30 year old system which was probably the problem.
Re- reading the cmighty Agile's advice and a cheap offer on Amazon convinced me to install a Honeywell bypass valve , as a last resort following flushings, Output adjustments, pump changes and multi combinations of different zone starts.
The result was breathtaking - I now have a heating system and the boiler at long last does what I tell it to do.
Thank you Agile!
 
Hi

Im hoping someone can explain to me why we keep getting the F23 error message and how we can prevent it happening again.

We have a combi boiler (downstairs) and a hot water cylinder (upstairs). As far as I understand it the combi heats the hot tap water downstairs directly, all the rads in the house, the underfloor heating we have in the upstairs bathrooms and the hot water cylinder upstairs.

A month ago we got the F23 error. A vaillant engineer said it was because we have the rads upstairs on low which is causing a significant temp diff between the combi flow and return which causes f23. He made some adjustments to the boiler and said it shouldnt happen again.

Yesterday we decided to test the piped underfloor heating we have in the upstairs bathrooms. Weve never used it before. The previous owner of the house said it may take 1-2 days to heat the floor tiles up which sounds like a long time to me but i know nothing about UFH. After leaving it on for 24h the tiles were still stone cold and the combi fell over with the f23 again.

Weve turned the UFH stat right down and darent try using it again!

So I guess its 2 questions really...

1) Anyone know whats going on with the combi and how we can stop f23?

2) Can someone explain my UFH? How come the tiles were still cold after 24h? When we turn the stat up the boiler fires up but it wasnt firing for that whole 24h period, it kept stopping and starting periodically. Also, surely the UFH wouldnt be running during the night when our heating is turned off? The previous owner said the UFH is on the same circuit as the towel rads but the towel rads have always worked fine and come on with the room rads when the UFH stat is turned right down. (ps the previous owner built this house).

We are confused :confused:

I had two error codes coming up on my vallaint ecoTEC plus 831 F23 and F72
Hi

Im hoping someone can explain to me why we keep getting the F23 error message and how we can prevent it happening again.

We have a combi boiler (downstairs) and a hot water cylinder (upstairs). As far as I understand it the combi heats the hot tap water downstairs directly, all the rads in the house, the underfloor heating we have in the upstairs bathrooms and the hot water cylinder upstairs.

A month ago we got the F23 error. A vaillant engineer said it was because we have the rads upstairs on low which is causing a significant temp diff between the combi flow and return which causes f23. He made some adjustments to the boiler and said it shouldnt happen again.

Yesterday we decided to test the piped underfloor heating we have in the upstairs bathrooms. Weve never used it before. The previous owner of the house said it may take 1-2 days to heat the floor tiles up which sounds like a long time to me but i know nothing about UFH. After leaving it on for 24h the tiles were still stone cold and the combi fell over with the f23 again.

Weve turned the UFH stat right down and darent try using it again!

So I guess its 2 questions really...

1) Anyone know whats going on with the combi and how we can stop f23?

2) Can someone explain my UFH? How come the tiles were still cold after 24h? When we turn the stat up the boiler fires up but it wasnt firing for that whole 24h period, it kept stopping and starting periodically. Also, surely the UFH wouldnt be running during the night when our heating is turned off? The previous owner said the UFH is on the same circuit as the towel rads but the towel rads have always worked fine and come on with the room rads when the UFH stat is turned right down. (ps the previous owner built this house).

We are confused :confused:
 
I had two error codes coming up on my vallaint ecoTEC plus 831 F23 and F72

I had two error codes coming up on my vallaint ecoTEC plus 831 F23 and F72 for about a month.

The problem was resolved by switching off the warm start. The warm start can be turned off by turning the water temperature to the cold side fully and the C icon on the screen should disappear.
 
Sponsored Links
I know that this thread is over 5 years old and hopefully all F23 problems on Ecotecs have now been resolved!
Unfortunately not mine. F23 started appearing 10 months ago on my 4 year old boiler and so for the last 6 months I have spent most of my time in the airing cupboard monitoring flow / return temps etc, etc, etc. My wife even bought me a stool to sit in there.
After 3 months I was told by the Vaillant engineer who serviced my boiler that no external bypass was required and it was my single pipe 30 year old system which was probably the problem.
Re- reading the cmighty Agile's advice and a cheap offer on Amazon convinced me to install a Honeywell bypass valve , as a last resort following flushings, Output adjustments, pump changes and multi combinations of different zone starts.
The result was breathtaking - I now have a heating system and the boiler at long last does what I tell it to do.
Thank you Agile!


Where is Agile's advice on this, I cannot see it in this thread.
 
Not at all, I cannot see anything from Agile about a bypass valve being probable or even possible cause.

My apologies, didn’t read it properly, didn’t know you wanted advice on bypass valves :notworthy:

I think yours is to do with your pump though?
 
Last edited:
My apologies, didn’t read it properly, didn’t know you wanted advice on bypass valves :notworthy:

I think yours is to do with your pump though?

NP

Don't know.

It was saying f24 but then went onto f23 which I think indicates a blockage?
 
The boiler hasn't come up with any error messages for the last 12 hours or so, but it isn't working correctly.

The boiler comes on, the water starts to heat, quickly rises to temperature set for rads then turns itself off. Cools down and repeats. The cycle lasts about 1 min.

Short Cycling?

I believe that the pump is working all the time but he radiators are barely warm.

Does this sound like the pump is not circulating the water efficiently?

ps the thermostat is set to 35 degrees C and the rad sympbol is constantly flashing so I believe it is const calling for heat
 
The boiler comes on, the water starts to heat, quickly rises to temperature set for rads then turns itself off. Cools down and repeats. The cycle lasts about 1 min.
sounds like low flow or all the flow is going through the bypass, either stuck open or excessive resistance in the main circuit.
 

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