Tank insulation

[gfkw47]

Hi
Last year we had our hot water system, which was electric immersion heater only, altered to provide additional heat from solar panels. Results appear to be satisfactory.

BUT in making the change the installers had to replace the hot water 1.5mtr cylinder (which had spray foam insulation), to a similar szed one but with a Gledhill "L" blue insulation cover. Not sure if Gledhill is the tank or the insulation cover or both.

With the solar system we can now monitor what heat loss takes place overnight. The cylinder gets to max temperature of 65deg all the way up from the entry point of the coil at the bottom of the tank to the top of the tank. But by the next morning, the top of the tank has usually lost about 7degs and reads about 58. While the bottom has usually dropped by about 14 deg to around 51 deg.

I know this heat accumulation is free when heated by the solar panels, but it still seems very wasteful, and in the winter months it is using electricity which is certainly not free.

Does this amount of heat loss sound normal - it may be that the old tank was losing a similar amount but we had no way of knowing. If it isnt normal any ideas what to do about it - does the Gledhill cover need replacing with something better? Or more insulation over the top of the existing one (although there is no space behind it to do this). The new tank size is 1500 x 450mm.

Sorry its so involved - but thanks for amyone who can help.

 

[Billy Bob Bob]

i think your worrying over nothing,but if your that concerned put a cylinder jacket around it,gledhill is the manufacturer of the cylinder

 

[gfkw47]

Thanks for the comment Mark - but are you saying this sort of heat loss is about normal?

 

[Plumbstar Tom]

not that i have ever measured the drop but i would expect it to be normal

Its only come to light now as you have the ability to see it

I would bet that it was worse on the old cylinder with the spray foam

 

[Mbear]

Do u seriously think the hot water will stay at the same temp overnight without heating it? Water cools down if it's not heated, it doesn't matter what you do ie adding insulation etc, it's still gona cool to an extent. I understand your green concerns about it being wasteful, look at it this way.... A thermal tea flask trys to keep the tea roasting for you but by 5pm it'll be cold, no matter how much you spend on a new top of the range flask it's still gona cool down, it may last a bit longer but the end result is the same matey

 

[justlead1]

Hi. The heat lost amount to approx 4kw of energy. Although more insulation can reduce this, it can create other issues by obstructing valves, thermostats, pumps and other components that make up a system. Any faults on the system would be difficult to identify and could lead to costly problems.

 

[gfkw47]

Of course I expect a heat loss - my question - if you read it carefully - simply asked if the heat loss I was experiencing was normal. Presumably someone out there has sufficient knowledge and experience to tell me if 14 deg loss of temp at the bottom of the tank is what I shopuld expect. If not what should it be - simple really!

 

[justlead1]

Hi, Why not direct your question to Gledhill I feel sure they can provide graphs and data that will satisfy your needs.

 

[Plumbstar Tom]

You seem to think that water twemperature is constant throughout your hot water cylinder which I must state is incorrect

The difference from the bottom to the top can be as high as 10 degrees dependant on conditions

This would explain why you feel the temperature has dropped 14 degrees at the bottom

You also have to question the accuracy of the thermometers used and thermostats

 

[gfkw47]

Thanks - good idea. I have just found their website and think this is the best way forward.
George