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Author Topic: Solar thermal, drain back system, suspect fault  (Read 412 times)
roys
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« on: October 15, 2020, 07:56:04 PM »

I have had a twin panel, twin flask drainback system, got it fitted about 12 years, worked faultlessly for the 1st 10 years, had two or three problems recently, pump seized, leaking pipes, however the more recent problem is a bit more worrying.
The flasks appear to be filling themselves past there max fill level, yesterday I drained it again down below the max level, looked at it today the the flasks are maxed out to the top again.
The hot water cylinder is a twin coil job one for the wood burner the other for the solar.  Is it possible that the coil has a split in it and is topping up the flasks? It is a gravity fed system so the feed and expansion tanks are above the cylinder which will give a slight head of pressure above the solar flasks.
My water is from a well and is a bit acidic so wondering if that has rotted the copper coil. Hot water cylinder was fitted the same time as the solar so about 12 years old.
What do you think, any other thoughts?
Cheers
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Philip R
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« Reply #1 on: October 15, 2020, 08:21:14 PM »

I think your deduction is a correct one, I wont say good because it isn't.
I would suggest a pressure test either air or water. check for pressure drop and eliminate any leakages from the test fittings. There is no easy way to do this other than some diy plumbing  the pressure gauge could be a manometer loop up to the attic, if you do not have a pressure gauge to hand.
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Philip R
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« Reply #2 on: October 15, 2020, 08:46:23 PM »

Is your cylinder made of copper? If the copper coil has been corroded due to the acidity of the water, the copper tank could be on its way too.
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roys
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« Reply #3 on: October 15, 2020, 09:23:17 PM »

Yip tank is made of copper.
What pressure do you reckon for pressure test 1B?
I can get a loan of one of the pressure test pumps that plumbers use.
Is the best way just to disconnect solar coil at cylinder blank one end of coil and pressurise up with pump, I suppose I could just take of the solar pipes at the coil and see if the coil just keeps leaking water into a bucket.
Thanks for reply.
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Philip R
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« Reply #4 on: October 16, 2020, 11:30:15 AM »

No need to go too high. I first suggest normal operating pressure of the solar thermal system. Then go higher say in 5psi increments.

The other method is to disconnect the solar heating tails off the cylinder, if allowable pipe movement facititates this. Does water from the cylinder drip out the bottom connection without ever stopping?
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roys
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« Reply #5 on: October 16, 2020, 01:06:40 PM »

Think it is time to order a new cylinder, it is a Newark cylinder so still on the go, that way I can get it touch and they will hopefully make me a like for like replacement maybe even in stainless, cost may say different.

When I look at the whole system more closely the solar side is knackered, the controller has just given up and I canít stop the weeping push fit connections in the drain back box which contains the flasks, pump and filter.
Anyone suggest next step for replacing it but keeping my two solar panels.
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donegal
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« Reply #6 on: October 16, 2020, 03:21:24 PM »

Is the drainback system an Aton system ?,  i have Aton drain back i bought second hand for my garage and had problems with the joints in the pump/flask area ,  but replacing the plastic pipes with microbore copper solved it, perhaps thats an option.

Regards
Tony
 
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roys
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« Reply #7 on: October 16, 2020, 08:21:22 PM »

Hi Tony, yes it is the Aton system, was thinking about 8mm microbore, not sure what to do about the controller though. Maybe have to learn PIC or Ardinuo or whatever it is😀 and make my own
Got any pics of your modified system please?
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donegal
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« Reply #8 on: October 16, 2020, 11:52:40 PM »

Roys,
 As usual, im no expert in this, but i fitted my second hand system 2 or 3 years ago and had a few problems in the first weeks. it being running trouble free since.

It might be worth checking the drainback valve in the top right of the container box as if this fails it wont allow the water to drain from the panels and you'll get high temperatures in the collectors, massive pressure in the system, leaks at joints, airlocks and it might possibly blow the water from the coil into the containers,  its a simple ball valve.
Theres also a filter in the same location, again that could cause problems if blocked.  both fitting can be simply unscrewed, the ball valve fitting needs removing first.

Which controller do you have ?, i have the pv system at 12v but do vaugly remember from the literature that the mains voltage controller can be replaced by a simple differential controller.  Have you got a copy of the installation literature ?

Tony
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roys
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« Reply #9 on: October 17, 2020, 09:07:35 AM »

Thanks Tony
I have cleaned the filter in the black casing top right, where is the ball valve?
It is the 24V controller for from two small solar pv panels.
Cheers Roys


* A4BC22AE-3C07-4701-A046-3089BA306940.jpeg (388.99 KB, 1152x864 - viewed 58 times.)
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donegal
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« Reply #10 on: October 17, 2020, 10:31:28 AM »

Roys,

The one way valve is just behind the filter, its probably horizontal.   ill send you the literature i have.  i did a quick bodge job on mine as i had better things to do on a suuny day, I removed it and put a slightly open stop valve in its place and never got back to change it, im not recommending that, but its why i cant remember exactly how it was placed. Its on a long list to do and while its working it will probably never be done.


Mines the same system, so it is 24v.

the pipes i replaced were around the pump



ill send on the literature i have as there are photos, which are more useful than the diagrams

Tony
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roys
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« Reply #11 on: October 17, 2020, 10:45:41 AM »

Thanks again Tony
I donít recall seeing that valve.
When you replaced the pipe work did you fit new compression fittings? Did you have to use some of the original fittings like at the bottom of the flask?
Cheers
Roys
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donegal
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« Reply #12 on: October 17, 2020, 10:53:57 AM »

roys,

i generally re-used the fittings,  i repalaced two with similar new push fitting, as the previous owner had tried to seal leaks a few times with plumbers tape.

I just happened to see the fittings in a local hardware store,  they were John guest fittings.

ignore the vertical pipe in the centre of the photo, its just sitting there for some reason Grin, nothing to do with the system

Regards
Tony

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