Programmable cylinder thermostat

[Chuck]

I would still be interested in what is driving this desire to have different temperature water at different times ??

A mistaken belief that it will save enough energy to be worthwhile, would be my guess.

 

[oz-plumber]

It may be worth noting that the maximum storage temperature of water in USA is set at 50 degrees with no increase in legionnaires. The evidence on which this was based was rejected by Joint Technical Committee for Plumbing Standards but Australia has similar guidelines.

We can store hot water at temperatures at less than 65C.
They are warm water systems, which can store water at 45C, but there are very strict guidelines to these and they must incorporate a UV filter.
With the UV filter, they need monthly service, which must be logged and the tubes and UV lights have to be replaced at set intervals.

We maintain a couple of systems for aged care facilities and the annual maintenance and upkeep on these systems is quite expensive.

 

[Ziggie]

Chris rquested that I say why I am asking this question.

There are three reasons:

I only have my hot water on for about 3 hours in 24 and I turn it off completely when I go on holiday. I have it set to 50 but run it for a couple of hours at 61 once a week.

While I acknowledge my cost savings would be minimal when you multiply the usage over the entire population it would be quite a saving on the environment. There is evidence that having the water heated to 61 once a week for two hours is sufficient in the domestic environment.

I can understand in the commercial world that 61 is a necessity, the number of people at risk in the domestic environment is low and possibly the number being seriously scalded is far greater.

 

[chris watkins]

How big is your cylinder & how much hot water do you use in the morning?
The likelihood is you will not be using all the higher temperature water that is floating at the top of the cylinder, when you come to heat the water again to the lower temperature it will simple be the lower section.

Of course it depends how big your cylinder is & how much hot water you use but I get away with heating my one once a day, just before most is used during the morning ablutions. It therefore sits for most of the time with only a small amount of hot water in the top section loosening heat because of the difference in temperature between it & the air in the cupboard.
Part L complaint indirect cylinders will heat the hot water in around 30-40 mins given that it is a correctly sized gas fired boiler with the thermostat set to >70 deg C flow.
Reducing the amount of time the boiler is firing to top-up the cylinder hot water is the more important thing here. Given your cylinder provides effectively less hot water due to your lower running temperatures your boiler will be firing & cycling more often which is inefficient.

Much more can be achieved by setting the systems up correctly & installing the required pipe insulation, both of which are low cost & last its lifetime, than by the use of so called "smart controls" which cost a fortune & don't solve the problems but "hey, look I can change the room set temperature from my phone while at work" (I am not suggesting this is you Ziggie but I see this a lot from clients around London)

It cost me on average £5.50 a week to heat my HW for a family of 4 adults, so you are correct Ziggie the cost savings due to your 11 degC temperature reduction would be negligible, & not worth the investment in the controls to achieve it, IMHO.