Is there a problem with my Dad's storage tank?

[Bettyboo]

My Dad heats his water and house with an oil fuelled boiler. He has an unvented storage tank which also has an immersion . The tank is covered with foam insulation. He lives alone and his tank is about the same size as my 250 litres unvented megaflo tank. His tank is set to 60 degrees on side of tank . He has the boiler heat the water for an hour in the morning for a shortish shower and washing up , (not much) .If he wants more hot water in evening for say a bath, he says he needs to heat water again for an hour.
However I find that my megaflo keeps my hot water hot for much longer, if I just heat water for 40mins. I can have a short shower say 5 -10 mins on day one and then say miss a shower the next day , do a little washing up but still have hot enough water on third day for a shower.
Could there be something wrong with his storage tank ?
thanks for your thoughts
Betty

 

[SJB060685]

To keep the stored water hotter for longer you want the cylinder constructed with materials with high specific heat and low thermal conductivity. Copper is a great conductor of heat and therefore will conduct heat to its surroundings more readily than other materials. The foam insulation is obviously to slow this transfer of heat down but doesn't completely stop it.
Most modern day cylinders are far more efficient at keeping the stored water hotter for longer.
When it comes to reheat times an older copper cylinder will take longer as the coil output is much smaller than modern day cylinders.

 

[Chuck]

However I find that my megaflo...

I think the difference in behaviour is most likely to be down to a difference in the heat exchanger coils between the two tanks and/or the circulation rate. A Megaflo can reheat fully in about 30 minutes, give or take, providing the CH can deliver enough heat. Not all models of cylinder perform this well. Also, some installers deliberately throttle the amount of heat that is supplied to the DHW tank to prevent it starving the radiators.

 

[John.g]

Something strange alright because if one assumes that the temp was a minimum of 42C after the hour then if the coil is heating say 200 Litres of that 250 litre cylinder then a coil output of ~ 5kw would achieve that and should still have a large volume remaining at ~ 38C in the evening even if its losing say 0.5C/hr.