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Solar Geyser Performance


spotity

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Hi All,

I have a 20 Tube Evacuated collector connected to a 200Litre geyser perfectly north facing with no shading.

The model is a Tasol with a 12V pump and geyser wise max and until recently I have not tracked the energy usage. 

I have now been monitoring it daily and on average I am using 8-12kwpd on my geyser alone (2 people). Heating at 3 AM and 4 PM.

From my initial investigation, it looks as though its syphoning at night (I check around 12 AM and 2 AM and usually the collector is at the same temperature at the geyser or 1 or 2°C higher, but more investigating has led me to believe that the system is barely heating any water at all during the day as well. 

Its 11:08 outside temperature is 22°C. The collector is at 41°C and the geyser is at 45°C, the pump is not on as the differential is set to 7°C. 

I am looking to get some feedback in terms of what others experience with their respective setups. I am going to replace the NRV this afternoon to see if that helps with the heat loss at night, but would appreciate any feedback from others who have similar setups?

 

 

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Have a similar set up, but am using almost no external power to heat water except on very overcast/rainy days. So I think there is definitely a problem somewhere in your system. 

Have easily reached 60-65 degrees in the last few sunny days in Cape Town - now with rain and cloud may need some external heating.

 

In summer temperatures are even higher and I occasionally shield some of the tubes. 

 

Should not lose more than 3-4 degrees overnight if the geyser is well insulated.

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Thanks for the response, I presumed the same. Just as a matter of interest, what is your collector's temperature at night? 

Thought that maybe it was the pump that was the issue, but then I would expect the collectors temperature to go a lot higher during the day, not entirely sure where to look now. The temperature decrease at night is one thing, but it doesn't seem as though I am getting up to temperature during the day either.   

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Been monitoring throughout the day, gaining about 7°C throughout the day. 


12PM: Geyser 44°C | Collector 54°C

2PM: Geyser 49°C | Collector 54°C

3:30PM: Geyser 52°C | Collector 57°C

The differential between the collector and the geyser is almost always 5-6 °C and nothing more, I've only seen the pump run once today. 

Edited by spotity
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My pump also runs when there is a differential of 7° so geyser and collector are never that far apart. Apart from the one instance where a circuit breaker tripped (for a non-pump -related reason) on the circuit with the pump. I have the pump on a different circuit from the geyser so that the pump can still run as an essential load during load shedding. If I recall correctly the collector was around a hundred degrees with the geyser at 60°.

But during a sunny day the pump will run every few minutes. I have never timed it exactly, but it could be about  10 minute intervals I think. A sunny day will easily add more then 20° to the geyser temperature.

I can't tell you where your problem is, but your system does seem to be underperforming.

 

 

 

 

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Hi All, I have a 200 litre tank and a 20 vacuum tube collector. Been up for 6 years now. We are coastal so set up is thermsyphon not pumped. My set up is for electrical heating (2 kW element) for 1 hr first thing in the morning. Element kicks in no more than 40 times a year usually on cold witer nights.

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39 minutes ago, spotity said:

Thanks for the response @Peter V any chance you know if you have non return valves on your setup? 

Not entirely sure. I know thre is something the installer called an atempuration valve which he told me bleeds cold water into the system if the temperature goes to high. This I'm told was a problem with the earlier vacuum tube systems which kept popping the RV on very hot days.

Something else to check - if your tubes have become opaque rather than the nice shiny black they have lost vacuum.

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Installed 2 NRVs (flap type) yesterday between the hot and cold side. Water tempreture in the collector dropped to 8c which I've never seen before, collector is now at 26, geyser is at 50 so will monitor and see how it goes today.  

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On 2023/04/20 at 11:13 AM, spotity said:

Hi All,

I have a 20 Tube Evacuated collector connected to a 200Litre geyser perfectly north facing with no shading.

The model is a Tasol with a 12V pump and geyser wise max and until recently I have not tracked the energy usage. 

I have now been monitoring it daily and on average I am using 8-12kwpd on my geyser alone (2 people). Heating at 3 AM and 4 PM.

