Evacuated solar tube

AchmatK

AchmatK

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I have a 20 tube ITS solar evacuated tube panel.

I have a feeling that some of the tubes might have failed. Is there a way to check which tube has failed or to test efficiency of each tube. I tried searching but couldn't find any info.

Tubes can be bought individually and I only needed to replace those not working. Problem is identifying which, if any, have failed.
 
Touch them.
If the vacuum is broken they'll be at the same temp as the water inside, else they will be a lot cooler
 
There is a coating on the inside that oxidizes when exposed to atmosphere. It should be at the bottom of the tube.
It will be silver when still good, see here: https://www.123zeroenergy.com/how-solar-vacuum-tubes-work.html
That is most likely not your problem, but there are so many ways these can fail, making it counter-productive to discuss here. Sadly, getting an installer who actually knows how these things work, is almost impossible. Good luck!
 
Thanks. They all still have the silver coating at the bottom.

I moved the panel from my previous house to my current house. It was connected to a 150l geyser before and temps would get as high as 90° on a clear day. Currently it's connected to a 200l geyser and only getting up to about 50°.

I knew having a bigger geyser would impact on the effectiveness but was not expecting such a drastic reduction. I will be looking at adding another panel in series to the current one after summer to see if it gets any better. Only had it in for just over a month now with very little clear days to see how it performs.
 
Thermosiphon or pumped? What direction does is face?
 
Pumped and facing 10° from north.

Just checked the temp now and the geyser is at 45°. Temp in the collector is at 50°. Pump is currently circulating.

Besides the geyser size the only other major difference is the pitch of the roof. My current roof is pitched at about 45° while the previous roof had a lower pitch closer to 35°.

The pipes from the geyser to the panel has covers on to protect against heat loss. The geyser is also directly below the panel in the ceiling.
 
That's crazy low. My 240l is getting to over 80 already. And it faces east
 
Then there definitely seems to be an issue. I have 20 tubes.

I will try and get up there over the weekend and touch each of the tubes to check the temp individually.
 
I also have a heat pump connected to the system but it's not currently working. I need to get someone in to service it and reconnect the power.

I closed off the taps to the heat pump but it will be my backup during the night and overcast days.

1 Solar during the day
2 Heat pump at night and overcast weather
3 Geyser element for when 1 & 2 are not working.
 
I took the output from the solar through a nice gas geyser with controlled output temp set point. So it automatically uses more gas on demand as the solar cools down =D
 
There could be so many issues here...
Firstly, make sure the pump is working. The green ones is prone to rust build-up. Those you have to clean once every 6 months.
Next is to check if the water actually gets to the collector on the vacuum tube.
Did you remember to put silicone grease on the ends of the vacuum tubes when installing them?
Did you also remember to use the cups at the bottom of the tubes to make sure they up all the way into the collector.
Do you have a non return valve in the system? Is it working correctly?
Did you install the 2 thermocouples correctly? Polarity does matter. Use a cup of boiling hot water to double check.

That is all I have for now...
 
wetkit said:
There could be so many issues here...
Firstly, make sure the pump is working. The green ones is prone to rust build-up. Those you have to clean once every 6 months.
Next is to check if the water actually gets to the collector on the vacuum tube.
Did you remember to put silicone grease on the ends of the vacuum tubes when installing them?
Did you also remember to use the cups at the bottom of the tubes to make sure they up all the way into the collector.
Do you have a non return valve in the system? Is it working correctly?
Did you install the 2 thermocouples correctly? Polarity does matter. Use a cup of boiling hot water to double check.

That is all I have for now...
Click to expand...
The circulation pump is new. Bought it when I installed it at my current house as they forgot to remove it from the previous house.

The water does get to the collector. I can see the temp in the collector through the geyser wise controller. The pump switches on when the temp differential between the geyser and collector is 7°. It is definitely heating up the water. Just not sure if all the tubes are being used.

I did not install it so not sure if they used silicon grease on the ends of the tubes.

I have all the cups at the bottom of the tubes.

Non return valves are installed and working.

Not sure about the thermo couplers. How would I check this?

It's heating the water in the collector and circulating to the geyser. The only problem is that it's not getting the temp to what I was expecting. That's why I'm thinking that one or some of the tubes has failed. I know that with an evacuated tube system, it will still work with failed tubes just that the output would be reduced. The problem is how to identify a failed tube.
 
Last edited:
Touch them. Failed tube is at water temp, ok tube is at air temp
 
I called ITS today and they said that most likely causes are that either some of the tubes could have failed or the manifold in the collector has scale build up.

They referred me to a company that can descale the collector and inspect each of the tubes. They also said that scale build up can affect the efficiency and it's good to have it descaled about every 10 years.
 
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