Vailant EcoTec pro 28 boiler issue

[bigH]

Hello,
I have a new Vailant EcoTec pro 28 boiler. I have been told in the manual to set the boiler to 75 degrees and allow the room thermostat to control the heating. However I notice when the thermostat timer switches off the boiler, it periodically fires up for about 15 seconds and goes through the anti-cycle period and shuts down. This happens throughout the day, so my question is this normal? I am worried that my gas bill will go through roof due to this

H.

Thanks in advance.

 

[ScottishGasMan]

You will probably find that the "WarmStart" Function (have a look at the manual) is active, which intermitantly heats for brief periods to keep the water warm so when you open a hot tap the boiler gets the hot water out at the right temp almost straight away.

 

[bigH]

Hello ScottishGasMan,
I believe you maybe referring to the “comfort” setting on these boilers for keeping the hot water at a particular temperature all the time which I have switched off. I thought this is for the hot water and not the heating of the room? I check and see the manual again but I can’t remember seeing any “warmstart” function for the heating.

H.

 

[ScottishGasMan]

Yes I am talking about the comfort/warmstart/preheat for the hot water not for heating,

when the boiler is coming on by its self are the radiators heating? does the radiator symbol come on, on the display?

 

[bigH]

No, the heating does not come. The radiator symbol is not flashing to indicate that it is calling for heat. I just see the flame symbol come on showing that it is drawing gas for a few seconds and then the anti-cycle symbol comes afterwards.

H.

 

[ScottishGasMan]

Odd. Think you need to see why the boilers activating using the S.Codes

Per the manual
13.2.1 Calling up Live Monitor (status codes)
You can call up the boiler status codes in the display which
provide information on the current operating status of the
boiler.
> Press the left-hand and right-hand selector
buttons ("i") at the same time

the manual will list a set of codes which essentially tell you what the boilers thinking, if you can have that showing while its running (even while its doing its over run/anti cycle after its fired) that can tell us if its firing for a sudden intermitant heating demand or hot water pre heat or hot water demand.

if you have the hot water comfort/pre heat off, then by the sounds of it, you may have a dead leg in the hot water system which mains fluctuations cause a sudden and short demand. to test, quite often all you need to do it run a cold tap at a decent rate for a min, then shut it off quickly and see if the boiler suddenly runs for a few moments.

 

[bigH]

Ok, so I dropped the boiler temperature to 55 degrees and now noticed that every 30 to 45 minutes it goes through the following S codes for a few minutes when the room thermostats are switch off:

S.00 - Heating, no heat demand
S.02 - Heating mode pump flow
S.03 - Heating mode, ignition
S.04 – Heating mode, burner on
S.07 – Heating mode, pump over run
S.08 – Heating mode, burner anti-cycling time

Then it goes back to S.00


H.

 

[ScottishGasMan]

It's getting a signal to run the heating. Very unlikley to be a boiler fault. Possibly 24v link left in, or incorrectly wired controls, get your installer back out

 

[ScottishGasMan]

Out of curiosity, had it been zoned? Ie motorised valves fitted to allow seperate heating of say upstairs and diwnstairs

 

[bigH]

I do not what zone means but I do have individual danfoss thermostats in every room, Actual it is a flat so thermostats in the living room, bedroom and a TRV in the hall way.

H.

 

[ScottishGasMan]

Hmm odd it would show heating demand, but not have any heat on the rads. Contact installer or get vaillant out on warranty call, they will soon tell you if it's the boilers fault or not

 

[bigH]

Hello,
Just to let you know that the issue has been resolved now, due to the 24v link on the boiler been removed. I now noticed that when the thermostat is off I see code S.30 on the boiler indicating that the thermostat is blocking it from firing up the heating. This proves that the thermostat is controlling boiler.

bigH.