Need Info on DC pump to circulate water in solar pool heater

**Naptown** · 09-17-2012, 05:08 PM

there are several major flaws to your system.
you have almost 880 feet of pipe in one loop.
first off you need to take the 4 coils out of series and connect in a reverse parallel configuration using at minimum 1 1/4" pipe for the supply and return.
Search here for how to plumb this it is a topic that has been discussed many times.
That will reduce the pressure drop considerably on the array and bring the temperatures in the collectors down to where it will actually produce an appreciable amount of heat. (Having very hot discharge water will reduce the BTU output dramatically in these type of systems. You want to go for higher flow rate and lower temperature at the outlet ideally only a few degrees of difference from inlet to outlet.)
Try that with the pump you have although for the most part the filter pump is what is used unless you only filter at night.

Actually it appears you have them in reverse parallel however you will never be able to get enough flow through the headers (inlet and outlet pipes to get any real flow through the collectors.

**inetdog** · 09-17-2012, 05:53 PM

Originally posted by Naptown

there are several major flaws to your system.
you have almost 880 feet of pipe in one loop.
first off you need to take the 4 coils out of series and connect in a reverse parallel configuration using at minimum 1 1/4" pipe for the supply and return.
Search here for how to plumb this it is a topic that has been discussed many times.
That will reduce the pressure drop considerably on the array and bring the temperatures in the collectors down to where it will actually produce an appreciable amount of heat. (Having very hot discharge water will reduce the BTU output dramatically in these type of systems. You want to go for higher flow rate and lower temperature at the outlet ideally only a few degrees of difference from inlet to outlet.)
Try that with the pump you have although for the most part the filter pump is what is used unless you only filter at night.

Actually it appears you have them in reverse parallel however you will never be able to get enough flow through the headers (inlet and outlet pipes to get any real flow through the collectors.

I have never heard the term "reverse parallel". Could you explain it, and why it would be better here than "normal" (?) parallel?

**Naptown** · 09-17-2012, 05:59 PM

Originally posted by inetdog

I have never heard the term "reverse parallel". Could you explain it, and why it would be better here than "normal" (?) parallel?

It evens out the flow through the collectors to a great extent without the need for balancing valves etc

Very similar to connecting batteries on the diagonal

reverse prallel collector plumbing horizontal.pdf

**inetdog** · 09-17-2012, 06:03 PM

Originally posted by Naptown

It evens out the flow through the collectors to a great extent without the need for balancing valves etc

Very similar to connecting batteries on the diagonal

[ATTACH]2287[/ATTACH]

I see.
The equivalent of diagonal wiring for parallel batteries. But you still need a big enough header, just like you need a heavy bus or interconnect wire for batteries and the equivalent of the battery to CC link needs to be of higher gauge wire than the individual battery cables.

Thanks!

**mcaimless** · 09-18-2012, 10:19 AM

Yes, I made a mistake in my original post, they are in parallel, not series. I used 1/2 pipe for supply and discharge because that was the outlet size of the pump I was using. I didn't see any use in using pipe that is larger than the pump outlet. I realize that most use their pool pump--that does have 1 1/2" outlet and allows for larger manifold size for the piping-- but I'm trying to utilize solar power to circulate the water in this case. Here in Arizona, our power rates are very high during the daytime so pool pumps run at night to keep costs down. I'd like to run this system entirely with solar and make it cost-free to run.

I guess my original question was what size should the solar panel be to run the larger pump? The specifications on the pump are:

Power: DC12~24V
Current: 3.5A@24V, 1.6A@12V
Output: 40.0L/m (635 GPH) @24V or 380GPH @ 12V
Pressure: 9.3psi @24V
Motor: DC 3 phase coil, more torque and quiet
Power: 84Watt/ 19.2Watt
Speed control(3 wires): 0-5V analog

Again, this pump has a 1/2" outlet so I don't see any use to run larger pipe to the collectors. I guess I just have to hope that the water will circulate as it is...

**inetdog** · 09-18-2012, 12:00 PM

Originally posted by mcaimless

I didn't see any use in using pipe that is larger than the pump outlet.

Well, by the same token, I should not use any wiring that is physically larger than the wire inside the fuse that is protecting it.

The resistance to flow inside a long run of pipe will still be dependent on the size of the pipe, and you want to minimize that resistance by using larger pipe. The flow rate of the pump will be dependent on the back pressure, which in turn is dependent on the size and length of the pipe.
Since you have multiple coils of collector tubing, the point where they come together (the manifold) needs to be even larger so that the pressures at the ends of each coil are similar. That will produce more equal flow across all of the coils. The reverse parallel arrangement, if you use it, will help some, but it will still be better with a larger manifold.
Once you get past the section joining all of the coils, you may want to reduce the pipe size some, but it will still be beneficial to run pipe which is larger than the pump outlet if that is a long run.

**mcaimless** · 09-18-2012, 12:01 PM

OK, that makes sense. Any idea what size panel would work with that pump? Thanks.

**clarkakevin** · 03-07-2015, 07:37 PM

Just looking for the exact same information. Did you solve your problem? I'm new to arizona and this seems like a great way to save money.

**dolejh** · 05-28-2015, 09:29 AM

posting so i can download pictures...

thanks

**inetdog** · 05-28-2015, 03:58 PM

posting so i can download pictures...

Originally posted by dolejh

thanks

Doing that by bumping an inactive thread is probably not the best way to establish a good reputation.

**dolejh** · 05-28-2015, 04:33 PM

I appreciate your comments - perhaps a PM would have been a better way to offer your advice. Replying with your comment also "bumps". Perhaps if there wasn't a 1 post min to download a picture I wouldn't have made a post to begin with. I was only searching for information.

Thanks for your advice.

Cheers
JD

PS - I tried to send this to your in a PM as I myself suggested - but there is a 10 post min for that... now back to more important things.

**inetdog** · 05-28-2015, 05:32 PM

Originally posted by dolejh

I appreciate your comments - perhaps a PM would have been a better way to offer your advice. Replying with your comment also "bumps". Perhaps if there wasn't a 1 post min to download a picture I wouldn't have made a post to begin with. I was only searching for information.

Thanks for your advice.

Cheers
JD

PS - I tried to send this to your in a PM as I myself suggested - but there is a 10 post min for that... now back to more important things.

People who need only one post to get started usually post in the introduction topic, http://www.solarpaneltalk.com/forumd...ourselves-here.

Need Info on DC pump to circulate water in solar pool heater

Need Info on DC pump to circulate water in solar pool heater

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