Being efficient with hot water

[spursfan323]

Currently we run the hot water every 8 hours daily, for an hour each time. I'm wondering if this is unnecessary and inefficient.

We need enough daily water for 1 bath, 2 showers, a couple of washing machine and dishwasher loads (although am I correct that these machines take in cold water and heat it themselves?).

Boiler is Vaillant Ecotec 630 and sealed unvented cylinder is telford tempest.

Can anyone advise what would be a more efficient option?

Many thanks

 

[D_Hailsham]

If your washing machine/dishwasher has two hoses it uses hot and cold fill. If only one hose it's cold fill only.

Hot and cold fill can be converted to cold fill only by using a Y adaptor on the cold supply. You will still need two hoses connected to the machine, but the "hot" hose will now carry cold water.

As for heating the cylinder, how often you need to do it will depend on how much you use. With a well insulated tank a tank full of water at 60C will last a long time.

As an example our HW is timed as follows:

9pm to 12.30am
12noon to 2pm

The evening heat ensures we have enough water for showers before bed (three people) and there is still enough water for morning ablutions and any washing up done during the morning. The boiler usually doesn't come on until all three of us have showered.

The lunch time heat ensures there is enough water during the afternoon and for evening washing up.

The boiler is not on all the time as it is controlled by the thermostat on the cylinder which only closes when the temperature has dropped by about 10C.

 

[dcawkwell]

Eight hours daily?

I find setting the hot water on for 2 hours in the morning and 2 hours in the evening is enough.

 

[Charnwood]

every 8 hours daily, for an hour each time.

One hour, three times daily, cawky. That's 3 hours a day, one less than yourself.

 

[spursfan323]

If your washing machine/dishwasher has two hoses it uses hot and cold fill. If only one hose it's cold fill only.

....

As for heating the cylinder, how often you need to do it will depend on how much you use. With a well insulated tank a tank full of water at 60C will last a long time.

As an example our HW is timed as follows:

9pm to 12.30am
12noon to 2pm

The evening heat ensures we have enough water for showers before bed (three people) and there is still enough water for morning ablutions and any washing up done during the morning. The boiler usually doesn't come on until all three of us have showered.

The lunch time heat ensures there is enough water during the afternoon and for evening washing up.

The boiler is not on all the time as it is controlled by the thermostat on the cylinder which only closes when the temperature has dropped by about 10C.

It is cold fill only.

The cylinder is self-insulated from what I understand - I lagged the pipes in the loft myself so relatively little heat loss there.

From what I understand you have your HW for 5.5h a day - a lot more than my 3 - and there i was thinking I can get away with less!

However from observation it appears to me that throughout those 3 hours the boiler does indeed work flat out (pausing occasionally to 'cycle') so perhaps I could get away with less.

Would you suggest 1 x 2 hours or 2 x 1 hour?

 

[D_Hailsham]

From what I understand you have your HW for 5.5h a day - a lot more than my 3 - and there i was thinking I can get away with less!

But don't forget that the boiler is not ON for all the 5.5 hours. The time periods are just a 'window' during which the boiler can come on if the temperature of the cylinder water has dropped low enough

However from observation it appears to me that throughout those 3 hours the boiler does indeed work flat out (pausing occasionally to 'cycle') so perhaps I could get away with less.

If your central heating is on, that could account for some of the time.

The only way to find out what you need to do is to experiment.

Get the cylinder full of hot water and then turn the HW OFF at the programmer. Now draw off hot water, as usual, until the water is not hot enough, i.e you don't need to mix it with cold to get a use-able temperature.. This give the maximum time you can go before reheating is necessary.

Don't forget that, for a 10 minute shower of 10 litres/min at 40C with hot water at 60C and cold at 20C, you will only use 50 litres of hot water. Assuming a 200 litre cylinder the water temperature will drop from 60C to 50C, so the cylinder thermostat would kick in. However there is still enough hot water for a second shower at 40C, though this time you will need 67 litres of hot water; and, by the time you had finished, the cylinder water would be down to 40C.

 

[spursfan323]

Thanks a lot for your detailed response

If I recall correctly, my cylinder thermostat is set to 55-60. Is that correct practice?

 

[D_Hailsham]

Thanks a lot for your detailed response

If I recall correctly, my cylinder thermostat is set to 55-60. Is that correct practice?

It really needs to be at 60C. The reason for setting it at a high temperature is to ensure any legionella bacteria which might be in the water are killed off.

 

[JohnD]

55C will kill them, but not instantly. However you mention it is an unvented so the fresh chlorinated water from the main that refills it is not likely to have a lot of live stuff in it, as it might if you had an open cold tank in a warm loft.

If the cylinder is being maintained at 55C, the stored water will be safe. Even at 50C the bacteria will not grow and multiply, and your incoming supply should be already be safe.

 

[big-all]

theres only me and my son in our house
i wash the dishes every other day [by hand] turn the water on for the dishes for 45 mins
my son has a shower every day i hand wash in the basin at least once every day[usually cold water in the summer ] and bath once a week when i leave the water on for an hour

i use about 55L as my big fat aarse fill most off the bath[5" deep turns to around 8" ] now the water wont be piping hot on day two but its summer time

and during the winter the water comes on with the heating anyway

i would suggest you reduce the heating times by 10 mins in turn each session more and more until its noticeable then increase one session by 5 mins altrenating between the three untill you get the best compromise with possibly one or more small increases till the balance is correct

 

[conny]

Don't forget that during the winter the filling water will be colder than in the summer so will take longer to reach required temperature.

 

[spursfan323]

i would suggest you reduce the heating times by 10 mins in turn each session more and more until its noticeable then increase one session by 5 mins altrenating between the three untill you get the best compromise with possibly one or more small increases till the balance is correct

thanks for the suggestion, although it sounds too laborious and finicky for a perfectionist like myself... we'll see...

 

[big-all]

the point is once you know the minimum you can work with you can decide whats is a price you want to pay for extra comfort

if you save say £10 a month on your fuel bills it wont be worth the effort if you get complaints
but if you have a £40 saving a month get complaints then giving £10 back and saving £30 its worth the trouble

the only way you will find out is by trial and error

my total lighting bill for my whole house is between £10 and £18 ---------for the whole year less than the weekly cost of some houses`
i have 95% led lights and use between 28 and 60 w per hour for the whole house that is between 3 and 5p a day for around 10 hrs for all lighting

its mostly 6w bulbs[60-70w equivilent] great for most 10 sqm areas but 10w give a better light for sitting rooms 75- 90w are better

when i first bought led bulbs 2 or 3 years ago they where poorish output but newer versions are more efficient

the point i am really making
is you start with a 3/3.5/4.5/5 corn type bulb the output is poor to just about ok but you stick with the bulbs as they where around 5 to £10 each so an investment
you then as better bulbs come along replace the ones that most bother you with better bulbs and trickle down the bulbs to replace lower powered untill no bulbs bother anyone
yes it take effort and time but eventually for little or no cost in your case with a little effort you save money

 

[D_Hailsham]

If the cylinder is being maintained at 55C, the stored water will be safe. Even at 50C the bacteria will not grow and multiply, and your incoming supply should be already be safe.

Personally, I would prefer the bacteria dead, no matter how few there are.

The relevant temperatures are:

[code:1]
70°C to 80°C - Disinfection range
66°C - Legionella die within 2 minutes
60°C - Legionella die within 3 minutes
55°C - Legionella die within 5 to 6 hours
20°C to 45°C - Legionella multiply
20°C and below - Legionella are dormant[/code:1]

I recently read something (can't find it now) saying that the maximum permitted supply temperature from the cold water mains is 25C.