Hot water-on a timer or on constant?

[mckenzie]

We usually have the hot water on a timer, just like the central heating. It comes on first thing, goes off when everyone has left for school / work and comes back on in the evening. At the weekends, it's on all day.

DH has just had a cold shower because we forgot that its bank holiday Monday and not the weekend and so now he wants to leave the hot water on constant so that he never has a cold shower ever again.

I say that it's a waste of energy and money but he is saying that it's proven that it's actually more cost effective to keep it heated all the time rather than allow it to cool and then re heat it.

Anyone know the facts about this please?

yes, more modern washing machines only have cold fill. I believe it is because they use so little that even the hot pipes would still run cold for the first gallon or so.

If you have a cylinder, then even in a rented home, make sure it has good insulation - either factory-fitted foam, and/or one or two red jackets, which are currently heavily subsidised and can be bought for £3 - you will get your money back in saved energy in a matter of weeks. Some foam pipe lagging will also save you money.

We do have a jacket on the tank and insulation on the pipes, and had a new boiler fitted last year after ours died a death.

We have a 12 year old 'estate' house. We recently put a megaflo in and I keep the HW on all the time- the main problem we have is with the timer- it's a older style one that doesn't allow you to set different days on it, just on/off/on/off.

Can you easily change it to a digital one where I can change it for each day to reflect the days I'm at home, at work or weekends?

yes

depends what make and model it is, sometimes they are on a standard backplate and a more modern one just plugs on, but it is essential to check the connections on old and new even if it is the same make. The main makers provide a conversion chart for popular programmers, and in my experience will send you a special chart if you have an unusual programmer and you tell them the old and the new one.

ACL/Drayton/Invensys are the same company, and also make some programmers branded with the boiler makers name, so are very common and usually quite easy especially if old and new are both made by them. If you get in a muddle a heating engineer will be able to do it. You can also get a programmable room stat that enables you to set different temperatures for different times of day and different days of the week, and this too will swap for the old room stat very easily. Heating the house uses much more energy than heating the water so is more urgent to get right.

Honeywell, Danfoss and Siemens are other good brands and might or might not be equally easy.

Many thanks- where do you get timers from?! Online?

Ours is a Potterton miniminder E.

I remember them.

I think it had the standard ACL wallplate. There's a screw under the bottom. After disconnecting the power, you slacken the screw and pull out the bottom, it tilts away from the claws on the top where a plug on the timer fits into slots on the backplate.

An ACL Drayton Lifestyle LP722 would replace it, ask the makers to send you the connection conversion diagram and ask if it fits the same backplate, if you like the look of it. It is vital that the connections are correct, they can be moved if not identical. www.draytoncontrols.co.uk/LPProgrammerRange.aspx Programmer means separate control of heating and hot water; timer means single-channel heating control only (as used on a combi). The "7" in 722 means you can programme seven days into it.

Make sure you don't buy the Si version, which has a feature that stops it working every year or so to force you to get the boiler serviced.

Personally I wouldn't have a wireless one, it just gives an extra complication that can go wrong.

Here are some examples

The ones with a rotating clockface and a couple of buttons are still made because they are so intuitive and easy to operate without needing the instructions. I put an SM2 in for my old mum because she couldn't work the 722.

PigletJohn I'm not understanding much of that but my God you sound impressive!

PigletJohn- last year I asked the question on DIYnot and apart from some snidey remarks, I got no useful reply at all- yet here we are on MN!

DH often gets me to ask questions on here as we usually get answers.

Thanks very much for yours!

I can offer the definitive answer to you, as a heating engineer of many years and a holder of a BsC in environmental science...:
Piglet john is 'spot on' basically, i have just left an old lady with HW on permanently, and here is why:, she has a modern system thats working well, her cylinder 'tops up' with heat when its dropped a few degrees, (not everytime a little bit has been used), which could be a whole day without the boiler firing...as fizzylemonade has already pointed out, the heat loss from cylinder is negligible, the heat loss from pipes to boiler and boiler itslef can be significant, but only in the summer, in the winter that's useful heat to the house...
The reasons to leave it on are obvious, you'll always have all the hot water you need, just incase your kids want back to back baths at 10 am.., the boiler will finish reheating the first bath before you can wash, and drain it... its a 'luxury' that costs pence per year, so treat yourselves!!
BUT.........
there are many flawed systems where the boiler fires for the whole time whilst the HW is on, these are amoungst others too complicated to mention, : old systems without cylinder thermostats, and new systems where the condensing boilers cooler flow temps can cause a situation where it just can't satisfy the 60+deg that the cylinder wants, if you have one of these (does it keep whirring all the time!?), then you do need to use it for a bit in the morning etc..., but that's no you knowing how others can save money, you have a crappy system that needs an engineer to sort it!!
one classic myth that we are constantly debunking is;, leaving the heating on 24 hrs saves money!!, also the 'put the radiators under the windows', theory , both total BS..
I cant beleive people wade in here with nothing but a hunch!! your getting in the way of valuable info, and mumsnet, i dont care that this thread is over a year old, that is irrelevant!!!

so i feel that i should add some extra info for those keen to learn, and save gas usage..
if you have a condensing (steam from flue), boiler that is just heating hot water, (in summer for example), its best to have it as hot as it goes, as it will heat cylinder better/faster more economically..
conversely, when using heating, you should have it as low as possible for reasons of free latent heat from the condensing, and also so that a more even room temp is maintained... so here the problem, if you turn it down in the winter with heating on, it sometimes cant heat the hot water, and will try all day long, (or take agonisingly long for the last few degrees),causing the problems mentioned in this thread.... if this the case, then best to only heat HW with heating for a few hours here and there...
easy to tell:, leave hw on 24 hrs, it should only fire up for 10 15 mins here and there , and not for hours if no one has used any....