Solar panel configuration dilemma

[JasonLion]

The color is purely cosmetic, it is exactly the same pipe and you work with it in the same way. By the by, the bell end pipes are available in white as well.

 

[mas985]

Here is/was my thought...and I bet I am over thinking this (please let me know), but in this case where I am trying to get my low speed to run the panels reliably, might long sweeps verses short ones be the difference. As we discuss this it becomes even more apparent in my thick head that I should put all six panels in parallel to also reduce loss.

Replacing 90s before the VRV will help because of the reduced pressure loss makes the pressure higher at the VRV. However, replacing the 90s after the VRV will hurt because it would reduce the head loss after the VRV and the pressure at the VRV would drop. The difference in head loss for each 90 at 45 GPM is about 0.25 feet of head. Not much to write home about unless you have a lot of 90s.

I know I am confused about this. I had been thinking of the vacuum release being at the very top of the system, and thought it might leak if it did not have enough pressure on the water side.

Normally, I would recommend placing the VRV at the top of the panels because it make priming and draining a bit more efficient but it isn't necessary either. Some solar installers will place the VRV on the supply pipe right above the pad to make replacement easier. This also has the effect of reducing the amount of pressure the pump needs to produce to keep the VRV close. So it may possible to run on low speed even with the VRV. To make sure it is possible, what is the filter pressure with and without solar on high and low speed? Also, I can tell you what changing the 90s will do if you tell me how many 90s we are talking about and where they would be (pre vs post VRV on the supply pipe above the pad).

 

[linen]

Is there a VRV that you recommend?

To make sure it is possible, what is the filter pressure with and without solar on high and low speed?

Unfortunately, I did not write down my different pressures last season, and my memory is probably not too reliable. I have not opened the pool yet, so when I do this weekend (I hope to open this weekend) I can get the no solar panel readings. I will not be able to get the pressure readings with solar panels reading since they need to be installed/reinstalled perferably in their final configuration. Any thoughts at how to best proceed?

Also, I can tell you what changing the 90s will do if you tell me how many 90s we are talking about and where they would be (pre vs post VRV on the supply pipe above the pad).

I am willing to put the VRV wherever makes the most sense. Here it goes from memory (I am at work still).

From pump outlet:
1. I go flexible (1.5") to the top mount valve at filter( approximately 1.5' head).
2. from filter I go flexible pvc (1.5" for about 4')
3. to a sch40 45 deg
4. through a ball valve
5. then 7' 1.5" pipe
6. then a 90 (could be either long or short)
7. then another 90 (long or short)
8. then I reach the panels (they have 1.5" headers).

Flow goes through the panels to the highest point (and I could put a VRV here if you thought it was best):
1. then a 90 (long or short)
2. then 21' of 1.5"
3. then a 90 (could be long or short)
4. then 13' of 1.5" pipe, then a 90 (long or short)
5. then another 90 (long or short)
6. then 10' 1.5" pipe (I am now back at the pad level.

Don't know if this detail is helpful, but back at the pad level:
1. a long 90(already dwv)
2. then through the intex swg
3. then a ball valve
4. then a long 90
5. then 2' 1.5" pipe
6. then a long 90
7 then ~12' 1.5" pipe (underground now)
8. then a long 90
9. then ~4.5' 1.5" pipe
10. then a long 90
11. and I am at the return.

 

[mas985]

Wow! All from memory. I usually have to guess at most of that stuff when doing this.

Anyway, I didn't see any tees or 3-way valves. Are you running solar all the time or do you have a way to bypass it?

If you can bypass solar, where is the cut-in/out in the above list of fittings?

Also, what size eyeball is in the return?

I want to see how close I can get to actual pressure.

 

[linen]

Wow! All from memory. I usually have to guess at most of that stuff when doing this.

Anyway, I didn't see any tees or 3-way valves. Are you running solar all the time or do you have a way to bypass it?

If you can bypass solar, where is the cut-in/out in the above list of fittings?

