How much pump for my Solar setup?

[Nubo]

Well, I installed my SunHeater panels on the roof. These are 2 2x20 panels with one-way flow (costco kit different that what's on their website).

The highest point of the panels is about 16 feet above ground level. The plumbing from the pool runs about 50 feet to the riser, through the panels (serially), down the return, and then another 50 feet back to the pool. I plumbed with 1" irrigation pipe. The distance was necessary to reach from the pool location to the nearest south-facing roof.

After hookup I found there was no flow back into the pool. After unhooking various sections I find that some water would return to the pool location but insufficient pressure to overcome the climb back into the pool plus the back-pressure on the inlet hose.

So, I guess I need a more powerful pump?

The question is, how powerful? The existing pump is the Intex model that came with the pool. It's 1.1 Amps. No horsepower or CFM rating that I can see. I want to get decent flow but don't want something too powerful either. Not sure how to determine a properly sized pump. Any recommendations?

Thanks!

 

[mas985]

You should only need 16 feet plus 1-2 feet of extra head or about 18 feet of maximum head on the pump so it is surprising that the pump would not have enough to at least prime the panels.

1.1 Amps would indicate something close to 1 braking HP which should be more than enough.

What does the pressure on the filter read with and without the solar panels?

 

[Nubo]

mmm... it's a pretty basic unit, no pressure indicators. The flexible connection from the output side of the pump to the pvc does seem to take on some pressure. I disconnect the flexibile coupling from the first panel and get a flow, but not that impressive. With the return line connected to the pool there is no return flow from the panels. With the return line disconnected from the pool , some water does trickle and returns to the base of the pool but it is a very weak stream.

The return flexible connection from the panels doesn't actually fill with water, I can just feel the weak tricle running through it. There's a diverter between the panels but it doesn't seem to have much effect on the flow whether it's set to bypass or not. The flow just seems to be just about out of gas by the time it reaches the discharge (high point) of the panels.

Pump is 1.1A at 120V. I'm calculating about 0.17 HP by converting the wattage. I don't know if pump HP are rated by electrical consumption or by actual output, but this one seems fairly minimal.

 

[mas985]

I'm sorry I must have been thinking 11 Amps instead of 1.1 amps but you're right 1.1 Amps @ 120v is very low HP so it could very well be a problem for your pump. Probably not enough head for the lift.

Not much you can do other than:

1) Put the panels on the ground, OR
2) Replace the pump or add a booster

 

[launboy]

I would replace that pump with a bigger one. I think 1/2 HP would be sufficient. You are kind of limited to how much water you will actually get to flow through 50' of 1" pipe. I don't know if a 3/4 HP pump would be just right or too big for the pipe but I'm sure someone here does.

Look on eBay and your local Craigslist(http://www.craigslist.com) for pumps, there are a lot of great deals to be had out there.

Good luck,
Adam

 

[Nubo]

I figured I'd drop in on a local pool store, figuring they'd have a wide array of pumps to look at. Well, first they tried to sell me a 1 1/2 horsepower pump! When I suggested I really didn't want to overpressurize my solar panels and waste electricity in the process, they told me they could special order a pump but the smallest available was 3/4 HP. My goodness! And the prices are much more than I paid for the pool!

According to Intex, the pump I have puts out 800 gph (no psi given). Since it's got enough head to just get over the top, I figure a modest increase should be enough. Again, I don't want to stress all those connections and panels on the roof. I'm going to order the 1500 gph version from Intex, which has a fairly reasonable price and doesn't feel like overkill.

 

[Nubo]

...You are kind of limited to how much water you will actually get to flow through 50' of 1" pipe....

Funny; standing in the Home Depot, I figured I'd splurge and "overbuild" the thing with 1" pipe! :lol:

 

[mas985]

When looking for a pump make sure the maximum head is at least 5' higher than the lift of the panels above the pump. The pump will be much more efficient though if it has even higher head than that.

Unfortunately, it will be hard to find a pump with head needed that is less than $250. You might want to relocate the panels instead to a lower elevation. That might me a less expensive solution.

Also, I would agree that 1" pipe is really too small for that application unless it is very short in length.

 

[Nubo]

When looking for a pump make sure the maximum head is at least 5' higher than the lift of the panels above the pump. The pump will be much more efficient though if it has even higher head than that.

Unfortunately, it will be hard to find a pump with head needed that is less than $250. You might want to relocate the panels instead to a lower elevation. That might me a less expensive solution.

Also, I would agree that 1" pipe is really too small for that application unless it is very short in length.

Thanks mas985,

I notice you are geographically nearby, and are using solar panels at about 65% area. What length of pool season are you getting?

 

[mas985]

Actually, my pool area is smaller than the dimesion lead you to believe (~550 sqft) since it is a free form pool so my solar covers over 87% of the pool area.

Depending on the weather, nobody really likes to swim much when the air temp is too low, we swam as early as late March and as late as mid November. But again, it is usually when the air temp gets into the 80's and we have a string of warm days where the pool has a chance to warm up. A pool cover really helps during the extreme times.

I can usually get about 8 degrees per day rise per day on average and when it is really hot, I can sometimes get up to 10 degrees per day.

There were a couple of reason's why I went with the solar size I did:

1) Front of the house faces south so I wanted to fill the entire second story roof with the panels so they wouldn't be so noticeable. Most people don't notice that I have panels on the front of the house.

2) I am fairly lazy when it comes to the cover so I really don't want to use it June-Sept. The heat gain is sufficient to keep the water close to 90 degrees during this period without a cover. Beyond this time, I usually need a cover but then we don't swim as often so it isn't such a hassle.

3) The incremental cost for larger panels really wasn't that much more so I filled the roof.

 

[Nubo]

To update -- I finally did get the new Intex pump; hooked it up, and guess what? No flow. :grrrr:

Apparently the increased gph of this model may have more to do with the larger diameter inlets/outlets than with PSI (which Intex doesn't provide). Oh well, one last thing to try -- thanks for the "booster" idea. I hooked up the old and new pumps serially, using the old one to feed the new one. Voila! Now have decent flow though the system. Much of the solar day had passed but getting 6 degrees differential between inlet and outlet. Didn't measure GPH though, so no clue at this point how many BTU.

Still only consuming about 3 amps, so not too bad. I find that once the panels are primed, the original pump can handle the job all by itself but in order to take advantage of that I'll need separate timers for each pump.

When/if we get a larger pool I'll look for something with a bit more capacity (and a psi rating) as well as probably more panels. A nice sunny day today (though windy) and sunny forecast for the rest of the week; will be interesting to see how much gain we get by evening and over the week. Pool temp was 60F at sunrise.

Well, the project is actually fun now that it's finally working!

Next step is to take down the overgrown eucalyptus that is robbing me of 2 hours of sun!!