It seems my solar EV tubes geyser is not heating as it did when it was installed. I have cleaned the tubes, but still it does not go over about 55 degrees.

All I can think of is scaling. What is the easiest to "de-scale" or clean it. Or could there be some other problem. It is been running for about something like 8 years without any issues. Having the same issue at the in-laws.

Thanks guys

7 hours ago, JacquesVDM said:

It seems my solar EV tubes geyser is not heating as it did when it was installed.

I had that EXACT same issue, used to get easy up to 85 deg, then struggling to reach 65.

In my case in turned out that:
1) Some of the tubes lost their vacuum and there was no replacement parts after going 9 years - this is the one I suspect could be your problem.
2) Pump starting making noises when it ran so I was in for a replacement.
3) Geyser started leaking after 9 years and not 10 years as advertised.
4) Geyserwise control board got damaged with the last round of power failures.

Thanks TTT. I am also thinking the vaccum is not what it was. Have just drained it and there is no scaling I can see. Don't have a pump, so nr 2 is out. At least not leaking and geyser wise is still OK. 

Is there a way to determine if a tube has lost its vacuum? 

6 hours ago, JacquesVDM said:

Have just drained it and there is no scaling I can see

I am no expert on solar geysers but I did install and assemble my geyser myself, and there were a few things I noticed on the ev tubes while installing them.

1. There is a possibility of the copper rods inside the glass ev tubes sliding down, due to gravity/vibration. Especially with time and not making good “contact” with the manifold heating area. - These can be pushed back up when removing and re-inserting to eliminate this issue.

2. Also there is a heatsink paste that improved the “contact” of the copper rods in the manifold and it might be worth while to check if it still exists especially after 9 years. - check it out while removing.

These were logical observations of what can go wrong while I done my installation😎

3. A small issue I experienced was the temperature sensor was not making good contact in the port where it sits and it was only reading 55 Deg on the display and by moving the sensor around and pushing it up, the reading shot up to about 80 Deg. This temperature sensor wire is very thin and the gland do not lock the cable tight so it could slide out and give false readings.

You might of already checked this, but if not its worth looking at before thinking of geyser replacement.🙂

Is that a high pressure geyser? The low pressure ones that I have have a large hole right through into the tank. You push the tube all the way into the tank.

1 hour ago, DeepBass9 said:

Is that a high pressure geyser?

Yes, this is a high pressure geyser. The rods on this one can only push in about 50mm so if it is not pushed in deep enough you will loose efficiency. 

Today I did a test without any assistance with electrical power. Also no hot water was used.

Started last night with 46 degrees. 42 degrees this morning. And it reached 62 late afternoon. Maybe I must just wait for summer to fully kick in. 

On 2019/08/17 at 5:41 PM, JacquesVDM said:

 

Is there a way to determine if a tube has lost its vacuum? 

Can't you just feel if the tubes are hot or cold when the sun is out

How would a tube lose its vacuum without it being cracked or broken?

8 hours ago, Clint said:

Can't you just feel if the tubes are hot or cold when the sun is out

Yes, if you take one tube out and in the sun you can feel the heat , just be careful because the copper rod will burn you, use a cloth or gloves you can also measure with thermometer 

You should be able to see the status of the vacuum by looking at the bottom of the vacuum tube. It should be a silvery colour which turns white when the vacuum is lost. 

This component of the vacuum tube is called the "Getter" and i quote from the Soltrain training manual.

"The getter is another component evacuated tubes have in common. it is used in order to maintain the vacuum inside. During the manufacturing of most evacuated tubes the getter is inductively exposed to high temperatures. This causes the bottom of the evacuated tube to be coated with a pure layer of barium. This barium layer eliminates any CO, CO2, N2, O2, H2O and H2 out-gassed from the evacuated tube during storage and operation. The barium layer also provides a clear visual indicator of the vacuum status. The silver coloured barium layer will turn white if the vacuum is ever lost. This makes it easy to determine whether or not a tube is in good condition. 

13 hours ago, JacquesVDM said:

Started last night with 46 degrees. 42 degrees this morning. And it reached 62 late afternoon. Maybe I must just wait for summer to fully kick in.

So thats a temperature difference of 20 degrees which i would be happy with, in winter, considering your low inclination angle of your collector.

The energy your tank gained from the collector = Tank Volume (150L) × Heat Capacity of water (1.16 kwh/m3C) × Delta Temp (20) = 3.48 kwH

 

Thanks Carl.

Will have a look next time I'm on the roof to see if it is silvery or white.

(As I do have extra PV to heat it electrical, I am not too much worried at the moment.)