How is yours piped, the pre-1970s way or the later way? Is your inhibitor at required concentration?
That's right, but with a vented system, you would expect to see evidence of a leak somewhere.
Is there a future for vented systems?
- Thread starter sirocosm
- Start date
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Do you mean a combined feed and vent pipe? I suppose that could be OK, but it seems to me a cheapo way of doing it. My house was piped that way when I moved in 20-odd years ago, but when I upgraded the system I changed it to separate feed and vent. Been fine fine since.
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There is, feed the shower with mains pressure water that is heated by it passing through a second coil in the vented hot water cylinder. Bath and basins supplied under gravity from the hot water in the cylinder
My vote goes for the simplicity and reliability of vented systems.
I think this is what in the UK is called a thermal store.
Is a feed and expansion tank with all its associated piping (including overflow), really simpler than a PTRV, drain, and an expansion vessel?
A lot of trust in placed in the Pressure Relief valve to open and dump excessive pressure. How is that valve tested to ensure it will open before the pressure in the system ( due a fault maybe ) become dangerously high.
One of the "valid" reasons for installing a combi when it is not the best option for the family's lifestyle is the redcution of work for the installer.
One reason for an installer installing unvented systems is the possibility the installer gets the work of carrying out the essential annual service of the system.
A lot of that is also driven by cost, the customer wants a system installed for the cheapest price, installing an open vented system isn't as cheap as a combi.
To be honest any heating/hw system, open vented or unvented should be regularly checked and serviced. Most of the reasons for systems failing, outwith basic electrical faults, is a lack of regular checks and maintenance.
I guess the simplicity of an open vented system is in it's operation, it's low working pressure and self regulating pressure control is inherently safer than anything held under pressure that has to have numerous safety devices attached and working properly IMO.
That being said I love my unvented HW and my loft conversion.
I was arguing about simplicity rather than safety.
Here is what a standard water heater looked like in Canada when I lived there, and I have not heard of one exploding do to PRV failure. Notice the PRV just dumps on the basement floor, there is no expansion tank or check valve, and the device uses air from the room for combustion. Before I moved to Europe, I had never seen anything else for heating water, except the electric version of the same. They probably make more sophisticated high efficiency ones now, but I bet there are still a lot of these in service.
I guess it's not really about if they do explode rather than if there's is a chance of them exploding then it's obvious which is safer. A vented system could never get to the point of pressurising enough to explode like this. That and a vented system is as simple as it gets in operation albeit it has more in the way of pipework and cisterns etc but I'd certainly agree it can be easier to install an unvented system
Deliberately plugging the PRV and removing the thermostat is not a very realistic scenario. And I suppose you could also do that with a vented cylinder, just plug the vent pipe and do the same.
With CH an accidental blockage by debris in the system is a possibility. Or corrosion of the valve mechanism.
There can be, and almost always is, a great deal of debris in a typical North American water heater.
They run until they rust out, but they don't seem to explode.
In a CH system with a sealed boiler there is also a PRV on the boiler, so I guess both would need to be somehow blocked. I suppose it is also possible for a vent pipe to get blocked, but that also seems unlikely.
Of course not but an unvented system that hasn't been installed properly without suitable safety devices or those devices being circumvented (have personally seen that) or an old PRV that can jam shut and an old cylinder stat that can fail closed circuit is possible however rare, otherwise they wouldn't have numerous backups.
This isn't about deliberately plugging these things or forcing them to fail, rather being improperly installed or failing due to age or non servicing and then what the outcome would be.
This isn't about deliberately plugging these things or forcing them to fail, rather being improperly installed or failing due to age or non servicing and then what the outcome would be.
But in practice, this does not seem to happen. Even in Canada where all they have is a single PRV, and there is a gas flame directly under the cylinder.
And what makes a vented systems any safer? What happens if the entire mess in the loft freezes solid? IMO a vented cylinder should also be required to have a PRV for the same reason.
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