New diverter valve. Boiler over heating

[trevorbayliss]

I had my vaillant diverter valve changed today. Ecotec plus.

Heating has been on this evening ok. But when we ran a bath the HW must have switched off. It gives a F20 error code which looks like overheating.

So I think the HW has caused this issue? We have only discovered this at 11pm so need to go to bed. I have messaged the engineer so hope he can come back.

Any idea on why this has happened? The diverter was a genuine brass one

 

[Johntheo5]

There might be air trapped somewhere if the boiler's internal vent was left shut off on refilling the system.
Suggest turning the DHW temperature setting to its minimum and open a hot tap but not fully and see does the boiler remain firing, if it does gradually increase the temperature setting to its original, if the boiler still keeps firing open every hot tap + shower fully, if it then flags a F20, probably a blocked plate heat exchanger.
Is the CH working?
Whay was the diverter valve changed?.

 

[trevorbayliss]

Boiler doesn’t work now even when heating only comes on. Burner fired up for about 20 seconds then cuts off.

 

[trevorbayliss]

There might be air trapped somewhere if the boiler's internal vent was left shut off on refilling the system.
Suggest turning the DHW temperature setting to its minimum and open a hot tap but not fully and see does the boiler remain firing, if it does gradually increase the temperature setting to its original, if the boiler still keeps firing open every hot tap + shower fully, if it then flags a F20, probably a blocked plate heat exchanger.
Is the CH working?
Whay was the diverter valve changed?

DV was changed as it was leaking. No leaks now. I will try what you said. A new AAV was also fitted. So it might be an air issue.

 

[trevorbayliss]

I’ve just tried the HW and it won’t fire.

He had to drain down the boiler and removed the secondary HE because a screw on the DV wouldn’t come off using a screw driver. The screw had sheared off. He got it off with grips.

 

[trevorbayliss]

Could the HE have become blocked when it was put back?

 

[trevorbayliss]

Now it says F 75, which is connected to the pump.

Could any electrics have been damaged when doing this work?

 

[trevorbayliss]

A new boiler sensor was added a few months ago as a separate issue from all this. The boiler was taking in water as the valve wasn’t closed fully but I thought this was a sensor issue.

That has been sorted now, but reading about the F75 issues it seems new pressure sensors are needed.

Boiler is 16 1/2 yrs old. I was thinking just replace the boiler. But decided to just replace the DV. Now all these problems.

 

[DP]

A new boiler sensor was added a few months ago as a separate issue from all this. The boiler was taking in water as the valve wasn’t closed fully but I thought this was a sensor issue.

That has been sorted now, but reading about the F75 issues it seems new pressure sensors are needed.

Boiler is 16 1/2 yrs old. I was thinking just replace the boiler. But decided to just replace the DV. Now all these problems.

Appliances need regular maintenance. Not saying it should be done every 12 months, just that it should not be ignored.
Boiler you have is still a good boiler that does not mean it should go to a skip, a full service will work wonders.

 

[Johntheo5]

Now it says F 75, which is connected to the pump.

Could any electrics have been damaged when doing this work?

Was the boiler tested after doing the repairs?

Possible that the boiler pressure gauge is faulty or blocked, if there is not sufficient pressure then the pump shich has to see a change in pressure when it starts will flag F75 if not.
What is the boiler pressure now?, suggest increasing it by say 0.3/0.4 bar to not greater than 1.8bar.

 

[trevorbayliss]

I have no idea if it was tested.

Pressure last night was 1.5 on filling

This morning it’s 1.3

Engineer will call later this morning.

I think something has happened to the pump

Can anyone tell me what to here when you do a purge. Last night after googling this issue I ran the P.0 purge. It ran for about 5 minutes. Didn’t hear any air coming out.

 

[trevorbayliss]

Appliances need regular maintenance. Not saying it should be done every 12 months, just that it should not be ignored.
Boiler you have is still a good boiler that does not mean it should go to a skip, a full service will work wonders.

Ok. Can you tell me what needs to be done on a service. I have it done every few years. Last done in jan this year. All engineers do is clean out the main burner. I’ve watched before and my burner is quite clean inside. Then it’s a new seal and that seems all they do.

I have a mag pro 2 filter as well so my system is pretty clean.

 

[Johntheo5]

Can anyone tell me what to here when you do a purge. Last night after googling this issue I ran the P.0 purge. It ran for about 5 minutes. Didn’t hear any air coming out.

Don't know what happens with the boiler purge but most A rated circulating pumps do not now have a centre venting screw so, on installation, you can run this purge schedule, it just runs for ~ 10 minutes and speeds the pump up and down and stops it frequently during this period, don't know how effective it is at purging air from the system, it almost certainly purges air from the pump, I've never used it.

 

[CountryFan]

If you can hear the pump when reset then unlikely to be this and more the low water pressure sensor. Regarding the F20, sounds like maybe the return valve is closed under the boiler from changing the diverter, easily done if distracted.

 

[trevorbayliss]

Looks like it’s the HW plate heat exchanger.

I treated it before the diverter was changed on the day with spirit of salts. I guess I didn’t allow enough time to dissolve the line scale.

It sounds like it is all gunked up in there.

I’m going to try treating it again and if it doesn’t work I will get a new one.