Is there a future for vented systems?

[siricosm]

Coming from Canada, and having lived in Europe for some years, I was a bit surprised that people still install vented heating systems in the UK. As a kid I lived in a 1912 house with original cast iron boiler and radiators, and I remember the expansion tank with sight glass, it was in my room, but new vented systems disappeared decades ago.

Does any country other than the UK still use vented systems? Either for heating or hot water?

Surely sealed systems are much better, especially since radiators are mostly made of mild steel?

 

[Scott_D]

I don’t think they are still installed.
Boilers are replaced with out sealing old systems. But you wouldn’t install a new vented system.

 

[EvilDrPorkChop]

Personally I wouldn't install any new systems as a Vented system, they would all be sealed systems that be for HW and CH systems.

On existing heating systems we always try to replace Vented ones and convert them into sealed - the most easy way to do this is replace the heat only boiler with a system boiler. I find 9/10 it's easy enough to do this and saves hassle down the line.

IMO if a system is vented it should be converted to sealed when it comes to replace the boiler.

 

[Chuck]

I was a bit surprised that people still install vented heating systems in the UK.

Why do you think this is the case? It's true that there are still a reasonable number of heating systems that are vented because they were installed decades ago and are still working okay with the original boiler. But these are normally converted to sealed or 'semi-sealed' systems when the boiler is replaced. The heat exchanger in a modern boiler isn't going to last long unless the system is sealed.

Vented hot water systems, on the other hand, are still relatively common because (a) the DHW tanks last a long time and (b) not all properties have a water supply that is adequate from the point of view of pressure and/or flow for an unvented system. Unvented cylinders are also relatively expensive to install.

 

[siricosm]

Why do you think this is the case? It's true that there are still a reasonable number of systems that are vented because they were installed decades ago and are still working okay with the original boiler. But these are normally converted to sealed or 'semi-sealed' systems when the boiler is replaced. The heat exchanger in a modern boiler isn't going to last long unless the system is sealed.

Are not the exchangers in most modern boilers now stainless? mostly to prevent corrosion from the outside rather than the inside, since they are condensing.

Nevertheless, companies such as Worcester, Buderus and Vaillant make open vented boilers variants specifically for the UK market, although they don't sell them at home, or anywhere else that I know of. It just seems a bit weird.

Why is the UK so slow to adopt sealed systems? It was only 1986 that unvented cylinders became legal here. In Canada you would be hard pressed to find anyone that didn't have an unvented cylinder in 1986.

 

[Chuck]

Are not the exchangers in most modern boilers now stainless? mostly to prevent corrosion from the outside rather than the inside, since they are condensing.

That's not the problem. The problem is that the HXs have narrow channels, which get blocked by the circulating oxides, etc. from the rest of the system.

Boiler companies sell boilers that are (a) legal and (b) profitable.

I don't know the details of the history. My guess is that the UK regulators were worried about safety and/or the water companies (who essentially controlled the regulations) were worried about the capacity of their distribution network. The climate in this country means that having a CW tank in the roof is a viable solution and the distribution network was sized on this basis.

 

[siricosm]

Here is a typical gas fired cylinder from North America. It consists of a gas ring below a mild steel tank, often lined to slow corrosion. Probably the same design since the 50s, maybe earlier. The pressure relief valve just dumps onto the basement floor. Depending on the water supply hardness, they either scale up or rot. Never heard of one exploding. Changing them is a DIY job in most places.

[automerge]1577924383[/automerge]

That's not the problem. The problem is that the HXs have narrow channels, which get blocked by the circulating oxides, etc. from the rest of the system.

Boiler companies sell boilers that are (a) legal and (b) profitable.

I don't know the details of the history. My guess is that the UK regulators were worried about safety and/or the water companies (who essentially controlled the regulations) were worried about the capacity of their distribution network. The climate in this country means that having a CW tank in the roof is a viable solution and the distribution network was sized on this basis.

I beg to differ. The move from mild steel or cast exchangers to stainless was to combat rot from corrosive fireside condensate.

 

[Chuck]

Never heard of one exploding.

You have now:

Water Heater Explosions |

www.simplyjustice.com

I beg to differ. The move from mild steel or cast exchangers to stainless was to combat rot from corrosive fireside condensate.

This is irrelevant to the point I was making, which concerned why modern boilers are not attached to vented heating systems.

 

[centralheatking]

Open vented systems are ideal for larger houses with multiple bathrooms. They provide copious volumes of high level intermediate cold water storage essential where local demands on the utility mains water supply exceed its ability to satisfy. Sealed systems are ideal for smaller properties and modern toy box houses with limited utility space. Originally larger homes had a well and water was pumped up a roof tank made of slate sheets. centralheatking

 

[John.g]

There is most certainly a future for existing vented systems, mine was installed over 42 years ago and I still have have my original (3) upstairs rads. The key factor in both systems is to avoid/detect any leakage(s). My system is still in pristine condition even though I have only added the odd drop of inhibitor over the years.
I have a bit of a bee in my bonnet re the recommended E.vessel pre charge and filling pressures as some boiler manufacturers were and still might be recommending that the pre charge and filling pressures are the same, if so, then there is no water reserve whatsoever in the E.vessel with a cold boiler which results in more (nuisance) frequent top ups but in lots of cases the top up PRV is left open all the time ("auto fill" mode) so one doesn't know of any leakage(s). Of course the same can be said of vented systems with a mains (ballcock) supplied F&E tank, I have a isolating (service) valve on mine which is "permanently" closed and I open it a few times per year to check for any make up/leaks, strangely enough I have never seen it making up even though one would think that there should be some slight evaporation from the open topped F&E tank.

