Hot water storage tank - do you let your heating run all day?

[maggiethecat]

Before moving here never had this type of heating where water from tank is heated up. British gas service engineer has said that it's better to keep heat for taps running all day rather than on timed programme (unlike my central heating which is timed).

Does this sound right?

[ilovepowerhoop]

it is a myth that it is more economical to leave it running all day. My hot water is on for 1-2 hours twice a day and we gave sufficient hot water. I dread to think what it would cost to have it on all the time.

[ChippyMinton]

I'd say it depends when you need hot water. My washing machine and dishwasher are both cold-fill so we really only use hot water in the bathroom.

Mine is on a timer for the evenings (kids baths/showers) then stays on for a bit to reheat. Then comes on early morning for showers. The tank is well insulated so the water doesn't cool down much overnight.

If I need hot water during the day, say if a DC is doing a sport or coming home from a camp, I just over-ride the timer.

[maggiethecat]

I've got into the mindset that whenever I turn the tap on I should be using hot (not necessarily boiling) water. But I've been re-thinking this.

I'm going to try timed for when we need it at night etc and see how it works!

[lalalonglegs]

We have a Megaflo and it is on for half an hour in the morning and half an hour in the evening and that is more than enough.

[specialsubject]

he's not an engineer, he's a gas salesman!

your tank should be properly insulated so the water stays hot. As an example, for those who want baths/showers in the evening, hot water should be heated just before those and then reheated as necessary until all ablutions done. Whatever is left should then remain hot until at least lunchtime the next day.

any leftover washing up waits until the evening.

[LilMissSunshine9]

I have storage tank I heat my water for 30 mins in the morning and 20 mins in the evening - but there is only one of me so for me that is enough hot water for me per day. Don't run it constantly that will bring in a huge bill!

My timer is set to heat water at 6am so I have hot water for a shower when i wake up at 7am then it heats again in the evening at 7pm so washing up and shower at night.

The amount of water is also important because your storage tank only holds a certain amount of water which is kept hot if you go through that volume then you need to heat more.

[PigletJohn]

It is a hot water cylinder not a tank. A tank is open at the top and more accurately called a water storage cistern.

It should be well insulated (what colour is yours?) and will stay hot all day losing little heat.

There is a slight advantage in boiler efficiency if it does not run for two minutes to top up the cylinder every time you fill a basin.

Depending on how big your cylinder is, and the rate at which you use hot water, it will generally not run out if you heat it for an hour before you get up in the morning and an hour before you come home at night. A bath will use about a cylinderful of hot water but if the boiler is running it will be reheated by the time you have finished and towelled off.

A modern boiler will heat a modern cylinder in about 20 minutes and give about 100 litres of hot water. Unvented cylinders such as Megaflos are usually bigger. Older boilers and cylinders will take longer, sonetimes this can be improved by converting to fully pumped, if it takes more than an hour.

An electric immersion heater is far less pwerful than a boiler and will take some hours to heat a cylinder.

If your cylinder and hot pipes are not well insulated you are tipping money down the drain.

[PigletJohn]

P.s.
If you leave your HW turned on 24 hours a day and the cylinder and pipes are well insulated, heat loss costs will be trivial. It is running the boiler for multiple short periods that wastes energy. For this reason a cylinder can be more efficient and economical than a combi but you will only notice it in summer, when you should be using less than a cubic metre of gas a day.

[maggiethecat]

I have heeded all your good advice and we are having adequate supply. Don't know what that will translate to in terms of energy consumption but it seems more sensible.

Piglet, we have 2 green cylinders - not sure if insulated or not.

[PigletJohn]

green is a factory-applied rigid foam insulation. It is not quite as good as the later blue, but it is good. You will save a little more wasted energy by insulating further. As you have a green cylinder I would start by insulating the hot pipes. If you happen to see a red cylinder jacket at a good price it will save a bit more.

It is unusual to have two cylinders in one house. Is one of them half-sized and perched on top of the bigger one?

Megalfos are white; they are extremely well insulated, and (certainly the newer ones) have a very efficient heating coil inside so they heat fast.

If you have a look at your gas meter once a week or so you can track your average daily usage, which will be very low in summer.

[maggiethecat]

the 2 cylinders are side by side with what appears to be an interconnecting metal rod.

Will check usage

[PigletJohn]

that's unusual

what size are they?

how many bathrooms have you got?

the connector is more likely a copper pipe, is it hot?

[maggiethecat]

about 110 cm high and about 120 cm circumference; one bathroom and a downstairs shower.

copper connector warm although main piping that leads from one cylinder to another, vertical pipe is very hot.

[PigletJohn]

each sounds fairly small. They are usually about 18" (450mm) to 24" (600mm) in diameter, excluding the insulation, about 30mm thick.

could it be there was not room for a single bigger one? You don't have solar heating, or Economy 7 electrical?

is there a (hot) copper pipe running from the bottom of one to the top of the other, rather than them appearing to be in tandem?

here are some more typical sizes...

[PigletJohn]

I reckon yours will be 400mm diameter, and probably 1050mm tall.

that gives a capacity of 114 litres, which is about a bathfull. If doubled up, depending on how it is done, you could run a power shower (which is pumped, and very extravagant with water) as well

Mine is 450 x 1200, and I think smaller would be too small for a decent bath if you wanted to wash up or something at the same time, so perhaps your second cylinder was needed because one was insufficient.

[maggiethecat]

think space may have been issue. no solar heating; dont know about economy 7 electrical.

some things in this house were done in a very odd way!