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Author Topic: Solar thermal not circulating  (Read 4518 times)
chris wills
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« on: May 15, 2019, 01:04:56 PM »

We have a solar thermal system, 30 thermomax tubes into a cylinder, for our hot water only, backed up with an immersion heater.
It has stopped working over the last few weeks, the water does not circulate.
The pump is fine, no issues with that, is there some sort of air valve on the tubes that maybe causing a lock of some sorts?
Pressure is fine.
Any first thoughts, I suspect a blockage somewhere.
« Last Edit: June 10, 2019, 04:31:51 PM by chris wills » Logged
chris wills
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« Reply #1 on: May 28, 2019, 09:10:51 PM »

Is there a way I can flush the tubes on the roof only?
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ecogeorge
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« Reply #2 on: May 28, 2019, 11:24:52 PM »

How do you know its not circulating -silly q  but you haven't said.
Is collector temp v  high.
What happens if you run the pump manually ?
more info please .
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Westie
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« Reply #3 on: May 29, 2019, 11:50:42 AM »

Is there a way I can flush the tubes on the roof only?

It's pretty unlikely to be a blockage in the collector, they're generally 22mm straight through. As George said the question to resolve is whether there is circulation , quite a hard thing to prove in most solar thermal systems. The pump is where i would start, it can be energised and quietly buzzing away but not actually spinning .eg stuck. Some pumps allow you to remove a centre screw and see if shaft is spinning but be careful and only work on the system when it's cold and close the valves either side before you take the screw plug out (if you have one).

youtu.be/QFYnwT08aCQ

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4kwp south facing array  SMA 4000TL grid connected.  2x30tube Navitron solar thermal panels (east/west). Arada 5kw S/C WBS. 25000Ltr underground rain water tank. KTM E-Bike  Cool
chris wills
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« Reply #4 on: June 10, 2019, 04:41:07 PM »

Thanks for the feedback, I actually have 30 tubes which I have now corrected in my first post.
The pump is working fine, I did inspect through the large screw on it and was fine, sometime ago. In any case I replaced the pump just to see how it was and no change.

In answer to some of the questions:

1. Tubes are Thermomax DF100
2. At its highest the roof temp reaches about 102 degrees, but the return pipe is all but luke warm, which indicates to me non-circulation?
3. All the electrics are OK, pump come on when it should
4. When you say manually run the pump, do you just mean switching it on myself? whats the difference between auto and manual in this case?

I was thinking issue with the tubes?
I really need help here to rectify it as I am living on an immersion heater booster to the storage tank, not the best.



* IMG_0009.JPG (153.91 KB, 480x640 - viewed 256 times.)
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Iain
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« Reply #5 on: June 10, 2019, 04:49:17 PM »

Hi
If the pump is fine, I would think it is either air, however if the pressure in the system is good how did the air get in, so possibly unlikely.
Is there a non return valve in the system? If so could that be stuck?
My system has an upstand in the pipe in the loft with a manual vent valve on. So mine is easy to check for air. Has your a bleed salve in the loft?

Just a quick question, how did you vent the air after changing the pump?


Iain
« Last Edit: June 10, 2019, 08:03:35 PM by Iain » Logged

1.98kWp PV (11 x Sharp 180 and SB 2.5)
20 x 65mm Thermal and 180ltr unvented
Powervault 4Kw - G200 Lithium-Ion (LiFePO4)
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daveluck_uk
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« Reply #6 on: June 10, 2019, 07:55:48 PM »

if it was all working and then just stopped and the pump is OK....it'll be air...undo bleed screw, let out the air,  top up with antifreeze, re-pressurise, jobs a good un.

Depending on your skill set you might need to get someone in!
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todthedog
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« Reply #7 on: June 10, 2019, 09:07:18 PM »

A garden sprayer is great for re-pressurising
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chris wills
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« Reply #8 on: June 11, 2019, 07:52:26 AM »

When the pump was changed, I shut off the 2 valves either side of it before removal.
The air bleed is near to the pump, but could there be one on the roof too? Maybe this would do it? Where would it be on the Thermomax tubes?
Where could the non-return valve be?
Many thanks for your feedback guys, food for thought.

Also do you know anyone in South Wales area who could look at it?

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chris wills
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« Reply #9 on: June 16, 2019, 03:40:25 PM »

Heres an image of my pump setup, I realise its not all connected through a pump station.
Does this pump need to be fitted vertically or is it OK as it is?


* IMG_8810.JPG (342.15 KB, 810x1080 - viewed 146 times.)
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chris wills
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« Reply #10 on: June 16, 2019, 03:41:17 PM »

A garden sprayer is great for re-pressurising


How do you use a garden sprayer to pressurise?
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Iain
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« Reply #11 on: June 16, 2019, 03:55:54 PM »

Hi
You have 2 options for re pressurising.

Mains cold water via a filling loop (same as a boiler filling loop) only suitable if your mains cold is nearby.

Or a garden sprayer with an adaptor on the end to attach to a filling loop. This allows you to add an inhibitor and re pressurise the system.

I do a bit of both.
The garden sprayer is used to inject the solar inhibitor, I then use the mains to take the pressure up to 1 bar.

Iain
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1.98kWp PV (11 x Sharp 180 and SB 2.5)
20 x 65mm Thermal and 180ltr unvented
Powervault 4Kw - G200 Lithium-Ion (LiFePO4)
9000ltr rainwater storage   Plymouth
Philip R
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« Reply #12 on: June 16, 2019, 04:07:38 PM »

Chris,
Your pump is incorrectly mounted.
The shaft should lay horizontally as per the instructions. The pump bearings are not designed as thrust bearings, so you will damage the pump quickly like this.
Isolate the pump, loosen the 52mm unions. Rotate till shaft horizontal and junction box either at sides or on top, but not bottommost.
Philip R
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chris wills
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« Reply #13 on: June 16, 2019, 04:32:09 PM »

Chris,
Your pump is incorrectly mounted.
The shaft should lay horizontally as per the instructions. The pump bearings are not designed as thrust bearings, so you will damage the pump quickly like this.
Isolate the pump, loosen the 52mm unions. Rotate till shaft horizontal and junction box either at sides or on top, but not bottommost.
Philip R

Hi Phillip,

Can you explain more please, what do you mean shaft horizontal? I did read that the bleed valve should point downwards for air purposes, is this the case?
Thanks for your feedback.
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chris wills
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« Reply #14 on: June 16, 2019, 04:33:17 PM »

Hi
You have 2 options for re pressurising.

Mains cold water via a filling loop (same as a boiler filling loop) only suitable if your mains cold is nearby.

Or a garden sprayer with an adaptor on the end to attach to a filling loop. This allows you to add an inhibitor and re pressurise the system.

I do a bit of both.
The garden sprayer is used to inject the solar inhibitor, I then use the mains to take the pressure up to 1 bar.

Iain

Hi Iain,

How do you do this? Do you have any pictures?
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