Water Not staying hot for long with Tempest Cylinder 250L

[Chris1012]

I have had a tempest Unvented Cylinder installed in our cellar just over a year ago when we had our loft converted.
From what I remember, The cylinder provides hot feed to only our two of our three bathrooms and kitchen sink.

The Cylinder is scheduled to heat up for an hour every morning at 5am-6am, hot water draw off from combi boiler.
During the summer, we would manage to have 2 showers in the morning lasting 10-15min in total for both showers, run one bath that takes 5-10mins to fill and a 5-10min shower for our kids in the evening.

Now it is Autumn/Winter, I am finding that come the evening the water from the cylinder is luke warm and therefore not hot enough for a shower or bath.
Is this normal?

Our Cellar is not insulated and would naturally is the coldest room of the house.

Should this be expected or could there be something wrong?

 

[Jones82]

Generally hot water cylinders are heated for an hour or two morning and night. So I would start by adding another programme for 4-6pm and go from there. Don't forget the cold water temperature is now cooler this time of year so the cylinder will take longer to heat up and lose its heat quicker due to a cooler ambient temperature in the basement.

Even with two programmes I find I sometimes have to boost my hot water time clock if we have baths on an evening.

 

[Scott_D]

Does the boiler fire and valve open to the cylinder when there is hot water demand?
Can you test the temp at the hot water outlet on the cylinder? Could be a shower mixer passing

 

[king of pipes]

As above you have to increase the reheat time come autumn / winter months as the incoming water temperature is colder . Kop

 

[IND_Nick]

As mentioned above you may need another time slot for the cylinder to reheat during the day. If it has been installed correctly it should be insulated on the hot water pipework meaning that heat loss is reduced. I would comment that almost all the I unvented cylinders I see are not insulated sufficiently. Also it should have a thermostat in series so once up to temp it will not call for more demand from boiler, ie if the hot water had not been used it won't ask the boiler for more heat regardless of what times the controller are set to come on, hope that makes sense.

 

[Chuck]

Should this be expected or could there be something wrong?

Using average figures, which you can adjust fto make more accurate for your precise circumastances, I'd estimate:

A good quality 250 litre unvented cylinder will supply about 310 litre of mixed water at 40°C. (This is actually the figure for a Megaflo because I can't find the V40 spec for Tempest online.)

Unless your showers are 'eco' models they'll use about 15 litre / minute of 40°C water, i.e. about 225 litre for 15 minutes. An average bath in the UK uses about 80 litre of water at 40°C which brings the total up to 305 litres, which is consistent with you being just about out of hot water in the evening.

Try giving the HW a mid-afternoon boost of about 30 minutes.

 

[townfanjon]

I will chuck ( see what I did there ) another opinion in here , just leave the cylinder on all the time .