Main Boiler (baxi) HW temp issue - now CH doing same

[champians]

Hi folks, spent a while on these forums already but can't quite find something to suit my problem.

Main Combi Eco 30 boiler. (similar to many baxis)

Was working fine then started to have an issue with the hot water. basically when the boiler was called burner would cycle in and out rather than staying constant resulting in luke warm water at best. CH was working fine at that point.

Diverter valve seems fine as the problem happened whether or not CH flow valves were open.

I managed to solve the issue with a bodge where if i had the heating on max for a while so it was north of say 70 degrees I could use the hot water passing the HE to warm the HW as opposed to the heat from the burner. Not ideal but worked enough for a fast shower.

Now I can't even do that as the CH is now playing the same game, cycling on and off the burner while not getting north or 50 degrees (its set to 80).

I've checked the magnoclean filter and thats pretty clean, put a new thermistor on and generally spent a bunch of time trying stuff and reading up but with the CH now struggling to heat the radiators with the burner cycling in and out im thinking its new boiler time unless I can come up with a fix.

Any suggestions or advice greatly appreciated.

Thanks Ian

 

[DP]

24, 25 and 26

For heating what lights are on and what is the number on 27
For Hot water again what lights and what number when 24 goes out.

 

[Deleted member 267285]

Could be the diverter (I know you think it’s ok) and could be the hall affect sensor for the hot water.

 

[ianmcd]

Most likely the diverter valve cartridge

 

[champians]

View attachment 291857

24, 25 and 26

For heating what lights are on and what is the number on 27
For Hot water again what lights and what number when 24 goes out.

Hi, when heating is on 25 is lit. 24 turns on and off along with the burner. 27 shows for example 40 even though its set on a target temp of 80 and its been on for a few hours. It will usually spend around an hour cycling on and off the burner with the temp varrying between 38 and 42 to eventually push slightly higher then varrying between 40 to 44. Once it gets to 50 its doesn't seem to be able to push much higher.

For HW 26 lights as soon as the water is called. the burner light 24 again goes on and off with the burner. The temp readout doesn't move any higher (no more than a few degrees variation as above) but will quite quickly drop so lets say I have it on 50 degrees showing when the water is called it will be in the high 30s if you leave the tap running for a few minutes.

thanks

 

[champians]

Could be the diverter (I know you think it’s ok) and could be the hall affect sensor for the hot water.

thanks Im assuming its ok as with the CH shut off I still got the issue with the HW not holding temp so based on that test assumed ok. I swapped it a few years back and have had the motor off the top to check the pin and thats moving freely but if you think its gone again would swapping the cartridge in the valve be worth a try?

sensor wise the thermistor I've changed what does that control exactly? thanks

 

[Deleted member 267285]

sensor wise the thermistor I've changed what does that control exactly? thanks

No idea, as you haven’t said which one you changed.

thanks Im assuming its ok as with the CH shut off I still got the issue with the HW not holding temp so based on that test assumed ok.

Do you mean the flow isolation valve or just turned off? Imo, yes, the diverter could have failed again.

 

[DP]

You need an engineer to look at the boiler.

You seem to have at least two faults going by your description

If display refuses to ramp up during heating ( left pipe under boiler should be hot) Poor circulation possibly

for hot water, display should indicate around 70 with bath tap at full flow. The flame light should stay on for the duration unless display is high 80 or water at tap is at 65 degree or so

Burner going out during demand for some reason, could be circulation or control issue.

 

[DP]

Thermistor could be the issue
Hope you got the correct one
Which one did you change

 

[champians]

No idea, as you haven’t said which one you changed.

Do you mean the flow isolation valve or just turned off? Imo, yes, the diverter could have failed again.

Hi, I changed the temp sensor going into the diverter valve. Didn't seem to help though.

To stop the flow I just turned off the CH quarter turn valve on the CH out under the boiler.

I'll get hold of another cartridge for the diverter valve cheers

 

[champians]

You need an engineer to look at the boiler.

You seem to have at least two faults going by your description

If display refuses to ramp up during heating ( left pipe under boiler should be hot) Poor circulation possibly

for hot water, display should indicate around 70 with bath tap at full flow. The flame light should stay on for the duration unless display is high 80 or water at tap is at 65 degree or so

Burner going out during demand for some reason, could be circulation or control issue.

