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Solar Heating Temps down


Sidewinder
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Hi you water solar fundi's out there,

I have a 5 year old 2 x 12 tube, 350 liter (1 x 200 liter in series with 1 x 150 liter) geyser, with Wilo pump at my property. Backup is a Heat Pump. Now that tenant has moved out, I have been observing the temps of the controller. It shows Geyser temp @ 40 Deg after a sunny day at 5 pm, with no hot water drawn. The Heat pump is temporary disabled. I remember after system was installed, that 50 deg + was achieved, so Heat pump hardly did any work.

Question: Is the temp drop normal seasonal, or do I need to service the tubes on the roof? Have done the cleaning part (mostly dust and bird poo), was more thinking along the lines of where the tube's copper element fits into the collector, that the losses are occurring.

The pump is working correctly, switching on when collector temp is >8 deg. Initially thought it may be an airlock or something, but then I would expect the collector's temp to skyrocket for a few seconds before the pump kicks in. All temp changes are gradual.

Any advice/tips etc.?

Thanks

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I haven't pulled one of the tubes yet. So the construction is not 100% clear. I thinking its a longish copper blob closely coupled to the collector tube, through which the water flows and heats up, so if it was scaling, it would be inside the collector. 

Or does it actually operate differently. I don't think the seal at the top where the tube fits into the collector would withstand Municipal water pressure.

But thanks, may need to pull a tube and inspect this weekend.

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I haven't looked at high pressure tubes, but on low pressure systems, the tube just pushes into the seal and is held there by the frame. One of my geysers started leaking a few weeks ago after some monkeys used it as a jungle gym. I had to pull out the leaking tubes, clean off a small ring of scale that had formed around the seal and re insert. The monkeys had moved the tubes so they weren't sealing due to the scale. Our water is quite soft, but there is some scale build up. The tubes are the lowest part of the system so I would imagine if your water is hard you would get quite a lot of scale or sediment building up there.  

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17 hours ago, DeepBass9 said:

Have you got scale on the inside of the tubes perhaps?

That was also my first instinct. I remember chatting to a client of mine that was considering Solar Geysers , in Rustenburg area  , but the installers said that it would not be feasible as the water is quite hard there and the scale buildup is bad. He also showed me all the geaser elements that he replaced over the years and it is amazing how bad the scale was on them.

Keep in mind he has a borehole .. 

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@Sidewinder it sounds like you have a Heat Pipe Evacuated Tube Collector. They come in 2 types of connections "Wet" and "Dry"

The "Wet" connection is where the fluid of the solar loop flows directly over the condenser of the heat pipe. Removing the tube breaks the water boundary and is therefore more of a hassle to replace.

In the "Dry" connection type the heat pipe condenser fits into a header tube allowing you to remove and install tubes without having to drain the geyser.

From my personal, limited experience i would look at your equipment in the following sequence:

1) Pump: If you have a cast iron pump then magnetic particles inside the water attach to the pump body resulting in restricted flow.

2) Non Return Valve: This can get blocked up from calcification build up. While you are inspecting the NRV you may as well also look at the pump isolation valves for blockages.

3) Temperature Probes: The tempertaure probes could be faulty. Check the collector sensor probe first as it is exposed to higher temperatures (especially during stagnation) and inspect for corrosion. 

4) Collector Blockage: Inspect for any restrictions. 

 

 

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2 hours ago, PaulF007 said:

That was also my first instinct. I remember chatting to a client of mine that was considering Solar Geysers , in Rustenburg area  , but the installers said that it would not be feasible as the water is quite hard there and the scale buildup is bad. He also showed me all the geaser elements that he replaced over the years and it is amazing how bad the scale was on them.

Keep in mind he has a borehole .. 

I've also heard in the Northern Cape they also scale up helluva quickly.

