Solar geyser pump circulation time

[JayMc]

Hey guys,

I read that the geyserwise system works on the premise that the solar geyser pump will turn on when the collector temperature is 7deg higher than the geyser temp, it then stays on for x duration and turns off again, then repeats the cycle. My question. Should the solar geyser pump be running continuously throughout the day (provided the collector output temp is higher than the input collector temp)? OR, should the pump toggle on and off throughout the day pushing bursts of hot water into the geyser?

Edited November 16, 2022 by JayMc

[zsde]

The Geyserwise control allows you to set the differential temp anywhere from 7C to 15C. So you could set it to 10C. The default is set to 7C.
When the Panel temp sensor is higher than the geyser temp sensor by the amount that you dialed in, the pump starts to circulate the water until the panel temp is equal to the current geyser temp. It then switches off until the panel temp hits the differential setting again.
Once the Geyser reaches 80C, the pump is inhibited. 
So the pump will toggle on and off for as long as there is enough solar energy to heat up the water.
 

Edited November 16, 2022 by zsde

[JayMc]

Thanks for the reply! Ye, that's how I understood it. I had a solar geyser installed but the pump was connected to a solar panel so it literally runs the whole day provided there is sun. 

 

I've moved the pump over to a smart switch so now I control when it goes on and off but I was quite curious to know which is the better heating system, 1. pump on all day (provided output temp is higher than input) or 2. pump toggles on and off.

[zsde]

Running the pump all day with the standard panels provided would bring nothing much. The standard flat panels or tubes won't have enough time to heat the flowing water inside. If you were to make your own collector, lets say out of  a 100m of black pipes, then a low volume pump would be ideal to circulate permanently as that water would come out boiling at the geyser on sunny days.
But with the industry conversion kits the differential switching is the only real effective option.

 

[JayMc]

I have a split system with 20 evacuated collectors. 

 

I have 3 sensors and all data is brought into my Home Assistant. I have a sensor on the collector output (but I now see it's positioned too far away from the output side), a sensor on the collector inlet side and a sensor on the geyser hot output. 

 

I had the pump running all day but have now created an automation in Node Red to basically toggle the pump. Keen to see how this performs!

[zsde]

Do keep us posted with your results.
I have had my flat panel conversion done nearly 4 years ago now. It has served me well albeit with less than expected performance. It did save a lot on my energy costs at the time.
Post my PV installation in Aug2021, I came to the conclusion that extra PV panels and an inverter that can handle the Geyser element is so much more efficient and effective. With hindsight a PV installation from the start would have been a more cost effective option.
Be that as it may, I now use my excess PV to heat the Geyser with it's element to the Geyserwise max of 65C for element heating. The Flat panel then takes it from there to 80C if there is enough solar left in the day.

Edited November 16, 2022 by zsde

[JayMc]

Will do. I feel much the same. I have a solar install and typically have the inverter power the geyser element. I've just been flummoxed at the relatively poor performance of this solar geyser - I had it redone as part of an insurance claim. 

 

Keen to see how the collectors perform now with the new pump config.

 

Thanks for your inputs! 

[JayMc]

Right. Here's my first stab at the automation. I haven't used the temperature differential as the trigger for the pump, rather a set 10min off and then 10min on, within a specific time period. However, if the collector output matches the collector input, the pump will stop and wait for 10min, then try again.

Will play around with this and see how it performs. So far, it's looking good.

Will change the pump on/off times to work with temperature differentials - like the geyserwise system.

Here's a screengrab from this morning as well as my Node-Red flow.

 

 

Edited November 17, 2022 by JayMc