Air vent

[KurtP3]

I have a drainback system with the tanks about 20 ft below the flat panel collector. I am wondering if I need an air vent at or near the top HW outlet pipe and if so what kind so that it automatically discharges air when refilling. It will have to be outside at the top of the system, or inside about 12" lower.

[LucMan]

As long as you maintain an airspace in your drain back tank, size it correctly , and slope your supply and return lines back towards the tank no vents are required.

[KurtP3]

I like that answer. Minimizes complexity and heat loss, even though there is one shown in this diagrm: https://www.energy.gov/sites/default...n%20Back_0.jpg

I'm now in the process of checking for leaks and was wondering what the best method to use for patching small cracks in the collector piping, especially at intersections or T's.

[LucMan]

Go to AET solar web site and find the DB manual in the recourses area. Follow the schematic. Only a pump in the piping to the collectors and back to the tank.
To repair copper leaks you can use soft solder or silver brazing rod. Silver braze works the best and can withstand higher temps and pressures. Requires a lot more heat to melt it to the copper, won't work with a propane torch, you'll need acetylene B or mc tank.

[KurtP3]

Now my drain back tank shown in the photo has an overflow tube and no air vent connection at the top surface as sketched in the attached diagram from SolarHot USA. I bought the system (barely) used so am trying to piece this together. Maybe I don't need an air vent, despite.

I don't know why the schematic shows the drain back connection from the HW In to panel collector since it is not at the lowest point.

As an aside, the heat exchanger HW tank in the background is the replacement for the resistance heater tank when it fails (soon). There is a (WT1) storage tank not shown I was going to use as indicated in the attached schematic.

Thanks for your help.
Drainback tank 2.jpg

[Plisken]

Apologies for jumping threads but I don’t see a way to post a new post. Im wondering if anyone knows of an alternative to AET DB exchange Drainback tanks as they aren’t making them anymore.
thanks
Steve

[azdave]

Apologies for jumping threads but I don’t see a way to post a new post. Im wondering if anyone knows of an alternative to AET DB exchange Drainback tanks as they aren’t making them anymore.
thanks
Steve

I don't know about your tanks question but this forum has a delay time between when you first join to when you can post a new topic. It is not very clear that there is a delay for new members to post a new topic so we quite often get people jumping into an old thread like this.

[littleharbor2]

Apologies for jumping threads but I don’t see a way to post a new post. Im wondering if anyone knows of an alternative to AET DB exchange Drainback tanks as they aren’t making them anymore.
thanks
Steve

Top left area of this page, click on "Forums". Choose the appropriate category and you should see "New Topic" toward the left side of the page, above the list of posts.. Click on that to get started.