Programmable cylinder thermostat

[Ziggie]

Currently have Nest system.
Would really like to be able to have a programmable cylinder thermostat that allows different temperatures at different times.

Realise I need to have 61 degrees for a couple of hours once a week. Would want low temperature (e.g. 40 degrees at lunch time for the washing up). Would want higher temp first thing to deal with showers for the family,

Any hardware available?

 

[Chuck]

Would really like to be able to have a programmable cylinder thermostat that allows different temperatures at different times.

Think again. You are proposing to modify your system so that it breeds legionella and delivers 'hot' water that is sometimes tepid and sometimes scalding, which will cause injuries to unsuspecting users.

If you want to save energy get a better insulated tank, or improve the exisiting.

 

[Millsy 82]

Have mixer taps installed and add a bit of cold when you want it cooler.

 

[gmartine]

Thermostatic taps are available for kitchens and bathrooms.

 

[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 top of the cylinder, when you come to heat the water again to the lower temperature it will simple be the lower section. (unless you want to have an anti-stratification pump installed to mix it all up.
A few things which may be worth taking into account.
1. As other already stated Hot water is required to be stored at no less than 55deg C but it is normally set to 60 - 65. Any more in hard water areas & the scale starts to deposit at a much faster rate.
2. Effective dish washing normally requirers hot water at around 50+ to help with the grease.
3. Water for ablutions (washing) is around 40 degC so will be a mix of hot & cold water. Your cylinder will have been sized to take account of this so if you reduce the stored hot water temperature you will effectively be reducing the amount hot water available.

There is often a reason why hardware isn't out there & there is a good reason why Plumbers have to study for a minimum of 4 year to understand how whole systems work.

 

[oz-plumber]

If you want something that will suit your requirements, look up Rinnai Hot Water.
Gas fired continuous flow water heaters.
You can even get control pads to set the desired temperatures you want.

If you want a shower at 42C, then you press 42C into the bathroom control pad and you get 42C.
If you want 55C at kitchen sink, press 55C into kitchen control pad.

We use heaps of them over here

 

[quality]

We do this all the time with heat pumps but not to sure how to do it with a Nest controller. If the water is used regular then its not sat long enough to cause any issue especially if heated to 60 + at least once a week

 

[Basher]

To answer Ziggie’s original question - yes there is such hardware on the market. Based on having a temp. sensor on the tank that talks to a programmer.

Whether it’s a good idea, or worth the expense, I won’t comment.

There doesn’t appear to be anything you can add to Nest at the moment, so it would mean changing the system to one of these below.

Owl intuition
Owl Intuition Hot Water Tank Sensor (TBTE3H) - Smart Green Shop

Honeywell Evohome Smart Hot Water Kit
Honeywell evohome Hot Water Kit ATF500DHW

I have no experience of these, and they get mixed reviews. Just sayin...

 

[Ziggie]

Thanks to all for information and help.
I am aware of dual temperature thermostats that programme 61 degrees for one hour a week and use a set temperature for the remainder. The one I know needs a pocket in the tank which mine does not have.

There is conversations on the web about scalding and legionella.

I will research all the options provided and again thanks everyone for their input

 

[OffshoreGas]

Think again. You are proposing to modify your system so that it breeds legionella and delivers 'hot' water that is sometimes tepid and sometimes scalding, which will cause injuries to unsuspecting users.

If you want to save energy get a better insulated tank, or improve the exisiting.

But other than that its a great idea?
It could be done quite easily with a conventional control system, don't think you'll have much luck with the Nest etc "Smart" controls

 

[Brambles]

Evohome will only give you a fixed temperature up to + or - 1 degree. You can adjust it, but you cannot program it within a timer or set a “legionella” facility.

 

[Ziggie]

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.

 

[OffshoreGas]

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.

HSE guidance says water should be stored at 60C or higher, that's all a judge would care about it anyone were to suffer ill effects.

 

[chris watkins]

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

 

[OffshoreGas]

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

Energy saving? Which would be negligible in a well insulated tank.

 

[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.