The unvented cylinder annual inspection myth?

And as scary as Basil Brush.

I think someone who puts themselves forward as some sort of heating expert but doesn't understand the importance of good science is a lot scarier.

Tim

It think it amazing when someone doesn't know when something goes boom.

So you still can't understand the relevance of the difference between a 3kw input and a 10kw input then?

Tim

I can't imagine any sealed heat store losing heat faster than a 3 kW heater can put heat in. Therefore a 3 kW heater will cause such a system to explode if the safety measures are disabled. In fact I have known an /uninsulated/ vented tank boil when an immersion heater stat went faulty.

Possibly not. My point is though that it's incredibly bad "science" to mess about with a variable and assume that it won't make any difference. You can't assume that it will make no difference.

True, but that's at atmospheric pressure. BP rises with pressure.

I'm not denying that there is a risk of explosion, but like all risks, it needs to be put in perspective. How many deaths have there been in the UK from exploding unvented cylinders? There was a recent death from an unvented cylinder that I can remember.

Tim

I remebber a couple of recent fatal incidents with vented cylinders... never heard of any with unvented in this country yet.

IIRC not caused by failure of the cylinder but by bad installations allowing hot water to circulate via the plastic header tank leading to its failure.

Maybe the guidelines regarding installation and/or inspection mean that bad installations are very rare.

Damn! I'm getting dangerously close to agreeing with this man ;-)

(The only difference is I'm thinking "a few" rather than "many".)

Correction: incidents with vented *systems*, not the cylinders per se. It was the plastic cold water storage tanks in the attic that actually collapsed: the cylinders did not.

And in those cases if the vented cylinders had had the same sorts of thermostats on the immersion elements that are mandatory for unvented systems the incidents almost certainly would not have happened.

B*ggerit! Meant "vented" in that last sentence.

Tim

I come across a number of places where I find the immersion heater switched on despite the central heating system working. To many householders it's just a switch in the airing cupboard that does something magical and if it happens to be switched on and everything works, they leave it that way.

Having the main thermostat and the safety cutout both fail to danger is extremely unlikely and I'm sure the probability of any given unvented installation being subjected to these conditions is very, very remote. However as the number of unvented installations - and installations that aren't safety checked periodically - increases, so the probability of

I haven't seen the episode for some time but I don't remember them saying they'd changed the heating element. What wattage would be normal for a 52 (US) gallon tank? Isn't that somewhat larger than a typical UK cylinder that would have a 3kW immersion heater? Cases of real-life explosions mentioned here -

There are millions of vented systems, not many unvented ones.

That's why you have a heat leak radiator (and a thermostatically controlled stove)

My particular take on that, which I have mentioned before, was a property I lived in for a short while. The immersion heater had a time switch - the sort with segments that click in or out. The previous occupant (and owner) had wondered why the water was always hot when she only ran it for an hour or two a day. But the switch was wired the wtrong way round - the 'on' poistion for a segment had the effect of 'off' (and vice versa). So inadvertently it was ON 22/24.

You are a very confused man. But, probably clear in your own mind.

This one wants to see bodies first before the are outlawed. There is no need for unvented cylinders when vented heat banks are around. Zero risk is what you aim for.

There are many unvented cylinders poorly installed by cowboys. 90% of these unvented cylinder will not be tested each year as they should be. When they get old and the valves fail, then expect booms - probably in 10, 20 years time,a few a year.

longer.