Less hot water than usual

[psd99]

Hey guys
I Got a 250 litre megaflow tank worked ok for the last 4 years.

in the last few weeks i have noticed that the hot water is running out quicker than usual...

The system was installed about 4 years ago and I just upped my hot water times from 2 x 1.5 hour spells to 2 x 2 hour spells

Despite doing this. Person number 1 has a bath and by its the 3rd persons time the water goes totally cold. This was not occurring say 2 months ago.

what could the fix or problem be for this? Hope it is nothing too expensive to fix

 

[psd99]

So let me define the scenarios....

person 1 has a shower
Person 2 has a bucket bath
Person 3 loves a full bath
But in the past this seemed to all be ok
Recently once person3 tries to fill the bath up the water is cold and then the hw has to be turned on


I also have an immersion option and recently been using that + google hot water to heat the water quicker
Not sure if i am getting that right though.

 

[psd99]

So once all the hot water ran out tonight

I put the boost on for 1 hour but the boiler fired up for around 40 minutes to heat the water up and now the water is very hot
Google app suggested the hot water was still on for the last 20 mins but the boiler light was off as clearly the water was hot enough

does 40 mins of the boiler firing up for a 250litre tank
Sound long enough to u?

So in theory i put the hot water on for 4 hours a day and it looks like it would only heat it up for 40-80 minutes in total. Mmmm

let me know what u all think...

 

[psd99]

Ah right that is interesting

so what kind of schedule should I be setting?

Imagine it was set 24 hours a day for example

person 1 shower at 5pm
Person 2 530
Person 3 6pm

are u telling me that if the schedule is set 24/7 then while that person 2/3 has a shower/bath water will regenerate and reheat once it gets cold?

at what point will the boiler actually start to heat the water if in the above scenario?

 

[psd99]

But also another point is that this did not happen before
Just the last few weeks but yes i could certainly increase the hot water times like to run much longer periods

 

[psd99]

so what does your nest/smart device water schedule look like?

 

[psd99]

I have a combi boiler so not relevent.

With a system boiler like you have the hot water should be on constant and it will only come on when it needs to refill the tank.

thanks I have implemented your suggestion and hopefully it will make the difference.

 

[psd99]

Hi,
You’ve had your answer but we also have a system boiler and megaflo. The tank is so well insulated that the cupboard in which it is installed is only mildly warm. We just leave the water heating on 24/7 and it just works totally seamlessly and never “runs out” regardless of any usage which we have ever thrown at it...the tank doesn’t lose much heat at all as above.

based on your schedule of 24/7

how many hours a day do u think the boiler actually fires up to heat the water?

 

[psd99]

This wont be much help on that question as it is very hard to tell at this time of year, as it is nearly always on to try and heat the house

As close as i can get is very vague but probably for an hour or so after using lots of water, but i guess time to run will depend on the power of the boiler too....it really doesnt run for long, but given the lack of loss at the tank you may as well just leave it on and do its thing

yes I have adjusted the schedule now
I think I agree on here about the immersion it should be there for last resort or say we need the water in quicker time!

I was worried If I left the water on 24/7 then the boiler would keep running but obviously this is very untrue and the water only heats up if and when required.

 

[psd99]

A Megaflow does not "fill" from the boiler. (I am presuming/hoping this is a typo) Otherwise your bath water would be less than desirable.
Any replenishment comes from the cold water supply. The water is heated up via a coil inside the tank which the boiler circulates water through. Its a lot colder coming in at this time of year, which means the boiler takes longer to get your water tank to temperature. So if you are going to use timed schedules, that's fine, just increase them from Nov-March.
If you want to pay more for your hot water, by all means, use the immersion. But its not as cost effective as the boiler. IMO the immersion is there as an emergency, and as such is switched off.
Ours is set up to heat hot water for 1 hour a day normally, with a boost option if necessary. At this time of year, I generally increase that to 90 mins.



Quoted, because its correct.

well I increased the timings from 2. x 1.5hr to 2 x 2 hour
but it didn't make a difference
this time last year I was all good that's why it feels like a mystery still.

testing 24/7 now though

 

[psd99]

That should be plenty, even at this time of year.

Possible simple scenarios:
Someone has turned thermostat down on the Megaflow.
Thermostat faulty, or turning off too soon.
Boiler turned down or set to eco mode, possibly after a service. (Speaking from experience)

I can`t think of anything else. Well, I can, but would probably require a visit from a plumber.

As for having on 24/7, that will be fine. I don`t think its the final solution, as something has clearly changed, but the boiler will only run when the thermostat tells it that the water in the tank has cooled enough to require heating.

Let me know the outcome. I am intrigued.

thanks yep set it 24/7 for now

I think it might be a faulty thermostat personally or there is talk online about sediment buildup impacting the amount of water in the tank that can be used for hot water.

but cba to spend extra money this time of year with xmas coming up

 

[psd99]

So if its a 250litre tank
How much of the 250 is actually usable?

would it be roughly 33%less or the full amount?