Hello Guys. 

This forum is my last resort. 
Gentlemen a while ago our town received some serious hail and we had to get insurance to come replace the Evacuated Tube and whole manifold for the tubes as it was quite aged as I understand. The guys came out and replaced the manifold and tubes, but since the replacement the system doesn't get as hot as what it did in my personal opinion, I have had to put my solar geyser on every night since winter started as we have had some nice days. When I climb on the roof to check the system the inlet to the manifold is cooking hot but the outlet is luke warm (See attached pictures). Please if anyone can assist in answering the following. 

1) Is it possible that the manifold is not working properly ? 

2) Why is the outlet pipe back into the geyser not getting as hot as the inlet pipe ? 

3) Should I get the insurance or plumber to replace the manifold ? 

4) Is it possible that the Thermosyphon system is not working properly ? 

The temperatures in winter are lower I understand that completely, but I have a true north facing geyser and it does get quite hot up there. I cannot hold my hand on the inlet pipe for long else I will burn. Is the system not working properly ? Please see attached pictures. 

As of this post right now it has been 21'C today. Pure Sun. 

Edited July 20, 20241 yr by Great Whit3

3 hours ago, Great Whit3 said:

Hello Guys. 

This forum is my last resort. 
Gentlemen a while ago our town received some serious hail and we had to get insurance to come replace the Evacuated Tube and whole manifold for the tubes as it was quite aged as I understand. The guys came out and replaced the manifold and tubes, but since the replacement the system doesn't get as hot as what it did in my personal opinion, I have had to put my solar geyser on every night since winter started as we have had some nice days. When I climb on the roof to check the system the inlet to the manifold is cooking hot but the outlet is luke warm (See attached pictures). Please if anyone can assist in answering the following. 

1) Is it possible that the manifold is not working properly ? 

2) Why is the outlet pipe back into the geyser not getting as hot as the inlet pipe ? 

3) Should I get the insurance or plumber to replace the manifold ? 

4) Is it possible that the Thermosyphon system is not working properly ? 

The temperatures in winter are lower I understand that completely, but I have a true north facing geyser and it does get quite hot up there. I cannot hold my hand on the inlet pipe for long else I will burn. Is the system not working properly ? Please see attached pictures. 

As of this post right now it has been 21'C today. Pure Sun. 

Are you sure that the legends in the pictures are correct?

Just wondering if the hot pipe is not the output from manifold to geyser and the cold pipe the inlet to the manifold. 

Just grasping at straws  as I don't know solar geysers. 

Edited July 20, 20241 yr by Scorp007

Whichever side is hot, that is the output of the manifold, and the direction the water will be flowing towards. Possibly the installers never put enough thermal paste on the copper rods that push into the manifold, therefore not enough heat is transferred, compared to your old installation.

9 hours ago, Great Whit3 said:

4) Is it possible that the Thermosyphon system is not working properly ?

If the direction of flow has changed, possibly yes.

Has the length and height of the pipes changed with this new refit?

Do you have non-return valves installed that could prevent a reverse-flow thermosiphon from being set up? Can't make it out on the images.

Just based on the pictures I would think that the pipe from the manifold that is hot should be connected to the hot water from the geyser. That means the vertical pipe with the lagging insulation. 

The pipe tagged outlet to geyser at the bottom of the geyser to manifold that is cold seems to be correct. 

My reasoning is the hot water from manifold is now directly next to the cold water inlet. 

Currently both pipes to/from the manifold are connected to the bottom of geyser being the cold part of the geyser. 

Again coming from a lay person when talking solar geysers. 

 

Edited July 21, 20241 yr by Scorp007

14 hours ago, TimCam said:

Whichever side is hot, that is the output of the manifold, and the direction the water will be flowing towards. Possibly the installers never put enough thermal paste on the copper rods that push into the manifold, therefore not enough heat is transferred, compared to your old installation.

If the direction of flow has changed, possibly yes.

Has the length and height of the pipes changed with this new refit?

Is it possible that the manifold is the wrong way around as hot rises. 

14 hours ago, TimCam said:

Whichever side is hot, that is the output of the manifold, and the direction the water will be flowing towards. Possibly the installers never put enough thermal paste on the copper rods that push into the manifold, therefore not enough heat is transferred, compared to your old installation.

If the direction of flow has changed, possibly yes.

Has the length and height of the pipes changed with this new refit?

I don't think they used any thermal paste as I was present on site of the day they installed? Is this an important effect to do ? 

