Questions about Solar and PVC crush resistance

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jugger2500

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LifeTime Supporter
Jul 3, 2008
40
South Eastern PA
I just got a couple used solar panels off craig's list that are in decent shape. I am in the process of determining how I am going to plumb these and I am curious why a vacuum breaker would be required? If it is not present wouldn't the water just stay in the pipes and in the solar panels? Is the vacuum breaker an absolute must?

Also, why wouldn't you want some water to stay in the panels some time? for example instead of running the pump all day long I've been thinking I may try running the pump for 5 minutes every hour or so to flush the warmer water out of the panels and replace it with cooler water. Is this not a good idea? If not then why isn't it?

Also, does anybody happen to know the crush resistance of schedule 40 PVC? Once I mount the panels on top of my shed I will need to run the pipes under my driveway (just stone, not paved) and want to see if I can just direct bury the PCV (planning about about 1ft deep) or if I would need put put them inside of something.

I'd be open to suggestions if anybody has any on preventing the pipes from getting crushed. I thought about getting 1/2 block cinder blocks and putting them in there or even pouring concrete, but both of those options seem like a real pain. I also thought about the schedule 40 gray conduit but I don't think that would gain me anything.

All thoughts are appreciated.
 
I don't have a vacuum breaker, yet, but I run my 3 panels all day long when the sun is out. The thing is, when you turn off the pump it creates a vacuum in the panels and if it's sunny the water can get so hot that the panels will begin to deform, or, so I've been told.

If you're worried about crushing the PVC you could always test a couple of short pieces. Also, you could put the sections under the driveway in a steel pipe slightly larger then the PVC pipe.

HTH,
Adam
 
jugger2500 said:
I just got a couple used solar panels off craig's list that are in decent shape. I am in the process of determining how I am going to plumb these and I am curious why a vacuum breaker would be required? If it is not present wouldn't the water just stay in the pipes and in the solar panels? Is the vacuum breaker an absolute must?
Click to expand...

I'm thinking of solar panels. TN seems to have some pretty cold nights recently. My water is down to 74.
Where can I find some info on purchasing, installation, use ......?
Thanks
 
If the panels are mounted on the ground, a vacuum release valve is not really necessary and may not even open depending on the height relative to the pool. However, if mounted on the roof or shed, it is a good idea to have a vacuum breaker to remove the water from the panels when the pump is not running for a couple of reasons.

First, in winter, you really don't want any water in the panels that might freeze and it is much easier to have a vacuum breaker than it is to manually drain the panels.

Second, in summer, you really don't water in the panels when the pump is off and during the day when it is hot. If the panels are on the roof, a significant vacuum in the panels will occur and could collapse the panel if the plastic gets too hot. This is especially true on a two story roof but less likely on a one story roof.

Next, the heat transfer in the panels is proportional to the temperature difference of the water and the incident energy of the sun. So by letting the water heat up in the panels, you are actually reduce the heat transfer to the water. The maximum heat transfer is achieved by maximizing the water flow through the panels so the faster the water travels through the panels, the faster the pool will heat up. However, you don't want too much pressure in the panels either as that could also damage the panels so generally up to 60 GPM is sufficient to get maximum heat transfer.
 
Pooltime,

(odd - the url did not go through in my previous post)

I used SolarSwim - solarswim dot net - to supply panels and install end-to-end. I had a challenge initially scheduling their installation (busy season I suppose) - but they eventually came out and did a fine job from all I can tell. They completed the job in 1 1/2 days, before the rest of the pool was done, so all is well.

Please give my regards to Bob if you decide to work with him (tell him I was the one who sent the unfriendly fax)

Patrick
 
It works great ! We can gain 3-8 deg F in a day although there are lots of tall trees around. It also cools the house so we don't need A/C. Very important to lengthen the short pool season in NJ.

The pool get's 1/3 exposure to sun - and that only part of the day - and the roof faces mostly east and trees cast a partial shadow on the panles part of the day so conditions are not ideal, but under the circumstances I am very happy with the system. Our Jandy controller automates the whole thing. I set the pump to run at 40 gpm with solar and 30 gpm without. That's a tad under the manufacturer recommended 1 gpm / 10 sq ft of panels but close enough to the optimal point. Pump power consulmption increases from 160 watts to 620 watts but not running A/C saves much more electricity than the difference.

We have too much heat loss at night right now so we have to figure something out. I don't want a solar cover and I can't have an automatic one with the shape of pool I have. A little concerned about using a solar pil and what it does to the pool chemistry.

The whole system costs about as much as a good gas heater with installation so it's a great deal - and I just can't burn fossil fuel to have warmer water in the pool.
 
Patrick:

So far you have sold me, I will tell Bob he owes you some of his comission check :) What size system did you do vs the surface area of your pool?

We face South and have full sun exposure from 11am or so until sunset with no real tree blockage so hopefully will benefit greatly.

We were in the same boat as you as far as cover, we had an old solar cover which worked great, however it was too much for my wife to take off alone with our two small kids. We looked at differnet automatic covers, however becuase of the dimensions of our pool there was no where the tracks could go to keep under their maximum allowable width. We tried the solar fish liquid stuff for one season and agreed with the general idea here that they don't do too much good. We have actually had decent luck with solar sun rings; even after the cold nights and rain we had for the past week or so, we are still low to mid 80s in the pool. Ideally with the solar panels we can keep upper 80s.

Can you give me some info on the Jandy control system you use, I would be interested to see if we could automate all of this once installed.

Thanks,
Eric
 

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Hi Eric

all in my signature - 750 sq ft free form, 480 sq ft solar as recommended by the installer. Sounds like such a system might work well for you - but for a 40K gal pool you may want to use more panels than I have to heat the water quickly - 600 - 800 sq ft I would say.

It will take some pump power to move water through these panels to get them to work efficiently around here ...

Patrick
 
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