High pressure in solar panels

lborne

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Jun 29, 2009
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Vero Beach, FL
I have a spillover spa with my pool and only one pump - very basic. When in spa mode, suction and return are in the spa only and because some of the jets can be closed, the pressure is higher than when the pump is circulating the pool. Pool circulating pressure is about 7 psi and when in spa mode is varies from 12 to 20 psi depending on how many jets are closed. Of course, when in spa mode I shut off flow to the solar panels. Problem is, the valve that regulates flow to the panels is the kind that has a small hole in it to allow the panels to drain when the pump is off. So the panels are seeing the full pressure of the spa. I noticed it when a few of the spa jets were closed and the panels started leaking at the fittings. I am thinking I should replace the valve with one without a hole, as draining the panels is not a big deal here in south Florida where there is no risk of freeze. Thoughts?
 

JohnT

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Draining the panels is a big deal for you. If the panels are full of water and it isn't flowing, it can get hot enough to deform the panels.

I find it surprising you see so much pressure at the panels. Do you have a diagram of your plumbing or can you describe how the pool/spa mode are selected and where the solar valve and others are relative to each other and the pump and filter?
 

mas985

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When the solar valve is in the off mode, the drain check valve in the solar valve should prevent the flow into the panels. I would take apart the valve and check the rubber seal. Also, you need to have check valve on the return side as well and that needs to be in working order. If both of the valves work properly and the panels are empty to begin with, then the panels should not fill with water or experience the high pressure. But they do tend to leak after many years of service so they may need to be replaced.
 

lborne

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Jun 29, 2009
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Vero Beach, FL
https://picasaweb.google.com/lh/photo/mw6yYQ00ihSf4g7mex-RjdMTjNZETYmyPJy0liipFm0?feat=directlink
You can see the valve is set so water goes up to the solar panels. On the way back down, there is a check valve. There is a small hole in the 3-way valve that allows the panels to drain. But it also allows water to fill the solar panels even when it is in the off position. This slowly fills the panels and then they will be at pressure no matter what - with a small flow all the time due to this hole.

The pressure is at the filter - so it is less up top, but I prefer not to have pressure on the panels when they are not in use.

I guess my question is, how can you ensure the panels will drain without having the small hole in the 3-way valve?
 

mas985

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There is a small hole in the 3-way valve that allows the panels to drain
OK, maybe I misunderstood. Is that a true solar valve or a standard valve with a hole drilled in it?

A true solar valve has a tiny check valve in place of the hole so water only flows in one direction when the panels drain but prevents the panels from filling when the valve is in the off position. If you have a standard valve with a hole, you can get a true solar valve to replace it. Who is the manufacture of the valve?
 

pooldv

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If it is a Jandy or a Pentair valve you can buy a solar valve, remove the guts and put it in the existing housing without having to replumb.
 

lborne

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Jun 29, 2009
467
Vero Beach, FL
YES! It is a standard valve with a hole drilled in it. Not sure of the model, but I will check and buy the valve with the check valve instead of the hole.

What happens when the system is running and water is flowing through the solar panels, but then the controller shuts it off because it has reached the desired temp? There is still water in the panels and it will heat up until the pump stops and it can drain.

Thanks
 

pooldv

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I'm pretty sure mine starts to drain right away. With the valve closed it will not pressurize the vacuum release valve and it should start draining.
 

Isaac-1

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The panels will drain if there is a vacuum release valve installed (usually at the panels, either all the way at the top, or at the bottom corner). The check valve style solar valve will let the water drain bck down the cold feed size below the VRV, an alternative to the Solar valve with the built in check valve is a bypass bridge (this would still need a small valve without a hole drilled in it). This makes the solar feed piping look like an H with a small 1/2 inch PVC bridge across, usually with a valve as a restrictor control set to allow only a trickle of water through (there are other ways to make a flow restrictor, but an inline valve is easy and cheap.)

Here is a picture of my setup with bridge that doubles as manual panel drain, it was built with fittings on hand so is a bit creative in places. Note equipment is behind the wall

attachment.php


p.s. for your installation you would want the bridge above the return check valve
 

mas985

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Solar panels will not drain until the pump shuts off because the pressure on the other side of both check valves prevents them from opening. Even without check valves, the panels will not drain because of the pump pressure. And yes the water in the panels will continue to heat up. That is just the way it works and no way around it unless you shut off the pump or drop the rpm enough so the panels drain.
 

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mas985

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The panels will drain to a level of approximately the filter PSI * 2.31 and assuming the VRV is above that level. So for example, if you have the panels on a 25' roof with the VRV at the top and the filter pressure is less than 11 PSI, then the panels have drained but not much of the supply or return pipe has drained. At 1100 RPM, pressure is probably very low and so most of the system will drain.
 

Isaac-1

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mas985, I think that should be it would drain to a height of the post filter pressure in PSI * 2.31 as conventional filter pressure gauges measure the pre-filter pressure.
 

mas985

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I was simplifying some. The filter pressure is the upper limit of water height and there is some margin because the gauge is higher than the ground height so that offsets some of the loss of the filter and plumbing (~3'). There may or may not be more than that depending on the setup. In my case, it is pretty close to that and since the OP has a large cart too, I assumed the same.
 

lborne

Well-known member
Jun 29, 2009
467
Vero Beach, FL
p.s. for your installation you would want the bridge above the return check valve

If you look back at my photo, you will see a small valve T-d into the solar panel input line. Not shown is a similar setup above the return checkvalve. If I use the washing machine hose to connect the two, would that work?

Thanks
 

pooldv

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I can't see a pic when I click that picasa link. Is there and IMG code? Copy it and paste it in the post. Or up,oad the pics to Photobucket and copy and paste the IMG code to the right of the pic to embed it in your post.
 

lborne

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Jun 29, 2009
467
Vero Beach, FL
I can't see a pic when I click that picasa link. Is there and IMG code? Copy it and paste it in the post. Or up,oad the pics to Photobucket and copy and paste the IMG code to the right of the pic to embed it in your post.

This is the best I can do. I used to have no problem inserting images, but now it says they are all too large even if they are 200k.

https://lh3.googleusercontent.com/-eaoho6RYS0M/VwwN3XadvRI/AAAAAAABaE0/wSf-pmJhP9M2QyjFf_rbqBeLZBpNeaUCwCCo/s800-Ic42/valve.jpg
 

mas985

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As long as you connect the two lines on the panel side of the check & 3-way valves, the panels will drain (with pump off) but will not fill up again if the "fixed" 3-way valve is off.
 

Isaac-1

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If you are trying to attach images and use storage space at TFP instead of an image hosting provider chances are you have used up all your space, basic members only get a small amount space (256K) so just room for a couple of typical low res photos, if you want more you have to become a supporter (see the big button in the upper left of the page), a one time bronze level $30 donation will get you 10 megs of image storage, $10 off a TF-100 test kit from TF Testkits, etc.

Ike
 

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