Equipment Design Questions

[Sailracer]

I have a number of questions that I am struggling to find answers to and hope the experienced folks on this forum can help.

Background: My equipment setup is shown in the schematic. My pool is irregular shaped and I guess somewhere around 25K gallons. The solar heater was just installed and I installed the SWG a couple seasons ago. My Nautilus FNS60 DE filter just failed as I tried to open the pool this year. It would cost $200 to replace the clamp band that failed, which is ridiculous, so I am using this opportunity to go to a sand filter. I like to run my pump on low most of the time for 10 to 12 hours a day to give the SWG enough run time to generate enough chlorine. In the diagram, all black piping is 1.5". The return to the pool is 2" and the orange lines for the polaris and booster pump are 3/4". I have pretty much stopped using the propane heater after estimating that heating the pool for a weekend used about $100 worth of propane.

Problem: With the pump on low, the chlorine generator often fills with air or maybe gas from the generator and not all of the generating plates are immersed. When the polaris pump comes on, it drops even more and shuts down due to no detection of water flow. My initial testing with the the solar panels shows that the pressure drop they cause makes this problem even worse.

Question 1: Why does air/gas accumulate in the SWG? Is it a byproduct of the chlorine generation?
Question 2: Is the expansion from 1.5" to 2" pipe after the SWG reducing the backpressure and letting the air build up? If so, should I move the SWG to location C so it is at a higher pressure point?
Question 3: When I reconfigure for the new filter, should I put in a set of bypass valves for the propane heater to reduce the pressure loss it causes?
Question 4: Should I move the solar heater to location A so the booster pump is running water through the panels and not the main pump to remove its head increase from the main pump?
Question 5 Is there a difference in pressure loss between DE filters and Sand filters? Will my pump on the .25HP setting still be able to move water through the sand filter?

Thanks in advance for any assistance!

 

[Sailracer]

I've had a few more thoughts as I browse other posts on these boards and learn new things. Here is one way I came up with to reconfigure the equipment.



The propane heater would be on a bypass so it is not normally exposed to the high chlorine levels from the generator. Water would only be routed through it on the several days a year I turn it on.

The solar heater (which is on the ground rather than a roof so the startup load on the pump is little) would be moved to the Polaris booster pump where it would get some small flow due to the main pump and more flow when the booster pump is on. OR if the SWG flow would benefit from having more head loss after it, I could put the solar heater between it and the return.

Thoughts?

 

[pooldv]

Your first post was better. Put a 3way solar valve at the tee going to solar and a check valve on the return. Plumb in a bypass for the propane heater. SWG needs to be last.

 

[jblizzle]

1. Yes. Chlorine and Hydrogen gas ... this is why the SWG MUST be the very last piece of equipment before going back to the pool
2. The pipe size has nothing to do with it, the SWG needs to go to location B
3. Bypass is optional, if you are doing the plumbing would not hurt.
4. No. Booster pump is designed for low flow high pressure. Solar is most efficient at high flow rates and lower pressure
5. Headloss is different (I think large cartridges are the lowest), but the pump will still move water through any of them.

I agree with pooldv. You should get rid of the shutoff valves around the solar and put a solar 3-way valve on the solar inlet and a good flapper type check valve on the solar return. You also usually need a check valve right after the filter due to having the solar for when it drains, although if yours is on the ground that might not be needed. I would likely plumb it in anyway.

So it should go:
Pump > filter > check valve > solar 3-way valve > solar return check valve > heater > SWG > pool

 

[Sailracer]

The problem with going Pump > filter > check valve > solar 3-way valve > solar return check valve > heater > SWG > which is essentially how it is today except for independent valves and no check valves, is the water flow is too low for the SWG to work when my pump is on low speed.

What about this as an alternative:
(removed due to space limitations)

It moves the heaters to a parallel connection with the SWG and hopefully I can use the valves to keep the flow through the solar panels low and have most of the water going through the SWG. I'm still a little worried there will not be enough flow through the SWG- it depends on how much moving the propane heater out of SWG path increases the flow. I have been trying to find the manual for the heater to see if it has an automatic bypass. If it does, then I would not expect to get any waterflow gains out of this arrangement compared to what I have today.

Thanks!

 

[jblizzle]

Solar works best at high flow rates.

What you drew will not provide more flow for the SWG because you are splitting the flow.

Your pump may just be too small to run the SWG on low.

 

[Sailracer]

Your pump may just be too small to run the SWG on low.

That is becoming my fear. Would that be expected? The pool equipment is very slightly above the pool level (maybe 1 foot). The 3 suction lines of 1.5" pipe average about 25ft in length and the 2" return line averages maybe 40ft. I can't find the curves for my pump, but maybe I can find an equivalent and estimate my head and arrive at what the GPM should be on low. I have no idea how old the pump is. Maybe it will die soon so I can get a variable speed

Could this be a flaw with the Circupool RJ design where it's inverted U shape allows the hydrogen to accumulate at the top at lower flow rates? I notice their newer models have more of a straight through design.

 

[jblizzle]

I don't know the flow rate that is required for that swg. I know my Hayward requires about 15 gallons per minute and I easily get that on low speed of my pump. At least until the filter gets dirty.

 

[Sailracer]

I ended up going with this config:



The new propane heater bypass will hopefully increase my GPM on low enough that the SWG can run with the solar panels switched in. The glue is drying now and I will hopefully be able to test and report results this evening.

 

[Sailracer]

Update: The bypass of the heater definitely improved the flow with the pump on low, but it wasn't quite enough. The SWG still fills with gas, though it takes it a little longer than it used to. I think my next experiment will be to re-plumb my solar panels in parallel rather than in series to try to reduce the head loss through them.

 

[mas985]

Turn your cell upside down so the gas doesn't build up.