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Old 12-22-20, 11:44 AM   #12
Helper EcoRenovator
Join Date: Mar 2012
Location: Warwick, Rhode Island
Posts: 85
Thanks: 21
Thanked 27 Times in 16 Posts

I built a drainback system using 2 evacuated tube collectors. 20 tubes per/collector.
My system has been working flawlessly for over 8 years now..

No antifreeze in system
No pressure in system at all
No stagnation issues whatsoever even on the hottest days of summer.

I think one of the biggest keys in a drainback system is the size copper used for drainback. I use 3/4 copper. 1/2 inch copper to me just doesn't allow the water to drain back quick enough.
I use 3/4 to and from collectors and thru my whole system.

My system cycles even on cloudy days in the winter.. and some days even when it's snowing which is crazy but evacuated tube collectors are just fantastic.

The only tweak I made to my drainback piping after installation was I added a T fitting to the drainback line right where the hot water was entering back into the drainback tank on TOP. I installed a ball valve to the T fitting and cracked it open so I could allow air to enter the pipe during drainback mode. I also added a pressure relief valve at the highest point of the evacuated tube collector. This valve allows a tiny bit of air to enter the system during drainback mode so that a vacum is not created, thus slowing the water from draining.

by doing that the returning hot water returned 20 times quicker then before.

My system is a bit different in that my solar heated water returns to my 6 gal drainback tank (use to be 6 gal hot water heater) then travels into a coil located inside my 40 gal insulated storage tank so the heated coil is surrounded by domestic hot water.

So my pre heated 70 to 120 degree storage tank water feeds my Tankless hot water heater.

My goal was to STOP feeding my tankless hot water heater 48 degree ground water.
My tankless has to use more energy to heat ground water from 48 up to 110 degrees for use with tap water / showers etc. (domestic hot water use)

By having my domestic hot water preheated via solar I am saving MILLIONS. (ok ok not millions but I'm saving, rest assured)

That's about it..

My drainback tank is located in my basement next to my storage tank and every drop of water running thru the collectors drains right back without any problems very quickly once the pump shuts off.

My 2 evacuated tube collectors are mounted side by side and tilted for quick draining.

I have PDF files of my system if anyone wants to see them just shoot me an email.

Nice to see everyone involved with solar. Every little bit helps.

(To the gentleman from Hong Kong...Parabolic's pointing at evacuated tube collectors? Holy moley look out... and don't be afraid of evacuated tube collectors draining. They drain faster then flat panel hot water collectors guaranteed)

Take care
Pat from Warwick, RI

Please Note:
Comments and/or suggestions I make here at the forums on 'your' projects as well as my own have all been carefully and scientifically calculated by 'the seat of my pants'
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Last edited by solarhotairpanels; 12-24-20 at 07:05 PM..
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