Something that I have noticed with my newly installed EV tubes is that the temp probe at the EV tubes displays the same temp as the geyser at night, surely the outside temp at the EV tubes should be "colder" as the night progresses?

 

@Antony  I have installed a oneway valve in the hot water pipe from the solar heater. Unfortunately we seem to have calcium or such like in the water which clogs up the valve in time. I was told by a friend that he installed a loop in the hot water outlet of the solar heater. The loop goes down some distance and then back up to connect back to the hot feed to the geyser. That apparently stopped thermosyphon flow of hot water from the geyser to the solar heater.

Edited October 3, 20186 yr by ebrsa

2 hours ago, ebrsa said:

 I was told by a friend that he installed a loop in the hot water outlet of the solar heater. The loop goes down some distance and then back up to connect back to the hot feed to the geyser. That apparently stopped thermosyphon flow of hot water from the geyser to the solar heater.

Good morning Ebrsa, I have the loop as well on both the cold and hot water ends.

@Antony  I hope to install one loop on the heater output side on Monday and will see if it makes a difference. The loop will go from the outlet down to the flat roof and back again and then to the geyser top inlet. My geyser is an Xtreme which has solar inlet and outlets and is also on the roof. When installed I will report back.

Edited October 4, 20186 yr by ebrsa

I have a gap geyser which I installed verically. There is a removable metal access place which I had two brass fittings silver soldered onto for the supply to EV tubes. A short elbow into the geyser  provides the cold out to the tubes and about 10 cm longer vertical tube is the hot water return. I find that even that way I loose about 20l  to thermosyphon as the water settles into layer of diffrent temperatures. Otherwise you can see if you can set the min pump switch on temperature to say 50°C or you might find the controller sees the temp difference big enough the EV tubes and geyser and starts to cycle the circulation pump and you loose even more hot water.

I had also installed a one way valve in my setup and found that it had failed after a short period. There are two different types of one way valves. The one has a spring action which keeps it closed (the one I originally used and failed). The other has a flap and the back pressure keeps it closed. The later valve is the one that should work better with hot water. There is also a caution that this valve as far as I have seen should be installed horizontally as it can cause shuddering in the pipes which I have experienced on onother installation.

The one way valves with a flapper don't really work as it's a closed loop so there is little to no back pressure to keep it closed

I have installed mine vertically and that worked fine but now is probably not doing its job due to suspected calcium or other deposits. Need to take it out to find the reason. I suppose a loop to prevent thermosyphon flow is the simplest and most elegant solution.

On 2018/10/04 at 8:15 AM, ebrsa said:

@Antony  I hope to install one loop on the heater output side on Monday and will see if it makes a difference. The loop will go from the outlet down to the flat roof and back again and then to the geyser top inlet. My geyser is an Xtreme which has solar inlet and outlets and is also on the roof. When installed I will report back.

Hi Ersa, did you manage to make this change and has it made any difference.

I went to bed at 11pm last night and my geyser was 59 degrees, this morning it was at 42 degrees and the element switched on at 4:30 (it is set at 4:30 if temp drops below 40)

Therefore I have to assume the pump is still running and circulating the water, and dropping the temp below 40 degrees, this is such a waste.

I will have to switch off the timer, but I still need to determine why it is dropping.

@Anthony we were away from home for a while so I still have to install the loop. Since the Geyserwise has an indicator for the pump, you should just look at that to see if the pump is running. A problem with Geyserwise indicated temperature is that the probe is at the bottom op the geyser, so the moment you open a tap the bottom temperature drops. Before I installed the Geyserwise, I used an Arduino based homemade controller which had probes at the top and bottom pipe inlet and outlet as well as the solar heater outlet. While the bottom temperature dropped soon, the top dropped very little during the night.

Perhaps you should install an Arduino based temperature gauge to measure the outlet temperature. I got my circuit and Arduino program from a US website that since closed down. If you PM me your e-mail address, I will send the instructions and my modified program to you should you want to use that to determine what is really happening. Or you could just Google for an Arduino temperature guage. I am sure there are some to be found on the Internet.

 

On 2018/10/07 at 8:11 PM, seant said:

The one way valves with a flapper don't really work as it's a closed loop so there is little to no back pressure to keep it closed

Its been a while now and I have had 2 flapper type 1 way valves fail on me, the latest only lasted a month...

Has anyone got a perfect anti loop suggestion, i.e. a diagram of sorts, I suspect my loops are incorrect. Any other suggestions are welcome. I hate loosing my water temp to the elements, especially in winter.

