What is the most economical way to program the hot water timer?

[mjgreen81]

Hello all,

I just moved in to a new house with a reasonably old CH/HW setup. I've got a roughly 20 year old (regularly serviced) boiler and a large HW cylinder.

The heating control allows me to program the HW to come on/off twice a day. Initially I have programmed it to come on for a few hours in the morning and a few hours in the evening.

I noticed that when I went to give my baby daughter a bath at around 4pm (just before the evening switch on) I had relatively little HW.

This made me wonder if the way I have programmed it is the most efficient? Does the system use more gas if I let the water in the cylinder cool throughout the day? Or would it be better to program it to be on during a larger chunk of the day so that the system doesn't have to work as hard to heat the water?

I hope that makes sense. Any advice appreciated

 

[Old Salt]

Take a meter reading, set the programme as it is now and then take a further meter reading after a couple of days at the same time of day.

Then set the programmer to stay on and repeat the process to see which method suits you best.

You must take into account potential changes in lifestyle. Washing clothes, running baths or showers etc. and the longer you can leave it between readings the better your estimate of useage will be.

 

[Mottie]

We have a well insulated cylinder and I leave our hot water on 24/7. Just the two of us, both have a decent shower every night, odd bit of washing hands and pots that don’t go in the dishwasher, not been using the heating lately and we have a gas hob. For the last week our gas usage has been between 33p and 44p per day. Hardly worth putting it on the timer and running out of hot water.

 

[MeldrewsMate]

The most economical way is to leave it switched off, however if you want hot water I suggest that you time it to be heated just before it is required. The hotter the water, the greater the rate of heat loss.
Insulation is your friend here. Insulate the cylinder with an old quilt over the top (the top part gets the hottest), and properly insulate the hot pipe coming off the top of the cylinder for as far as you can.
Generally babies are bathed in cooler water than adults, so do the washing up before adults bathe, before baby gets his/hers.
It sounds obvious, but use as little hot water as you can - ie if showering, turn off the water flow once you're wet, and turn it back on only to wash the soap off. Give baby a shallow bath; a yellow plastic duck needs only 12.8mm of water to float.

 

[charlie275]

With a well insulated cylinder the difference may not be so much. Mine has two jackets on top of the foam insulation and generally is good for 24 hrs. It depends of course, but definitely start with that.

Some timers have the (hidden) option for 3 on/offs per day, if that would suit. It will be in the installation manual, unless of course it's obviously not, e.g. clockwork timer.

What temperature does the water get to if left on permanently? If it's too hot then it's relying on the timer to switch off. Adjust the cylinder thermostat to suit and set the timer for longer periods.

Generally I think it would be more efficient to would have both heating and hot water on similar program cycles, so the boiler and central heating circuit are not having to warm up more than necessary. What I do, though I have no idea what it saves, is set the timer program so that hot water comes on after end of a heating period. This resets the motorised valve (assuming Y-plan) so it is not stuck on consuming electricity (it otherwise gets pretty warm when in this state).

Also I have a timer on the immersion heater and set that to come on early morning for a brief period before the end of cheap rate (assumes a day/night tariff). Brief enough that it will cut out before the immersion thermostat (which have a tendency to fail)..

 

[Harry Bloomfield]

As above, the cheapest way is to simply leave it completely off, next cheapest is to only heat the water when you know you are going to need it/use it. Heating it up to only have it go cold in the cylinder is just wasteful. A well insulated cylinder means once it is heated, it will remain hot for longer, if it is not used.

Until a couple of years ago, I ran mine to produce a fully heated cylinder twice per day, then set it to do a boost if I was intending to have a bath during the day. I'm retired, in usually at home during the day. I then changed that to it being on from the morning through to the early evening. The difference in cost was negligible, but it was much more convenient. If you are out at work all day, then two heated periods seem sensible during the week days, on all day at the weekends when you are home.

 

[Bod ...]

We have a well insulated cylinder and I leave our hot water on 24/7. Just the two of us, both have a decent shower every night, odd bit of washing hands and pots that don’t go in the dishwasher, not been using the heating lately and we have a gas hob. For the last week our gas usage has been between 33p and 44p per day. Hardly worth putting it on the timer and running out of hot water.

I agree but you also need the hot water pipes insulated well within the airing cupboard.

 

[Mottie]

I agree but you also need the hot water pipes insulated well within the airing cupboard.

Possibly but with the hot water pipes insulated it would cease to be an airing cupboard. I’m happy to sacrifice a little heat to air our clothes. When we first moved in many years ago, we had a floor standing boiler in the kitchen with gravity hot water. The hot water tank was in the airing cupboard next to the boiler but it was fitted at the top of the cupboard. The 'airing cupboard' just didn’t work. I moved it down to the bottom of the cupboard and converted the system to fully pumped. Even now with a much better insulated cylinder, it’s no way as warm as it used to be.

 

[Bod ...]

Possibly but with the hot water pipes insulated it would cease to be an airing cupboard. I’m happy to sacrifice a little heat to air our clothes. When we first moved in many years ago, we had a floor standing boiler in the kitchen with gravity hot water. The hot water tank was in the airing cupboard next to the boiler but it was fitted at the top of the cupboard. The 'airing cupboard' just didn’t work. I moved it down to the bottom of the cupboard and converted the system to fully pumped. Even now with a much better insulated cylinder, it’s no way as warm as it used to be.

But the primarys from the boiler would do that. And you wouldn't have to make any sacrifice.

 

[Bod ...]

Regs state now that all pipes need to be insulated within a meter of the cylinder... The old girls don't like it...

 

[Mottie]

But the primarys from the boiler would do that. And you wouldn't have to make any sacrifice.

So just insulate the hot water out pipe?

This pipe?

 

[Harry Bloomfield]

For the last week our gas usage has been between 33p and 44p per day. Hardly worth putting it on the timer and running out of hot water.

My average was also 44p (with the standing charge subtracted), that was hand washing up once per day, a tiny bit of heating on the colder evenings, three baths, electric shower. Hot water set to be maintained hot from 09:30 through 19:00. Tank is insulated, but pipes were not originally - I have since added 'some' insulation.

 

[JohnD]

What colour is your hot water cylinder, and what size is it?

@mjgreen81

 

[Harry Bloomfield]

What colour is your hot water cylinder, and what size is it?

120L and yellow, installed around 1985. Yes, I know they are better insulated these days, but no problem so nothing to fix.

 

[Bod ...]

So just insulate the hot water out pipe?

This pipe?
View attachment 270856

Yes insulate that one and the rest of the other pipes will will air your clothes and waste you money. Also worth insulating the cold pipes to protect against condensation.