Solar Plumbing Layout ?s

[jblizzle]

OK, my turn to ask for advice again. Got my new motor and re-plumbed equipment pad squared away. Now that the nights have cooled and the water is only around 80 degrees, time to get this solar system installed. Here are 2 possibilities:

Option 1:

Option 2:

I had been planning on Option 1 and only currently have a single vacuum breaker, but looking on the roof again, that would require about 20 more feet of pipe than Option 2 and routing the pipe around the "stuff" at the top might be difficult (and really there is not as much roof above and below the panels as shown). I think I should be able to get the hot pipe to go over the cold pipe in the corner of Option 2 and still maintain enough pipe slope.

Questions:
1. While the 6 panels should have less resistance than the 4 panels, will the MUCH longer run of pipe possibly make things unbalanced in Option 1?

2. Any issues with using the 2 vacuum breakers in Option 2? Besides the added expense and twice as many to go bad / leak?

3. Would the Low Point Drain(s) (rarely needed) be better at the entrance to the panels? Or should I even bother with them since I have the vacuum releases and an actual solar 3-way valve at the pad to allow draining?

4. With the 3-way at the pad and check valve on the hot water return, it there a point to putting ball valves on the risers to the roof? Currently the pipes are just cut and I am running the pump without water shooting out, so maybe isolation valves would serve no purpose.

5. Anything wrong with using short sections of flex PVC at the connections to the panels to allow panels to be tilted and leave flexibility?

6. Can anyone think of a better way to layout the plumbing? (honestly it is not going to be as simple as I drew since the roof barely has enough width for the 4 panels, so creativity with fittings is likely)

Thanks for any opinions/thoughts.

 

[jongig]

First I'm guessing you're using 2 inch pipe for all the piping.
1. Yes the system will be unballanced but it's not enough to matter at all. The problem would be if you draw water out of the top of each panel group and then tie the two together at a lower point as in drawing 2. You could actually short out the second group and maybe not get any production from the second group. You need to fill both panel groups and tie them together and then your return will be just above that. This way both panel groups have to fill up with water.
2. I don't see a need for a vacuum breaker unless you have a reason to remove the water from the roof, i.e. freezing. It's easier on the pump to not use a vacuum beaker. I have a valve as the pipes go up from the pump that comes off a T and when open it lets air go up to the roof and the roof solar drains down.
3. I don't like anything on the roof that could cause a leak or a problem, KISS, (keep it super simple).
4. In the manuals it usualls shows isolation valves, added cost and never used. If you need to do work just shut off the pump.
4. If you use spa-flex PVC pipe and the glue for it I don't see any problem and it's probably a good idea iin your climate. I like spa-flex but some of it has ribs and is not glueable.
5. In drawing one, where you have the small circle labeled vacuum release, this is where your return connection should be. Below that where you show the T and return is wrong because you can have short circuiting. You have to draw the water in your return above both panel groups so that you have no chance of one group not filling up with water. There is not much friction in the panels and if you do it wrong you'll not get the heat you should.

I use a IR thermometer to test the groups and I look for one group to be much different than the other. As long as they are not 5 degrees apart you're fine.

 

[jongig]

Here is mine, I could have done the plumbing in parallel or series but to make the plumbing easier and KISS I chose series. It’s hard to see but the water on the larger lower group enters the left hand side and exits the top right. Then the water follows a pipe along the top of that group and enters the bottom right of the smaller top group. Then the water exits the top left of that group and comes back down off the roof. If you look at the pipe labeled blue and just near the bottom you can see the T that has a plug in it, remove the plug and the water drains down. My point here is that you don’t the valve on the roof.

 

[jongig]

My point to this was that I could see yours being easier to plumb in series and probably a cleaner looking install instead of having the pipe run across the top of the roof. You also have no concern with short circuiting if you do it in series. You might try to make the case that when one feeds another you have loss of efficiency, good luck trying to calculate that and I know the calculation.

 

[mas985]

1. While the 6 panels should have less resistance than the 4 panels, will the MUCH longer run of pipe possibly make things unbalanced in Option 1?

Probably not. Straight pipe does not have a lot of head loss and even adding the elbows, it is not going to be all that signifcant so the panels will probably be fairly balanced.

2. Any issues with using the 2 vacuum breakers in Option 2? Besides the added expense and twice as many to go bad / leak?

I don't think option 2 is necessary and just complicates things so I would not recommend that route.

