Vaillant boiler coming on then dying

[JonathanM]

Thank you, this is a little more technical but I will think it over to try and understand.

What I understand, though, is that potentially not enough water going through the boiler could be the problem. How should the water going through the boiler be increased to prevent this? And if this doesn't work, do you recommend the heat exchanger being replaced before any other big changes?

You also asked about the tradesman and whether he did anything after pouring the F3 in the water trough. What did you interpret from my answer?

I hope my questions are not annoying, I'm really interested in all this stuff.

I'm reaching the limit of my knowledge, too, I'm afraid. I just try to answer basic things, and signpost people in the right direction. I'm an enthusiastic amateur!

I would say turn up the pump speed as a test, back to where it was. It might be be noisy, but it should send more water through, and it might help with diagnosis. I can't see a downside. Hopefully, others might advise if it's a problem.

CBW mentioned those valves might not be open enough. That's above my pay grade, but worth pursuing.

From your answer about the F3, I interpreted that it doesn't seem to follow the advice I've seen elsewhere. The F3 is in the tank, but has it actually got into the system. And, if it has, it's supposed to be drained out of the system after a few weeks/months. Where is the water trough, you mentioned?

I'm really interested in this stuff, too, but I don't want to mislead you about my capabilities.

 

[TheGirl]

Is the feed and expansion tank in the loft full of water and if it is have you checked the pipe feeding the heating system isn't blocked. If there isn't any water then has the ballcock failed.

Unfortunately, I have only ever accessed the loft with tradesmen so I am not sure if it is full of water, Mister Banks, and whether the ballcock has failed.

I also don't know where the pipe feeding the heating system is and how to check it.

This is the part where I stumble- checking stuff.

Thank you for entering the conversation.

 

[kidgreen61]

Sounds to me as though the system is full of muck and needs a proper flush out to clean it.
Problem is, that the boiler may be clogged solid with muck and may be uneconomic to repair.

 

[TheGirl]

I'm reaching the limit of my knowledge, too, I'm afraid. I just try to answer basic things, and signpost people in the right direction. I'm an enthusiastic amateur!

I would say turn up the pump speed as a test, back to where it was. It might be be noisy, but it should send more water through, and it might help with diagnosis. I can't see a downside. Hopefully, others might advise if it's a problem.

CBW mentioned those valves might not be open enough. That's above my pay grade, but worth pursuing.

From your answer about the F3, I interpreted that it doesn't seem to follow the advice I've seen elsewhere. The F3 is in the tank, but has it actually got into the system. And, if it has, it's supposed to be drained out of the system after a few weeks/months. Where is the water trough, you mentioned?

I'm really interested in this stuff, too, but I don't want to mislead you about my capabilities.

Thank you for your honesty, I really appreciate it.

If they turn up the pump speed, and it works, they will ask me to stick with that but it's such a horrific noise, I just don't want to go there. I asked the supervisor if he could replace it with a quieter one when he came out to investigate the noise, he said no, as it had just been newly replaced. So he ended up turning the speed down. The previous pump was silent and wonderful as a result.

Okay about pursuing CBW's valve recommendation- I hope it doesn't make the pump more noisy.

The water trough is in the loft and the tradesman said that the F3 would slowly get into the system and clean it up. It was never drained from the system.

Thank you, Jonathan...

 

[TheGirl]

Sounds to me as though the system is full of muck and needs a proper flush out to clean it.
Problem is, that the boiler may be clogged solid with muck and may be uneconomic to repair.

I understand, thanks kidgreen61. Is there an easy way for me to check this muck without accessing the loft or doing anything technical?

If uneconomical to repair and it has to be replaced, what steps should first be taken about cleaning the system? I worry that a shortcut will be taken, the system will not be cleaned properly, they put a new boiler in and the same scenario occurs.

 

[kidgreen61]

I understand, thanks kidgreen61. Is there an easy way for me to check this muck without accessing the loft or doing anything technical?

