Solar Hot water panel hook up

Check the path length for a water molecule that enters and travels a riser to the exit. If the length is equal for each 3/8" riser path, they are both correct.

Sounds like a "ladder" or "harp" style collector. Generally you supply and return from opposite corners. You want every tube to get equal flow by having the fluid paths equal.

Also 1-1.5 gallons of storage per square foot of collector would provide a good portion of your DHW. Six collectors for just DHW may be a bit overkill. Most home packages, for a family of four, would be 60- 80 gallons of storage with two or 3 collectors, 32- 40 square feet of collector or so. If you oversize the array it could lead to over-heating issues in the summer months.

You could pipe a drainback system which would address overheating, but you still have more square footage than you need with 126 square feet.

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A few things to keep in mind

Flat plate panels at best heat up water to 80 degrees above the outside temperature (usually closer to 60 F). Hook them up in parallel (not in series).
Install a good check valve on the system and make sure it works, otherwise the system will thermosyphon at night and cool your storage down.
You really should consider a separate smaller storage tank as the large mass of water in your main tank will mean most of the time you will have some slightly warm water and no hot water. Typically panels are matched to a much smaller tank size. With some controls you could possibly set up a small storage tank off the panels and then when it reaches temperature than dump to storage.

Would you mind posting some pics when you're done? Right now I heat with an Englander furnace, but we hate forced air and want to go with hot water heat in the future. Since it will be a scratch built system I want to incorporate solar from the get-go.

You might want to pressure test the panels before hooking them up. That's a lot of water to heat with solar, an 80 to 100 gal tank is the most I see, except for home heating applications. Though if you are preheating before an electric tank that might be fine. Adding an electric heater to a 1200 gal tank will spin your meter like mad. Have you considered a on demand, some work in conjunction with solar preheated water.

I have a 64Sq Ft home built pex/alum collector tied to 450 gallon unpressurized storage. it is draindown solar system, which pumps and drains dircectly to and from storage. It works good with outside sunny temps in mid 80s on up, with storage tank temps ranging between 115 and 125 usually. What the above folks are saying is true, get a smaller tank and you will have hotter water from your solar and a longer heating season. I have good service with my solar system since may, but with smaller tank it would be better. Basically with solar (at least my system) you will get so much gain every time the water passes thru collector. I gain on average under 15 degrees on my system with each pass thru collector. You might do better since your collector is copper, but flow rate is important. It takes a long time at 5-6 gallons per minute to get big storage volume up to temp. A smaller storage will decrease the time it takes to heat it up and you will get much hotter temps which will help carry you thru days with no sun. With 1200 gallons, it will be slow going to heat it up that volume and it is amazing how much the DWH will reduce temps if you use much.

My collector will kick on on sunny winter days for several hours. If storage tank is 150 degrees, water will come back about 165 degrees, but again does not add much when volume of water and shrort winter days are factored in.

I recently purchased another 120sq ft of collectors that will increase total area to 184sq ft. I will add a 250 gallon stainless tank that came with the collectors that I will use as draindown system for solar with 120' DHW 1/2 copper coil and elimiante the larger tank from the solar set up, but keep for boiler . My additional tank will have a 60ft 3/4 copper loop from wood boiler for when solar not working, basically added as another zone off boiler.

On another note, I would not want a pressurized solar system. I know they sell lots of commercial systems this way. If your pump fails or electric service is cut (if AC pump) in hot weather, that thing will make steam if your relief valve does not open. Plus you should monitor water ph really close. My drain down system has work without issues since installed last fall. during pump outage, sytems drains out.