Less hot water than usual

psd99

psd99

psd99

Soldato
Joined
7 Sep 2008
Posts
5,597
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
 
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.
 
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...
 
Ideally with a megaflow system boiler your hot water should be on constantly.

The tank only holds heated water once that is depleted it tries to fill it's self from the boiler but if the boiler is set to timed it will fill with cold as it expects you to have the immersion on to heat the water between the boilers on and off times.

When the boiler is set to constant it will only heat the water as it is needed to fill the tank (it has a retro grade system to move the water around to keep it all at a set temperature) the tank in its self is only a holding vessel unless you have the immersion turned on.

To use the tank the way it's intended the hot water should be on constant or on between Persons 1&3 using the water. There for keeping the tank full of hot water. The tank is extremely well insulated to the point of a 2% temperature drop over 24 hrs (with a modern megaflow that is) with no extra heating.
 
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?
 
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 said:
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?
Click to expand...

That's just it the tank does not "get cold" its used up there for if the boiler is not on it cannot refill the tank with hot water so its feeds off the only other source the cold tap expecting you to have the immersion heater on.
The MegoFlow system is designed for high availability not storage and consumption as traditional tank systems were. Having the boiler on 24/7 does not mean that it is running keeping the tank at temperature 24/7 it only comes on to refill the tank when its needed possibly for as little as 5-10mins to refill the water used, having such a system on a timer as you have that is very restrictive is actually detrimental to the life expectancy of the tank and boiler. The Tank by its nature should be kept full and by keeping it full it will maintain its own temperature (water under pressure stays hotter for longer). By only running the boiler to fill the tank puts more strain on the boiler and uses more gas in the log run, short burns to maintain a full tank rather than long burns that may not fill or heat the tank fully.

Over the last few weeks we have experienced a rapid drop in temperature meaning you incoming water supply will have also experienced this rapid drop in temp, this means the boiler has to work harder to maintain the 60oC temp the megaflow will most likely be set to (overly hot tbh but that's another story).

Over a 24hr period if all showers and baths are within a 3hr window then I would expect the boiler to only fire up after each bath/shower to refill the tank. As I have already said the tank does not "get cold" it just empties..
 
BigBoy said:
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.
Click to expand...

thanks I have implemented your suggestion and hopefully it will make the difference.
 
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.
 
We have the same system although a slightly larger tank and we have ours set for a hour in the morning and an hour in the evening. Although the hot water only runs the bath as we have an electric shower (something I should sortout really) but we never really have any issues with running out of hot water at all. The immersion heater is never used but if the boiler died we could turn it on and still have hot water.
 
psd99 said:
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
Click to expand...

I'd blame person1 having a shower. Now that it's getting colder outside, the cold mains temperature will be lower and they'll need to compensate by using more hot water just to maintain the shower temperature they are used to.
 
BigBoy said:
Ideally with a megaflow system boiler your hot water should be on constantly.

The tank only holds heated water once that is depleted it tries to fill it's self from the boiler but if the boiler is set to timed it will fill with cold as it expects you to have the immersion on to heat the water between the boilers on and off times. When the boiler is set to constant it will only heat the water as it is needed to fill the tank (it has a retro grade system to move the water around to keep it all at a set temperature) the tank in its self is only a holding vessel unless you have the immersion turned on.
Click to expand...

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.:eek:
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.

touch said:
I'd blame person1 having a shower. Now that it's getting colder outside, the cold mains temperature will be lower and they'll need to compensate by using more hot water just to maintain the shower temperature they are used to.
Click to expand...

Quoted, because its correct. :p
 
Jez said:
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.
Click to expand...

based on your schedule of 24/7

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

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 :)
 
Jez said:
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 :p

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 :)
Click to expand...


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.
 
Countcussy said:
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.:eek:
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. :p
Click to expand...


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 :)
 
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. :)
 
Countcussy said:
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.:eek:
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. :p
Click to expand...
That's odd, all of the megaflow systems I have installed for the last 10years have been gas boiler fed...
 
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