Cylinder advice

BobT36

Had a combi in all the houses I rented for years, just with handset shower heads.
Moved into a house with a system boiler / unvented cylinder setup (Ideal Logic Heat H24 Boiler with Prostel 150 S150PL 146l Cylinder). 
Bit of an ancient thermostat (Off, On, Timer, Once) with an old dial for the heating temp.

Not really had time to read up on how to use it "properly" yet, but not finding it fun. Had a few showers where the water ran out midway, so having to put the hot water on well ahead of time now. Currently just manual control.

Large-ish 4 bed detached, boiler in kitchen, cylinder in upstairs bedroom cupboard, 2 bathrooms, 200mm rainfall shower heads.

I thought the point of a cylinder / system boiler setup was to manage multiple showers at once? 
This one can only store enough hot water for ONE shower, one pot wash, and a few handwashes in the day. It certainly wouldn't be able to manage two showers at once (yet to test pressure but presume ok) as both would be without hot water halfway.

Irritating having to remember to switch it on (or guess with a timer), and I hate the anxiety of wondering whether I'll run out halfway through due to not being able to see how much is left.
This takes me back to when I was a little un' and "having to put the hot water on".

• Are there no cylinders / thermostats / boilers with indicators / guages on how much hot water is left? (Such as "10 mins worth at the current flow")
• Is there not a better setup, where water is heated and stored in the tank, but when it runs out a combi-style system kicks in to heat on-demand (albeit at lower temp / pressure)?
• Which is cheaper, heat on-demand with combi (set to eco mode so only kicks in when water demand), or heat with system and store in cylinder? (And potentially heating too much, which gets lost throughout the day or too little and run out).
• Maybe I just need a bigger cylinder? (Space permitting). 

Suddenly the pressure dropping when someone flushes a toilet or something in my old houses, wasn't too bad..

housebuyer143

If you have just moved in it will take a bit of trial and error to get it right. I like you, came from a combi to a tank set up. 

Firstly, your tank is a little small for a 4 bed house I personally think. I have a 170ltr tank and I can get about 25-30 mins showers out of it before it runs cold. Half that if running two at once. If all your family take long showers at the same time then this set up isn't likely to work for you with the tank you currently have. 

Secondly, you need to work out if you either want it heating all the time or certain times a day? Do you use water constantly? If so, you can leave it on and it will top up as and when needed and you are less likely to run out. I can heat mine for 30 mins in the morning and 30 in the evening and that will fully heat the tank and we never run out of hot water for the most part, although planning does come into it, because if my son and husband just had a shower and I then want one I will go and switch the water on and then wait 20 mins because I know I won't get one out of it as well. 

As far as I know there isn't a combi back up system. If you have a big family, have the space and really want a tank you can get much bigger ones 300ltr, which obviously will double the amount of water you can store. 

In terms of what's cheaper, I can't really comment but I personally like my tank. When the boiler went down recently we still had hot water and two showers at once result in no lost pressure like it does a combi. 

You might just need to do some tests to make the current set up work for you based on how your family plans to use the hot water. 

ComicGeek

With modern boilers there is really no need to programme short periods of hot water heating. Just have the hot water programmer on all day, and it will make sure that the cylinder gets reheated. The boiler stops when the cylinder is at temperature, so it's not running any more than when you're trying to set short periods of operation.

The hot water programme is not for when you want hot water, it is for when you want to heat up the cylinder. In the old days hot water cylinders used to lose a lot of heat so you would wait until you needed it to heat it up - modern insulated cylinders lose hardly any heat over a 24 hr period so no need to wait.

I have a 180 litre cylinder, which is slightly bigger than yours but still fairly small. I have our hot water programme running from 8am to 10pm, all year round. If you have early showers in the morning, then set the start time 30 minutes before the first shower.

tacpot12

I agree with ComicGeek's assertion that a system with a cylinder thermostat could essentially be left to heat the hot water all day and it would not be too inefficient, but in reality, you will save a little by having the hot water programmed to be on from an hour before you might want to have hot water available, and to not be heated after the latest time you might want there to be hotwater. Also if everyone is out during the day, you can also turn the hot water heating off until the earliest anyone might be home. 

I'm not away of any sort of meter for your cylinder that would tell you how much hot water you have. Part of the issue is that such a meter would need calibrating for the flow of one shower, and would be instantly wrong if two people started to shower at the same time. However, as a by-product of having Weather Compensation fitted to my boiler, I now have an indicator light next to the boiler that shows me if the cylinder thermostat is calling for heat. I find this very useful as if the light is off I know I have a full tank of hot water. This was installed by running a mains cable from the valve that controls the flow of heating water into the cylinder to a position near the boiler and connecting a 240V LED to it. It's an easy job for an electrician, although it might be disruptive if there is no easy access to a route for the cable. 