If uneconomical to repair and it has to be replaced, what steps should first be taken about cleaning the system? I worry that a shortcut will be taken, the system will not be cleaned properly, they put a new boiler in and the same scenario occurs.

There is no shortcut I'm afraid, it sounds as though the system needs powerflushing properly, which should remove the muck from the rads & pipes, but some boiler heat exchangers can be difficult to clean, given their narrow waterways.

Just chucking a bottle of cleaner in the header tank in the loft is like putting a plaster on an amputated limb.

 

[TheGirl]

There is no shortcut I'm afraid, it sounds as though the system needs powerflushing properly, which should remove the muck from the rads & pipes, but some boiler heat exchangers can be difficult to clean, given their narrow waterways.

Just chucking a bottle of cleaner in the header tank in the loft is like putting a plaster on an amputated limb.

Yes, it felt very much blasé at the time.

In that case, do these options sound reasonable (if the other recommendations of valve opening/pump speed don't do the trick)?

Either: proper powerflush then change the heat exchanger

Or: proper powerflush then replace boiler

I guess what I'm asking is: even if they decide to install a new boiler, is a proper powerflush a necessity as a first step in either scenario?

 

[Harry Bloomfield]

I guess what I'm asking is: even if they decide to install a new boiler, is a proper powerflush a necessity as a first step in either scenario?

Yes!

 

[MeldrewsMate]

For the record I think @Mottie 's response is the correct one. I find it irritating enough to go back to a customer's house to find problems caused by well meaning but incompetent relatives or neighbours; and that's even though I'd be paid to correct them. Your landlord may not react well if he/she believes you to have contributed to a problem. You may have read somewhere that such and such a boiler is better than a.n.other, but a simple Google search of 'such and such boiler problems' will no doubt contradict this in just about every case.

Leaving that to one side, and dealing with your landlord's heating problem, there appears to be a number of symptoms which have a common element to them, and that is low flow through the boiler.
Low flow can be caused by a poor pump performance; despite its newness, all circularing pumps are designed to pump water, not air.
If the loft (header) tank has run dry there will be a lack of water to pump.
If the feed pipe between loft tank and heating system is blocked the water from a fully functioning header tank can not get into the system, therefore leading to a lack of water to pump.
If the heating water if full of s.h.1.t.e (sometimes called sludge, or debris) then the pump will not pump it effectively, leading to low flow.
If the pump impellor is substantially blocked with debris released by a cleaning agent then it will not pump effectively; no prizes for guessing what that leads to.
If the hydraulic circuit that the pump is connected to is restricted there will be low flow.
The slower speed the pump runs at, the lower will be its flow output.
A pump impellor may become unbalanced by debris, and an unbalanced impellor will cause excessive vibration/noise.
If the boiler has a semi-blocked heat exchanger this contributes towards a restricted hydraulic circuit.

Do you need more convincing?
Read up on the specific heat capacity of water, and the relationship between Joules and Watts; then you can work out why low flow through the boiler leads to a rapid rise in boiler water temperature.

Now to the only piece of evidence that contradicts the low flow theory: the boiler display shows a slow temperature rise on first firing, but on subsequent firings the temperature rises rapidly.
Why doesn't it rise rapidly on first firing? Could it be that you (or the control system) turn the boiler power OFF overnight? This would invoke the boiler's slow start-up routine (if it has one, and here my knowledge of the Vaillant system is limited), which would effectively give it minimum power output (small flame size) for several minutes. This would not be the case for subsequent firings.
Could it be that loose debris falls away from the pump or boiler overnight, but re-collects at a narrow point once circulation re-starts (highly unlikely, but possible).
Could it be something else?

