Repairing fiberglass over gunite

[Dirk]

I'm the party pooper...

It's not uncommon to run a solar heater as a completely independent system. Given your electrical cost constraints, that might be a great way to go. Never having done that myself won't keep me from chiming in about it, though!!

Depending on the panels, you might have to look into some sort of rudimentary filtering. You need to pump clean water through most panels, many of which have very small collector tubes that won't tolerate particulates.

More importantly: there's a common misconception about the amount of flow needed by solar panels. Stop me if you know this already. The myth being the slower the water goes through the panels, the hotter it'll get, the better it'll heat your pool. To get maximum efficiency out of solar heaters, you actually pump a lot of water through them and only raise the heat of the water a degree or two. Super-heated water running slowly out of your solar return will do very little to heat your pool.

Similar to your plan, I run my pool off PV panels, so with those and the solar panels, my pool heating/filtering/sanitizing is "free" (not counting wear and tear, maintenance, etc). So I'm with ya there. But the eight solar panels required to do a decent job of heating my 12K pool need 40GPM of flow! That's a big Pentair VS running at 2200RPM. Granted, I have to also push that water through a filter, NG heater, SWG, etc, so I got a lot of resistance, which you'll be eliminating to some degree. But you're still going to have to push a lot of water. Something to consider when you select your motor and PV panel. I'm guessing they're not going to be as lightweight as you might be counting on...

I think where the panels are mounted are not so critical. If they're on the roof, then the water you'll be pumping up there is being pulled down by the water coming back. So you're really only needing to overcome the friction of the water through the pipes. But you do have to force a lot of water through the panels, so there's that. And since you have to drain solar panels at least once a day, you'll have to fill them once a day, so while you don't need much horsepower to keep the water moving, you do need a good amount to get the initial fill of the system. So that's something else to consider when selecting the pump.

I'm sure there's some math you can do. You'll need to identify the brand and number of solar panels, and figure out their collective flow rate requirement, then add in the pipes and filter, etc, to calculate the required pump size. (I think these are "head" calculations, but I don't even know the terms, let alone the math!). Hopefully someone else here can fill in the blanks...

 

[sktn77a]

I'd be surprized if you can find a 12 volt pump that will run roof-mounted solar pool heater panels. My in-laws have solar panels on their roof and run it 12 hours a day (Sacramento.... SMUD!!!) with their main pump, but they save way more on heating than they use in pump electricity - indeed, they frequently have to bypass the solar panels to keep the water temperature down!

If I remember correctly, you can no longer buy and install single speed pumps in Los Angeles County. Have you considered using your existing pump until it dies and then installing a VS pump? You could then see how low you could run it and still get good circulation to the solar panels.

As an aside, I used to build and repair fiberglass kayaks back in the day (waaaay back) - miserable job, what was I thinking?! You've elevated the art to a whole new level in my book!!!

 

[Dirk]

I'd be surprized if you can find a 12 volt pump that will run roof-mounted solar pool heater panels. My in-laws have solar panels on their roof and run it 12 hours a day (Sacramento.... SMUD!!!) with their main pump, but they save way more on heating than they use in pump electricity - indeed, they frequently have to bypass the solar panels to keep the water temperature down!

If I remember correctly, you can no longer buy and install single speed pumps in Los Angeles County. Have you considered using your existing pump until it dies and then installing a VS pump? You could then see how low you could run it and still get good circulation to the solar panels.

As an aside, I used to build and repair fiberglass kayaks back in the day (waaaay back) - miserable job, what was I thinking?! You've elevated the art to a whole new level in my book!!!

If the OP is not currently running a VS pump, that might be the better solution. The overall money he'd save on switching to a VS pump would eventually pay for the pump, and might be less electricity with solar than his current pump without it.

I circumvent the PG&E problem (even with PV solar I still am subjected to PG&E time of use issues) by shutting down solar heating by 3:00PM (might be different in your area?). My pool usually heats up by 1 or 2, so that's no problem.

 

[rcpilot]

My 2hp pump only knows one speed unfortunately and agree the VS pump would be ideal and save more money on the long run.

Here is an interesting calculator for mixed bodies of water average... and your right Dirk about requiring enough flow, I will need about 5000 gallons through the panel (6 hr of strong sunlight) to make a significant temp rise on my 15k gallon pool. Needing a pump around 13-15/gpm is not doable with a 12v system.

Calculator: Mix Liquids (e.g. Water) of Different Temperatures

 

[Dirk]

See if there are any rebates floating around. Sell your old pump for $100 (that's what I got for mine), and the ROI on a new VS pump might be better than you think. Subtract the cost of the second pump you were going to buy, and whatever the extra plumbing and second filter would have cost, and a new pump might look even better.

When buying a new pump, consider automation. Not necessarily buying it now, but just think about future-proofing. Your pump, SWG and automation should be of the same brand. So if you think there's a possibility you'd ever upgrade to any of those, a little pre-planning can go a long way. You're going to want some sort of solar controller, so that's part of the equation, too. My ET runs my pool and solar and pump and SWG, all nice a neat, from the pad, inside my home, and from any computer or smart phone. Hey, it's only money!!

 

[rcpilot]

Well my city of Burbank have a $400 rebate for an in city purchase of a variable speed pool pump. I ordered a VS Pentair through HD for $700 so my out of pocket cost is $300 bucks.

 

[Dirk]

Nice! Can you post the exact model number and/or add it to your signature? We can double-check that it is compatible with Pentair's automation offerings (unless you already did that).

 

[sktn77a]

I'm guessing it's the Pentair Superflow VS at that price. Not the most flexible when it comes to automation. Great rebate, though!

 

[rcpilot]

Model # 342001 yes it is the superflow vs version. I could have purchased any VS pump as long as it is in Burbank and get the $400 rebate. No need for automation but it does have low power digital control if it needs it. The only thing I have is the pump, I only use it cycling/filtering the water and I use a robot cleaner for cleaning. Now I have a solar heater which I have hooked up. I installed a valve on the return line that I can turn just enough so water will flow some to the solar heater which is 6' above the pool pump. I will leave the valve setting throughout the summer and just adjust the water temp with pump on during the day or more at night. So far pool temp has been going up 1 degree per day currently at 82 degree at the surface.

 

[Dirk]

OK, the 342001 Superflow will not give you all the goods if you ever upgrade to Pentair automation. You can make it work, just not as well as their IntelliFlo series. Just something to consider if you haven't opened the box yet. Here's the answer to the question I posed about it to our resident Pentair pump expert, Jim:

That is the Pentair SuperFlo VS... it has no RS-485 serial port so can not be "fully" controlled. What it does have is a 5 VDC output that can be routed through relay contacts that can select a speed. One relay per speed up to 4 speeds. So, it makes your VS pump a 4 speed pump. Each relay sends the 5 volts back to the pump on a special cable. (The cable looks like a RS-485 cable, but it is not..)

Four speeds is more than most people need, but you need 4 empty relays on an EasyTouch (or whatever) to use it. You can set the speeds you want at the pump, but the automation can only select those speeds, you can't on the fly adjust from say 1200 to 1250.