Vacuum release not closing

[Sticky]

Hi yes another VRV question .

So i have a VF intellflo ,oversize cartridge filter , SunTouch and three Heliocol SunX SX40 panels , from the pic you can see the VRV is at the top of the layout .

I have to run the VF at 45GPM to close the VRV .

I move the VRV to the opposite lower corner after reading Hot2suns good site .

VF still needs to run at 40GPM .

Installer says there might be an issue with air being trapped at top of panels .

The flow for the panels is suggested at 4GPM each so 12GPM .

12GPM flow is to low to run the pump at but I think 40GPM is to high for efficiency or is it ? .

Oh and plumbing from the gutter is 1.5 inch , gutter down is 2inch .

The outlet pipe is a thick wall pvc to cope with the pressure .

The red handled ball valve is to allow the panels to drain .

Also any tips on where to mount the sensor ? The panels face east so morning sun .

 

[Isaac-1]

My two immediate thoughts are you need to let some of the water bypass the panels so you don't over pressurize them, and second that the VRV may need to be replaced if it is still leaking when installed at the bottom of the panels.

Ike

 

[Sticky]

So bypass would be to open the red handled ball valve more ? but would this allow the VRV to open less pressure .

The max pressure for the panel is stated at 600kpa (87psi) reading on filter show 37kpa .

Iam running at 40GPM and there is a small amount of bubbles still .

I have another VRV which when I blow thru it closes easily I think it a different design .

 

[Isaac-1]

You may be runnning at 40GM, but without a flow meter you don't know how much is bypassing the solar panels. I would suggest when you have good direct sunlight on a warm day to be on the roof and close the red valve until the panels start feeling warm under the sunlight, then open it back up a little until they feel cool. A correctly operating solar panel should have enough water flow through it that it DOES NOT feel warm to the touch.

As to pressure that 87 psi is burst pressure, all solar panels benefit from being exposed to MINIMUM operating pressure, this is easy to confirm by mounting a temporary pressure gauge in place of your VRV if it is located at the panels.

See http://www.h2otsun.com/vahe.html and http://www.h2otsun.com/pools/

Ike

p.s. read the second link fist

 

[Sticky]

Hi Ike

I have already read h2sun site (I wish the installer had ) and understand about getting optimal flow and is what Iam aiming for , for 3 panels at 4gpm each I think 40gpm is a not , I would be happy with 30gpm , I will try to get a pressure gauge today . Until I know the pressure at the panel you dont know if 40gpm is right or not ? yes ? . The red 1 inch valve is for drainage ? not flow control I was told thou it would have some effect .



I was think what I need is a valve at the top to let air out when priming and one at the bottom to let air in when draining

 

[Isaac-1]

One VRV should be all you need, there will not be that much air trapped in the panels compared to the air space in the larger plumbing pipes when purging air at start up, either way a considerable amount of air should be expected through the returns. As to the red valve, I suspect with it 100% open you would have little or no flow at all through the panels regardless of why the installer placed it there.

If opening it does not reduce the pressure seen at the VRV mount temporary gauge point chances are most of the pressure is being caused by a down stream restriction in the system, such as under sized return eyeball fittings, etc.

My 11 4x12 panels operate at a pressure of only about 1-2 psi and I get a flow rate of over 35 gpm through them according to my flow meter.

Ike

 

[Sticky]

I have attached a pic of what the installer has used as a VRV , it is not a made for purpose valve .

Here is a link that describes its applications http://www.bidgeepumps.com.au/store/index.php?main_page=product_info&products_id=2192 . hope that works .

If not here are some details :

High pressure rating: Foot and nonreturn valves are rated to a pressure of 1400 kPa (200 psi) (static shutoff) at 200 Celsius to meet the requirements of high pressure systems.
Low pressure shutoff: Foot and nonreturn valves are designed to seal off at 20 kPa of pressure making them well suited to gravity feed systems.

I wonder if this is the cause of my woes , it may work with the pumps they use normally 600-1000watts but the VF is another matter .

The installer said to put the GPM up to whatever would close the valve completely approx 48GPM .

I will also get a pressure gauge tomorrow .

I have a new VRV i bought ages ago I am going to try that tomorrow .

The panels are cool to touch moving the red handle seemed to reduce flow significantly thru the panel also seem to let more air in .

 

[Isaac-1]

Did they say why they would use that instead of a part designed to be a VRV?

 

[Bama Rambler]

A non-return valve is what we know as a check valve. They say that it's a piston type valve so it takes a certain flow of water to seal it off. Once it's sealed it takes 20 kpa (3 psig) of pressure to keep it sealed. It looks like the valve is probably 20' above the pump so that means you would need about 12 psi at the pump to keep it closed, IF it was a sealed system. In your situation you have the flow through the panels AND the flow through the "bypass/drain" valve robbing pressure at the check valve, so it doesn't surprise me that it takes almost 50 gpm to keep the valve closed. Using a different type valve that requires less sealing pressure will help and also closing the "bypass/drain" valve will help.
However, closing the "bypass/drain" valve will hurt you because you'll have to closely monitor the pump to make sure you don't try to force too much water through the panels.

