Willis Heating System

[ericmark]

Is that not specified, to prevent pump-over, the rise in pressure when the pump runs?

There was a council house in Somerset where the gap was not enough, and when the thermostat stuck and the hot water circulated into a thermal plastic tank which failed and killed a baby. This is why there is a minium gap.

I think thermal plastic heater tanks should be banned, but they hope a cut-out will be enough, blame the electrician not the plumber it seems.

 

[SUNRAY]

Is that not specified, to prevent pump-over, the rise in pressure when the pump runs?

This bit isn't pumped

 

[SUNRAY]

The external heater doesn't have to be level with the storage vessel

Just to confuse the situation further the heat source may be higher than the storage vessel.View attachment 408441
I have expectation there would be reduced efficacy/efficiency.

I recall a friends non pumped heating installation in a very old house with a solid fuel boiler and a radiator one floor below it which was only ever 'warm to the touch' at best until he rerouted the heating return pipe from upper floors down via the lower floor to include the lowest radiator.

 

[JohnW2]

Interestingly, this is not a universal truth; water at 4 degrees C is relatively hotter than water at 1 degree C, but it is not lighter (more buoyant)

Yes, we take it so much for granted, but water is unique in so many ways! As you imply, water has its highest density at 4C, with a lower density at any temperature above or below (including ice) 4C. However, although your comment illustrates your knowledge, it's clearly totally irrelevant to our discussion

Pond life survives by capitalising on this curious quirk, that a pond will stratify with 4 degree water at the bottom

True, but some species of aquatic life might have preferred water to behave like most (all?) other materials, such that the ice sank to the bottom and they could carry on living above it

Betamax was a better system than VHS...

Arguably yes. By pure co-incidence, I spent most of last weekend digitising some ancient recordings I have from 40+ years ago (mainly 'footage of my daughters' earliest years) which existed on Betamax tapes. Not only had the tapes (and their content) largely survived but, to my surprise, once I had blown off all the dust, the Betamax machine which has not been used for decades also 'worked first time' without needing any 'attention'!

 

[JohnW2]

However, I see your point, you buy a tank with boss already in place for an immersion heater, why mess around putting one outside it even if it works better, It is not the £43 for the unit, it is the cost of the installation.

To be fair, a cylinder without any immersion boss is likely to be a little cheaper than one with one or two bosses, therefore at least partially offsetting the cost of a Willis heater - and I don't really think that the time/cost taken to install a Will is a significant issue.

However, I don't think that robin's 'point' was as you seem to imply, since he appears to be a fan of Willis systems.

Willis system clearly works, there are too many installed for it not to work.

As you say, it clearly must 'work' in some senses and to some extent, but I am currently far from 'properly understanding'.

All sorts of alternatives to standard approaches would (and do) 'work' but that does not necessarily mean that the offer any advantage over the standard approach, nor necessarily even that they are 'at least s good as' the standard approach,

The problem has existed as far back as I can remember, if the expansion pipe is too close to the top of the water, the water can circulate. This shows how much heating hot water can cause it to rise.

 

[JohnW2]

Just as in siphoning from one container, to another, the hot will try to match levels, between the two cylinders. There will also be bubbles of steam formed around the element, rising, and assisting the movement.

I'm thinking -watch this space

 

[JohnW2]

Gravity - hot water is lighter than cold water.

Again, I'm thinking, so this gets added to the space that I'm afraid you will have to watch for a while

 

[SUNRAY]

But we are talking about water over 4°C.

V2000 was better than both.

However, I see your point, you buy a tank with boss already in place for an immersion heater, why mess around putting one outside it even if it works better, It is not the £43 for the unit, it is the cost of the installation.

Willis system clearly works, there are too many installed for it not to work. The problem has existed as far back as I can remember, if the expansion pipe is too close to the top of the water, the water can circulate. This shows how much heating hot water can cause it to rise.

Where did this come from?

Shouldn't that be the highest point of the vent pipe should be a minimum of 450mm above the maximum possible water level, ie the overflow and terminate at least 2" above it?

Or possibly above the inlet which has to be above the overflow (I'm out of touch on this)