VAILLANT ECOTEC PLUS 831 - hot water sometimes runs cold

[Aardvark35]

We have an intermittant fault with our 5/6 year old boiler. The hot water will occasionally run cold after a couple of mins and the boiler shows an S.53 fault code. Turning tap/shower off for a minute or so cures the problem. Water also runs cold if taps turned on high. Engineer came out about 4 weeks ago and was mystifed as although the water was running cold, the boiler was showing that the burner was operating and temperature reading as it should. He phoned Vaillant who said Heat exchanger was blocked. New HE ordered and fitted. No difference. A little scale in the old HE but water was perfectly clean with no sludge or bits. Another call to Vaillant who offered no help. Engineer suggested pump could be at fault as he'd replaced several on this model. Said he would order new one and come back. Not seen him since. Does anyone have any ideas please?

 

[mickyg]

left hand rubber hose or canoe filter blocked or dodgy pump. 30mins to check which one tbh. Maybe you should get a new engineer.

 

[mario500]

Mickyg you is good man

 

[GasNewb]

Turn on your hot water and watch the boiler. While hot water is drawn off, does the burner flame show up, go off, then show up, go off and so on?

Am i right in understanding that when showering/running a bath, the water comes through hot then goes cold, then gets hot again and goes cold again etc?

 

[mickyg]

Turn on your hot water and watch the boiler. While hot water is drawn off, does the burner flame show up, go off, then show up, go off and so on?

Am i right in understanding that when showering/running a bath, the water comes through hot then goes cold, then gets hot again and goes cold again etc?

if its showing S53 its probably lighting and staying at low flame, prob the temp on the display is getting to no more than around 60c when it should normally be around 75 on hot water. The F&R ntc's are detecting to great a difference hence why its modulating down and it will just sit there. The plate's dont often get blocked on these, but the canoe filter does, as does the LH hose and the pump impellor.

 

[GasNewb]

Ah okay, i thought the temp would get hot and the boiler would stop firing, then cool and then fire again. But it makes sense what you say MICKYG, my nickname of GASNEWB literally means i'm a newb! Thanks for the insight.

 

[mickyg]

Ah okay, i thought the temp would get hot and the boiler would stop firing, then cool and then fire again. But it makes sense what you say MICKYG, my nickname of GASNEWB literally means i'm a newb! Thanks for the insight.

this behaviour is unique to this particular boiler. Your description of operation would be accurate for most other boilers with a blocked plate or similar problem.

 

[Agile]

Mick, do you mean unique to the Ecotec Plus?

Or unique to the 831?

Or to the Ecotec Plus 831 only

Tony

 

[Aardvark35]

Many thanks Mickyg. I guess I'd better find a good engineer and get the items you suggested checked out!

 

[mickyg]

Mick, do you mean unique to the Ecotec Plus?

its unique to the entire Group Service range of boilers tbh. I think its having the return sensor which alot of boilers lack that makes the difference. Being able to measure the Delta T and not allowing it to go above circa 23C so just sits at low temp. It confuses people though, you'd be amazed the amount of different parts ive seen changed because of it lol

 

[Agile]

I dont see anything wrong with a return sensor in fact its a big advantage and can greatly increase efficiency.

Where it seems to be wrongly specced is the fact that it apparently locks the boiler in a low power without apparently letting it resume normal operation if the conditions get better.

The later Biasi have a sensible flue temp sensor which is proportional and just backs off the power. Bet that will have fooled some engineers trying to find a fault!

Tony

 

[pushoz]

Hope you guys can help we have exactly the same problem. We have the same boiler which is 5 1/2 years old. Had BG out on Christmas Eve as the pressure sensor when and the engineer "kindly" removed the HE plate to clean it for us and then recommend that we had a Magnabooster fitted. Ever since we have had a problem with our hot water running cold. They came out today and fitted a new temperature sensor and it seemed to be fine ran the hot water twice since they've left and the on second time no hot water again. Both times they have said "oh you probably need a power flush but then they have checked the water and said we don't need a powerflush.

When they come out again, we've got a service contract to try and save us some money, what should I be asking them to do?

 

[Agile]

You should ask them to fix your boiler properly!

The three possibilities are listed above. Refer the BG guys to this forum if they dont know what to do.

Tony

 

[RDSboiler]

Mine is also just over 5 years old - we had a problem with heating on all the time and called the guy to fix it. New diverter valve but not right - several visits and still not right. We now have control over the heating but the hot water doesn't work. If we call for hot water we get some briefly and then it goes off, cools and slowly comes back to only lukewarm at best before off again and cycles like this. Meanwhile the boiler is going mad - temperature gauge goes up to 85C, safety cut out comes in and off goes the burner, temp drops and back it comes, but now the flow goes into the heatting system and the pipes to radiators gets Hot. Doesn't matter where we have the hot water temp control set - that may affect how long it takes to get to 85 but that's all. It makes no difference whether the heating is on or off, the energy all goes to the rads and the hot water (after the first burst of hot) remains lukewarm.

The technician says its the electronics and he is seeing 20V on all the Diverter valve wires. But we didn't see these symptoms with the jammed diverter valve. And I can't see how a diverter "halfway would do this.

The tecnician offered a workaround for tonight which seems like bad news - he suggested when we want hot water we turn off the heating and close the valve to the heating system filter thus blocking the heating system and preventing that "stealing" the heat from the hot water. Do this and you haver to be quick to stop the water in the boiler boiling as the 85 degree cut out doesnt!

Any ideas before I shell out for a new board?

 

[The831Bunny]

PCB was damaged by the leaking DV in the first place and needs replacing, or the engineer has not attached the motor to the DV spindle correctly.