Vaillant Ecotec plus 831 - heating working......sort of.

shewdz

Happy New year all!

Looking for some advice beyond my limited boiler knowledge.

Bit of history, 14 year old vaillant Ecotec plus 832 boiler. All worked well. 2 years ago a small leak appeared and only hot water when the heating was on. Classic diverter valve failure. All replaced and has worked well since......until....

Boxing day we found we could only get hot water when the heating was on again. This was followed by an f75 error code. I topped up the water in the boiler which cleared the error. Pump sounds like it's working fine. The next day we seem to get hot water on demand back, but the heating was now struggling in that initially it was firing up when the thermostat requested it, but only the radiators upstairs were getting hot, the downstairs ones were only warm or cold. This points to a circulation issue maybe? Pump issue? Blockage in the pipes? Or is it another diverter valve issue and it is just restricting the pump from pushing the hot water around the system? I also noticed when I put the hot water on, the boiler fired up to the CH temp (65oC) not the hot water temp (45oC), and both the CH and HW outputs from the boiler get very hot. Again suggesting the diverter valve is playing up or passing?

Anyway! I have boiler only cover (with a £90 excess but covered all parts and labour) and I also have the normal local boiler engineer who usually services the boiler. It would be cheaper to use the boiler cover if it was definitely an issue with the boiler, but if it was anything to do with the pipes/radiators, they wouldn't look at that. Or if it's more likely that it was an issue with the pipes, the only option would be a local heating engineers. 

It's not a problem I can sort myself, so happy to get someone in to fix it, just go about it as economically as possible. Anyone had similar issues? I'm currently swaying more towards a boiler issue and using the boiler cover option. 

Thanks for any help. 

IOWJJBTM2025

We previously had problems with our boiler - the same model. We kept losing pressure on the heating system and after recharging it would work for a shorter periods each time we filled with more water. There was a diaphragm (rubber balloon) which had to be inflated. A remember the BG Engineer using a foot pump to inflate. Re-inflating this kept us going for less than a day and they replaced the rubber balloon because it was no longer holding air.

shewdz

IOWJJBTM2025 said:

We previously had problems with our boiler - the same model. We kept losing pressure on the heating system and after recharging it would work for a shorter periods each time we filled with more water. There was a diaphragm (rubber balloon) which had to be inflated. A remember the BG Engineer using a foot pump to inflate. Re-inflating this kept us going for less than a day and they replaced the rubber balloon because it was no longer holding air.

Ah, good point. It had a major service last year and the diaphragm had perished and was replaced. So on this occasion unlikely to be that again (I hope). And I suppose it now reads that the boiler is problematic, but other then perishables that have been changed when needed, it has otherwise been a rock solid boiler. 

WIAWSNB

IOWJJBTM2025 said:

We previously had problems with our boiler - the same model. We kept losing pressure on the heating system and after recharging it would work for a shorter periods each time we filled with more water. There was a diaphragm (rubber balloon) which had to be inflated. A remember the BG Engineer using a foot pump to inflate. Re-inflating this kept us going for less than a day and they replaced the rubber balloon because it was no longer holding air.

That is almost certainly the 'Expansion Vessel'. It is a metal chamber, usually a bulbous-but-flattish rectangle, usually coloured a rusty-red, and it does have a rubber diaphragm in its middle.

On one side is pressurised air - supplied via a Schrader valve (car tyre, hence the foot pump) - and the other has system water. The idea is that when your boiler system heats up, the sealed 'system' water expands and has to go 'somewhere'. That place is one side of the EV, and it pushes the diaphragm against the compressed air. The system pressure therefore remains pretty constant. When your boiler cools down, the EV returns that excess water back to the 'system'.

It goes wrong when the 'air' side either leaks or looses pressure. Then, the system water side has nowhere to go, so the system pressure soars until it hits ~3 bar, the safety limit. At this point, a valve opens, and dumps this excess water safely outside, but that means that when the system cools, there's less water in it = 'lost pressure'. So, you have to keep topping it up. It's a viscous circle (cough).

I can't see this being the issue in the OP's case. 