Also, what size eyeball is in the return?

I want to see how close I can get to actual pressure.

Not as good a memory as I thought. The picture below shows my valving for the solar. When I took it, I realized that there are two long 90's coming from the panels that I missed in my list. The pipe coming from the filter is the flexible pvc (so that would be number two on my first list) and the pipe coming back from my solar should be at number 6 in my second list (10' feet total, with 6 feet above the valves, 4 feet below). Also, there is another 1' foot elevation I forgot from the multiport up to where the flexible pvc attaches to those valves. If it would be helpful, I can recreate the lists with these new additions.

[attachment=0:lfzzndi8]SolarValves2.JPG[/attachment:lfzzndi8]

As you can see, I kind of pieced that together having never done it before. Any of it can be changed if need be.

Eyeball is 0.75"

Thanks so much for helping on this Mark! I feel guilty, since I should be of more help here with my engineering. Let me know if you have some math/engineering for me to do. I should probably learn some of this.

 

[mas985]

If it would be helpful, I can recreate the lists with these new additions.

Yes it would and could you add the runs from the pool to the pad?

 

[linen]

Yes it would and could you add the runs from the pool to the pad?

Will do! May take me a little time today. I appreciate your help!

 

[linen]

Here is the updated plumbing list. Most of it is accurate I think...doing it from memory after looking at it again last night in the dark. 17-29 only exists in my mind right now as to how I would route the water to the 6 panels in parellel.

Starting from the pool:
1. Widemouth skimmer with molded 1.5" nipple.
2. Fernco straight coulpler to 1'5" pipe.
3. 4' 1.5" pipe (vertical down)
4. long 90
5. 10' 1.5" pipe (horizontal, underground)
6. long 90
7. 2' 1.5" pipe (vertical up)
8. long 90
9. ball valve
10. Pump leaf basket (pump is a hayward SP15922S vertical discharge)
11. Flexible 1.5" hose to multiport (approx 1.75' head to multiport)
12. 20" Hayward meteor filter (~ 2.0 sq. ft)
13. 4' 1.5" Flexible pvc 4' 1.5" (goes up vertically ~1', part of it in picture)
14. short sch40 45 (in picture)
I am now at the valve setup in my previous post picture where I go on to solar:
15. ball valve (in picture)
16. 6' 1.5" pipe (vertical up)
17. 90 (could be long or short)
18. 45 (sch40)
19. 3' 1.5" pipe (1' vertical down at an angle to get to the panel)
20. 45 (sch40)
21. 90 (long or short)
Now I am at the lower left solar panel.
22. Through 6 2'X20" panels in parrelel. Panels have 1.5" headers.
23. Leaving the panels, a 90 (long or short)
24. 21' 1.5" pipe (horizontal)
25. 90 (long or short)
26. 13' 1.5" pipe (running down the roof, my roof is 6/12, so a drop of 6.5' vertically).
27. 90 (long or short)
28. 1.5' 1.5" pipe (horizontal)
29. 90 (long or short)
30. 5.5' 1.5" pipe (vertical down)
31. long 90 (in picture)
32. long 90 (in picture...I could switch out this and the previous 90s and use 2 45s)
33. ball valve (in picture on right)
I am now back to where solar meets up with the non solar loop.
34. 3.5' 1.5" pipe (vertical down)
35. long 90
36. Intex swg (with adapters probably equal to ~2' horizontal piping)
37. ball valve
38. long 90
39. 2' 1.5" pipe (vertical down)
40. long 90
41. 12' 1.5" pipe (horizontal underground now)
42. long 90
43. 4.5' 1.5" pipe (vertical up)
44. long 90
45. Return eyeball 0.75"

Thanks again!

 

[mas985]

First I modeled the system without solar so once you have an actual pressure measurement with and without solar, I can recalibrate the model. For my first cut, I get about 17.5 PSI at the filter and around 43 GPM @ 49' of head.