From my initial investigation, it looks as though its syphoning at night (I check around 12 AM and 2 AM and usually the collector is at the same temperature at the geyser or 1 or 2°C higher, but more investigating has led me to believe that the system is barely heating any water at all during the day as well. 

Its 11:08 outside temperature is 22°C. The collector is at 41°C and the geyser is at 45°C, the pump is not on as the differential is set to 7°C. 

I am looking to get some feedback in terms of what others experience with their respective setups. I am going to replace the NRV this afternoon to see if that helps with the heat loss at night, but would appreciate any feedback from others who have similar setups?

I have a thermosyphon split setup with 18 tubes and 300l geyser.
There is a U bend in the pipe to prevent reverse circulation.
The tubes raise the temperature by 15-18C from 9:00-16:00

image.thumb.png.dbb9dd84c9607d99d076bc2e433eb4f3.png

I only recently started recording the temperature with a GeserWise TSE WiFi/Tuya module.
If the water is below 65C at 10:30am, I boost the water using electricity to 65C as I have excess Solar PV.
There was no electrical boost in the above chart.

My thermosyphon system was installed in 2010 and I got my Solar PV in 2021.
Today I would just install a normal geyser and a few more PV panels as this is cheaper and more robust than tubes.

Edited by system32
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Thanks for the feedback @system32, in your case the geyser is above the panel so the hot water will naturally rise to the geyser, my tubes are 1,5 - 2 meters above my geyser and need to be pumped up - there is no way to stop it unless I add a NRV or a very long loop.

Today was the first day, and it went over 70C, will see how it holds through the night.

Also changed out my GeyserWise Max for the new WiFi-enabled version and brought it into my HA to monitor. 

Started at 63 after I installed the board at around 17:00, now at 34C which I definitely wasn't seeing before.  

Sorry for the shitting screenshot, haven't yet graphed it out. 

image.png.b683162ce601a7602354aa632a6f6c4c.png

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Hi everyone

I installed a 16 tube system on my sisters roof with a 12v panel and pump.

The pump was very noisy and failed about 4 months later.

I went to my suppliers and bought a plastic pump which to my surprise was a Grunfos.

A lot more expensive about R1400 vs R470

It works extremely well and very quiet

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So the temperature loss during the night seems to be resolved now. 

Last night I lost 6C between 8PM and 4AM, collector drops 50C plus at night, down to the low 10's. 

image.png.3acb2397e864c02a1050d511ca987ff7.png

 

Not sure if this is inline with what's to be expected and would need to compare with another system.

At the moment it seems to be gaining about 1C per hour from the below. My differential is set to 7C for collector before pumping.  

image.thumb.png.769cbcdf6923e69766a77c83f187e9f9.png

Edited by spotity
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On 2023/04/26 at 3:11 PM, spotity said:

So the temperature loss during the night seems to be resolved now. 

Last night I lost 6C between 8PM and 4AM, collector drops 50C plus at night, down to the low 10's. 

image.png.3acb2397e864c02a1050d511ca987ff7.png

 

Not sure if this is inline with what's to be expected and would need to compare with another system.

At the moment it seems to be gaining about 1C per hour from the below. My differential is set to 7C for collector before pumping.  

image.thumb.png.769cbcdf6923e69766a77c83f187e9f9.png

What did you do to resolve this issue

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5 hours ago, spotity said:

Flap type non return valves on the pump side and hot side of the panel so the hot water can't travel to the panel. 

Those brass ones? with the cap in the middle

Pump side? Where exactly on the pump side

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13 minutes ago, Dannler said:

Those brass ones? with the cap in the middle

Pump side? Where exactly on the pump side

Yup, a brass one - Image below.

I installed on the vertical pipe that goes to the tubes, Excuse the basic paint drawing below, but hopefully, it clarifies. 

 

 

 

Non return valve check valve swing type 20mm female thread

image.png.762067d0e11fa42c562354614efe748e.png

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