Heat leaking out of hot water tank?

[tonymorris24]

Hi everyone

Would love some advice! We have a hot water cylinder which lost 14 degrees (48 to 34) in four hours, with no demand/usage. So I think the heat is escaping. The circulation pump (which you can see in the photo) is off, so could passive convection be the reason? The pump is always warm despite not running.

Hot water seems to come out remarkably soon from the taps. The cylinder is on the ground floor, recharged by a GSHP. Should a heat trap (found phrase on the internet!) on the internet?

Should I try turning off one of the taps/valves to see what impact that has, as a test? Which one - the black handle connected to the top of the tank or the red handle (by the circulation pump) connected to the bottom?

Thank you!!

 

[ShaunCorbs]

It will add resistance so it can’t gravity flow and yes as there’s nothing to stop it every time you open the hot tap it can pull cold water from the return circuit as it’s teed into the cold main

 

[tonymorris24]

Turn the secondary pump off via elec and red lever valve and retest

I just wanted to say a quick thank you for your help with this. In the end I turned off the red handle and the convection stopped. As a result the hot water tank only loses a few degrees over the course of the day and not the entire volume of hot water. Excellent!

 

[benjycov]

I have the same problem as the original poster. 500ltr tank heated by GSHP plus immersion situated on the ground floor, i am monitoring cylinder temperature, inlet, outlets and the secondary return temperature so I have a pretty clear picture of what's going on. I'm losing 30C passively over 24 hours which equates 17.4kwH vs the manufacturer standing loss of 2.81kwH. I know the loss is convection because the secondary return pipe is pretty much always 30C (and hotter while the secondary pump is running).

My first problem is that there is no check valve between the secondary pump and the tank, however even when I close the valves around the secondary pump (thus closing the secondary return to the tank), I still get 30C temp on the secondary return (the boiler cupboard itself remains around the same ambient temp as the house).

Thus the problem is convection, the question is how do i fix it?. Googling tells me that heat traps/loops but all the results seem to be US related, and no references to the UK... I assume physics works the same in the UK thus the solution should work but I find it strange that there are no references to people doing this in the UK?!

 

[ShaunCorbs]

If you close the pump valves the pipe will stay warm for a bit might be best to turn the pump off and shut the pump
Valves for a week to see your Heatloss stays the same or drops