Economical use of a hot water tank

Shrimply

Hi guys,

Wondering if anyone can help or offer advice. I recently moved into a flat and it’s the first time I’ve lived alone and I’ve never had any experience of a boiler that wasn’t a combi. But this flat has an old gas boiler (Ideal Mexico 2) and a hot water tank, which is not huge but does not have its own thermostat, it is also not as well insulated as it could do to be, looking at the flat energy report (which is otherwise very positive)

Based on how I believe these things work, I’m really struggling to justify filling the hot water tank for running hot water. My friends have been mocking me for this, but while running hot water would be very nice it all seems a bit daft. I’m hardly in the flat, the shower is electric and apart from running hot water I use maybe a kettleful of water a day to wash dishes, and a kettleful every couple of mornings to shave with.

While I’m struggling to find a lot of information about how much energy it would require to fill the tank etc, I can’t see how it can possible be more economically than boiling the kettle.

I’ve noticed that while the boiler is lighten (which it will be once I have the heating on) it appears to keep a small tank of water above it warmish, which takes the chill of the running water, for washing hands etc

I’m just wondering if anyone can offer any help or advice, am I being stupid about this? It just seems an awful waste of energy to fill a whole hot water tank for what little hot water I use.

Thanks

Pincher

I assume you don't want to convert the shower to use the cylinder hot water, and spend hundreds. Just lag the cylinder better, and run the boiler 15 minute a day. An 18kW boiler will use 5kWh, at 3.5p per kWh. That is 17p a day.

CashStrapped

If you are hardly in the flat, and do not use much hot water, and you are happy with how you live at the moment then thats fine. It is probably cheaper than using your tank.

It is not wasteful to fill and store hot water in a tank as long as you know you are probably going to use it and/or it is a well insulated tank.

Does it have a loose jacket on at the moment? Or is it just bare copper?

You can do a test yourself to find the cost. Record the gas meter, fire up the boiler and heat the tank (may take 1 hr or so), then take a meter reading.

Out of interest, have you started using the heating yet? If it is an old heat only boiler, you may find when you use the heating, the tank gets hot anyway, depending on how your controlls are set-up.

JJ_Egan

Not worth it if you are just using a few kettles of water .
I heat the tank when i know i want a lot of water and it tends to last as tank has poly jacket and a few old cushions / pillows shoved around .

netwizzy

i just tend to schedule things i need hot water for at a certain time of the day. much like yourself, i don't use too much hot water, so i leave my boiler off and only turn it on when i need it once a day when i take a shower. but if i need to do the dishes (and the water is really, really cold), i just do the dishes right after my shower or before. i'll do this 90% of the time, and only leave the boiler on when i absolutely need to have hot water right away.

Shrimply

Thanks all,

I should of mentioned the flat is rented, so I'm not able to do any major re-plumbing. It's nice to know you generally don't think I'm crazy.

This is probably going to sound dim, so I apologise, the tank isn't bare copper, it's the green colour that I represent with hot water tanks, I don't know what sort of coat this is though. But it says on the energy report that fitting a better insulated one would be advised.

I haven't started the heating for any length of time yet, but they are two separate systems right? I have separate setting the heating and hot water. I was under the impression that the water in the central heating system would never go anywhere near the hot water tank.

Am I being stupid though, in my head the hot water cylinder is always full, so if you only have the boiler on for a short while you will get lots of luke warm hot water, not a small amount of actually hot water. If this is wrong I guess it makes less sense to boil kettles, if you can more or less only heat the hot water you need.

I promise I have some time trying to research the system although I'm sure it doesn't seem that way.

Pincher

Shrimply wrote: »

I should of mentioned the flat is rented, so I'm not able to do any major re-plumbing.

But it says on the energy report that fitting a better insulated one would be advised.

Out of season clothes in plastic bags. Old curtains. Newspaper.

Shrimply wrote: »

Am I being stupid though, in my head the hot water cylinder is always full, so if you only have the boiler on for a short while you will get lots of luke warm hot water, not a small amount of actually hot water. If this is wrong I guess it makes less sense to boil kettles, if you can more or less only heat the hot water you need.

Fully heated, the hot water is ~65 degrees, which will make a baby cry, and the social services will take him away. You end up turning the cold knob to cool it down anyway. If you have 40 degrees water, all you have to do is turn the hot knob, which actually saves time.


You can push the BOOST button, but they are usually 1 hour count down timers, so if you forget to switch it off, you will end up with a full tank of fully heated hot water.


With the programmer, you can set a smaller interval.

matelodave

It's likely that your hot water tank is connected to the central heating system and will be heated by the central heating boiler.

It may also have an immersion heater (usually a round thing about 3" in diameter either in the top or side of the tank with a cable coming out to a switch on the wall).
Using an immersion heater is generally more expensive than using the boiler to heat the tank but if it's top mounted and you only need a few gallons of hot water then it's probably cheaper to use it instead of the central heating which will try to heat the whole tank. Make sure you turn it off though when it's not required.

Regarding heating & and hot water from the boiler a lot will depend on how the system is configured.
If your tank has a thermostat you should be able to have central heating on without heating the tank otherwise you will end up with a hot tank when you run the heating. You need to check if the tank has a thermostat, if there's a motorised valve in the pipework (usually near the tank) and whether you've got a room thermostat somewhere. You need all three to run the heating independently from the hot water.

An extra insulation jacket can be bought from B&Q or Wickes if you feel your existing insulation is inadequate. Alternatively an old quilt or sleeping bag can be wrapped around and over the top of the tank.

sniggings

Will be cheaper the way you are doing things, but if it starts getting you down, I know it did me, having to boil kettles for dishes etc, then heating the boiler is not as expensive as you think, buy a good jacket for the boiler and heat the tank once a day and it'll probably cost 20p for a tank full.

Shrimply

Thanks again guys,

I've finally given in and turned the heating on tonight but if anything it's really left me with more questions than answers. The good news is it works, and heats the flat quickly.

matelodave wrote: »

You need to check if the tank has a thermostat, if there's a motorised valve in the pipework (usually near the tank) and whether you've got a room thermostat somewhere. You need all three to run the heating independently from the hot water.

So I don't know about the motorised valve but the tank doesn't have a thermostat and there isn't a room themostat. I can say with certainty thought that the hot water tank does not heat up when the heating is on.

My main concern is that the pilot light in the boiler seems very large compared to what I would expect, and have experienced with combi boilers in the past.

I also don't really understand, even when there heating and hot water are off the boiler seems to constantly switch on and off to heat a small tank of water that sits at the top of the boiler, and this and the pipes exiting the boiler are always hot. Is this normal? ( the boiler is a Ideal Mexico CF40). It seems like it's wasting gas and achieving nothing? Am I missing something?

Richie-from-the-Boro

Installers maintenance manual

Use guide