I have been looking at fitting an evacuated tube retrofit system to by existing 150l geyser. Contacted the one installer who said I can fit either 15 tube or 20 tube kit to the 150l geyser. He said the 15 tube would only heat the geyser to about 40 degrees or so in winter and the 20 tube can heat the water to around 60 degrees in winter. He also said the 20 tube system will cause the water to heat to more than 60 degrees in summer and he would need to come out and remove some of the tubes in summer to prevent overheating. For which he is going to charge a callout fee of around R750. Anyone out there with an evacuated tube retrofit system that can comment on the number of tubes needed and overheating in summer? I would have assumed these systems have something in place that would prevent the geyser from overheating instead of going onto the roof and removing tubes. I don't know much about these systems and dont like being taken for a ride. Anyone with experience with these things I would appreciate your advice.

Unfortunately one can't turn off the sun, so it's impossible to stop the heating. Only way to cool them is to tap off some hot water. Also, reviving a tube or two is very, very easy to do yourself should you want to. 

Regarding how hot they'll get, that largely depends on how much water your home uses. I will be very surprised if your water gets problematically hot though. I'm using you'll have a geyserwise which you can set to cool the water overnight should there be a couple of days of low water usage (e.g. when you're away). 

 

3 hours ago, Speedster said:

one can't turn off the sun

nope, but you can put a shade cloth over half the tubes for summer if you believe it neccessary

3 hours ago, Vin said:

Anyone with experience with these things I would appreciate your advice.

we have a 100 liter low pressure solar hot water cylinder... 12 evacuated glass tubes, yup gets pretty toasty in summer and even now, its a hot shower in the early evening requiring a dose of cold water added to it...

some shade cloth wrapped around a few of the tubes in summer should be good enough, I'd think... anders soek jy 'n afdakkie vir die ding in die somer 🙂

9 minutes ago, Kalahari Meerkat said:

nope, but you can put a shade cloth over half the tubes for summer if you believe it neccessary

we have a 100 liter low pressure solar hot water cylinder... 12 evacuated glass tubes, yup gets pretty toasty in summer and even now, its a hot shower in the early evening requiring a dose of cold water added to it...

some shade cloth wrapped around a few of the tubes in summer should be good enough, I'd think... anders soek jy 'n afdakkie vir die ding in die somer 🙂

My neighbour at the previous place had about 60 tubes on his roof and he'd drop some shade cloth over some of the panels in the summer. This certainly worked for him, but only necessary because he heavily overspecced on the tubes. 

I have a 20 tube system, and in summer it can get to 80 deg C. This is not a problem for the geyser, pump or system itself, as there are safety release valves for pressure and temperature installed. When the temp is 80, just use more cold water in the mix for shower or basin. 👍

54 minutes ago, TimCam said:

I have a 20 tube system, and in summer it can get to 80 deg C. This is not a problem for the geyser, pump or system itself, as there are safety release valves for pressure and temperature installed. When the temp is 80, just use more cold water in the mix for shower or basin. 👍

Thanks for sharing. 80 degrees sounds really hectic. I get a lot of direct sun where I plan to install this on my roof. It will easily reach 80 degrees then im sure if I go with the 20 tubes. I should maybe consider a smaller system say 16 tubes. It interesting that you say the geyser can handle the high temps. Do the standard temperature and pressure valves in the existing geyser get replaced as part of the retrofit system? Would not carrying such a high temperature constantly in an electric geyser cause it to fail prematurely?

Thanks a lot for the detailed replies guys. I definitely have something to work with now to make my decision. For my needs we dont really need hot water throughout the day mostly in early morning or early evening. The newer geyser is pretty well insulated with usage in the evening the water temperature could drop to about 40 in the early morning which should be fine for a shower. If I can reduce my usage of the geyser electric element by 80 percent I think it will be worth it.

3 hours ago, Vin said:

Thanks for sharing. 80 degrees sounds really hectic. I get a lot of direct sun where I plan to install this on my roof. It will easily reach 80 degrees then im sure if I go with the 20 tubes. I should maybe consider a smaller system say 16 tubes. It interesting that you say the geyser can handle the high temps. Do the standard temperature and pressure valves in the existing geyser get replaced as part of the retrofit system? Would not carrying such a high temperature constantly in an electric geyser cause it to fail prematurely?

If possible rather go with a 20 tube system especially for winter and overcast days in summer. At worst you will "blow" a little hot water onto the roof on very hot days, and if you have JoJo tanks catching rain water from the gutters, you loose nothing.

How much water would typically be lost when the water gets too hot? Is it a matter of losing a little bit or being without hot water and needing all the water to be reheated again.

Just now, Wanderer said:

How much water would typically be lost when the water gets too hot? Is it a matter of losing a little bit or being without hot water and needing all the water to be reheated again.

Just a little bit

3 hours ago, Speedster said:

Just a little bit

Ours go to a Yo Yo tank so difficult to say. 10-20 lt. The vale opens at 80 degree C. After the valve is closed and geyser refilled it is 60. If it is a very hot day we just a use more water to keep it below 80 if we are around. 

Hi

I have a 20-tube retrofit for my 150l geyser. It works well in summer however in winter it is useless as the tubes are older and not that efficient.

