Donate to Remove ads

Got a credit card? use our Credit Card & Finance Calculators

Thanks to johnstevens77,Bhoddhisatva,scotia,Anonymous,Cornytiv34, for Donating to support the site

Vailant combi boiler question

Does what it says on the tin
brightncheerful
Lemon Quarter
Posts: 2210
Joined: November 4th, 2016, 4:00 pm
Has thanked: 424 times
Been thanked: 800 times

Vailant combi boiler question

#380429

Postby brightncheerful » January 24th, 2021, 10:50 pm

Our Vailant combie boiler is randomly making banging noise which only occur when the hot water is running for a while, such as when using the shower.

When the noises first started I called our maintenance company to check and their chap said that it was probably a propellor banging against the side of its casing, he made some adjustments that seemed to do the trick. At the last annual service, September 2020, I mentioned the issue to the person of the maintenance company that did the service but he couldn't find anything wrong. Recently the noises have returned so someone else from the maintenance company inspected - a reputable company - and, allowing for the fact he couldn't replicate the noise, he reckons it is the heat exchanger becoming too hot when the hot water has been running for some time. Part of the reason also might be gunge in the pipework.

The boiler is about 14 years old. The recommendation is to get a new boiler, Bosch (the maintenance company are accredited suppliers and installers) and have the radiators power-washed.

Assuming it is the heat exchanger (the larger of the two) and allowing for the age of the boiler would you think it more economical in the long run to get a new boiler (Bosch are offering a free 12 year guarantee) than replace the heat exchanger in the Vailant?

Power washing the radiators seems sensible, they've never been done since installation when the property was built in 1999.

supremetwo
Lemon Quarter
Posts: 1007
Joined: November 8th, 2016, 2:20 am
Has thanked: 130 times
Been thanked: 196 times

Re: Vailant combi boiler question

#380442

Postby supremetwo » January 25th, 2021, 1:06 am

brightncheerful wrote:Our Vailant combie boiler is randomly making banging noise which only occur when the hot water is running for a while, such as when using the shower.

When the noises first started I called our maintenance company to check and their chap said that it was probably a propellor banging against the side of its casing, he made some adjustments that seemed to do the trick. At the last annual service, September 2020, I mentioned the issue to the person of the maintenance company that did the service but he couldn't find anything wrong. Recently the noises have returned so someone else from the maintenance company inspected - a reputable company - and, allowing for the fact he couldn't replicate the noise, he reckons it is the heat exchanger becoming too hot when the hot water has been running for some time. Part of the reason also might be gunge in the pipework.

The boiler is about 14 years old. The recommendation is to get a new boiler, Bosch (the maintenance company are accredited suppliers and installers) and have the radiators power-washed.

Assuming it is the heat exchanger (the larger of the two) and allowing for the age of the boiler would you think it more economical in the long run to get a new boiler (Bosch are offering a free 12 year guarantee) than replace the heat exchanger in the Vailant?

Power washing the radiators seems sensible, they've never been done since installation when the property was built in 1999.


If it's gunge in the pipework, what records do you have that the maintenance company have been checking and maintaining the inhibitor concentration in your system? This should be part of an annual service.

Does it also have a magnetic trap, which also has to be cleaned annually?

Mike4
Lemon Half
Posts: 7086
Joined: November 24th, 2016, 3:29 am
Has thanked: 1637 times
Been thanked: 3794 times

Re: Vailant combi boiler question

#380461

Postby Mike4 » January 25th, 2021, 7:27 am

brightncheerful wrote:Our Vailant combie boiler is randomly making banging noise which only occur when the hot water is running for a while, such as when using the shower.

When the noises first started I called our maintenance company to check and their chap said that it was probably a propellor banging against the side of its casing, he made some adjustments that seemed to do the trick. At the last annual service, September 2020, I mentioned the issue to the person of the maintenance company that did the service but he couldn't find anything wrong. Recently the noises have returned so someone else from the maintenance company inspected - a reputable company - and, allowing for the fact he couldn't replicate the noise, he reckons it is the heat exchanger becoming too hot when the hot water has been running for some time. Part of the reason also might be gunge in the pipework.

The boiler is about 14 years old. The recommendation is to get a new boiler, Bosch (the maintenance company are accredited suppliers and installers) and have the radiators power-washed.

Assuming it is the heat exchanger (the larger of the two) and allowing for the age of the boiler would you think it more economical in the long run to get a new boiler (Bosch are offering a free 12 year guarantee) than replace the heat exchanger in the Vailant?

Power washing the radiators seems sensible, they've never been done since installation when the property was built in 1999.


