Willis Heating System

[JohnW2]

John - you seem to be forgetting the fact that other people have very different needs to yourself.

I must say I would have thought that my household was very 'typical' as regards 'needs' for hot water, but that's not really relevant.

I am not a salesman, attempting to sell you a Willis system, I am simply pointing out the differences to what you have, and potential advantages. With that, I will leave the thread, as it is becoming simply repetitive.

You surely must realise that my interest is not in relation to my own use but, rather, an academic/intellectual interest in trying to understand the workings of this system, and to understand why a system which was invented a long time ago, and which has some 'champions' (who believe that it offers 'clear advantages'), has been taken up by such a minute proportion of the world's population.

However, you may be pleased to know that, although it is nothing to do with the technicalities of the system (i.e. 'how/why it works and behaves), I think that I may have accidentally 'seen the light' as regards this discussion, in realising that there is some serious 'chalk and cheese' involved. It didn't 'sink in' at the time, but, on reflection, what I wrote in a recent post (coupled with a link that EFLI recently posted) has made me suddenly 'see this light'.

Throughout this discussion, I have been thinking as someone who has bought into the concept of using 'stored hot water' and therefore rarely, if ever, has a need for 'newly heated water'. However, the link recently posted by EFLI reminds me what this is all about, when it says:

Typical use time: > Shower: 10 minutes, > Dish Washing: 5 minutes, > Hair Washing: 5 minutes ....
So, for a shower (typical requirement – 35 litres @ 40°C), the Economiser will heat only the top 35 litres of the cylinder in about 10 minutes, and the unit should then be switched off.
For maximum efficiency, we recommend that the Economiser be fitted in conjunction with a timer (such as the ELEMEX T1). This will ensure that the heater is switched off after the required time. You can then set it and forget it.

So, this system is being aimed at people who have totally abandoned the concept of using stored hot water but, rather, want to heat up (from cold) just the amount of water they need for each task (be it a shower, washing up, hair washing, simple hand washing or whatever). That requires them to anticipate their need to undertake each of the tasks by setting a timer for the requisite heating time (or trying to remember when to switch it off) and then waiting that amount of time before they can undertake the task. I could do essentially the same with immersions (albeit, as you have pointed out, slightly less efficiently/quickly, because of a little mixing of heated water with cold) but there is absolutely no way that I would want such tedium and disruption in my life.

I would therefore suggest that anyone contemplating a Willis system should instead seriously consider perhaosspending their money on some decent insulation for their DHW cylinder. They would then (like I do) always have essentially unlimited amounts of immediately available hot water, immediately enough for anything (including a bath, should they choose to take one) without any hassle or need to anticipate how much hot water they would next need, and when - and if their primary/only water heating were by electricity, then they might also be able reduce costs by taking advantage of tariffs with 'off-peak' periods.

 

[Harry Bloomfield]

I would therefore suggest that anyone contemplating a Willis system should instead seriously consider perhaosspending their money on some decent insulation for their DHW cylinder. They would then (like I do) always have essentially unlimited amounts of immediately available hot water, immediately enough for anything (including a bath, should they choose to take one) without any hassle or need to anticipate how much hot water they would next need, and when - and if their primary/only water heating were by electricity, then they might also be able reduce costs by taking advantage of tariffs with 'off-peak' periods.

Basically, horses, for courses!

 

[JohnW2]

Basically, horses, for courses!

I suppose that's one way of putting it!

[ as an 'aside of detail', to start with ..... Regarding ....​

So, for a shower (typical requirement – 35 litres @ 40°C), the Economiser will heat only the top 35 litres of the cylinder in about 10 minutes ...

... assuming that Physics and Maths are the same in Ireland as elsewhere, by my calculation to heat 35 L of water from, say, 18°C to 40°C would require about 898 Wh, about18 minutes (not 10) with a 3 kW heater and, in practice, the cold supply could well be a fair bit lower than 18°C, so it could take a fair bit more than that. ]​

Having now realised what we're talking about, in some senses, the Willis idea ('abandoning the concept of stored hot water') seems to be a bit of a joke since, at least in terms of 'time', it's no different from or better than real-time instantaneous water heating ....

Working with my figures, if one's cold water is at 18°C and one wants/needs 35 L at 40°C, then (ignoring 'losses') a 100% efficient 3kW heater is going to take about 18 minutes to achieve that, no matter what the 'heating arrangement'. One can either do that in the conventional 'instantaneous heating' fashion, by watching the heated water 'trickle out' painfully slowly for18 minutes, or one can twiddle one's thumbs for 18 minutes whilst waiting for a Willis heater to heat the water and transfer it (with some 'losses') into a cylinder for temporary storage prior to use. Either way, it will be 18 minutes from 'switch-on' to when one's desired amount of heated water has become available. I suppose some people might be happy with that'wait', but I certainly don't see it as an advantage over traditional stored hot water.

In fact, what w're talking about reminds me of my grandparents' hours in my early years. During summer (coa fire with back boiler not in use) when they wanted hot water for washing, washing up or whatever, they had to wait whilst it heated up in a kettle or galvanised bucket on the gas stove!