I have also seen mentioned (on here) that some boiler manufacturers will not honour their warranties if the E.vessel is found to be of insufficient capacity which I find rather strange to say the least as a E.vessel is not a safety device, per se, since it can and does fail (ruptured diaphragm), the boiler PRV IS the safety device and is or should be always set to the working pressure of the boiler which in some cases now is 2.5 bar, it was formerly, in most cases, 3.0 bar.

A bit off topic but a plumbing friend of mine told me that he found it much easier to remove the baffles from a grant oil condensing boiler if he reduced the system pressure to 0 bar.

 

[siricosm]

Open vented systems are ideal for larger houses with multiple bathrooms. They provide copious volumes of high level intermediate cold water storage essential where local demands on the utility mains water supply exceed its ability to satisfy. Sealed systems are ideal for smaller properties and modern toy box houses with limited utility space. Originally larger homes had a well and water was pumped up a roof tank made of slate sheets. centralheatking

I was thinking mostly for heating rather than fresh water, but I suppose in the case where mains supply is very poor then there could be some benefit to buffering that with a tank in the loft, although I would have though a pressurized system like what you use for a well would be better.

Is there are reason there are so many places with poor mains supply in the UK?
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You have now:

Water Heater Explosions |

www.simplyjustice.com

That site lists stats for fires, not explosions, although there is a lot of talk there about explosions. Perhaps they couldn't find many actual explosions? It is always possible that some yo-yo screws a plug in the PRV, but even then I doubt it would explode.

Notice there is no expansion tank on that system? Ours didn't have one either.

 

[garygvl]

There would be some debate about that flue in this country

 

[EvilDrPorkChop]

There would be some debate about that flue in this country

I was about to say that, we might be still on Vented systems but at least the majority of new appliances are Room Sealed!!

 

[ShaunCorbs]

I still install vented systems normally find / tend to install them in the middle of no where as the water pressure isn’t great so you haven’t got the pressure to seal or enough for a combi

and they don’t want to go down the route of break tanks and pumps etc

so yes they do have there place

 

[JCplumb]

Most of the new builds round here are vented, never occurred to me that it was because demand could surpass supply. Makes sense now.

 

[centralheatking]

Most of the new builds round here are vented, never occurred to me that it was because demand could surpass supply. Makes sense now.

The whole point of high level intermediate cold water storage is that the tank can recover its capacity after peak demand has ceased ....2x per day....centralheatking

 

[siricosm]

Most of the new builds round here are vented, never occurred to me that it was because demand could surpass supply. Makes sense now.

I would have thought that in areas with new builds, the development plans would include good enough infrastructure that storage tanks are not required. Again, it seems a bit peculiar to the UK.

 

[John.g]

Here, Irish Water informed me that their "policy" is to supply water at their stopcock at 2.0 bar. Also even though not quite clear or else not enforced that all water supplies in the house bar one kitchen tap must be supplied via a break tank, so either gravity or pumped after that.

 

[siricosm]

Here, Irish Water informed me that their "policy" is to supply water at their stopcock at 2.0 bar. Also even though not quite clear or else not enforced that all water supplies in the house bar one kitchen tap must be supplied via a break tank, so either gravity or pumped after that.

My god, that seems archaic. I am surprised people put up with that.

 

[John.g]

No only archaic but bordering on pure genius as supplying water at 2 bar as against say 5 bar will save ~ 36% of water leakage rates without repairing/replacing any pipework!

 

[centralheatking]

I would have thought that in areas with new builds, the development plans would include good enough infrastructure that storage tanks are not required. Again, it seems a bit peculiar to the UK.

Well the plans do not so I live in a real world and advise accordingly chking

 

[fixitflav]

Are not the exchangers in most modern boilers now stainless? mostly to prevent corrosion from the outside rather than the inside, since they are condensing.

It's not just the boiler heat exchanger, it's the rads as well.

 

[siricosm]

It's not just the boiler heat exchanger, it's the rads as well.

In a sealed system corrosion of plain steel rads is not a problem, provided there are no leaks. Inhibitor or not, rust can only happen with available oxygen, and once it is used up, corrosion stops.

Condensing boilers need to deal with corrosive flue condensate. In older steel boilers it was recommended to keep return temperatures high enough to prevent flue gas condensation.

 

[centralheatking]

In a sealed system corrosion of plain steel rads is not a problem, provided there are no leaks. Inhibitor or not, rust can only happen with available oxygen, and once it is used up, corrosion stops.

Condensing boilers need to deal with corrosive flue condensate. In older steel boilers it was recommended to keep return temperatures high enough to prevent flue gas condensation.

I live in the real world...all heating systems leak or admit air. sealed systems included god knows no system is perfect, loads of new boilers drip, the install might not be perfect, esp when coupled to an existing system....its no bodies fault but thats the reality ....dirty ch water , blocked up hex , burnt out diverter valves and rough running pumps. centralheatking