WIAWSNB

shewdz said:

Happy New year all!
Looking for some advice beyond my limited boiler knowledge.
Bit of history, 14 year old vaillant Ecotec plus 832 boiler. All worked well. 2 years ago a small leak appeared and only hot water when the heating was on. Classic diverter valve failure. All replaced and has worked well since......until....
Boxing day we found we could only get hot water when the heating was on again. This was followed by an f75 error code. I topped up the water in the boiler which cleared the error. Pump sounds like it's working fine. The next day we seem to get hot water on demand back, but the heating was now struggling in that initially it was firing up when the thermostat requested it, but only the radiators upstairs were getting hot, the downstairs ones were only warm or cold. This points to a circulation issue maybe? Pump issue? Blockage in the pipes? Or is it another diverter valve issue and it is just restricting the pump from pushing the hot water around the system? I also noticed when I put the hot water on, the boiler fired up to the CH temp (65oC) not the hot water temp (45oC), and both the CH and HW outputs from the boiler get very hot. Again suggesting the diverter valve is playing up or passing?
Anyway! I have boiler only cover (with a £90 excess but covered all parts and labour) and I also have the normal local boiler engineer who usually services the boiler. It would be cheaper to use the boiler cover if it was definitely an issue with the boiler, but if it was anything to do with the pipes/radiators, they wouldn't look at that. Or if it's more likely that it was an issue with the pipes, the only option would be a local heating engineers. 
It's not a problem I can sort myself, so happy to get someone in to fix it, just go about it as economically as possible. Anyone had similar issues? I'm currently swaying more towards a boiler issue and using the boiler cover option. 

Always best to start a new thread. So please do so if you can.

Meanwhile...

"a small leak appeared" Where?

Do you have a magnetic filter fitted? If so, when was it last checked? What was found?

shewdz

WIAWSNB said:

shewdz said:

Happy New year all!
Looking for some advice beyond my limited boiler knowledge.
Bit of history, 14 year old vaillant Ecotec plus 832 boiler. All worked well. 2 years ago a small leak appeared and only hot water when the heating was on. Classic diverter valve failure. All replaced and has worked well since......until....
Boxing day we found we could only get hot water when the heating was on again. This was followed by an f75 error code. I topped up the water in the boiler which cleared the error. Pump sounds like it's working fine. The next day we seem to get hot water on demand back, but the heating was now struggling in that initially it was firing up when the thermostat requested it, but only the radiators upstairs were getting hot, the downstairs ones were only warm or cold. This points to a circulation issue maybe? Pump issue? Blockage in the pipes? Or is it another diverter valve issue and it is just restricting the pump from pushing the hot water around the system? I also noticed when I put the hot water on, the boiler fired up to the CH temp (65oC) not the hot water temp (45oC), and both the CH and HW outputs from the boiler get very hot. Again suggesting the diverter valve is playing up or passing?
Anyway! I have boiler only cover (with a £90 excess but covered all parts and labour) and I also have the normal local boiler engineer who usually services the boiler. It would be cheaper to use the boiler cover if it was definitely an issue with the boiler, but if it was anything to do with the pipes/radiators, they wouldn't look at that. Or if it's more likely that it was an issue with the pipes, the only option would be a local heating engineers. 
It's not a problem I can sort myself, so happy to get someone in to fix it, just go about it as economically as possible. Anyone had similar issues? I'm currently swaying more towards a boiler issue and using the boiler cover option. 

Always best to start a new thread. So please do so if you can.

Meanwhile...

"a small leak appeared" Where?

Do you have a magnetic filter fitted? If so, when was it last checked? What was found?

The leak was 2 years ago and was coming from the diverter valve so the whole valve was replaced. No leak this time round. 

Magnetic filter fitted and cleaned out every year with the service, but nothing too bad found. 

The thing that's throwing me is that the situation seems to be changing. I was sure it was the diverter valve when we only got hot water with the heating on. Now the hot water seems fine and works on command. But the heating is now struggling to heat all the radiators ( hot upstairs, mostly warm down stairs with the odd on pretty much cold). Possibly a failed/failing diverter cartridge thats position is slightly moving restricting the flow to the radiators? 

plumb1_2

Most probably a failing pump.

I’ve got a Vaillant about 15 yrs old now 
So far replaced the rubber tubes from the Hx to copper pipes, did that on day one, as they were known to deteriorate .and get crap into hx.

 Don’t think they do them now? I an,t searching.

2x diverter valves 
1x pcb board 
1x pump

i have a pump, pcb and diverter valve in box’s ready to swap if needed.

shewdz

plumb1_2 said:

Most probably a failing pump.

I’ve got a Vaillant about 15 yrs old now 
So far replaced the rubber tubes from the Hx to copper pipes, did that on day one, as they were known to deteriorate .and get crap into hx.

 Don’t think they do them now? I an,t searching.

2x diverter valves 
1x pcb board 
1x pump

i have a pump, pcb and diverter valve in box’s ready to swap if needed.

Which is my least favourite option financially. Is there any reason a failing pump would give the same symptoms of a failing diverter valve? ( Hot water only when the heating is on) ?