3. Would the Low Point Drain(s) (rarely needed) be better at the entrance to the panels? Or should I even bother with them since I have the vacuum releases and an actual solar 3-way valve at the pad to allow draining?

If your objective is to run on low speed, you will need the VRV at a fairly low point on the supply side right above the pad. If not, I would still suggest putting it on the supply side just because there is less probability any issues keeping the valve closed.

4. With the 3-way at the pad and check valve on the hot water return, it there a point to putting ball valves on the risers to the roof? Currently the pipes are just cut and I am running the pump without water shooting out, so maybe isolation valves would serve no purpose.

Those are optional and would only be used if you had to do repairs on the panels.

5. Anything wrong with using short sections of flex PVC at the connections to the panels to allow panels to be tilted and leave flexibility?

No but you really don't need much of a tilt. You just don't want water to collect in the bottom pipe on the terminated end. It won't take much to prevent that. If the roof is fairly flat, then it won't matter much anyway.

6. Can anyone think of a better way to layout the plumbing? (honestly it is not going to be as simple as I drew since the roof barely has enough width for the 4 panels, so creativity with fittings is likely)

My only suggestion is that if you were to place the VRV on the return side, I would put it between the two panels. But given your pump and filter, I think a supply side VRV might be a better choice and ensure there is no issue with closing the VRV and keeping it closed even with a dirty filter.

Also. I would not plumb the panel in series as that will be less efficient for both heat transfer and energy. In this case, I see no reason to plumb them in series. The plumbing layout is not that complex.

 

[jblizzle]

Thanks for the replies. After spending a lot of time on the roof moving things around and visualizing ... I had found that Option 1 was really the best way to lay things out. I agree that going with a serial setup might be too much "load" for the pump and not be as efficient at heating.

Everything is going to be 2". Not planning on running on low speed. Not going to put isolation valves ... since obviously since I had the pump currently running and not water is spewing out of the cut pipes by the house, the check valve and 3-way are doing there job at isolating the solar already.

The roof is pretty flat and I have already got the panels set at a tilt (maybe a little more exaggerated than I needed). Today I am hoping to do all the PVC.

Mark, given the lower flow of my pump, I see your point about putting the VRV on the supply side. A couple questions:

A: Where would you suggest? By the wall on the way up to the roof or just when I get to the roof line? Or in the corner between the 2 banks? Or at the far end of the supply pipe?

B: When I orient the Tee for the VRV, should it be done such that the VRV is vertical (above the pipe) or horizontal (so the water is sure to apply pressure)? I can not see how this matters, but would like confirmation.

Thanks.

 

[mas985]

A: The intent is to break the vacuum so for that it really doesn't matter where. However, putting it closest to the 6 panels, might allow the siphon on the return side to drain those panels first before the 4 panels can completely drain and break the siphon. Once the siphon is broken, you have to rely on gravity to drain the remaining water and given the distance of the far panels, my inclination is try and drain those first or least given them a head start. The 4 panel side shouldn't be an issue.

B: It depends on the type of VRV. Some of the older types could only be put in vertical. But if it is the end cap type, I don't think it matters.

 

[jblizzle]

Ah, I see. So somewhere near where the supply enters the 6-panels might be best.

I guess I still did not realize that a majority of the water is drained UP the panels and down the return when the VRV is on the supply side. I suppose if the VRV was at the top, then the water would drain down the supply side.

My VRV is PVC, and i can see a large spring inside. Just realized I can uncrew it and see the spring holding a ball to the outside, then a screen and holes to the outside. Given this design, seems like it should not matter the orientation, although i think I will put it vertical.

Thanks again. If you think of anything else, let me know. Getting ready to start the PVC ... why did it have to be 100 again this weekend Not sure if I will get it done today or not.

 

[mas985]

Just a few followup questions just to make sure I am giving you sound advice. Being from a very hot climate, one thing you need to be a little concerned about given the right conditions is collapsing PVC. This is a fairly rare event but there will probably be very hot days where you will not be using solar and there will still be water sitting in the pipe and panels heating up. So I just wanted to confirm that this is a single story roof and the roof pitch is fairly shallow. I don't think the vacuum would be high enough in this situation to be a an issue but I just wanted to make sure that I remembered correctly.

 

[jblizzle]

Yes. Single story and less than 15 degree slope as I recall.

Still think the vrv on the supply side near the 6 panels is the best place? I will certainly keep an eye on the pvc pipe up top.