 

[linen]

First I modeled the system without solar so once you have an actual pressure measurement with and without solar, I can recalibrate the model. For my first cut, I get about 17.5 PSI at the filter and around 43 GPM @ 49' of head.

Thanks Mark!

43 gpm is not as bad as I thought it might be, though I would assume that goes down a bit when we get the solar in the flow? Does that translate into 22.5 gpm on low, or would it be slightly higher due to the reduction in pressure loss due to lower flow rates?

Did you use the filter pressure I gave you previously for this simulation/estimation? Would getting actual accurate pressures (both filter pressure and supply side vacuum) without the solar installed help with how to install the panels? I'm thinking of details like where to put the VRV and is the small margin gained going with long 90s worth it in my attempt to run on low? I could open pretty quick tomorrow and get updated pressure information, if I do that instead of installing and plumbing the panels first. I suppose I could make a flow measurement at the same time...is there a preferred method to do this?

How much is my 1.5" plumbing on my supply side hurting me? I have been considering digging it up and redoing...though I am leaning towards not doing it this season.

Is my 3/4" eyeball return ideal, or should i change it out?

On another note, if I might ask, what are you using to do the simulations?

 

[mas985]

43 gpm is not as bad as I thought it might be, though I would assume that goes down a bit when we get the solar in the flow?

Absolutely

Does that translate into 22.5 gpm on low, or would it be slightly higher due to the reduction in pressure loss due to lower flow rates?

Yes, approximately 1/2 the flow rate. If you had any check valves, it can be a little less than half depending the type of check valve. Speaking of which, if/when you add the VRV, you will probably need to add a check valve as well so the panels don't drain through the filter.

Did you use the filter pressure I gave you previously for this simulation/estimation?

No, this is based upon only the plumbing description.

Would getting actual accurate pressures (both filter pressure and supply side vacuum) without the solar installed help with how to install the panels?

Absolutely. You can also take the measurements with your current solar setup. Measuring both pressure and suction is probably the most accurate method of determining flow rate and plumbing head loss. A stand automobile vacuum gauge will work well or even one you get on ebay is good enough.

As for the contributions, here is what I came up with:

Suction Head Loss (ft) 1.7
Pad Head Loss (ft) 22.6 (backwash valve and filter are most of this)
Return Head Loss (ft) 5.4
Jet Head Loss (ft) 19.5 (larger eyeballs would reduce this but this may actually help the VRV)
Total Head Loss (ft) 49.1

On another note, if I might ask, what are you using to do the simulations?

It is basically a spreadsheet that I put together that calculates the operating point from the head loss in the plumbing and the pump head curve intersection (iterative process).

 

[linen]

if/when you add the VRV, you will probably need to add a check valve as well so the panels don't drain through the filter.

Thinking through this...our process for turning on the panels: pump is running on high and red handle valve open, open left blue handle valve (supply to panels, open right blue valve (return from panels), then slowly close the red handle valve. Continue to run on high until any air bubbles cease going to the pool, then flip the switch to low flow.

To turn off the panels, open red valve, close right (return from panels) blue valve, close left (supply to panels) blue valve.

With this procedure, would a check valve be needed since the valve would be closed?

Also, in this scenario, is the risk of not having a VRV that the panels/plumbing gets hot and over pressurizes?

If I have a VRV, I assume the check valve would need to be between the filter and my solar cutover/bypass valves?

You can also take the measurements with your current solar setup.

I can't unless I put the old piping back up on the roof.

A stand automobile vacuum gauge will work well or even one you get on ebay is good enough.

I already have a vacuum gauge connected to my pump basket drain port itching to tell me how low it is

Suction Head Loss (ft) 1.7

I was expecting this to be alot higher due to the 1.5" diameter.

Pad Head Loss (ft) 22.6 (backwash valve and filter are most of this)

How much does this improve if I go up to something like a S244T (3 sq. ft.) sand filter, or is a good portion due to the valve?