@Anthony how the time flies. I have meanwhile installed the loop on my EV tube heater outlet but the Geyserwise still shows about 7C drop during the night. It turns the mains on for about 20 minutes at 4am. Usually I  have to manually turn mains heating on for showers in the morning. Main problem is the Geyserwise sensing temperature at the bottom of the geyser so to see the true state I need a temperature gauge at the heater outlet. First step should probably be to turn the mains off and see how much the temperature drops during the night. That enquires that no hot water tap be opened during measuring, no mean feat in a household,  even of two in my case. 

59 minutes ago, ebrsa said:

Geyserwise still shows about 7C drop during the night.

Titbit.
Our new geyser mounted vertical - more efficient they say - shows 65deg at say 5pm:
- No-one uses any hotwater until 7am - geyser is on 45deg celcius.
- Someone uses it, it shows 25deg C yet still the water coming out needs cold water added.

Vertical geysers are seriously different.

22 hours ago, ebrsa said:

@Anthony how the time flies. I have meanwhile installed the loop on my EV tube heater outlet but the Geyserwise still shows about 7C drop during the night. It turns the mains on for about 20 minutes at 4am. Usually I  have to manually turn mains heating on for showers in the morning. Main problem is the Geyserwise sensing temperature at the bottom of the geyser so to see the true state I need a temperature gauge at the heater outlet. First step should probably be to turn the mains off and see how much the temperature drops during the night. That enquires that no hot water tap be opened during measuring, no mean feat in a household,  even of two in my case. 

This morning at around 5am, my geyser was 35 degrees and so is my EV temp sensor, this is a clear indication my system must be siphoning...

My Geyserwise switches on at 4:30 to increase temp to 35, should it not be already at 35, just to have a warm enough shower at least. Keep in mind I have 3 long haired lasses in the house.

@The Terrible Triplett my geyser is an Xtream which is horizontal. To my knowledge it has baffles inside to improve stratification of water which by nature is particularly poor at it. Yesterday the Geyserwise showed a temperature of 35C but a very sensitive photographic thermometer of days gone by showed 38C under the running tap. Since it is a 200 litre tank,  it is hot  enough for me and wife to have showers. @Anthony I will switch off the grid boost at 4:00 and check the temperatures of geyser,  solar heater and tap water tomorrow and see what transpires. A sunny day was forecast for today but right now at 10:00 we are enshrouded in fog. 

11 minutes ago, ebrsa said:

Yesterday the Geyserwise showed a temperature of 35C ...

How our geyser has a temp on the Geyserwise of 25C and I cannot stand under that hot water, have to use cold water AND 25C shown is hot enough for my wife ... in our case I think the temp sensor is in the wrong place on the the vertical geyser.

Guys, just watch out for low water temps and legionairres disease. Got to take it up to above 55°C at least every few days.

25 minutes ago, plonkster said:

Guys, just watch out for low water temps and legionairres disease. Got to take it up to above 55°C at least every few days.

Are you sure it is 55°C?

The bacteria multiply where temperatures are between 20-45°C and nutrients are available. The bacteria are dormant below 20°C and do not survive above 60°C.

And here: http://www.hse.gov.uk/legionnaires/assets/docs/hot-cold-legionella-checks.pdf

All geysers go up to 65°C each afternoon. 

How can geysers be thermosiphoning at night? That makes no sense. Are the tubes higher than the geyser? It must be just loss via conduction through the pipes. Are all the pipes lagged? The tubes shouldn't lose heat as they have a vacuum between the water and the air.

8 minutes ago, DeepBass9 said:

How can geysers be thermosiphoning at night?

My old EV tube system had a feature, in Geyserwise, that when you go on holiday, that you set it that it cools off at night.

I finally got around to doing a test yesterday. Geyser temperature went up to 47C.  This morning it is 37C but heat exchanger is at 11C. Some hot water was used,  hence the substantial drop in temperature. Pipes are all insulated as far as possible. So it would seem that the loop or flapper check valve,  mounted so that flow through it  is vertical, or both are doing a good job. @The Terrible Triplett my Geyserwise still have the holiday cooling feature.  Not that I use it as it runs the pump continuously during the night and my pump is powered by a separate 20W solar panel with 33Ah battery and running it during the night will destroy the battery in no time. So temperature does go to middle 70C during summer. 

I raised the issue of Legionnaires disease with our municipality in the past but the reply from a person whose knowledge I trust was that it requires stagnant water. So perhaps when one returns from holiday it would be advisable to heat up the geyser water above 55C for some time. Since it is a lung disease, it is usually transmitted by inhaling fine droplets during a shower. At least that is the extent of my knowledge from information found on the Internet.