Final Solar Plumbing Options

[shep377]

So I have my panels on the roof, and I am about to tie them into my system. The family is quite excited about having warmer water! The temp is 62deg, not the kids have been in swimming, but not for long!

I am down to two different designs for my tie-in plumbing and I thought I would get some opinions... and why...

Option 1 - has more flexibility of control, but more path for water and more complication. This solution has a dedicated bypass valve for some % of water to route solar vs direct return:

Option 2 - is more simple, and I could use the 3-way valve partially open to allow for bypass of some % of the water to route to solar vs direct return:

I do think that simpler is often better, but if there is some reason why I would want to pick one over the other then now is the time. I have no intentions of buying an automatic valve anytime in the near future that I can foresee...

Cheers all. Solar is almost here ...oh, and BBB rules again! Although it is cold, the water is crystal clear and running perfectly!

 

[Isaac-1]

Option 1 is best if you are ever going to upgrade to an automatic controller, something that I highly recommend (I did it the manual way for years), otherwise option 2 will work. You get much more effective heat with the use of a solar controller and that really is the whole point, it no only turns on the solar when the sun light gets the panels hot enough, but maybe more importantly it turns off the flow when they cool down, in my area we get frequent afternoon thermal thunderstorms in the spring and summer months which not only block the sunlight, but dump cold rain onto the solar panels, if not for a solar controller this would be sucking heat out of the pool when the solar heat is in use in the late spring.

Ike

p.s. note with a little shopping you can get a basic solar controller, valve and sensors for about $200-$250.

 

[mas985]

Why wouldn't option 2 work with a controller? All you would need is an actuator on the 3-way valve. In fact, that is how mine is setup.

 

[Isaac-1]

Most actuators can not be fine tuned for partital flow. At best you get about 25% positions.

Sent from my GT-I9000 using Tapatalk 2

 

[mas985]

The bypass adjustment may be somewhat limited with the cam but option 2 still doesn't preclude you from using a controller although I think the adjustment is better than 25%. Besides the cam in the Goldline actuators, you can also adjust the stop switch and get almost infinite adjustment.

 

[shep377]

I thought I would give an update to the solar installation! It is up and running now quite well and I have pictures

After discussion here I decided on the method of plumbing that incorporated all the great ideas:

Notice just above the 3-way valve and above the check valve I have some clear PVC - I love to put little pieces of this into my plumbing so I can actually see what is going on in there! I also added another pressure gauge just above the 3-way valve (you can only see a shadow of it in the picture) so I can monitor the pressure I am putting through the solar.

Filter pressure gauge solar off runs 12-14PSI.
Filter pressure gauge solar on runs about 16PSI.

When I adjust the bypass ball valve (bottom horizontal valve) I can get the solar to run at 8-10PSI, which moves water nicely through the system, and the roof is 15' high at the peak, so the pressure is about 0-1PSI I think by the time it rises to the top of the solar panels. (1PSI ~ 0.48ft vertical? or something like that). I am very happy with my pressures as I was worried about pushing too much PSI through the panels.

Thanks everyone for inputs and forum posts!
Cheers

 

[mas985]

Remember that solar efficiency drops off with flow rate so if you bypass too much, you won't get as much heat out of the panels. Plus most panels can handle quite a bit of pressure.

 

[shep377]

Yes - I have read again and again here that heating a lot of water a little bit, is better then heating a little water a lot.

But, from everything I was reading said that the difference between making solar panels last 5 years vs 25 years is keeping the pressure in the system near 8PSI, dropping from there as the water heads up the panels.
(reference here)

I can see that the amount of water I am pushing through is definitely enough to fill my 1.5" return line at a good clip - I can see this by my clear PVC. I am still playing, but I was going to target 8PSI going into the bottom elevation of the panels... then use the old heat test: put a hand on the panels, if they are HOT then I am not flowing enough water.

 

[Isaac-1]

Another good write up on the the effects of pressure by the same people http://h2otsun.com/vahe.html

 

[mas985]

But, from everything I was reading said that the difference between making solar panels last 5 years vs 25 years is keeping the pressure in the system near 8PSI, dropping from there as the water heads up the panels.

I think you misunderstood what they were saying. That is 8 PSI AT the panels, not at the filter. You seem to be targeting 0-1 PSI at the panels which can be a problem for the VRV.

Filter pressure gauge solar on runs about 16PSI.

If the filter pressure is 16 PSI and the height of the panels is 15' then the pressure at the panels is below at least 9.5 PSI and probably below 8 PSI because of the head loss to the panels is at least 1.5 PSI. So you may not need to bypass any water.

 

[shep377]

Hmmm... so I have a pressure gauge on the lines running vertically to the solar. If the bottom of the panels are 10' above the gauge, and I want to run 8PSI at the bottom of the panels, then 10'~5PSI, so I want that gauge to run about 13PSI?

The panels are on a sloped roof so they run about 6' up, so by the top of the panels, I will loose another 3, so if I was to put another gauge at the top of the panels it might read somewhere around 5PSI.

(all math rough and just to get the idea - please don't comment on bad numbers! )

 

[mas985]

Hmmm... so I have a pressure gauge on the lines running vertically to the solar. If the bottom of the panels are 10' above the gauge, and I want to run 8PSI at the bottom of the panels, then 10'~5PSI, so I want that gauge to run about 13PSI?

There is also head loss in the filter, valves and piping to the panels which will drop the pressure. Are you using all 1.5" pipe and is your filter backwash valve 1.5"? Also, how big are your panels and is your pump a SuperPump or a Super II?

 

[shep377]

All my lines are 1.5". The pump is a SuperPump. I haven't actually closed the bypass fully yet. I opened the solar valve when the bypass was fully open, then I slowly closed the bypass until my pressure on the solar pressure gauge line was at about 10PSI. This also brought a full flow of water down the return line without any issues. The water returning was about 2deg warmer then the water going in.

The rise from my filter to the bottom of panels is about 10' vertical and about 30' of tiger flex. The top of my panels is about 16' vertical from my filter (about 6' rise in the panels bottom to top).

 

[mas985]

With 30' of pipe and all those valves, you will be losing at least 8 PSI from both the rise and the dynamic head loss. So you can easily operate the filter at 16 PSI and perhaps even more.

 

[Isaac-1]

A flow meter might be in order to optimize things, but I can tell you with my panels I am getting about 45 GPM of flow at full diversion through the panels and about 7 psi of back pressure measured just after the flow meter going to the panels. (Optimum for me would be 54 GPM, but it is enough to be well over minimum flow) All underground plumbing is 1.5 inch, headers and pipe going to the roof top solar is 2 inch, panels are about 12-14 feet above gauge level.

Ike