Posted from my Droid with Tapatalk ... sorry if my response is short

 

[mas985]

Still think the vrv on the supply side near the 6 panels is the best place?

Yes, there shouldn't be an issue with a single story roof and I suspect that when you aren't running solar, the pump will be on low speed so that will help the panels/pipe to drain.

 

[jblizzle]

Well, I did not get everything done last weekend ... why is it still over 100 degrees out???? Got the panels installed and got the return plumbing done between the panels.

Here is the way I am currently planning with the possible new VRV location:

There is very little room to play with the pipes above and below the panels.

One thing I have a question on is the return line after the panels. I was going to plumb straight over from where the 2 bank connected and then down the roof ... but then got to thinking about the previous comment that it could result in water returning from bank 2 before bank 1 was full. The pipes are at the peak of the roof already, but should I extend them up a few inches at least to have a loop over the top to ensure everything is full before the water heads back to the pool?

Hope to finish it up this weekend ... assuming it is a little cooler out.

 

[mas985]

I don't think the loop is necessary nor will it really accomplish anything.

 

[jblizzle]

I was thinking about the draining and just realized something that may not be ideal.

I got one of the solar 3-ways (with the check valve) to allow the panels to drain back down the supply side. But, I am currently going to be running in manual mode, so the 3-way will be left on the solar circuit. This means that water will not be able to drain down the supply pipes. So, putting the VRV where it is, hopefully the panels will be able to mostly drain over the top and down the return side. {I guess if I put the VRV at the high point, that would mean basically everything would need to drain down the supply pipes ... so another reason to put it lower}

- Since I have a VRV, there should not be any vacuum, so does it cause a problem if the panels do not drain all the way and possible stay hot?
- Once I have a controller, don't they usually turn the solar valve off each night which would allow them to drain down the supply pipe?

Of course when it actually gets cold here, I will open up my drains on the roof to make sure there is not water to freeze ... uncommon, but last year Tucson ran out of plumbing supplies when everyone's outdoor water pipes and spiggots froze and broke. The wind chill certainly made a difference.

 

[mas985]

I might have misread your post but are you saying that you currently have a standard 3-way instead of a solar 3-way?

If so, one solution is the adjust the 3-way for just a tiny bit of bypass. In other words, do not completely shut off the bypass route. That way the supply side can also drain, albeit slower.

You can also modify a standard 3-way, drill a small hole in the valve, to allow for draining. This is the way solar installers use to do it before the solar valve.

 

[jblizzle]

No I have the solar 3-way (with the built-it little check valve). But, if I leave the valve set to solar, then nothing will pass the check valve (at this point almost seems like I should have just used a regular valve and drilled a hole in it ... and saved myself a little $).

As far as not seeing the forest for the trees .... leaving the valve cracked slightly is an obvious solution I overlooked. So, when I set the solar open I will try to leave it open a bit while doing this manually. Once I have a controller (that closes the solar every night), I will not have the issue or need to leave a little bypass as it will be able to drain through the check valve in the solar valve.

 

[mas985]

Ok, now I understand. Leaving the valve open slightly will solve that.

But I have one other option, sorry I just keep thinking of things. I put a separate bypass in my solar even though I could adjust the bypass with the three way valve. I did this because adjusting the cam in the actuator can be pain at times and so I wanted a separate way to adjust the bypass. I used a 1" line with a ball valve for the bypass between the supply and return lines. This allows infinite flexibility in adjusting the bypass amount and still making sure the VRV remains closed. Plus it is pretty easy to optimize this way without fooling with the solar valve and actuator. This also has a side effect of allowing the supply side to drain faster than through the solar check valve alone. Just a thought.

 

[jblizzle]

Hmmm ... understand the idea, can't picture where it would go. Wish I would have considered it when I redid the pad plumbing. Not sure I have room ... depending where it connects.

Can you suggest where it would go? Is it from the solar supply to the solar return (before or after the check valve)?

 

[mas985]

The ideal location is where the pipe starts up the wall. If the pipe separation is small, you can offset the tees so you can place the bypass diagonally above both pipes. Here is how I did it:

 

[jblizzle]

Well, I wrote the below before I saw your post. I can do that at the house easy as I have not connected it to the roof yet. So the idea would be to just open it a bit to maintain the max flow through the panels and allow the drainage.


I think I have an idea that would work. Here is the plumbing (not showing the solar lines connected ... but they are now):

I can go from the vertical solar supply (missing on the right) and tie it to the horizontal pipe running back by the filter, right?