Jet Head Loss (ft) 19.5 (larger eyeballs would reduce this but this may actually help the VRV)

Wow, that is alot! I would not have guessed so much of my total head loss was there. Per the VRV comment, is that assuming it is at the top of the panels, or also if it is just above the solar cutover valve?

 

[mas985]

With this procedure, would a check valve be needed since the valve would be closed?

No it wouldn't be needed. You just want to make sure you don't get draining through the filter.

Also, in this scenario, is the risk of not having a VRV that the panels/plumbing gets hot and over pressurizes?

Mostly, the VRV is for self draining but since you don't have automatic solar valve, maybe that isn't all that important. Also, there is probably little risk given your location so you could probably do without the VRV.

One thing you could do is plumb in a tee for a threaded VRV and just plug it for now or even put a valve on it for manual venting and draining. That way if you decide you want self draining panels, you can easily add the VRV. It just needs to be a few feet above the pool level and filter.

If I have a VRV, I assume the check valve would need to be between the filter and my solar cutover/bypass valves?

Yes because they would be self draining at that point.

I was expecting this to be alot higher due to the 1.5" diameter.

That is because it is total suction head loss = dynamic + static. There is 3 feet of static head gain because the water level, I assumed, was above the pump level. Let me know if that is not the case.

How much does this improve if I go up to something like a S244T (3 sq. ft.) sand filter, or is a good portion due to the valve?

I just realized I uses the wrong curve for your filter. Sometimes it takes a couple of iterations to get everything right. Here are the updated numbers with both filters (the first number is your current filter, the second number is with a filter change):

Water Flow (gpm) 45.2 45.6
Suction Head Loss (ft) 2.2 2.3
Pad Head Loss (ft) 17.7 17.0
Return Head Loss (ft) 5.7 5.7
Jet Head Loss (ft) 21.9 22.2
Total Head Loss (ft) 47.5 47.3
Estimated Suction (in hg.) 1.96 2.03
Estimated Filter Pressure (PSI) 16.33 16.17
Input Power (Watts) 1151 1154
Gallons/Watt-hr 2.36 2.37

Sorry for the formatting, I wish there was an easier way to make tables. There is not much of a difference due to the filter change and most of the pad head loss is in the backwash valve.

Wow, that is alot! I would not have guessed so much of my total head loss was there. Per the VRV comment, is that assuming it is at the top of the panels, or also if it is just above the solar cutover valve?

A single eyeball going from 1.5" down to 3/4" can have a lot of head loss but that is what I consider good head loss because that energy is converted to exit velocity. But as for the VRV, if placed on the supply side a few feet above the filter/water line, the extra pressure caused by the eyeball can help keep the VRV closed on low speed.

 

[linen]

Mostly, the VRV is for self draining but since you don't have automatic solar valve, maybe that isn't all that important. Also, there is probably little risk given your location so you could probably do without the VRV.

Good to know.

One thing you could do is plumb in a tee for a threaded VRV and just plug it for now or even put a valve on it for manual venting and draining. That way if you decide you want self draining panels, you can easily add the VRV. It just needs to be a few feet above the pool level and filter.

That is a good idea. I am not familiar with pool VRVs, I have used Oatley air admitance valves in dwv applications, are the VRVs similar? Is something like this appropriate: http://www.homedepot.com/buy/plumbi...rim-kit-only-handles-not-included-167123.html

That is because it is total suction head loss = dynamic + static. There is 3 feet of static head gain because the water level, I assumed, was above the pump level. Let me know if that is not the case.

Yes, that is about right. I forgot about the pool head height.

I just realized I uses the wrong curve for your filter.

That may have been my fault, I called it a hayward meteor and I think it is a pentair 20" meteor filter...sorry about that.

There is not much of a difference due to the filter change and most of the pad head loss is in the backwash valve.

That is good to know. I assume if I hooked up my backup sand filter (it is a 19' jacuzzi laser) instead of my 20" meteor, the head loss change would be minimal? Are there other multiport valves (or others valves) that have significantly lower head loss?

