60 Solar Tubes not heating water

AlanD

I have a 60 tube system on my SSE facing roof since 2008. Unfortunately, it’s no longer heating the water and I need some help figuring out the issue.

Saturday and Sunday we had really great weather. We were away so there was no hot water usage. Tank temp was just 42.

A few things we have tried -

• Checked all three sensors to see do they read ok. With a cup of boiling water, the sensors all read accurately on the control unit.
• Cleaned all tubes (they were green)
• Replaced system fluid.

what else could be the issue?

what have we not checked?

our solar plumber is unable to find the issue

Jonathan

On a sunny day, what do the three sensors (collector, tank top and tank bottom) read?

Can you hear/see the pump kicking in when Tcollector is greater than Ttankbottom by the cut in temperature (usually around 6°C?

What does the pressure gauge read on the pump station?

AlanD

Good question, should have said that.

sensor at the top would max out at 49 on a day like today.

top of tank would be max 42

bottom of tank would be 35

I have the controller set to come on with an 8 degree differential and go off at 2. Although I have played around with this Over time.

the pump does come on when it hits the differential.

I can feel the hot water come in to the tank, holding the pipe.

issue seems to me it’s not heating up enough on the roof. We thought that cleaning the tubes would help. It didn’t. Plumber checked positioning of roof sensor and was happy with it

Irish Steve

Don't know your system in detail, but my suspicion would be that somehow, there's air in the system, which is preventing proper flow in the tubes, and the pump can't circulate a proper flow round the system. Proving that might be more complex, I'd be worried that your solar plumber is struggling to understand what's not working, it may be time for a second opinion from someone with good solar experience, but how you find that person is not something I can make sensible suggestions on.

Jonathan

https://www.boards.ie/discussion/comment/119132551#Comment_119132551

If that was case, I'd expect much higher collector temps. The low collector temps are a bit of a mystery.

Are any of the glass tubes cracked/broken?

AlanD

The plumber has only just removed air from the system.

in fact in years gone by, when it was heating well, and there was air in the system, the hot water tank would be boiling and there would just be a racket in the system.

to be fair to the plumber, he knows his stuff for solar.

AlanD

https://www.boards.ie/discussion/comment/119132779#Comment_119132779

In cleaning the tubes, the plumber broke one as he turned it. All the others are intact.

as a matter of interest, are replacement tubes expensive?

AlanD

Do solar tubes lose gas over time?