Solar plumbing check valve

[shep377]

I am plumbing my solar system for manual operation for now. The diagram is as follows.

I bought a check valve that also is a union that can be seperated. There is a spring in the middle that can be changed and came with 3 springs: 1/4lbs, 1/2lbs and 2lbs.

Which spring should I use?
There is some debate on this site... should I put in a second check valve in the solar supply line?
Am I missing anything substantial from my plumbing a solar system diagram? or other ideas on plumbing this?

Other info I can think of that may be helpful (or not): 1hp pump, all 1.5" plumbing, the solar system is about 15' at the highest from pump level and 11' at the lowest on the roof, the solar system is roughly 40' of plumbing away from the pump and consists of nine 4x10 panels that are the capillary tube style with 1.5" collector pipes at the header and footer...

Any other info I am missing please ask. Solar is a new project for me!

 

[JasonLion]

Use the lightest spring.

You also want a check valve right after the filter, so the panels draining down doesn't push water through the filter backwards.

 

[JohnT]

If the item with the 3 on it is a three-way valve, you don't really need the bypass line. You can just adjust the three-way to go through the panels, straight to the pool or a mix.

 

[shep377]

Lightest spring... check (no pun intended.. ok it was). so as follows in my modified pic.

As for draining the panels, they tell me that these panels are designed to not need draining because they will not collapse in the heat. BUT I was thinking of adding a vacuum relief valve to the highest left end of the return collector line and allowing it to drain when not in use. This way, the weight of the water is not sitting in the panels. How does the water flow to drain when the solar is turned off? I am missing something I think... if I imaging opening the top at the vacum relief valve, then I can't picture the water flow...

 

[shep377]

Yes... the 3 was supposed to be a 3-way valve... I wanted to make a picture because things are always better with a picture, but my drawing is not the best - sorry.

 

[mas985]

As for draining the panels, they tell me that these panels are designed to not need draining because they will not collapse in the heat.

That may be true but the PVC pipe can also collapse so it is a good idea to have a VRV.

How does the water flow to drain when the solar is turned off?

Water drains away from the VRV in opposite directions. Also, a solar valve has a small hole in the valve so water can continue to drain even though it is completely off.


You can also plumb the VRV on the supply side. This has the advantage in that it requires less pressure to keep it closed so if your filter gets dirty it won't open and allow air into the panels.

 

[shep377]

Ok, so I map place the VRV at the high end of the supply line (I did more reading on this site about it).

You mentioned that a solar valve often has a small hole in it to allow the draining when closed. Where is this hole and if the pressure is travelling along the lines at pump pressures, then how would water drain into that through a hole? if a hole entered the water lines, then I would think that water would push up into the system.

There is a check valve on the return, so it can't drain there, so the water must run back through the supply line... sorry, I still don't get this...

Also, jasonlion mentioned in another post, that optimally, we would want to have just over 0 PSI at the very top of the system. To accomplish this, would I open a cap at the highest point, then open the bypass valve until water came very slowly out the top of the system?

 

[jblizzle]

Well, unless you specifically got a solar 3-way (Pentair has them with a check valve in the diverter.), you will not have a hole. So many people drill a small hole in the diverter in the valve so that the water can drain through the valve back down the supply line even when the diverter is set to solar.

Another option is to add a small bypass between the solar supply and return above the return check valve. I did this also with a 1" PVC pipe and a ball valve. I have the ball valve slightly open so that both the supply and return lines can drain down the return line through the return check valve. While the pump is running, very little water likely jumps across that bypass instead of heading to the solar panels.

 

[JohnT]

There is a check valve on the return, so it can't drain there, so the water must run back through the supply line... sorry, I still don't get this...

The check valve on the return allows water to flow down out of the panels, and when they are off, the hole in the three-way allows the inlet side of the panels to drain through the returns as well.

 

[shep377]

Summary of draining:

IF my head pressure is low enough to be below the panels, then they will drain anytime the diverter to solar is off. (like these ones)

IF the head pressure is such that it is higher then the solar system top, then if I divert a % of the water to flow through the system , it will stay full until I shut the pump off for the night, then it will drain. I do not have a seperate low pressure return line for the solar heated water...

So this could be fine - it's full if I am using it during the day, and drains at night when the pump goes off.