To fix this I feed the 150l liter geyser into a gas geyser and set the gas geyser to 50 degrees as not to add cold water. I do have a Geyserwise controller and have changed my element in the geyser to 1.5kw to save the Geyserwise relay. I switch the element off and when the gas geyser gave me trouble I used the element as a backup.

That said you can still use your element with a Geyserwise controller to increase your temperature and you can do this at any time by setting the timers or even do it manually without a gas geyser.

If you do not want to use electricity ever then I suppose the shade cloth will work best.

I just spoke to another installer now advertising a 15 tube retrofit system on FB and he assures me the 15 tube system will be fine in Gauteng for winter on a 150l geyser. He said the systems are reaching around 50 degrees during the day at the moment. Conflicting information from two different installers. I should look for a 16-18 tube setup 🤣

Hi all, 

I have 24 tubes with they geyser below (pump system) with a geyser wise. The temperature at the tubes, according to the geyserwise) does not seem to ever get past 36 degrees even on really hot days. There is plenty of sunlight on the roof and the pope put of the collector is very hot to the touch. 

Is there perhaps a temperature setting on the collector system? 

I had a flatbed retrofit, that froze one winter. I replaced it with tubes. With power outages I had to get backup power to circulate water. With water outages I had to get backup water. I would go for tubes directly below the geyser on the roof if I had to. Now I have PV and a normal electric geyser. More energy can be directed to my geyser in winter and more to my pool in summer.

On 2022/08/07 at 2:11 PM, MrJay said:

Hi all, 

I have 24 tubes with they geyser below (pump system) with a geyser wise. The temperature at the tubes, according to the geyserwise) does not seem to ever get past 36 degrees even on really hot days. There is plenty of sunlight on the roof and the pope put of the collector is very hot to the touch. 

Is there perhaps a temperature setting on the collector system? 

You sure you have the probes connected properly / right way around?

On 2022/08/07 at 2:11 PM, MrJay said:

Hi all, 

I have 24 tubes with they geyser below (pump system) with a geyser wise. The temperature at the tubes, according to the geyserwise) does not seem to ever get past 36 degrees even on really hot days. There is plenty of sunlight on the roof and the pope put of the collector is very hot to the touch. 

Is there perhaps a temperature setting on the collector system? 

That seems like the air temperature and will screw up the pump control if it is the case. 24 tubes should get your geyser into the 80's (150l).

I been checking for some quotes on getting this installed on my 150l geyser. Just a word of warning for other people looking there are many fly by night guys doing these conversions at the moment and trying to make a quick buck. I contacted one of the companies yesterday advertising on FB. The company specializes in garage door spares so when I questioned them about what their actually experience is with solar water heater they said they have partnered with installer with over 20 years experience. Turns out the partner is just a private plumber. The system quoted on was kwikot. The installer then says he doesnt actually install kwikot but if the customer wants kwikot they the cost will be more. The system he is installing has solar controlled pump that runs all the time. If I am going on holiday I need to go in the ceiling to switch off the pump. Guy talks a big talk but red flags were going off in my head after that. Why would the pump need to run all the time? Shouldn't it be controlled to only circulate through the collector when the temp in the geyser drops below a certain temp? As much as I am quite hands on with DIY I don't look forward to ever going in the ceiling. In this day and age surely the pump can be controlled remotely so I dont have to go in the ceiling to switch it off each time I go away and again go back in the ceiling when I return to switch it on again. 🤣 This guy also assured me a 15 tube setup will be perfectly fine for winter. 

Hi all.  I just had a solar geyser retrofit installed for a 150 litre geyser (15 evacuator tubes, geyserwise max timer, 12V DC pump with 12 backup battery and 10W solar panel for pump).  Installation done on Wed 14 Sep 2022.  Cost me just under R15000.  Apollo tubes were provided.  Too soon to measure its efficiency in reducing my electricity consumption but I can say the system is ineffective for mornings especially if you require your water temperature to be more than 50 degrees. A typical household needs hot water mainly in the morning, say from 5am - 6am. That means the geyser should have been heating water from at least by 3am. But we know that around that time, there is no sunlight, therefore you'll have to use the grid. It is the same thing in the afternoon when people come back from work. That is between 6pm - 8pm. At around 4pm, the geyser temperature reaches its maximum around 55 degrees (this is measured on a day where the temperature is 27 degrees outside).  You may have to draw from the grid if you want the water to be >50 degrees. Therefore this system is more useful in the evenings but not so useful at the critical part of the day, that is, in the mornings.   So, I see the efficiency of this system to be far better in summer months than winter months.   There is a flaw in the geyserwise timer that I picked up today.  I have the timer to come on at 5:30am and go off at 7:30am.  I had loadshedding from 6am to 8am this morning.  But the timer indicated the “element was in use” (element indicator on the display was on).  This is misleading.

With the outside temp being at 27 degrees does not imply you will have to use grid power to reach 55 degrees. On sunshine days it should reach 55 without grid assistance.

I’ve just fitted a 30 tube system to my HP geyser of 250L and today it got to one 70 degrees Celsius.

I must say the reduction in electric usage so far, with the Geyserwise in play, is awesome. Over 40 reduction in power consumption.

Hi.  Is your system using heat pipes inside?

Evacuated tubes. I can send you the suppliers details but the parts are freely available to purchase online.

 

@VinRead this: Journal of Energy in Southern Africa. 

http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S1021-447X2017000100010

Edited July 20, 20232 yr by TaliaB