The unvented cylinder annual inspection myth?

This is a good sign, the therapy is working.

As few are serviced I would say many. Before the authorities tighen up and get them all annually serviced and tested properly (which takes time to test all failure systems), they have to see a death.

Reply to
Doctor Drivel
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Those who vehemently defend unvented cylinders over near zero risk DHW only vented heat banks, are plumbers who have the G3 approval ticket and make money out of it. Their own money making overrides any safety issues in their tiny heads.

Reply to
Doctor Drivel

Doctor Drivel coughed up some electrons that declared:

Not if the cylinder can lose 1kW by radiation/convection, in which case it will reach stable state and stay there forever.

Reply to
Tim S

Confused by idiocy, yes.

Zero risk is a goal of fools.

From the moment of conception until the day you die your life is filled with risk. Sensible risk reduction is what you aim for.

A car has far more killing potential but it requires no mandatory testing until it is at least 3 years old.

Tim

Reply to
Tim Downie

Don't bother with logic, he won't understand.

Tim

Reply to
Tim Downie

You really don't know.

Reply to
Doctor Drivel

But it's not zero is it? You can't ignore the deaths from vented cylinder systems if you are trying to prove that one system is safer than another.

(Sorry, I'm using logic again. Unfair I know.)

Tim

Reply to
Tim Downie

I seem to remember the recent infamous one (baby died on first day in new property IIRC) didn't have the cut out switch in the immersion so one failure and the plastic header tank gave way.

Reply to
Malcolm

Doctor Drivel coughed up some electrons that declared:

Neither do you...

Reduction ad absurbdum - 1mW will never blow such a cylinder up, unless the insulation was near perfect.

10kW is pretty likely to blow it up regardless of insulation, ambient temperatures etc.

Somewhere in betwee, there will acheivable equilibrium states that do not exceed the operational pressures of the vessel.

Is that too hard for you?

Reply to
Tim S

My recollection was that the vent from the safety relief valve had been lead into the plastic cold water storage tank and that when the immersion failed on hot water was dumped into the cold tank, causing the tank to collapse and scald the baby in the room below.

Reply to
Steve Firth

?

IIRC it was a vented cylinder that just boiled over through the expansion/vent pipe into the loft tank. Don't think there was any "safety relief valve" other than the open pipe. In fact, I think any sort of valve on an open vented system is illegal.

That bit's certainly right.

Tim

Reply to
Tim Downie

On Thu, 4 Dec 2008 15:09:31 -0000 someone who may be "Tim Downie" wrote this:-

Any sort of valve?

Can't an open vented system have a valve on the feed and expansion pipe? Can't have valves (presumably including taps) on the domestic hot water pipes? Can't have a pressure relief valve fitted in case some vulnerable pipework ices up? Every open vented system I have seen must be illegal.

Reply to
David Hansen

Bl**dy pedant. You know what I meant. Valve on the expansion/overflow.

Tim

Reply to
Tim Downie

Not quite. Plastic header tanks are designed to withstand such an event (although one would be advised to change them afterwards) for safety reasons, as there is the possibility of boiling water entering them. They can only do so if they are properly supported. This one wasn't, just supported by the joists. When it was subjected to the boiling water it

*deformed* and collapsed. It wouldn't have done if evenly supported underneath.
Reply to
Bob Mannix

Oh, righto, I thought it was a sealed system with a substandard installation.

Reply to
Steve Firth

Is it possible to buy non plastic header tanks?

I looked, but couldn;t find anything...

Reply to
Tim S

I was thinking of two - one where the plastic header tank got back filled with hot and failed, and another where a cylinder ruptured and dumped hot water on sleeping people below.

Indeed. Which makes dribble's claims even less convincing.

Reply to
John Rumm

Wouldn't have had a header tank in that case. ;-)

Tim

Reply to
Tim Downie

In which case you need to insulate it! (for practical domestic values of area, volume and max. temp)

Reply to
Andy Dingley

Andy Dingley coughed up some electrons that declared:

Yeah I know

It was a rebuttal to Dribble's generalised statement.

Reply to
Tim S

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