I had one over last time I had an issue but he couldn't fix it so I sorted myself in the end. Been fine for a few years but now having these issues. Its weird that the hot water went first and now the CH. Its as if the burner keeps getting turned off by some overheat or similar but having changed the thermistor in the diverter valve its made no odds. I thought it might be the pcb starting to play up maybe or possibly the pump if the flow is the issue. I'll try swapping the pump with a spare tomorrow.

For the display originally the HW would be turned on and the current temp on the display would just plummet. If you had the CH on alone then that was fine and it would get upto a decent hot temp for the rads fairly quickly. Running the CH for a while would get the display temp up to near 80. Therefore you could have some HW for a short while once tuned on as it would make use of the heat the CH had built up but again once the tap was running the value on the display would plummet.

Now the CH is really struggling to raise the temp on the display and the HW is doing as before. The burner just cuts in and out in and out in and out and therefore doesn't do a proper job ha. cheers for your suggestions

 

[DP]

Going by above reply, pump unlikely to be the issue as temperature would be high if pump goosed.

You have replaced the hot water thermistor.

If the guy who looked at the boiler could not sort the issue, perhaps he is not a repairer. Repairing boilers is a specialist task that is based on knowledge of boiler operation, lots of luck and past experience is a bonus but it can still fall flat on its face- fault finding that is. Anyone who says he can fix a fault every time is deluding himself

You are clutching straws, call in a professional or the boiler makers for a fixed price repair. Long run will be cheaper
Quit changing parts.

 

[champians]

Appreciate your help. I am an aircraft engineer and have installed full CH systems in the past so I do have plenty of experience but this issue has stumped me a little given how its occured. I know from heating engineers ive dealt with in the past it'd be a needle in a haystack trying to find one who knew enough to sort this first time. Having read the forums plenty have changed 4 or 5 parts not fixed it and given up. The boiler is 2009 so well out of any warrenty. I have a few spare parts so no issue swapping them to see if it helps.

Its something to do with whatever is causing the burner to turn on and off and given the HW did it first and now both the HW and CH i think its most likely electrical or sensor based to be honest though PCB looks fine without any dry joints.

If the boiler is set to HW only the preheat will get it upto temp fairly quickly after a tap is turned on and off to start the process and it will hold the flame throughout as does it but cuts off when the higher demand of warming water of an open tap is present. The CH which was fine up until the other day now can't get past the mid 40s due to the cycling on and off as the burner simply isn't on long enough to be effective. Here it kicks in with a big whoosh then goes out fairly soon after only to repeat over and over every 20 -30 secs.

I'd appreciate any other suggestions but will report back once ive sorted it cheers

 

[DP]

First thing I will say is fitting a heating system is the easy part. As an aircraft engineer if you could not do it, I would have to say you would not be a great engineer.

Now gloves are off and let us get down to nitty gritty

Has the boiler been flue gas analysed to see what the CO and CO2 reading is. When was the boiler serviced last.

It cannot be a sensor fault as that would display an E20 or E50
It is not an overheat issue else you would get E110.
Nor is it a circulation issue else primary temperature would be through the roof

The issue is failing to achieve temperature
have you checked the temperature on flow and return as well as cold in and hot out pipes.
Forget what the display shows- data from additional equipment s relevant here.

What is the flame rectification current and is it steady
What is the inlet gas pressure
What is the supply pressure at the gas meter.

I would be doing all this if asked to look at your boiler.
Ask me to service a 747, I would just stay in bed. So forget your daytime job and come back with data and you might just be able to fix the boiler under directions without throwing needless parts at it.

Age of boiler is a mute point. I am looking after boilers some are 40 years old and counting

 

[DP]

given the HW did it first and now both the HW and CH

The issue during hot water demand is evident right away as you are expecting water delivery to be hot.
Same issue during CH less so as rise in temperature gradual. If it did not function, you will in due course become aware. If operation was delayed or not upto scratch, your awareness will be delayed further.
Above is my though and experience doing tyhis task over a score and 10