Very high solar roof heating Splapool 1.5HP 2 speed not strong enough, need help

[alexmason]

Hi,

Might be doing something wrong here, but here's my setup: 2600' of 1/2" pvc on a 20 to 30' high roof, somewhat steep. I have nothing other a Y valve splitting betweed pool jet and roof. Pool is AG. The home water pump (the well pump) can prime the coil and fill it with water, but the Splapool 1.5hp doesn't push strong enough to keep it going even when primed, seems like the water is returning towards the pump even. I see other people making this work with 1hp pumps, am I missing something? As for pump suggestions, I would rather use 120V.

Thanks for your help

 

[duraleigh]

Welcome to the forum.

Once the panels are primed, there is no force whatsoever preventing your pool pump from circulating other than the head loss of the pipes.

Something is clearly amiss but I can't tell from your description what's wrong. If the water is flowing backwards, you have a valve closed or some restriction somewhere.

Again, once it is primed, any pump can circulate the water. Out of curiosity, why are you priming with a well pump....is it hooked up to your pool's circulatory system?

 

[JamesW]

Do you have panels or are you trying to move water through 2600' of 1/2" black tubing?.

Can you describe the design and installation?

 

[alexmason]

Hi, thanks for responding. I have one large 2600' long coil of 1/2" poly irrigation tubing.

I used the well pump to prime largely because I knew it was much stronger than pool one. They are not connected, I have to manually attach the garden hose to it.

 

[alexmason]

I have a spare Hayward ultra flo lx 1.5hp pump that I could add in series after the filter. I wonder if that will work...

 

[JamesW]

A pool pump is not designed to work like that. You need a pump that works with low flow high pressure like a well pump or booster pump.

Edit- A single tube design won't work. See below.

 

[mas985]

No that won't help. The problem is that there is way too much head loss in a 1/2" 2600' pipe. You need multiple parallel tubes to reduce the head loss. If you had 26x100' parallel runs, the pump could then produce enough flow for the solar to efficiently capture the heat.

 

[jblizzle]

I agree with Mark. Your solar setup is not properly designed. You need many more parallel runs. Solar heating works best at higher flow rates where you heat a lot of water only a few degrees.

Generally it is now less expensive to buy commercial panels that are properly designed with hundreds of parallel tubes than to DIY a setup using irrigation tube.

 

[JamesW]

I also agree with Mark. A single tube will not work from a hydraulic or heat transfer point of view.

Premade panels are probably the best option.

 

[alexmason]

I also agree with Mark. A single tube will not work from a hydraulic or heat transfer point of view.

Premade panels are probably the best option.

Thanks guys. But the piping is already laid. Pumping the well water through the piping warms it to bath-like temps. So then what I would need is one of those high-pressure and low flow pumps in series, on the solar panel side of the Y for use to warm it up. I can shut it down when I don't need it. As a lifter pump. Any suggestions on pump choice?

 

[mas985]

Pumping the well water through the piping warms it to bath-like temps.

That means you are losing a lot of heat to the surrounds but I understand that you don't want to make any changes at this point. Just keep in mind that you are probably losing more than half the heat that you could be capturing with a more efficient system. The goal in solar is to heat the water as little as possible through the panels (i.e. high as flow rate as possible) to minimize the heat loss to the surrounds. When the tubing feels hot, this means you are losing a lot heat. An efficient solar panel, is one where the panel feels cool. You want to add lots of BTU but not delta T.

As a lifter pump. Any suggestions on pump choice?

A cleaner booster pump might help some but you will still be limited on flow rates so the efficiency may still be low.

 

[jblizzle]

How is this all laid out? Any pictures?
It should not be too terribly hard to split the run into multiple parallel lengths.

 

[alexmason]

How is this all laid out? Any pictures?
It should not be too terribly hard to split the run into multiple parallel lengths.

I'm open to ideas, perhaps simple changes, like T-ing the spiral a few times would't be too hard, provided I can merge it back together in 1 run of poly pipe.

This is essentially the gist of it.

- - - Updated - - -

So I take the problem is specifically with the lenght of the tubing. I could easily T is off as 5 lenghts of 500, would that work?

- - - Updated - - -

So I take the problem is specifically with the lenght of the tubing. I could easily T is off as 5 lenghts of 500, would that work?

 

[mas985]

So I take the problem is specifically with the lenght of the tubing. I could easily T is off as 5 lenghts of 500, would that work?

Yes, that would help but I would go with double at 260' (i.e. 10 lines). But you don't want tees, you want separate lines with separate inputs and outputs. You can still keep the same coil, just cut the lines, and put in a 90 on each end. Combine half into a supply line and the other half into a return line. But you will also need larger pipe for the supply and return lines to and from the pump. In this case, you don't want the booster pump but just use a regular pool pump that has enough lift for the panels.

 

[alexmason]

Yes, you're right for the t. How about this: the feed and return are already 1/2", if I split both in 5, will it work? I'm looking for the least amount of work that will work

 

[jblizzle]

It should be fed with 2" PVC and I would want at least 10 parallel lines. That's what the previous owner put at my house before I ripped out that mess and put in true solar panels. I got tired of dealing with leaks.

 

[alexmason]

The problem is that the pool is far from the coils and that would imply buying so much 2" piping. I think I will go for the booster.

 

[mas985]

10 - 1/2" lines would be about the equivalent of 1 1/2" pipe so I wouldn't go less than that. 5 - 1/2" is only the equivalent of 1" line and you will still have a lot of head loss.

The booster is not guaranteed to improve things much and costs a lot more than doing the right way.

 

[jblizzle]

Yeah, I did not do the math. I realize that mine was (and is) fed by 1.5" PVC although I transitioned to 2" everywhere that I changed the plumbing.

What we are suggesting will work. Alternatives may not ... and will certainly not be as efficient at heating the pool.

Like I said, I had 2500' of irrigation too. Decided it was not enough sqft to get the heating that I wanted ... plus is sprang leaks all the time (likely due to the minimal freezing we get). Do you have a plan to drain all that tube for the winter? If water stays, it will freeze and damage the tubing.

 

[alexmason]

Yeah, I did not do the math. I realize that mine was (and is) fed by 1.5" PVC although I transitioned to 2" everywhere that I changed the plumbing.

What we are suggesting will work. Alternatives may not ... and will certainly not be as efficient at heating the pool.

Like I said, I had 2500' of irrigation too. Decided it was not enough sqft to get the heating that I wanted ... plus is sprang leaks all the time (likely due to the minimal freezing we get). Do you have a plan to drain all that tube for the winter? If water stays, it will freeze and damage the tubing.

Ok I'm convinced. I will convert to 2" from the pump out and then down to 10x 250-260' lenghts. Thanks guys.