Estimated Suction (in hg.) 1.96 2.03

This threw me a curve, I thought I would be able to measure my vacuum, but I think my gauge does not have the resolution needed since it goes down to ~29 in Hg vacuum.

 

[mas985]

I don't have a lot of data on filters so I just use the Pentair filter head loss numbers, which they publish, for all filters and assume they are similar for a similar size. Changing the filter size by 1" would make little difference anyway. This is one of the reasons that making small changes (replacing a few 90s with sweeps) doesn't change the picture in a big way. Everything adds up for sure but there are a lot of things that cause head loss so any one item is small in comparison. The largest single contributors to head loss are backwash valves, filters, heaters and sometimes eyeballs if you have few. Everything else is pretty small in comparison.

As for measuring the suction, yea that is one problem with low suction. Don't worry so much about that. If I got everything right, the filter pressure should be close to the prediction. It isn't all that important to be spot on anyway. The main purpose of this exercise was to determine the impact of changing the sweeps which we can still do once I have the baseline setup calibrated. Also, remind me what your filter pressure was when you had the old solar installed? The new setup should have less head loss if plumbed in parallel but I just want a comparison to work with.

 

[linen]

Also, remind me what your filter pressure was when you had the old solar installed?

Sorry it took so long for me to answer...kids baseball games. I recall 19 psi when pump was on high and filter was clean, I do not remember the low psi.

 

[linen]

I took a look at the installation manual that came with the two add on panels and it had this (which I don't think is in the online manual):

The optimum flow rate through a solar system is 1 to 4 gpm per panel.

An integrated disc at the mid-point within the "Inlet/Oulet" header automatically diverts the right amount of flow through the solar panel.

For reference, the date on the literature was 04/10.

I also made some measurements on the panels, the manifolds ID is small at 1.22" (smaller than I thought) and the hole ID in the disks (that I removed) is 0.29".

I do not know how to interpret the first quote since it sounds very generic, since this company, sungrabber which is now a part of fafco, also makes many different panels.

They write that information almost "generically", like the 1-4 ppm applies to any panel. Assuming they mean just this one, then that is pretty low, but it makes sense since these panels are designed to have the water go out and back before moving on to the next panel. So maybe the minimum flow they recommend is more like 2-8 gpm/panel for feeding the whole panel in on direction? But I don't think so since through searching I found the same 1-4 gpm for the "in ground" 2X20 version as well, with a ideal of 3 gpm.

Here are some older specs (2006)I have found:
above ground
in ground

They have curves for the panels!... but no description of whether or not the "disk" is in the agp ones (or the igp ones for that matter).

 

[linen]

Well pool is open, though it is a bit cloudy and my well water metals are showing post chlorination.

I have clean filter pressure readings no solar. 5 psi low (too low to measure vacuum on suction side) and 16.5 psi ( about 2 in Hg on suction side) on high. That is higher than I remember from last year but right where your estimation was (16.33 psi, 1.96 in Hg)!

WOW, I'd say your model is pretty well tuned Mark

 

[jblizzle]

What I have seen Mark mention is 0.1 gpm for each sqft. Your panels are each 40 sqft ... so that would be 4 gpm per panel. This matches their recommendation as well. And we know that these higher flow rates heat more efficiently.

I would think you would be best with all the panels in parallel with the disks removed ... that would give lower head loss. And then feed them with around 24 gpm.

Posted with Tapatalk ... sorry if I sound short ... hate typing on phone

 

[linen]

Yeah, that's what I am thinking as well, the big question is, can I run them reliably on low speed? I had some success last year when my filter was clean and I was running 2 panels in series with 2.
I am thinking I should be able to...if my pump can continue to handle the additional head loss (which it seemed to marginally last year but with all panels in parallel should now be better) and if the panels work decently at maybe 3 gpm each for a total of 18 gpm. With 45 gpm without panels on high speed, it seems like 18 on low with panels might be very possible. I am still assuming I will have to prime them on high.