A propeller banging on the casing strikes me as laughably unlikely suggestion. There is no "propeller" in your Vaillant other than possibly a tiny plastic one if you have a particularly early model of Vaillant. There is an "impeller" inside the premix fan (assuming yours is a steamer - you don't mention the model) sometimes a bit like a hamster wheel but these don't make the noise you describe.

The second suggestion that the heat exchanger (HEX) is getting too hot is probably closer to the mark. It's complicated. There are two heat exchangers in your Vaillant. The gas-to-water heat exchanger heats up radiator water (primary water, not drinking quality) which in turn is pumped through a water-to-water heat exchanger which uses it to heat up the hot tap water in real time as it passes through the boiler on its way to the hot taps and showers.

The water-to-water HEX is terribly prone to getting clogged up in which case it fails to transfer enough heat into the domestic tap water, leading to the electronics demanding MORE HEAT, so more gas is sent to and burned in the gas-to-water HEX to heats the radiator water to a higher temp in a (sometimes vain) attempt to get more heat transferred into the tap water. Eventually the gas-to-water HEX begins to boil the water being sent to the water-to-water heat exchanger, which makes a spectacular banging noise when it happens.

It shouldn't happen as the electronics are designed to notice and stop it, but this doesn't always happen. There are two ways the water-to-water HEX can be contaminated. Firstly it can get clogged with flakes of black muck coming from the radiator system and as S2 points out, there should be (but often isn't) a filter to catch this crud and which needs cleaning out periodically. Rarely done during a service as it can be a filthy, time-consuming and troublesome job which if missed, the customer is unlikely to notice. The second way is from water scale being deposited inside the water-to-water HEX.

Diagnosing which you have requires removal of the water-to-water HEX and inspecting it closely. For a quick fix just fit a new clean HEX while you inspect the old. Once you know the type of contamination you can then decide on a path to prevent it happening again. This is important as if you have a water scale problem, no amount of "power-washing" will stop it happening again. OTOH if it is black crud, fitting a water softener will also make no difference.

jackdaww
Lemon Quarter
Posts: 2081
Joined: November 4th, 2016, 11:53 am
Has thanked: 3203 times
Been thanked: 417 times

Re: Vailant combi boiler question

#380473

Postby jackdaww » January 25th, 2021, 8:50 am

a bit off topic ...

i have a simple (non combi) oil boiler.

i replaced the ecoflam burner myself last year - otherwise trouble free for 20 years .

no power washing of radiators has been done - i probably should.

i intend to keep this running as long as we're here ..

:)

Mike4
Lemon Half
Posts: 7086
Joined: November 24th, 2016, 3:29 am
Has thanked: 1637 times
Been thanked: 3794 times

Re: Vailant combi boiler question

#380488

Postby Mike4 » January 25th, 2021, 9:38 am

jackdaww wrote:a bit off topic ...

i have a simple (non combi) oil boiler.

i replaced the ecoflam burner myself last year - otherwise trouble free for 20 years .

no power washing of radiators has been done - i probably should.

i intend to keep this running as long as we're here ..

:)


Older oil boilers are a totally different beast. Shockingly crude structurally; usually knocked up out of plates of mild steel by a welder in a shed somewhere. Their terminal failure mode is rusting through, and turning into a colander. Their big advantage over gas boilers is as you describe, that all the technical bits are in one single assembly which is broadly universal and the same assembly is fitted into all oil boilers (prior to the law being changed and demanding oil boilers are condensing too now), so buying a whole new assembly is an attractive proposition over diagnosing a fault in the existing assembly. The burner assemblies are usually very simple go fix though and all parts freely available even on really old ones.

Having lobbed a new burner assembly in though, the next step is to adjust the combustion to minimise the pollution using a gas analyser. I hope you did this, but most people DIY fitting a new burner do it just by looking at the smokiness or otherwise of the exhaust. Highly unsatisfactory and leaves the boiler prone to early sooting up unless you happen to get the adjustment right by luck. Fitting the right size and spray pattern of nozzle is important too. Getting it serviced by an OFTEC oil technician will include checking the nozzle and setting the combustion correctly.

Power flushing the radiators is rarely necessary in my experience. It is a diagnosis gratefully seized upon by technicians faced with a fault they can't diagnose. It allows them to avoid admitting they don't know what is wrong so they blame deposits in the system which they obviously can't flush out now, thereby allowing them to get off site. Should you accept a kind offer to power flush for £750, the fault usually persists and you will be told the flushing was not wasted money as it needed doing anyway.