[Serious question!] Is there perhaps something about the attitudes to life, personalities (perhaps more 'laid back'?) or lifestyles of the Irish which makes them more prepared to sit around waiting for hot water to be created?

 

[robinbanks]

Irish [people] sit around waiting for hot water to be created

What an insultingly ignorance-filled read "The Universe According To JohnW2" would be

 

[JohnW2]

What an insultingly ignorance-filled read "The Universe According To JohnW2" would be

Goodness Anticipating, and in an attempt, to pre-empt, knee-jerk reactions like yours, I even prefaced my comment with "[Serious Question]", but seemingly to no avail

I have absolutely no 'negative', let alone "insulting or ignorance-filled", thoughts about Irish people - and would have had a problem if I did, since I've been married to one for over 50 years!

However, there undeniably are cultural differences between different groups, whether defined by geography, ethnicity, religion or whatever, and I was wondering if that might explain the situation we appear to have seen with the Willis system.

As I wrote, from the user's point of view, the main difference between the Willis system and (almost ubiquitous in UK) 'conventional alternatives' ('stored hot water', or true 'instantaneous heating, as, for example, with combis and electric showers) is that the user has to anticipate the need for hot water and then wait (for potentially quite significant periods of time) for it to be created. Many, maybe most, would probably regard that as 'inconvenient', hence undesirable.

The Willis system was 'invented' decades ago, and has apparently been widely deployed in the island of Ireland, particularly Northern Ireland, but seems to have been little used anywhere else in the world. Given that global communication has been pretty good for many decades, one imagines that a substantial proportion of plumbers etc. throughout the world must have become aware of the system but have nevertheless not seen a reason to significantly adopt to.

There is therefore a need to understand why something which some believe "offers clear advantages" has only been widely used in a geographical area which contains less than 0.1% of the world's population. The most likely explanation I have so far thought of is that of some sort of cultural difference which has resulted in a very different attitude to what most people in the world would probably regard as an 'undesirable inconvenience' which they would prefer not to have to live with.

I'm sure there must be other possible explanations and look forward to hearing of any suggestions.

My personal view remains that, at least in 'developed' countries, the only 'sensible' approaches to domestic hot water are to either have 'stored hot' water (with very well-insulated cylinder, and ideally gas-heated, at least in UK) or to have true 'instantaneous' heating, as in combis and electric showers etc., - although some people (including some here) would say that even the latter is usually 'not very sensible'.

 

[SUNRAY]

Goodness Anticipating, and in an attempt, to pre-empt, knee-jerk reactions like yours, I even prefaced my comment with "[Serious Question]", but seemingly to no avail

I have absolutely no 'negative', let alone "insulting or ignorance-filled", thoughts about Irish people - and would have had a problem if I did, since I've been married to one for over 50 years!

However, there undeniably are cultural differences between different groups, whether defined by geography, ethnicity, religion or whatever, and I was wondering if that might explain the situation we appear to have seen with the Willis system.

As I wrote, from the user's point of view, the main difference between the Willis system and (almost ubiquitous in UK) 'conventional alternatives' ('stored hot water', or true 'instantaneous heating, as, for example, with combis and electric showers) is that the user has to anticipate the need for hot water and then wait (for potentially quite significant periods of time) for it to be created. Many, maybe most, would probably regard that as 'inconvenient', hence undesirable.

The Willis system was 'invented' decades ago, and has apparently been widely deployed in the island of Ireland, particularly Northern Ireland, but seems to have been little used anywhere else in the world. Given that global communication has been pretty good for many decades, one imagines that a substantial proportion of plumbers etc. throughout the world must have become aware of the system but have nevertheless not seen a reason to significantly adopt to.

There is therefore a need to understand why something which some believe "offers clear advantages" has only been widely used in a geographical area which contains less than 0.1% of the world's population. The most likely explanation I have so far thought of is that of some sort of cultural difference which has resulted in a very different attitude to what most people in the world would probably regard as an 'undesirable inconvenience' which they would prefer not to have to live with.

I'm sure there must be other possible explanations and look forward to hearing of any suggestions.

My personal view remains that, at least in 'developed' countries, the only 'sensible' approaches to domestic hot water are to either have 'stored hot' water (with very well-insulated cylinder, and ideally gas-heated, at least in UK) or to have true 'instantaneous' heating, as in combis and electric showers etc., - although some people (including some here) would say that even the latter is usually 'not very sensible'.

Goodness me, my initial knee jerk reaction to Robins post was somewhat negative however this later reply is a bit of a shock.

What are the disadvantages to the Willis system? We have ploughed through 200+ posts, essentially discussing the differences between Willis heating and 'in vessel' heating, we have learnt some advantages of both over the other described but I see very little to indicate that either create a significant difference and certainly nothing to cause a situation such as:

The most likely explanation I have so far thought of is that of some sort of cultural difference which has resulted in a very different attitude to what most people in the world would probably regard as an 'undesirable inconvenience'

If I had reason to make a definitive choice between the 2 electric heating systems I think I'd find it very difficult to make a choice however as I've said so many times external heater(s) to the storage vessel is a common system in large installations where I'm sure the better option will be selected.
I can think of only one undesirable inconvenience when comparing 'internal' Vs 'external' heaters systems and that is the undesirable inconvenience of replacing an 'internal' immersion heater every few years. Changing a 'Willis' heater is a vastly simpler job.