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I changed a solar geyser last week that had a leak on it . the owner said it hadn't been performing . while dismantling I found that the heating pipes in out were almost completely blocked with rust sediment as they had been using the cast steel fittings and so I changed them with copper . the new geyser works much better.

on the subject of scale I know a guy that puts 5l vinegar in his geyser  leaves for a couple hours then drains . I could not believe the amount of crudd that came out

cheers

 

 

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Thanks for the feedback @maxomill,

200 liter one is 6 years old, with the 150 add a year later, and been in daily use since then, approx 5 years. Would not have thought scaling would be a problem this early, but hey, who knows what "additives" the Muni add to the water.:o

The system is 22mm copper pipes throughout, but i see no unions were used when terminating the pipes to the geysers, so disassembly and re-assembly is going to be a mission. May as well add the unions while I'm at it.

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Thinking what the deleted post's content was, I thought of the following. A blockage, or even a partial one, should not impede the system too much, as the pump would just take longer to circulate the warm water through the system, as it works on a delta temp principle.

And I think therein lies a possible indication of the problem. Not enough solar energy is being translated into heat, so I will concentrate my search to the collector/tube manifold, as @Carl suggested.

But before I take it apart, I will switch the pump off, and see if the T1 probe in the collector climbs to +- 185 Deg, :wub: as I've seen it do that before, doing previous maintenance.

Wish these Chinese controllers parameters can be logged and graphed, like what we do with ICC & EmonCms.

Anyone keen to de-crypt the bus (RS-232/488?) between the relay controller and the LCD display and feed it into a Pi?

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48 minutes ago, Sidewinder said:

Anyone keen to de-crypt the bus (RS-232/488?) between the relay controller and the LCD display and feed it into a Pi?

I have been toying with the idea for a while but rather than using the info from the controller or attempting to get it from it ,  the idea is to use the probes directly on something like a Arduino and read the data from there. I am pretty sure it should not be too difficult to do.  But I will need to steal some time some where else to play with the idea ... 

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@PaulF007,

That's a great idea, I have been googling that kind of setup. The cost of 2 x controllers (2 x R1,5k) is a lot more than a simple NodeMCU (R200) + relays (R150) to control. 

I have successfully logged my normal geyser's temps into EMONCMS. Just need to add the delta temps cals and switch that pump!, but yes time permitting, and I'm not that hot on C coding.

I've mentally added this to my long long to do list......

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After reading temps, I write directly to EMONCMS. 

Howto: Click on the Feeds button in EMONCMS, to the top right there is a API help button. Once you've read through the example, you'll see how easy it really is.

Just replace all the relevant info to suit your installation, e.g. ip address, which node to write to, names etc.

You should first try (the emoncms write command syntax from your browser that is on a pc on the same ip network.

If you get a response that says "OK", then when you refresh your Feeds page, the new node will appear automatically. E.G. Node 2. If you have an older ICC Emoncms installation, ICC (ver2 and up) is writing data to Node 0. Node 1 is not used anymore, was used by ICC pre ver 2.0.

Click on Node2 to open it, and the data variable will appear there.

Once you've done that successfully, you can edit your Arduino code and add the very same "write command" instruction in your main loop, and the data will appear every x second, depending on the delay you've set between temp reads.

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21 minutes ago, Sidewinder said:

Once you've done that successfully, you can edit your Arduino code and add the very same "write command" instruction in your main loop, and the data will appear every x second, depending on the delay you've set between temp reads.

Never mind again did not read to the end :D..  I personally prefer to send the data via mqtt that way you can also use it with other applications 

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No, ICC only reads and logs the Voltronic range of invertor's data, but included in that is EMONCMS and it's associated databases, SQL Lite, I think. Not an expert at that.

So you can read/write etc any data to the database via emoncms.

So even if you don't have ICC, if you have a pi or simular (linux) box, you can install emoncms and its goodies as a standalone setup.

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Just now, Sidewinder said:

So even if you don't have ICC, if you have a pi or simular (linux) box, you can install emoncms and its goodies as a standalone setup

Correct , I did a post somewhere on the forum where I did a "portable emoncms" that you could run in Windows , works quite well. 

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1 minute ago, Sidewinder said:

Cool, at least now readers can use Windows for this type of setup as well. I'm sure the data doesn't give a damn if it is Linux or Windows:lol:

Nope , and the nice part is you could backup the whole folder so if some were to go belly up it is just copy and start. My own system runs on Lubuntu as it is a little lighter on resources.

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