Curiously until a few weeks ago I had not in my whole career found a heating system that needed power flushing in order to fix it. Just before xmas though in Milton Keynes, I fixed a heating system by identifying a section of flexible pipe (connecting up a Gledhill Boilermate) that HAD to be blocked, and on draining and taking it out I found it 100% blocked with black flakes. Poking it out with a big screwdriver got the heating going again but not that well, and power flushing the whole radiator system two weeks later restored full performance.

jackdaww
Lemon Quarter
Posts: 2081
Joined: November 4th, 2016, 11:53 am
Has thanked: 3203 times
Been thanked: 417 times

Re: Vailant combi boiler question

#380498

Postby jackdaww » January 25th, 2021, 10:06 am

Mike4 wrote:
jackdaww wrote:a bit off topic ...

i have a simple (non combi) oil boiler.

i replaced the ecoflam burner myself last year - otherwise trouble free for 20 years .

no power washing of radiators has been done - i probably should.

i intend to keep this running as long as we're here ..

:)


Older oil boilers are a totally different beast. Shockingly crude structurally; usually knocked up out of plates of mild steel by a welder in a shed somewhere. Their terminal failure mode is rusting through, and turning into a colander. Their big advantage over gas boilers is as you describe, that all the technical bits are in one single assembly which is broadly universal and the same assembly is fitted into all oil boilers (prior to the law being changed and demanding oil boilers are condensing too now), so buying a whole new assembly is an attractive proposition over diagnosing a fault in the existing assembly. The burner assemblies are usually very simple go fix though and all parts freely available even on really old ones.

Having lobbed a new burner assembly in though, the next step is to adjust the combustion to minimise the pollution using a gas analyser. I hope you did this, but most people DIY fitting a new burner do it just by looking at the smokiness or otherwise of the exhaust. Highly unsatisfactory and leaves the boiler prone to early sooting up unless you happen to get the adjustment right by luck. Fitting the right size and spray pattern of nozzle is important too. Getting it serviced by an OFTEC oil technician will include checking the nozzle and setting the combustion correctly.

Power flushing the radiators is rarely necessary in my experience. It is a diagnosis gratefully seized upon by technicians faced with a fault they can't diagnose. It allows them to avoid admitting they don't know what is wrong so they blame deposits in the system which they obviously can't flush out now, thereby allowing them to get off site. Should you accept a kind offer to power flush for £750, the fault usually persists and you will be told the flushing was not wasted money as it needed doing anyway.

Curiously until a few weeks ago I had not in my whole career found a heating system that needed power flushing in order to fix it. Just before xmas though in Milton Keynes, I fixed a heating system by identifying a section of flexible pipe (connecting up a Gledhill Boilermate) that HAD to be blocked, and on draining and taking it out I found it 100% blocked with black flakes. Poking it out with a big screwdriver got the heating going again but not that well, and power flushing the whole radiator system two weeks later restored full performance.


=================================

many thanks mike4 for this useful info - one of the unsung benefits of TLF .

yes i did get it serviced and combustion checked , its a eurocal make .

after the service , the oil smell after boiler turnoff has gone - nice .

one remaining issue is that this burner is producing too much power for my radiators to deal with without cycling .

the nozzle is 0.55 and oil pressure 100psi .

:)

Mike4
Lemon Half
Posts: 7086
Joined: November 24th, 2016, 3:29 am
Has thanked: 1637 times
Been thanked: 3794 times

Re: Vailant combi boiler question

#380519

Postby Mike4 » January 25th, 2021, 10:47 am

jackdaww wrote:
many thanks mike4 for this useful info - one of the unsung benefits of TLF .

yes i did get it serviced and combustion checked , its a eurocal make .

after the service , the oil smell after boiler turnoff has gone - nice .

one remaining issue is that this burner is producing too much power for my radiators to deal with without cycling .

the nozzle is 0.55 and oil pressure 100psi .

:)


Yer welcome.

It's 15 years since I stopped doing oil so I'm a bit rusty, but many oil boilers are adjustable in output by changing the oil pressure. The boiler manual will tell you. 100psi looks to me to be at the lower end of the range already but fitting a smaller nozzle will have the same effect of reducing heat output. Ask your boiler bod at the next service about a smaller nozzle. You'll be going 'off piste' by fitting the wrong nozzle but I can't see any harm provided the gas analysis remains good.

Edit to add, your boiler bod will if he is any good, carry a huge box of nozzles to select from!

brightncheerful
Lemon Quarter
Posts: 2210
Joined: November 4th, 2016, 4:00 pm
Has thanked: 424 times
Been thanked: 800 times

Re: Vailant combi boiler question

#380610

Postby brightncheerful » January 25th, 2021, 2:14 pm

Mike4, thank you so much. Explanation also much easier for me to understand than our service bod tried to do so.

The quote for power flush the heating system which I take to mean all 14 radiators) is £400 plus Vat. (Actually i am assuming all, they didn't ask how many and i didn't tell them.) Would you think that.reasonable?


Return to “Building and DIY”

Who is online

Users browsing this forum: No registered users and 5 guests