Especially if it's been installed by a plumber as they insist on using some sort of glue and then the next plumber frequently tears the flimsy copper. Changing a 'Willis' vessel is a vastly simpler job.

 

[ericmark]

So if you have seen the light, now let me add solar into the mix. When using solar PV to heat DHW we have a sensor

so a current transformer monitors when we are exporting and how much, and the immersion heater is only activated when otherwise we would be exporting, and also only to a rate which will not cause an import, so the 3 kW unit may be working at only 200 watts.

We know the Willis will heat the top of the cylinder first, but when the immersion is not giving out a full 3 kW, will that top bit be warm enough? The whole idea is DHW is 60°C or more due to legionnaires, and the water at between 20-60°C is kept to a minimum, in winter I can't stop the CH from also heating the DHW, so regular the whole tank is hot. In summer, so the tank is regularly heated to over 60°C I have it set to use off-peak to also heat the water.

Without the off-peak, would the water get hot enough with the Willis system? If I am only putting ¼ a kWh into the domestic hot water, will it give me hot water at the taps, or increase the likelihood of legionnaires? Once I see

I know the DHW is safe, and seeing

or

I know it is working, but with a Willis does

really mean the tank is hot, or does it just mean the Willis unit has turned off, and the tank could still be cold?

 

[JohnW2]

Goodness me, my initial knee jerk reaction to Robins post was somewhat negative however this later reply is a bit of a shock.

As I wrote, I was expecting 'knee jerks', and did what I could to 'pre-empt' them, but without much success

What are the disadvantages to the Willis system? We have ploughed through 200+ posts, essentially discussing the differences between Willis heating and 'in vessel' heating, we have learnt some advantages of both over the other described but I see very little to indicate that either create a significant difference and certainly nothing to cause a situation such as: ...

Virtually everything I have thought and written in this very long thread has been about the 'technicalities' of the Willis system (i.e. how/why it works) (which is why I started this thread) and, thanks to some of the more useful input I've had here (including from yourself) I have now got my head a fair bit around that - although, as you probably realise, I still have 'uncertainties' about some aspects.

However, what has only just sunk in to my head is the fact that almost all the arguments being thrown at me, leading to assertions that the Willis system 'offered clear advantages', are based on the assumption that one has little/no stored hot water, so that the 'starting point' for everything people have been saying to me has been one in which all the water in the system (cylinder, pipework and Willis heater, if present) was 'cold'.

I now understand, and have conceded, that IF one has little/no stored hot water, then the Willis system offers some (small) advantages because even with a very high immersion, there is still a little mixing of heated water with cold, as the heated water 'rises up' to the top of the cylinder - something which doesn't happen with Willis. Also, if the Willis heater has been 'on' fairly recently, there may be a very small amount of 'stored hot water' in it available (within the external heater and pipework) for 'immediate use - but even that will presumably get diluted by (mixed with) cold water from the cylinder (probably at least 50:50).

However, moving to your question "What are the disadvantages of the Willis system?", the disadvantages (or, rather, per below, 'the lack of appreciable advantages') I've been talking about are nothing specifically to do with the Willis system but, rather, are (I would say fairly major) disadvantages of any system which did not have decent amounts of stored hot water. If you look, I think (hope) you'll find that I have rarely, if ever, talked about "disadvantages of Willis system" but, rather, have said why I don't see any appreciable advantages (other than those small ones mentioned in the previous paragraph - i.e. IF one is trying to use a system which has little/no stored heated water then the Willis system is 'almost as bad' as doing the same thing with a high immersion.

If I had reason to make a definitive choice between the 2 electric heating systems I think I'd find it very difficult to make a choice

As above, IFI had abandoned the concept of having decent volumes of stored hot water, then so would I - because I don't think that the small advantages of the Willis system (as above) are significant enough to be an issue. The important point is that I would not be considering any system (whether using an internal or external/Willis immersion) that did not provide with with decent volumes of stored hot water.

It's really much the same as the choice between a shower fed with stored hot water and an electric shower or shower fed by a 'combi' - I think that many/most people would agree that, when possible, the former is preferable.

I can think of only one undesirable inconvenience when comparing 'internal' Vs 'external' heaters systems and that is the undesirable inconvenience of replacing an 'internal' immersion heater every few years. Changing a 'Willis' heater is a vastly simpler job. ... Especially if it's been installed by a plumber as they insist on using some sort of glue and then the next plumber frequently tears the flimsy copper. Changing a 'Willis' vessel is a vastly simpler job.

Unfortunately (personal experience ), I have to agree with that, but I doubt that many people think that far ahead when choosing what system to install!

 

[JohnW2]

So if you have seen the light, now let me add solar into the mix. ...

As you may now realise, the light I have seen does not relate directly to the Willis system but, rather, to any system (whether the heating is internal or external to the DHW cylinder) that does not involve heating and storing a cylinder full of hot water.