Issues with hot water from cylinder.

housebuyer143

WIAWSNB said:

As Plumb says, that's a scarily high pressure - the shock on every valve, toilet, and tap must be significant.
Has no plumber recommended a Pressure Reducing Valve?

I know right!! 3 times an engineer from megaflow came out and none of them recommend reducing the pressure, in fact they had no idea what was up with it and were going to put an external expansion in.  It took me asking on here to find out I should reduce it and I did it and solved my issues. We have the house at 4bar now and are happy. 

It has been a huge improvement as before the taps were hard to turn on, the washing machine banged - nothing liked the high pressure! 

housebuyer143

bjorn_toby_wilde said:

Surprised a PRV wasn’t added to the system when the Megaflo itself was fitted. They do need a regular safety check. We combine it with the annual boiler service.

It has one, but it didn't stop the back flowing issue. Reducing the whole house pressure has resolved it mostly.

housebuyer143

Albermarle said:

housebuyer143 said:

I hope someone can advise - this is the first year I've noticed an issue. 
We have a 3 year old mega flow unvented cylinder 170ltrs. We have it heat 40 mins in the morning and 30 in the afternoon and we normally have enough hot water for 25 mins in the shower. 
What I have been noticing is that the water is only luke warm - this morning it's no hotter than it was last night even though it's been on 40 mins...

When we do get hot water, it's going cold in 10 mins when having a shower- or if someone uses it in the day, even a little it doesn't seem to be keeping it hot enough - it's like it mixes with the cold and it is all luke warm again??

If I put the boiler on for an extra hour, it seems to be really hot again.

*I have only noticed this the last 2 weeks, which could correspond with the sub zero temps we have had over night. 

Is this likely an issue with the tank, or does it sound like it's struggling to heat the cold water coming into the tank fully and I need to put it on more??

We have a 210L unvented tank, heated with a gas system boiler.
In warmer weather it is on 30 mins in the morning and 15 mins in the afternoon.
This is OK for on average 1.5 showers a day and 4 baths a week.
In this cold weather I have bumped it up to 35mins and 20 mins. Plus the boiler flow temperature has been increased from about 58 degrees to 63 degrees.
Everything nice and hot, although you have to turn the shower stat up a bit to account for the cold feed being colder.
Although I have to say we kind of stick to the max 4 minute rule for showers,and it sounds like yours are longer.

Do you know what your boiler flow temperature is, maybe its a bit low ?

How do I check the boiler flow temp? I have the heating set to 60 degrees, but I don't think I can alter the water one 

plumb1_2

Albermarle said:

plumb1_2 said:

There’s a bit more to servicing a megaflow,  checking pressure, operation of safety valves, testing electrical items.
7.5 bar is far to high, ideally should be about 3 bar, no wonder your loosing the air gap.

mr insurance we’ve had a fire/flood from our megaflow and caused £10k worth of damage. oh were sorry to hear that, have you been having it serviced by a G3 qualified engineer?  Ehhh sorry No, ok then claim closed.

I asked our plumber ( G3)  to service our Megaflow at the same time as the gas service.
When he arrived he said pretty much the same as the one the OP mentioned. There is nothing really that can be easily serviced.
He said something like if we check the pressure valves, we will have to replace them.

Servicing unvented cylinders has been mentioned before in other threads, but you always seem to get a variety of answers.

Each manufacturer has their own service requirements and these should be followed to comply. There is also a risk of Fire as. Well as flood and safe operation of the unit.

The average gas engineer will not be G3 qualified and will give you some excuse not to get involved. 

And saying if they test the valves they will have to replace them, is wrong. And a  prv should be on the supply pipe to the cylinder .

QrizB

housebuyer143 said:

Albermarle said:

Do you know what your boiler flow temperature is, maybe its a bit low ?

How do I check the boiler flow temp? I have the heating set to 60 degrees, but I don't think I can alter the water one 

Typically, a regular or system boiler (the sort you use with a HW tank) only has a single temperature setting.

60C should be sufficient (I run mine at 50C) but you might need to extend the tank heating time.

Does your Megaflow have a thermostat? What temperature is it set to? The tank stat should be set to a lower temp than the boiler flow temperature, and then you can set the tank heating times to be as long as the CH times.

Albermarle

housebuyer143 said:

Albermarle said:

housebuyer143 said:

I hope someone can advise - this is the first year I've noticed an issue. 
We have a 3 year old mega flow unvented cylinder 170ltrs. We have it heat 40 mins in the morning and 30 in the afternoon and we normally have enough hot water for 25 mins in the shower. 
What I have been noticing is that the water is only luke warm - this morning it's no hotter than it was last night even though it's been on 40 mins...

When we do get hot water, it's going cold in 10 mins when having a shower- or if someone uses it in the day, even a little it doesn't seem to be keeping it hot enough - it's like it mixes with the cold and it is all luke warm again??

If I put the boiler on for an extra hour, it seems to be really hot again.

*I have only noticed this the last 2 weeks, which could correspond with the sub zero temps we have had over night. 

Is this likely an issue with the tank, or does it sound like it's struggling to heat the cold water coming into the tank fully and I need to put it on more??

We have a 210L unvented tank, heated with a gas system boiler.
In warmer weather it is on 30 mins in the morning and 15 mins in the afternoon.
This is OK for on average 1.5 showers a day and 4 baths a week.
In this cold weather I have bumped it up to 35mins and 20 mins. Plus the boiler flow temperature has been increased from about 58 degrees to 63 degrees.
Everything nice and hot, although you have to turn the shower stat up a bit to account for the cold feed being colder.
Although I have to say we kind of stick to the max 4 minute rule for showers,and it sounds like yours are longer.

Do you know what your boiler flow temperature is, maybe its a bit low ?

How do I check the boiler flow temp? I have the heating set to 60 degrees, but I don't think I can alter the water one 

As said, if you set the heating to 60, it will be the same for the hot water.

Do you have the hot water timings on , whilst the heating is also on?
If so then maybe with the cold weather, the boiler is struggling to do both, if for example it is a bit underpowered for the size of the house/number of radiators.
If the heating has been on a while, when the hot water comes on then should normally not be a problem. However if they both come on together, early on a cold morning, then it could cause an issue.
In the morning I always set the hot water for a period before the heating comes on. 

Troytempest

With our, if we have the heating on at the same time the hot water is on then neither do very well. Best to knock the heating off and let the boiler only do hot water for an hour....

Slinky

I'd echo what others are saying about heating the water and CH at the same time. We have ours set to heat water only for 30 minutes in the morning, followed by the CH coming on when the hot water goes off.

ComicGeek

Why bother running the hot water for only 30/40 minutes at a time?? The cylinder will stop calling for heat when it's at temperature, as long as the cylinder stat is set lower than the boiler flow temperature.

Just have the hot water set to on all day - it won't use any more energy, and means that it will always be ready for use later in the day. Mine is set to run between 8am and 10pm each day, but the boiler only kicks in a couple of times each day - room heating runs from 6am, but the cylinder has already been heated up the night before so no conflict.

Your boiler temp of 60 degrees is probably too low for the size of cylinder. If you had a 300 litre cylinder then you could probably get away with a lower storage temperature, but 170 litres doesn't go far in the winter.

QrizB

ComicGeek said:

Your boiler temp of 60 degrees is probably too low for the size of cylinder. If you had a 300 litre cylinder then you could probably get away with a lower storage temperature, but 170 litres doesn't go far in the winter.

My 120-litre tank and 50C boiler temperature beg to differ. (OK we can't have three back-to-back showers.)