Firstly...I am NOT a plumber.

A few months back I was called by a neighbor to look at his setup which mirrored the OP issue. Hot water too cold.

On inspection I found that there is a THERMOSTATIC mixer valve which blends the hot and cold to a set output temperature and has to be installed (by statute?) on all new installations. Since his water supply is low pressure, I advised him to replace the high pressure thermostaic valve, that was installed by the plumber, with a low pressure one. Since I have had no feedback from my neighbor I  assume that fixed his problem.

Maybe see if you have a thermostatic valve in your system and if it is the correct one re water pressure and if it is correct whther it can be adjusted to increase the output temperature, which I am led to believe is possible on most of these devices.

Guys I came across my brother in law's geyser. The cold pipe runs under the tubes to the outlet of how mine is plumbed. The hot pipe on mine is the outlet of his going back into his geyser. I will contact the plumber this week. What's your guys thoughts? 

2 hours ago, Great Whit3 said:

I don't think they used any thermal paste as I was present on site of the day they installed? Is this an important effect to do ?

Should have used thermal paste, just like you do on a PC CPU and GPU between hot IC's and Heat syncs.

Good to see your brother in laws, setup. Hope your plumber corrects yours accordingly. 👍

My 20 tube setup uses a re-circulation pump, as the geyser is below the roof.

Edited July 21, 20241 yr by TimCam

Hi, I have a problem with the solar geyzer. Since last month it's been mixing cold & hot water, all the taps are having hot water only & the worst is when touching taps you become choked.so I reported the problem at the municipality since there was earthleakage.They came & fixed the electricity box.they said that its okay.last week there was a rupture of a pipe, I called the plumber.The plumber fixed the pipe but said the water is choking , meaning that there is electricity in the water.now I don't know what could be the problem. The plumber told me about the mixer for solar geyzer but couldn't find it at hardwares because they say solar geyzers doesn't have thermostat.should I change the geyzer?

Also discovered that my solar geyser often has the left (east) inlet side hot while the outlet (west) is cold. Busy building an IoT gadget to measure all the inlet/outlet/panel temperatures, mostly out of curiosity in my home assistant. Think I have figured the reasons for this... all geyser installations I have seen including my own is optimal for Northern Hemisphere. This is applicable to high pressure thermosyphon manifolded systems only, such as in this thread. Early morning, when there is no flow, the sun hits the eastern tube(s) and heats it up having a full sunrise exposed side. The thermosyphon pressure starts pushing up the water and the inlet is the closest. Flow starts in the wrong direction pulling in cold water from the outlet side. Once the flow is established, which significantly impacts the transfer efficiencies, it requires the entire panel to heat up quite a bit for the "true" thermosyphon pressure to correct the flow direction. On a colder/less radiant day this never corrects. This messes up the relationship between radiation intensity and geyser performance. Below some threshold, the heating efficiency drops off non-linear because the flow is limited being in the wrong direction and could stall for some time. Here are some ideas to mitigate the issue especially during colder days:

1. Lifted the western side of the panel manifold slightly by placing a brick under the frame at the top (there was a brick available close by hehehe). This slightly tilts the manifold up to assist the thermosyphon from east (inlet) to west.

2. Rotate the entire panel a few degrees anticlockwise. On a slanted roof like mine, this increased the tilt angle of the manifold (east - west) as per point 1 some more further improving thermosyphon effect. This is bit difficult in my case. Having a perfectly straight (horisontal manifold) installation in this case is detrimental for performance.

3. Cover the east most tube left side to prevent the early morning sun heating it more than the others. Only partially to allow it still getting full sun later on during the day. This should lower the chances of it pre-heating the inlet port, causing reverse flow in the morning.

4. A circulation pump to force the correct flow will eliminate and significantly improve colder day performance. Did buy a pump for other reasons and first want to see improvement results from above fixes. Think this happens to be the reason why GW is so successful to improve geyser performance by ensuring correct flow direction especially during colder days using their circulation pump setup.

5. On a new installation, rotate the entire hot water tank 180° with the inlet on the western side and adapt piping accordingly... southern "hemispherise" the installation. This will solve mostly the east rising sun issue on the inlet side.

6. Insulated the inlet and outlet lines between the panel and hot water tank. A lot of heat is lost during the day as the hot water circulates while exposed to the colder environment.

Trust this will help improve your system(s).

Edited April 21, 20251 yr by Jurie Vorster