If you are determined to go on an evidence gathering exercise then I suggest the following actions:-

1. At first start-up feel (or better, measure) both the incoming water temperature (return temp) and the outgoing (flow temp).
Does the return temp warm up as the flow temp warms? Does it remain cool/cold?
2. Feel the temperature on the pipework between the pump and the 3-port valve. Does it also get hot rapidly as the boiler fires?
3. Bleed a little water from a radiator. Is it like coloured water, or more like mud?
4. Read up and learn how to change the pump speed. Does the vibration/noise correlate to pump speed? Is the pump set on a fixed or variable speed?
5. Read up on how to open a pump isolation gate valve, then make sure both pump valves are fully open.
6. Find the neutral point, where the cold feed from the header tank meets the system (usually just upstream of the pump). Will a fridge magnet attach itself to the copper pipe at that point?
7. Is there water in the header tank, and does it resemble mud? Is its level a couple of inches above the cold feed outlet pipe?
8. Is the water surface in the header tank lower than the level in the (larger) domestic cold water storage tank?

These are all relevant actions, and should lead to good evidence gathering for your landlord or his contractor, though I reiterate that @Mottie was right, and there was absolutely no need to rear-up at his advice (given freely in his own time).

MM

 

[JonathanM]

and dealing with your landlord's heating problem

I don’t know why this topic has annoyed you so much, but clearly it has. The person experiencing the problem is the tenant, and she has every right to ask for basic information, so she can try to understand what the problem might be. Landlords often complain that tenants show no interest in their homes. The OP has already reached the point where she knows the problem is low flow, without the need for comments which are supercilious, patronising and overbearing.

 

[Harry Bloomfield]

I don’t know why this topic has annoyed you so much, but clearly it has. The person experiencing the problem is the tenant, and she has every right to ask for basic information, so she can try to understand what the problem might be. Landlords often complain that tenants show no interest in their homes. The OP has already reached the point where she knows the problem is low flow, without the need for comments which are supercilious, patronising and overbearing.

With all due respect, it is not the tenants problem to deal with. It's the tenants job to simply report it to the landlord and leave it to the experts to deal with. There can be nothing worse than an ill informed tenant, peering over the shoulder of someone with expertise, and advising them to try this, that or the other, because they have read up on it, on the Interweb and know better than the expert.

This tenants time would be better spent pulling a list together of the symptoms, and handing it to the expert to deal with.

 

[JonathanM]

There can be nothing worse than an ill informed tenant, peering over the shoulder of someone with expertise, and advising them to try this, that or the other, because they have read up on it, on the Interweb and know better than the expert.

This tenants time would be better spent pulling a list together of the symptoms, and handing it to the expert to deal with.

Would you say the same to a homeowner?

 

[Harry Bloomfield]

Would you say the same to a homeowner?

No, the homeowner owns the installation, so they have a close and direct financial interest in the outcome. As a tenant, their only interest as a third party and is limited to one of having it working, with no direct input.

 

[JonathanM]

No, the homeowner owns the installation, so they have a close and direct financial interest in the outcome. As a tenant, their only interest as a third party and is limited to one of having it working, with no direct input.

I think the tenant's only interest here is that the central heating system works. All she seems to be doing is asking questions, on this forum, so she has some idea what might be going on. I also think, as the person living with the problem, she is the person best placed to explain the issues to the tradesmen.

My experience of many landlords is that they will often lie through their teeth, try to do things the cheapest way possible, and try to blame the tenant and make them pay somehow. I can easily see a landlord in this situation refusing to pay for a powerflush, even if recommended by the gas engineer, and which you yourself said sounds like it is probably necessary.

 

[TheGirl]

I think the tenant's only interest here is that the central heating system works. All she seems to be doing is asking questions, on this forum, so she has some idea what might be going on. I also think, as the person living with the problem, she is the person best placed to explain the issues to the tradesmen.

My experience of many landlords is that they will often lie through their teeth, try to do things the cheapest way possible, and try to blame the tenant and make them pay somehow. I can easily see a landlord in this situation refusing to pay for a powerflush, even if recommended by the gas engineer, and which you yourself said sounds like it is probably necessary.

Good morning Jonathan, thank you very much for sticking up for me and understanding that I am conscientious alongside my purpose in being here.