Solar Heating Results

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bradatkins

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Aug 27, 2012
48
Sudbury, ON, Canada
Hey -

So I just finished installing my solar heating this weekend, and of course only squeaked out a couple of days of sun before the rain!

Here's the layout, it was about 8AM when I took this picture. My panels face East.
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Here's a picture of the pool:

8756785951_1f78d93440.jpg


Here's a picture of the start temp & time.

8756766153_b7aa7335c6.jpg


Here's a picture of the last temp taken around 1 or so. After that it started to be cloudy

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So I got 9 degrees in about 4 hours or so. I wasn't expecting that much of an increase, so my question is, does that sound right, or is perhaps the sensor on my salt system a little whacky? I can't wait till it's consistently sunny!

Thanks!
Brad
 
Ok cool. Ya the first night I lost everything (I forgot to change my programing from night to day) and ran the pump for 8 hours through the solar panels! :(

The next day, I started off at 63 and got up to 71 before mother nature attacked. So I lost a 3-5 degrees overnight but picked up 8 during the day.

Now it's cloudy and raining, so not much going on.
 
What is the size of the pool (surface area and volume) and the surface area of the panels? (no-sig, hint hint)

6-8 degrees is normal for my system and I can get up to 10 degrees on certain days. But when I use a cover, I only need 3-4 degrees rise.
 
Hey -

15x30 SWG AGP, 1HP Pump
8x20 Solar Heating

It's not a solar control, wish :)

The only thing I'm not sure of is I ran 1/2" OD Poly up to the roof and then it's 1.5" solar headers. Doesn't seem to be much of an issue, I was thinking of switching the Poly to PVC, but don't see much of a problem. Perhaps extra work for the pump/filter?

Thanks,
Brad
 
Exactly how are you measuring the water temperature?

If you are using the SWG, they are usually plumbed after the panels so the water temperature it is displaying is post panel and because of the small pipe, the flow through the panels will probably be slow and the temperature rise through the panels (input to output) will be very high and it won't give an accurate reading for the pool. Also, that is very inefficient installation and you are probably losing a lot of the heat back to the environment.

Also, do you have a temperature gauge before the panel input or a thermometer in the pool?
 
Hey -

The SWG cell is mounted on the return jet, which is I'm guessing how the the temperature is getting read. So it's getting the temp after it comes out of the panels. Of course, with the panel's turned off (diverted) it's coming right out of the pool. I do not have any thermometer's prior to the panels and I haven't put my pool thermometer in yet (waiting on my stairs).

You state that this is very inefficient but do not state why?
 

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It is inefficient because the small pipe causes lower flow rates (higher pump head loss = lower flow rates). The lower flow rate through the panels causes a higher temperature rise in the panels. Heat loss is proportional to temperature differences so a higher heat rise in the panels = more heat loss and the longer it will take to heat the water in the pool.

Also, since the SWG is post panel, during the heat of the day, measure the water temperature with the panels on vs off. Ideally, that temperature difference should be less than 5 degrees to maintain optimal efficiency. The lower the temperature difference, the more efficient the panels will be.

BTW, are you redirecting all the water through the panels?
 
OK that's what I thought about the smaller pipes. I had them already there so I figured I'd try it like that before switching them out for PVC all the way (plus there's been a run on PVC in the city so it's hard to get right now).

When it's sunny I'm redirecting all the water to the panels. When it's not sunny I'm directing the majority of the water away from the panels.
 
Ok, just a couple of observations, it looks like you probably have room for 1 or 2 more panels on the roof, secondly I agree you are likely not getting enough flow through the 1/2 inch pipe, with your small panel array you would probably be ok with 3/4 inch and almost certainly be ok with 1 inch, if you allowed some of the water to bypass the panels (the flow capacity of 3/4 inch pipe is about twice the capacity of 1/2 inch, and 1 inch is about twice the capacity of 3/4 inch, etc.). With optimal panel flow you should barely be able to tell the return water as warmer than the pool water.
 
Right now you are likely not getting enough water through the panels due to the 1" pipe restriction. Once you replace that with 1.5"+ pipe you may not need 100% of the flow through the panels which would pressurize the panels as Isaac stated. You just need enough flow such that the panels feel cool to the touch.
 
Yes, solar heating is more efficient with higher flow rates which means a smaller temp delta on more water. You want high flow rates, but not enough to be over pressurizing the panels.

You get more heat in the pool by adding a little heat to a lot of water through the panels than a lot of heat to very little water.
 

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