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Author Topic: Solar fittings and fixings  (Read 530 times)
taliz
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« on: October 03, 2018, 01:46:29 PM »

Hi all

I've decided to make use of the solar coil on my tank and I've got all the main items but am a bit foxed on the fittings and wondered if any can help?


1, The stainless DN16 pipe  I was going to use from the collectors down to the pump station  and from the pump station to the tank. This raises two questions.
    1a, The Output thread on the  pump station is fine and you can get a tight fit, however, on the collector side the thread is shorter so when The dn16 pipe  nut is on as far as it goes, there is a slight gap between the gasket in the nut and the flat edge on the male thread.  Is it ok to use two/three gaskets and plenty of ptfe tape on the thread
    1b, I tried one of the dn16 pipe nuts on an old 22mm compresion fitting and it dosen't fit. Therefore I assume that I will need two connectors to fasten the dn16 pipe to the tank The first being one of these
https://www.navitron.org.uk/duofit-adaptor-to-22mm-copper-pipe  followed by a straight 22mm coupler.  Is this the best way of doing this?

2, Air vent?? The collectors are on a flat roof so easy to get to. Whats the best way of doing this? My initial thought was a 3/4 female tee.  One side to screw onto collectors male thread. Put a standard 1/2inch brass radiator bleed valve into the top via a reducing bush. Then connect the dn16 pipe to the remaining branch via a dn16 coupler like this https://www.navitron.org.uk/store/solar-panels-hot-water/pipework-and-fittings/plumbing-fittings/twin-nipple-16..  Is there a better way of doing this?

Thnks in advance[/list][/list]
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Iain
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« Reply #1 on: October 03, 2018, 03:40:13 PM »

Hi
I just did all my pipework in 12mm copper. Easy to bend and connect up.
For an air vent I used an upstand of 22 mm ( about 300mm long, with a radiator bleed on the top). One on the outlet side of the pump and one inside the loft on the return leg of the collector. Works great. Any air slowly collects in the upstand and can be easily bled away. The top vent doesn't need to be right at the very top. Mine is about 300mm below the top point and works well.
Iain
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offthegridandy
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« Reply #2 on: October 03, 2018, 06:39:33 PM »

Question for the solar thermal experts.  Can you not fit an automatic air vent on the 300mm up stand so any air is automatically removed.  one of these.

https://www.screwfix.com/p/bottle-air-vent-15mm/34359?tc=LA2&ds_kid=92700020952478947&ds_rl=1249799&ds_rl=1245250&ds_rl=1249481&gclid=EAIaIQobChMIns7gs-rq3QIVqbztCh3D3wDVEAQYASABEgLv6fD_BwE&gclsrc=aw.ds&dclid=CM_d6bfq6t0CFdDcGwodWc8OhA

Or are they not safe at the working temperature?

Andy
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Antman
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« Reply #3 on: October 03, 2018, 06:49:53 PM »

Hi Andy
I think we had many discussions about auto air vents early on. The short answer is never use them on solar. They cannot withstand the high temps, and certainly not stagnation temps, and will at some point cause repeated loss of pressure issues.
The manual rad bleed valve is the way to go as once the initial air is purged it should never need to be touched again except during service/replacement of the fluid.
Regards
Antman
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offthegridandy
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« Reply #4 on: October 03, 2018, 08:12:50 PM »

Thanks for that Antman.
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u/floor heating from oil boiler cross linked to 12 Kw WBS
taliz
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« Reply #5 on: October 03, 2018, 10:02:12 PM »

Hi

I'm using the flexipipe so I can experiment moving the collectors around the flat roof. In winter when the sun is lower I may have to move them back to just outside the bathroom window to avoid  shading from a tree.  I was going to put the bleed valve straight into the tee but if I put it on an up-stand then I'll prob use a 22mm equal compression tee with adapters  left and right to go into the manifold and flexpipe.
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Fionn
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« Reply #6 on: October 03, 2018, 10:13:05 PM »

I find those automatic air vents are inclined to fail everywhere to be honest. They mask some symptoms of poorly performing systems - which is probably why some plumbers seem to love them.
It is much better to avoid getting air in the system in the first place and deal with any sources as they arrive.
I too used plain copper with high temperature insulation for my solar pipe runs, the DN16 was crazily expensive.
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Philip R
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« Reply #7 on: October 05, 2018, 12:10:24 AM »

AAVs are useful in bungalows where pipe distribution is in the attic. Try bleeding a bungalow heating system with manual bleeders or none at all when the pump is air locked and the attic is full of rockwool, no lights and no hardstanding areas.

Not a problem in two story building where upstairs radiators receive the initial air.

Good solar install would have gradiented attic pipework and a bleed facility at the high point, (AAV) which can be manually closed off.

Philip R
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