Or I could change all of plumbing (because I have seperate return lines for both return eyes) and have one eye return water to the pool normally, and one return water from solar under low pressure - then it would drain anytime solar is shut off. I could make this a 3-way valve that changes the one return line to operate normally or only use solar water.

Is it worth finding out my vertical pressure at a certain point to choose a method of installation?

I over-think everything.

 

[bigdaddy72]

Here is our setup on the outside of our garage. We have two arrays, each has a VCV at the top right side. They are a Heliocol setup.

 

[bigdaddy72]

Ok, so I map place the VRV at the high end of the supply line (I did more reading on this site about it).

You mentioned that a solar valve often has a small hole in it to allow the draining when closed. Where is this hole and if the pressure is travelling along the lines at pump pressures, then how would water drain into that through a hole? if a hole entered the water lines, then I would think that water would push up into the system.

There is a check valve on the return, so it can't drain there, so the water must run back through the supply line... sorry, I still don't get this...

Also, jasonlion mentioned in another post, that optimally, we would want to have just over 0 PSI at the very top of the system. To accomplish this, would I open a cap at the highest point, then open the bypass valve until water came very slowly out the top of the system?

If I remember correctly, on our solar setup, we only have one check valve on the system. There is no check valve between the filter and the 3way valve.

Here is a picture of the return check valve. It goes to a t which goes out to the return jets. The pipe going out is right from the 3 way/solar control valve.



Here is the 3 way with the setup

 

[shep377]

All this seems to stem from: When do I want the panels to drain?

If draining is anytime I don't put water through the solar system, then you have to place the system above head pressure height, or have some sort of low pressure return line.
VS
If draining is only when the pump turns off, then a VRV in the system will do it.

When does everyone have their solar setup to drain?

 

[mas985]

Normally, when the solar valve shuts off, the flow to the panels stops but unless the pump shuts off, water will probably still remain in the panels. However, the pressure without solar tends to drop so in some cases, the panels will partially drain but not all the pipe will. This is the way most systems work.

This generally is not an issue except for systems without VRVs. Problems can occur on very hot days when the solar valve shuts off but the pump keeps running and the water in the panels remains full. The water can then reach very high temperatures (140+) which reaches the melting point of PVC. If the pump should turn off while the water temperature is that hot, the vacuum of the draining water could possible collapse the pipes IF you don't have a VRV. The VRV releases the vacuum so the pipes won't collapse.


bigdaddy72 - You should have check valve after filter. This will prevent back flow through the filter which can clog impellers. It is like back-washing your filter through the pump.

 

[bigdaddy72]

bigdaddy72 - You should have check valve after filter. This will prevent back flow through the filter which can clog impellers. It is like back-washing your filter through the pump.

Impellers where?? In the pump? We have had it this way since day one and it has never had any issues. And it has been 7-8 years with zero issues with our solar system.

 

[Isaac-1]

I would keep the bypass loop you have and use a actuator compatible 3 way valve, that way if / when you decide to add a solar controller you will already have the plumbing in place. In my personal experience adding a controller gets you probably another 30% effective heating capacity from the solar panels, at least in my region where we often have afternoon thermal thunderstorms in the summer. The reality of manual solar control is you will either be late or early starting in the morning on a clear day, the same is true in the evening, and of course there is the issue of rain which cools the panels.

p.s. some filters have built in 1 way valves if yours does you don't need the check valve after the filter

 

[mas985]

Impellers where?? In the pump? We have had it this way since day one and it has never had any issues. And it has been 7-8 years with zero issues with our solar system.

Then you are very lucky but as a matter of practice and proper installation, systems with a VRV should always have a check valve between the filter and the solar valve. Check out some manufactures installation manuals:

http://www.heliocol.com/resources/manuals
http://www.fafco.com/files/06836C_Pool% ... -28-09.pdf
http://www.h2otsun.com/PG5ht.html

I would keep the bypass loop you have and use a actuator compatible 3 way valve, that way if / when you decide to add a solar controller you will already have the plumbing in place.

Actuators can be adjust so they don't fully close off the through path so a bypass is still not required although it does make it easier for fine adjustments.

 

[bigdaddy72]

Found out that our filter has the one way valve setup, so no need for the check after.

 

[mas985]

Found out that our filter has the one way valve setup, so no need for the check after.

That would be very unusual. What is the make/mode of the backwash valve?

 

[bigdaddy72]

Good question. I will check with the company that installed. I am going by there word...which after reading some nightmares on here, may be incorrect.