Non return Valves

[Gymbal]

Hi, Been looking at graphs of heatloss from my TS. Heavily insulated 310L navitron tank plus armaflex plus extra insulation around, but the heat loss from the flow sensor is relatively marked.  in 3 hours it drops from 45 to 42 degrees, without water being used. So.... if I fitted a NRV in the flow pipe, would this stop/slow retrograde conduction/convection?
As ever http://poolguyenergy.com then drop down to Kerroogarroo IM7. Red bottom of tank, Green flow blue top of tank, pink is return.

I appreciate any thoughts....

Ps when oil fires up it does cool the bottom of the tank initially.

[KLD]

Gymbal,

Where and how are your sensors mounted? If the flow and return sensors are located on the pipes and a bit removed from the tank, then I wouldn't expect them to stay warm for very long the solar pump switched off. And hey, it's less then 10L of water in the pipes, if you loose the heat over night that's in those pipes then that's not very much energy, so nothing to worry about.
The two sensors inside the tank (top and bottom) are the ones reporting the real issue. Between midnight and 6am you loose about 4°C top to bottom. At 310L volume that's nearly 1.5kWh, and in 24hours it adds up to 6kWh. And this is early in the season, with the store at relatively low temperatures. Compare these losses to the gain you had today: the top stayed at about 52°C , while the bottom climbed from 32°C to the same 52°C. On average you had a 10°C increase, equalling 3.6kWh. And it looks like your main time of HW usage is in the morning, so 12hours after the last solar input, or 3kWh of heat loss after the last input. Of you 3.6kWh that you harvested today you'll effectively be able to use a mere 0.6kWh.

Can you box the tank in, and backfill with insulation?
The panel goes down to quite low temps over night, so there's no indicator of back-thermosyphoning.

Klaus

[Gymbal]

Blue(top) is about 15cm from the top of the tank.
Green (flow) is about15 cm from the tank itself.
Red (Bottom) is at level of Solar input, very low down.
Pink is on return pump about 1m from tank.
The pipe run is quite long  probably 8m and 15mm piping well lag with thick armaflex. I wonder whether convection/conduction is slowing the cooling of the panel and causing the xs heat loss. Once I am not altering anything I will box and fill with insulation beads. currently wrapped in recycled glass matting.