how long to programme hot water for?

mr_mitch

Hengus wrote: »

What you need, if you haven't got one already, is a cylinder thermostat. Basic thermostats wrap around the tank and you can set the maximum temperature (usually 60C). When the tank reaches the set temperature it tells your boiler to shut down irrespective of the timer settings.

Could this be one?




Edit, sorry just seen the link you added. I guess we do have one.

System

You do indeed. If your tank is well insulated, then the heat loss will be negligible. I have a slightly more sophisticated thermostat which controls the water in the range 53 to 60c but the principle is the same. Turn your timer on for about an hour before you need hot water in the morning, and agin for an hour in the evening. If the water starts to run cool, then you just need to extend the timer times.

Looking back to my energy stats, I was using about 1cu metre of gas a day for hot water and hob cooking.

topicalcat

Pincher wrote: »

If you think about it, you never use the water at 65 degrees.
It is more energy efficient to heat the water up to say 45 degrees, which means you always get condensation during heating.
In this scenario, topping up frequently is not an issue.

The problem is germs. The reason that all plumbers set the cylinder stat to around 61 degrees or more is because there is a chance of germs growing if it's not hot enough.

The issue reference germs is potentially in extreme cases, fatal, or a risk of serious respiratory problems. You have all heard of Legionaires Disease. A particular problem if you take a shower and are breathing the spores from the water droplets. My system heats the water to 61 ish deg, a mixer valve on the cylinder outlet then mixes cold water with that very hot water to deliver it to taps and shower at about 45 deg. Heat the water to that temp once a day to kill the bacteria. Plan to do that just before you want to have a shower or bath as already suggested and you will be fine. Install one of those mixer valves to prevent being scalded by excessively hot water at the tap.

mr_mitch

topicalcat wrote: »

The issue reference germs is potentially in extreme cases, fatal, or a risk of serious respiratory problems. You have all heard of Legionaires Disease. A particular problem if you take a shower and are breathing the spores from the water droplets. My system heats the water to 61 ish deg, a mixer valve on the cylinder outlet then mixes cold water with that very hot water to deliver it to taps and shower at about 45 deg. Heat the water to that temp once a day to kill the bacteria. Plan to do that just before you want to have a shower or bath as already suggested and you will be fine. Install one of those mixer valves to prevent being scalded by excessively hot water at the tap.

In other words, judging by my picture of my cylinder temp. Dial above, I am at risk of legionnaires?

Pincher

mr_mitch wrote: »

In other words, judging by my picture of my cylinder temp. Dial above, I am at risk of legionnaires?

It's like if you raise the motorway speed limit, more people will die. There's a graph somewhere that shows the probability of Legionella survival falling as the temperature goes up.


They obviously make recommendations with a safety margin, but why risk it?


An observation. Obviously there are big and small cylinders, as well as 30kW and 12kW boilers. If I was to use up my cylinder so there's only cold water in it, it takes about 40 minutes to fully heat it so the cylinder stat clicks off. I set the timer to do 30 minutes in the morning, which is fine, because it doesn't start from a cold cylinder: but what if it did? Don't forget cold water is colder in winter.

Menuisier

The UK regulations for domestic hot water systems specify that "Hot water should be stored at not less than 60deg C and distributed at not less than 55deg C in order to minimise the growth of legionella bacteria." In practice many cylinder thermostats (as in the previous photo) are set at about 55 deg C as they are usually fitted near the bottom of the tank and this will give you a temperature of close to 60 at the top, so don't worry! If you have a modern boiler it will be a condensing type (now a legal requirement) and these should be set to output water from the boiler at 60deg C anyway. If set any higher they cease to operate in "condensing mode" and are therefore much less efficient. Older boilers typically used to output at 80 deg and some people have modern condensing boilers set to the same temp but this will use a lot more energy. In any case setting the cylinder thermostat higher than the output temp of the boiler is a waste of time because if the boiler is only set to 60 deg then the water in the cylinder can't be any hotter than this.

bnegative

mr_mitch wrote: »

Well the shower we had previously used to heat its water on the fly, so maybe he was thinking it may have been one of those.

It isn't.

I was

obviously pincher has never come across said system

Pincher

In fact, I haven't heard of an electric shower with a hot water feed, since it is usually fed by cold water.


I have speculated the possibility of a solar thermal store, supplying the shower with whatever temperature the sun makes, but suspect it wouldn't be allowed due to scald risk.

mr_mitch

Menuisier wrote: »

The UK regulations for domestic hot water systems specify that "Hot water should be stored at not less than 60deg C and distributed at not less than 55deg C in order to minimise the growth of legionella bacteria." In practice many cylinder thermostats (as in the previous photo) are set at about 55 deg C as they are usually fitted near the bottom of the tank and this will give you a temperature of close to 60 at the top, so don't worry! If you have a modern boiler it will be a condensing type (now a legal requirement) and these should be set to output water from the boiler at 60deg C anyway. If set any higher they cease to operate in "condensing mode" and are therefore much less efficient. Older boilers typically used to output at 80 deg and some people have modern condensing boilers set to the same temp but this will use a lot more energy. In any case setting the cylinder thermostat higher than the output temp of the boiler is a waste of time because if the boiler is only set to 60 deg then the water in the cylinder can't be any hotter than this.

I'm fairly sure our boiler is one of the older non condensing types.

To be honest I'm not entirely sure of the difference between condensing and non condensing? Although I do know its definitely not a combi boiler.

Also there is a temperature control on the boiler its self, but there are no temperatures on it as such. Just higher to lower... So how do I know whether my boiler is hot enough for it to make the cylinder rest its heat setting and click off?

System

mr_mitch wrote: »

Also there is a temperature control on the boiler its self, but there are no temperatures on it as such. Just higher to lower... So how do I know whether my boiler is hot enough for it to make the cylinder rest its heat setting and click off?

I have a 14 year old non-condensing boiler which may be slightly less efficient than a modern boiler but it works just fine. The manual says something along the lines of set the boiler control to 2/3 for HW and 5/6 for HW and CH. The 5/6 is really down to the size of your home and how big the radiators are. My boiler is on 5 at the moment and we are toasty. The hot water coming out of boiler will always be above 60C.