Albermarle

We have a 210l unvented tank for a 4 bed house with currently 4 adults living there. Gas boiler. 
Typically there will be 3 showers a day, or 2 showers and a bath.
Little hot water used for anything else apart from hand washing.
The hot water comes on for 35 minutes in the early morning ( before the heating ) and for 20 minutes in the afternoon.
The hot water never runs out. At worst it gets slightly less hot.

OP I think the issue could be the length of showers you are having? The recommended time to save water/ energy is maximum 4 minutes. We have had posters on here having showers in excess of 20 minutes ( or family members doing that) In that case of course the hot water will run out at some point.

Or you are just not heating the hot water for long enough. Also if it runs cold, it will take longer to heat up than if there is still warm water in the tank from before. As already said the heat loss from a modern hot water tank is pretty small.

Separately we have an issue if two people have a shower at once, but that is due to low mains water pressure, which can affect combis as well.

twopenny

How long are these showers?

I have a small tank and it will fill the bath half way. So 2 shortish showers I guess.

Would it be cheaper (along with some suggestions above) to have an electric shower? Yes, expensive to run but for short showers it's fine on cost.

BobT36

Interesting.. So it seems besides the smaller tank, my experiences are sort of normal and it's more of a "get used to it" (having a tank), sort of thing. And either indeed setting the timer for morning / afternoon, or just having it on permanently. 

Showers around 10 minutes but can go to 15. I suffer from eczema so need to give my skin a good rub. No idea how you can clean yourself well in 4 minutes! Personal preferences, though. 

I did a bit more research and found ONE brand that seems to do some sort of "Guage": https://www.mixergy.co.uk/
Apparently it's no-where near as good as it says (of course, typical marketing), and for heat pump / solar a standard, correctly set up Vailant tank or something would be better. Apparently it's not that bad when ran with a gas boiler though. 


Currently I just hate the anxiety of wondering if I'm going to run out of water again halfway through a shower lol, which tempted me to return to a combi, seeing as we're not getting the benefits of "being able to run two showers" which would be the point of a tank, anyway. However it sounds like if we upgrade the tank to a better size, we might actually be able to realise that benefit, plus working with the timings better (or just running it 24/7 unless out). 

FreeBear

BobT36 said: Moved into a house with a system boiler / unvented cylinder setup (Ideal Logic Heat H24 Boiler with Prostel 150 S150PL 146l Cylinder). 
Bit of an ancient thermostat (Off, On, Timer, Once) with an old dial for the heating temp.

The Ideal Logic appears to be a "current" model introduced in 2016. So reasonably efficient condensing boiler. It would be well worth upgrading the controls to something like a Drayton Wiser 2 channel with a thermostat on the tank. You might need to make a couple of small changes to the plumbing to get priority hot water. But being able to program different CH temperatures throughout the day coupled with intelligent hot water heating, you could save 10-15% on gas.

Southend_2

Is your hot water temperature set point too low? If you store the water at a higher temperature, each shower will use less from the tank than if stored lower. 

Albermarle

Southend_2 said:

Is your hot water temperature set point too low? If you store the water at a higher temperature, each shower will use less from the tank than if stored lower. 

It is a good point, but you would have to be careful that the hot water did not scald anybody out of the shower/tap. For that reason it is not recommended not to have the HW too hot .

The main problem is that the OP is having rather long showers, combined with only an average sized tank.

Kiran

Albermarle said:

Southend_2 said:

Is your hot water temperature set point too low? If you store the water at a higher temperature, each shower will use less from the tank than if stored lower. 

It is a good point, but you would have to be careful that the hot water did not scald anybody out of the shower/tap. For that reason it is not recommended not to have the HW too hot .

The main problem is that the OP is having rather long showers, combined with only an average sized tank.

You don't need to worry about the scalding issues with a mixer as they have built in blending valves, you do have to be careful on any taps that feed directly from the hot water though.

We've got a 200L tank that heats up to 55degrees. it then used to 2 adults to shower, 2 young kids to get ready for school and usually 1 adult and 1 child shower in the evening and that still leaves enough for washing up etc. We use our immersion to heat the tank as we use the solar, we do have solar thermal which is effective from about March/April until October so that does a decent amount but in the winter months we only have it heating for a couple of hours.

I'd check what temperature you are heating the water to, and also if the volume is not sufficient, have the tank reheating during the period you are likely to be taking showers