Sex and boilers

[Tootingbec]

Sorry, no sex, just needed to get some attention to my question! We have just moved to a house with a boiler and hot water cylinder system. Having only lived in properties with a combi boiler (i.e. on demand hot water) what is the most cost efficient way to heat the water?

I remember in my parents house they used have the hot water timer set to 'on' just twice a day. But the people we have bought the house from said they just kept the hot water timer set to 'on all day' - I presume the water stays hot in the tank and the boiler would only kick in if it dropped in temperature i.e. it is not like leaving the heating on all day!

Anyone out there who can help me in my boring question?

Thanks all!

Well you got me!

I believe, though this is only from a wife of a plumber so I may be wrong, that it is more energy efficient to leave the hot water on all day and let it top up as and when, than to heat a whole tank of water from cool twice a day. Certainly we keep ours on all day.

It is more efficient to have hot water and heating set to come to heat the water as required than to have it constantly on to maintain the temperature of the water/air. The easiest way to explain it is to imagine leaving the kettle on constantly even though you only have a few cups of tea a day. The better insulated the tank the less difference it will make, but it is still less energy efficient.

I think it's more energy efficient to have the heating on low all day so you dont have to heat up the whole house from cold.
But I am not sure this applies to hot water as the tank is relatively small, ie its not like having to heat the house up.
I set ours to come on twice a day as we dont use that much hot water, esp not in the day.

But I am not sure what is best in terms of energy efficiency, sorry.

Thanks all for the messages so far - you have highlighted my conumdrum! I can't work out if it uses more gas to heat the tank up twice a day or have it on constantly.

Hate the water tank thing! I wanted to top up my bath last night with hot water but of course I couldn't because I had used up all the hot water!

You mean you've got a cylinder, don't you? (or perhaps a Megaflow or similar?)

Most important thing is to have it well-insulated. Depending on age, it is going to be bare copper, with a red jacket; or yellow rigid plastic foam applied in the factory; or green foam, or blue foam. You can add one or even two red jackets over the top of you are obsessive like me, they are subsidised so only cost a few pounds at the moment, otherwise about £12 good grief it's only £2.99 today You should also insulate all the hot pipes, especially those between the boiler and the cylinder, and the one coming out of the top of the cylinder, with Climaflex or similar, the BS grade if there is room (it is as thick as your arm). While you're at it, do all the pipes in the loft, or unheated spaces such as garages and under the ground floor if you can.

A well insulated cylinder loses very little heat, somewhere between 2p worth and 8p worth of gas per day depending on whose calculations you believe. The water will stay hot for more than 24 hours. Set the cylinder stat for between 50C and 60C which will prevent growth of micro-organisms that like warm water. The boiler stat has to be set higher than the cylinder.

Then all you have to do is to set the boiler HW timer so that it does not keep running for short periods to top-up the cylinder (this is inefficient). A modern boiler can take a modern cylinder from all cold to all hot in about 20 minutes, so set the HW timer to come on half an hour before you get up in the morning, and half an hour before you get home at night (or before you have baths and showers if different) and to go off after you have finished having baths and showers. Your cylinder will typically hold more than 100 litre of hot water so that will usually be ample for washing up and so on during the day. You can tinker with the timer a bit if you feel the need. Most timers have an "advance" or similar button that will start the next cycle earlier, just once, without having to change the settings, and have an "all-day" setting that you can use e.g. at weekends when people might be having baths and showers outside the usual times.

p.s.

In the adverts, "Bylaw" or "Regulations" pipe lagging means it is to the BS for pipes in unheated spaces. The other stuff is thinner. Your pipes will be either 15mm or 22mm external diameter (or sometimes 28mm if you have an older house with an older HW system) and you must buy the pipe insulation to fit. You can cut and mitre it with a breaknife. Tape up joins and elbows to prevent it gaping or falling off.

Thanks PigletJohn - are you a plumber or just an obessive about heating and hot water like me?

I will check the jacket and pipe lagging as you suggest and will adjust the timings to be on twice a day. It is a relatively new boiler (4-5 years I think) so sounds like it should be pretty efficient at getting the water hot.

I'm barmy.

No advice but I just had to say what a brilliant thread title

When can we put the sex aside and get on to the boilers?