 

[Sticky]

Isaac I haven't asked them yet . only just realised this afternoon when I Googled it . No doubt they will say it is what they always use and have had no problem so therefore it is your problem lol .

Bama I am going to try another VRV tomorrow the bypass /drain I will just open enough to drain the panels need to drain .

I hope this solves the problem .

 

[Sticky]

ok quick update, put the other vrv on run at 40gph small amount of air still entering the system,.

i took the top of the vrv and the water was only just rising to where the white fitting is, i turned the red valve towards close until the water was just coming out he top, at this point the tap was nearly closed.

If i run at 35gpm large amounts of air enters the system until I block the VRV with my finger .

so what does this mean pressure and flow wise, all the panels are cool to touch so water is flowing through? .

I pulled apart the installers VRV and it is actually held shut to atmosphere by a spring (pics later) .

So it actually needs 20kpa to open it? but when it was at the top of the system it was open, I could seal it of with my hand .

So why is there not enough pressure/flow to close the VRV or still suck air thru a spring sealed non return valve. ???

 

[Sticky]

Siphon effect maybe not enough back pressure on the return line?

 

[Sticky]

Some pics, 3rdshows the new VRV, when I took the top off the water level was down near the white piece.

The 2nd is the other VRV pulled apart.

The 1st shows the solar going to the roof , pipe on the left is the supply it has a non return valve, is it needed I wonder cuasing restriction? .

On the right is Solar return this goes to two eyeballs 40mm 12inches below surface and another 40mm eyeball about 12inch off the bottom at the end of the pool.

Iam wonder if I need to restrict the flow here limiting flow to the surface outlets

or putting a valve with actuator to swicth flow completly to the deep end outlet.

 

[Isaac-1]

I think you are getting a siphon effect because of the placement location of the VRV, it appears to be located about 6 inches above the top header of the panel, meaning another 6 inches of water column above the point where the panels will flow water before the VRV will close. I suggest either lowering it to equal level with the top of the panels, or safer yet lowering it to the end of the lower header to provide a little safety positive pressure to operate the VRV. Moving it to the lower header I feel would certainly solve this problem, lowering it to top header level would probably solve it also, simply put it is installed way too high.

Ike

p.s. one more thing I think I see, your roof mounted temperature sensor (assuming it is used to control automatic valves with a solar controller) should be in contact with the panel, right now you are getting a temperature measurement of the probe suspended above the panel, not the panel itself which will be cooled by water. A simple solution to this would be a blob of black RTV silicone caulking to bridge the air gap.

 

[Sticky]

Sorry Isaac I forgot to mention that I moved it to the lower header where you have indicated . this is where if i take the top (the little cone thing) off the VRV the water just flows out a little , pump running at 40gpm with the red valve nearly closed .

This seems strange to me as I thought the path of least resistance would be thru the larger opening as against being pushed thru the small tubes . I was ready for the water to rush out but till I closed the red valve nearly the water water level was at the white fitting .

There is plenty of flow from the return lines ,the installer said I might need a on the solar return line (above the check valve ?)to create more pressure in the panels , I thought we wanted to avoid pressure but ? .

Must say thanks for your help so far

 

[Bama Rambler]

Close the bypass valve completely and see how much flow you get.

 

[Isaac-1]

Something odd is going on here, I am going to think on it a bit.

I am starting to think that the gravity flow rate of your return side plumbing exceeds the flow rate going to your panels and is therefore subjecting them to a partial vacuum when operating. So an appropriate solution at this point may be to add a restriction on the return side sort of like clogging a drain, just don't over do it. I think you said this feeds some eyeball fittings, if so you might try changing them out with ones that are one size smaller.

Ike

 

[Sticky]

I am thinking the same now re siphon effect , I reread the hot2sun site last night and I think I may have to many returns for the size of the solar system .


I have three returns two at surface and one at the bottom of the pool .

I did notice that when I blocked one of the surface returns that bubbles started to come from the bottom return then stopped .

I think air is getting trapped there and not enough pressure to forced it out the bottom so it takes the path of least resistance and goes to the surface returns .

I want to avoid putting in permanent restrictions so that the VF pump is not impeded on it's filter cycle .

So my idea is to put a motorized shut off valve at the point shown in the pic and adjust it till I get 1-2 psi in the panels .

 

[Isaac-1]

A simpler solution might be to just install a ball valve on the "red" from solar pipe

 

[Sticky]

A simpler solution might be to just install a ball valve on the "red" from solar pipe

ok so I blocked off the two shallow returns, I can run at 30gpm 250watts 1440rpm with no bubbles.

When I push the centre of the VRV water flows out quickly so there is more flow / pressure there.

Yes I could put a valve on the solar return but the other thing I noticed is the deep return does not flow due to the water wanting to go the easiest route of the shallow returns.

When I block the shallow returns (after solar has been running awhile) air comes out the deep return.

The pressure differential between the shallow and deep return is too great to push the air/water down and out .

I have to think about this some more, it looks like no easy solutions.

Should I test pressure at the VRV or flow or both ? , I need to buy these still to test.

Dave