pump too big for my solar plans??

[kjcole]

First, is my pump too big for my pool? I sure get a brisk return flow, and the filter reads about 10 psi when clean.

This spring I'd like to add solar to my system. I'm wondering if I should plan on valving that will allow me to down-regulate pressure through the panels (given my pump size and the fact that I'm planning on rack mounting my panels just a few feet above pool height, with my inlets within 10 feet of the filter). I'm worried that with a 1 1/2 HP pump and panels so close to pool height that I could end up with too much flow (and pressure) in the panels. I have a single standard pool return with a standard skimmer (both Lomart). Should I just plan on a ball valve ahead of the 3-way which would allow me to shunt some of the flow past the panels? If I do this, should I measure flow out of the panels to help me adjust the valve optimally, or are there simpler ways to adjust the shunt?

Should I be looking at panels with 2 inch manifold headers vs 1 1/2, or doesn't it matter? I'm planning on panels usually sold for in-ground pools (e.g., 4X8, 10, or 12 with a total about 50% of pool surface).

Also, should my SWG cell be placed before or after the panels (will the cell work more efficiently with warm water?)

Any other special plumbing considerations?

Thanks in advance. This has been my first year with a pool, and now I'm trying to design my own solar. I suspect that good solar is not as simple as just hooking up some panels to some PVC and pulling the lever. And a lot of the technical info on the web is either confusing or contradictory.

Kelly

 

[JasonLion]

Your pump is larger than it ideally should be. Larger pumps use more total electricity. Since your filter pressure is only 10 psi, there aren't going to be any problems from the large pump other than the electrical usage.

A three way valve will allow you to adjust the flow between the normal return(s) and the solar panels. Figuring out the ideal position for that valve will be a little tricky without a flow meter. Pushing too much flow through the panels can shorten their life significantly.

Larger manifold headers are better, but it is only a small difference. Usually there are other factors that are more important when selecting panels (like price).

Solar heat can be really really simple if you just lie the panels on the ground and are willing to manually drain them at the end of the season. Mounting and plumbing panels on a roof makes things complicated.

 

[kjcole]

Thanks Jason.

Since I run my pump from about 9-5 each day from May-September, would it make sense for me to install a different (smaller?) pump?

Also, I was planning on building a rack and orienting/plumbing for automatic drainback, and using check valves, vacuum breaker, etc, etc, plus an automatically controlled 3-way -- basically treating it more like an inground pool (and anticipating ~$1600 if I do the install). Am I over the top on this? Would I get the needed performance by purchasing the 2X20 panels sold for AGP, roll them out in the summer and roll them up for the winter? and use the savings to get a different pump?

Kelly

 

[JasonLion]

It isn't always worth it to replace a working pump. It depends on how high your electrical rates are and how much money you are willing to invest with a several year payback. Getting a smaller single speed pump will have a very long payback time. Getting a two speed pump or variable speed pump can have a much shorter payback time. If your electrical rates are low none of it might be worth it. If your rates are high you can have very rapid payback times in some cases.

The ideal way to setup the solar system depends on lots of factors. In general spending more money gets you convenience and aesthetics, and to a lesser extent efficiency. An automatic controller is very convenient and will improve efficiency unless you are very diligent. Racks can improve efficiency in some situations. Aesthetic choices vary from person to person. I am just saying that you can go very simple and it will work. Improvements from there cost more, but are usually worth it if you can afford it. If you are putting the entire system together yourself there are some advantages to starting really simple and then improving the parts that bother you. That way you find out which parts are important to you before spending the time/money to add a feature you might end up not caring about.

 

[mas985]

If you are worried about too much pressure in the panels, you can always install a solar bypass valve in addition to a solar controller valve. Basically, you just connect the supply and return solar pipes with a smaller pipe and ball valve somewhere close to the pad.

Usually, you can set the pressure by looking at what the filter pressure is with the valve 100% on and 100% off. With all of the water going through the solar panels, the pressure will be the highest and with the bypass fully on, the pressure will be the lowest. Depending on the size of the bypass, most if not all of the water could bypass the solar. Anyway, if the pressure on the filter reads higher than the panel pressure recommendations (which are pretty high by the way), then you can reduce the pressure by bypassing some of the water. You just need to be careful that you are not bypassing too much where there is little flow through the panel.

I prefer this method to adjusting the 3-way solar valve because it is a bit easier to do and you can then use the 3-way to just turn the solar on and off.

Note too that for elevated solar panels, the pressure is lower than the filter pressure by the height of the panels / 2.31. So for example, we I run my solar panels, the pressure in the filter is 28 PSI. Because the panels are 25' over the pad, the pressure in the panels cannot exceed 28 - 25/2.31 or 17 PSI. However, there is loss in the filter and pipes going up to the solar, so I once measured the actual solar pressure to be only 9 PSI. This is very low pressure even though I am putting close to 65 GPM through the panels. So I really don't need to bypass any of the water.

Even though you won't have much elevation on your panels, you may still not need to bypass much of the water. It really depends on the running pressure of the panels. If you plumb all of the panels in parallel and have quite a few of them, the pressure in each panel could be quite low.

Also, a 1.5 HP AG pump is probably no more powerful than my 1 HP IG pump. In fact, my guess is that it is less powerful. So, I am not sure you will actually have a problem but if you want to be safe, put in a solar bypass.

 

[kjcole]

Thanks to both of your for your terrific insights. I have a much better handle on this now. I'll report back here this spring (with pix and performance data) after I go solar. Our electric rates aren't too bad here, so sticking with my 1 1/2 SPL rated motor makes the most sense right now. I like the idea of an extra valve to tune flow through the panels, given the ease and low cost of plumbing it in.

Kelly