When is your hot water ON

whatatwit

Firefly wrote: »

Sorry, but I don't understand that bit.

Having Economy7 my immersion comes on in the early morning between 5 -6am and that's it for the day. I've reduced it from 1.5 to 1hr without noticing any difference. My tank is well lagged and it's in the airing cupboard.

Can you clarify the point above so that donuts like me can understand pls?

I take it to mean that the heater should be off before you start to use the water from the tank. Then you are heating a full tank that is static and once the tank it at the set temp, then the heater should switch off.
Whereas if you turned it on at 7.30 and started using the water at 7.45, cold water would be replacing the hot water drawn off and your heater would then be busy heating water again.

Is this any clearer, or have I caused more confusion....i know what i mean. :rotfl:

If, as indicated, you only heat water once a day, then your timer should be on for after you have finished using hot water, presuming you require hot water later on in the day.

spinningsheep

Well, we've just moved into a new house where the showers are electric and the hot water is very rarely used, but its on 24/7! reason being, the timer for the heating doesn't work. The previous owner told us she never used it, and just kept the heating on low all the time in winter and the water on low 24/7 year round. The thermostat on the wall is on 15 degrees and the theromostat on the boiler is set down to the lowest on there (no temp, just says warm) and the water tank is very well lagged, so the boiler hardly ever fires up at all. She ran it as a B&B before us, and even then she said the bills for the gas were very low. the house is very well insulated, plus we are using an open fire in the lounge that she never did, so we haven't had the heating on once this last fortnight, even when it has gotten cold.

Cardew

Firefly wrote: »

Sorry, but I don't understand that bit.

Having Economy7 my immersion comes on in the early morning between 5 -6am and that's it for the day. I've reduced it from 1.5 to 1hr without noticing any difference. My tank is well lagged and it's in the airing cupboard.

Can you clarify the point above so that donuts like me can understand pls?

Without going into the laws of thermodynamics, the greater the heat differential between water in the hot water tank and the air surrounding it, the greater the heat transfer.

So if you want to reduce losses from a HW tank, then the lower the temperature of the water in the tank, then the lower the losses.

To illustrate - a theoretical example:

1. You heat your water to your normal temperature, say 65C.

2. You switch the HW heating off.

3. You use every drop of the hot water in the tank.

4. The temperature of the water in the tank will now be no warmer than the temperature in the house.

5. You will now have no heat loss at all from the tank.

In practice, the more hot water you use(after the HW heating is off) then there is less HW in the tank and the lower the heat loss.

If you leave the HW heating on after you have had, say, a bath, then the water will be heated back up to 65C and your heat loss will be at a maximum.

However the point I was making above is twofold:

Firstly we are not talking big differences in cost as the heat loss is quite small, even for a tank at 65C.

Secondly, heat loss is something of a misnomer as the heat lost from the tank warms up the airing cupboard and rest of the house.

mute_posting

myozone wrote: »

10 minutes 8:30-8:40 then 20 minutes 13:20-13-40 - half hour a day cylinder stat set at ~50C

If you use the water for showering you may want to rise that stat slightly!

The stored water needs to be heated above 60 to prevent legionaires (sp?) bugs breeding.

Not that you'll be showering in 60 degree water but the water you blend with the cold water needs to be bug free - especially if you are spraying it over you in a fine mist (which is the perfect way to transmit the bugs btw)

HTH

MP

mark55man

Cardew wrote: »

Without going into the laws of thermodynamics, the greater the heat differential between water in the hot water tank and the air surrounding it, the greater the heat transfer.

So if you want to reduce losses from a HW tank, then the lower the temperature of the water in the tank, then the lower the losses.

To illustrate - a theoretical example:

1. You heat your water to your normal temperature, say 65C.

2. You switch the HW heating off.

3. You use every drop of the hot water in the tank.

4. The temperature of the water in the tank will now be no warmer than the temperature in the house.

5. You will now have no heat loss at all from the tank.
..snip..
.

Thanks Cardew.

do you mean at 4, when the tank fills back up again (which is after the water has been used and after the heating has gone off) then it will be at the temperature of the water that fills it, ie from the mains.

Cardew

mark88man wrote: »

Thanks Cardew.

do you mean at 4, when the tank fills back up again (which is after the water has been used and after the heating has gone off) then it will be at the temperature of the water that fills it, ie from the mains.

Yes that is correct.

Canucklehead

mute_posting wrote: »

If you use the water for showering you may want to rise that stat slightly!

The stored water needs to be heated above 60 to prevent legionaires (sp?) bugs breeding.

Not that you'll be showering in 60 degree water but the water you blend with the cold water needs to be bug free - especially if you are spraying it over you in a fine mist (which is the perfect way to transmit the bugs btw)

HTH

MP

Good morning: Safe hot water temperature advice is available from the IPHE

HTH

Canucklehead

mute_posting

Canucklehead wrote: »

Good morning: Safe hot water temperature advice is available from the IPHE

HTH

Canucklehead

Morning Canucklehead.

Just to clarify would you agree or disagree that the stored water should be kept above 60 (and blended to suit at point of use - i.e shower etc)

That document talks of the conflict of interest between stored water and usable water temps but doesn't (IMHO) give a definitive answer.

From my point of view, we were always instructed that it must be stored ABOVE 60 as it might not have been above 50/55 for long enough to kill the bugs.

MP

Canucklehead

mute_posting wrote: »

Morning Canucklehead.

Just to clarify would you agree or disagree that the stored water should be kept above 60 (and blended to suit at point of use - i.e shower etc)

That document talks of the conflict of interest between stored water and usable water temps but doesn't (IMHO) give a definitive answer.

From my point of view, we were always instructed that it must be stored ABOVE 60 as it might not have been above 50/55 for long enough to kill the bugs.

MP

Good afternoon: Minimum 60 degrees C for stored hot water...further info available in the Water Regs (1999) Guidance document .

HTH

Canucklehead

myozone

I feel we are all getting a little confused, It's really only a problem with recalculated water or stagnant water - I haven't heard of any cases with domestic water systems i.e. cold storage tank in a nice and warm loft space...