SWG size matters?

jeeman

Active member
Jun 3, 2010
31
I know that you want to get an SWG that is about twice the size. My pool is 15k gallons and I'm leaning towards the Circupool RJ-30. But the RJ-45 is just $75 more.

So, does that mean I can run the RJ-45 at a lower % and thus a lower wattage? Will the cell last longer than the RJ-30? I know that these are rated for a certain number of hours, but is that a certain number of hours at 100%?

Thanks, all! I love this forum!

Jeeman
 

svenpup

LifeTime Supporter
Nov 18, 2009
835
Sacramento, CA
The way the the % works is it cycles on and off like a microwave oven, not lowering the wattage. I doubt you will save electricity going to the larger cell, but the cell will last longer. The only real problem with going too big is that you lose granularity of control. Imagine that you are set to 5% and it is too much, but 4% is too low. If you cell was half the size this would equate to 10% and 8%, so you could set it to 9%.
 

Strannik

TFP Expert
LifeTime Supporter
Jul 24, 2007
874
Brisbane, Australia
the cells are usually rated at 100% output so if you run it at 50% the life will be longer

the SWG itself doesn't consume much electricity, so there isn't much saving there.

where you save with bigger unit is pump run time. pumps usually consume much more than SWG does.

so with bigger unit you can run your pump less.
 

jeeman

Active member
Jun 3, 2010
31
Strannik said:
the cells are usually rated at 100% output so if you run it at 50% the life will be longer

the SWG itself doesn't consume much electricity, so there isn't much saving there.

where you save with bigger unit is pump run time. pumps usually consume much more than SWG does.

so with bigger unit you can run your pump less.
Strannik, good point. I have the Intelliflo VF, so my runtime is always going to be more than the SWG, so no savings there. BTW, is there a minimum flow that any SWG needs? I always have mine running between 15-17gpm.

Jeeman
 

JasonLion

TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
37,880
Silver Spring, MD
Strannik said:
the cells are usually rated at 100% output so if you run it at 50% the life will be longer
While totally true, I don't feel this captures what is really happening. Cell life time can be thought of as producing some fixed total amount of chlorine over the life of the cell. If you buy a cell that is twice as large, it will produce twice as much chlorine in it's lifetime. Since you will actually adjust it to produce chlorine at the same rate, the pools needs some constant amount of chlorine/day regardless of cell size, the twice as large cell will last twice as long.

Yes, there is a minimum flow rate. It varies by brand/model. Typical flow requirements are between 15 and 40 GPM, depending on brand/model.
 

jeeman

Active member
Jun 3, 2010
31
Strannik said:
the cells are usually rated at 100% output so if you run it at 50% the life will be longer

the SWG itself doesn't consume much electricity, so there isn't much saving there.

where you save with bigger unit is pump run time. pumps usually consume much more than SWG does.

so with bigger unit you can run your pump less.
So then, for a 15k gallon pool, is it safe to say that an SWG for 20k gallons can be run about 100% for 3 years, an SWG for 30k gallons can be run at 50% for roughly 5-6 years, and an SWG for 45k gallons can be run at 33% for roughly around 8-9 years? I'm guessing the math doesn't work like that? Probably more like an extra year for each 15k gallon jump in size?

Jeeman
 

jeeman

Active member
Jun 3, 2010
31
JasonLion said:
Strannik said:
the cells are usually rated at 100% output so if you run it at 50% the life will be longer
While totally true, I don't feel this captures what is really happening. Cell life time can be thought of as producing some fixed total amount of chlorine over the life of the cell. If you buy a cell that is twice as large, it will produce twice as much chlorine in it's lifetime. Since you will actually adjust it to produce chlorine at the same rate, the pools needs some constant amount of chlorine/day regardless of cell size, the twice as large cell will last twice as long.

Yes, there is a minimum flow rate. It varies by brand/model. Typical flow requirements are between 15 and 40 GPM, depending on brand/model.
Jason,

Thanks for the post. It seems like the RJ 45 may be the way to go, for $100 more, even though I may lose some granularity of output. I don't think that will be a problem with the way the SoCal sun burns my chlorine away!

Jeeman
 

jparr

Well-known member
Jun 12, 2010
65
svenpup said:
The way the the % works is it cycles on and off like a microwave oven, not lowering the wattage. I doubt you will save electricity going to the larger cell, but the cell will last longer. The only real problem with going too big is that you lose granularity of control. Imagine that you are set to 5% and it is too much, but 4% is too low. If you cell was half the size this would equate to 10% and 8%, so you could set it to 9%.
My CircuPool unit appears to be varying the voltage depending on the output percentage. The cloudiness of the water leaving the cell gets heavier when the output is set higher, and I have never seen it not producing chlorine even when set to 40%.
 

jeeman

Active member
Jun 3, 2010
31
jparr said:
svenpup said:
The way the the % works is it cycles on and off like a microwave oven, not lowering the wattage. I doubt you will save electricity going to the larger cell, but the cell will last longer. The only real problem with going too big is that you lose granularity of control. Imagine that you are set to 5% and it is too much, but 4% is too low. If you cell was half the size this would equate to 10% and 8%, so you could set it to 9%.
My CircuPool unit appears to be varying the voltage depending on the output percentage. The cloudiness of the water leaving the cell gets heavier when the output is set higher, and I have never seen it not producing chlorine even when set to 40%.
jparr,
Your setup looks similar to what mine would be. What percentage do you run yours at? What FC do you maintain?

Jeeman
 

jparr

Well-known member
Jun 12, 2010
65
jeeman said:
jparr said:
svenpup said:
The way the the % works is it cycles on and off like a microwave oven, not lowering the wattage. I doubt you will save electricity going to the larger cell, but the cell will last longer. The only real problem with going too big is that you lose granularity of control. Imagine that you are set to 5% and it is too much, but 4% is too low. If you cell was half the size this would equate to 10% and 8%, so you could set it to 9%.
My CircuPool unit appears to be varying the voltage depending on the output percentage. The cloudiness of the water leaving the cell gets heavier when the output is set higher, and I have never seen it not producing chlorine even when set to 40%.
jparr,
Your setup looks similar to what mine would be. What percentage do you run yours at? What FC do you maintain?

Jeeman
I'm still dialing it in, but it seems that 40% or so running nine hours a day is able to maintain 8ppm FC. My FC dropped down to 5.5 after a heavy bather load, and was able to catch up and recover in about 24 hours using the super chlorinate feature (24 hours at 100%)
 

Strannik

TFP Expert
LifeTime Supporter
Jul 24, 2007
874
Brisbane, Australia
JasonLion said:
Strannik said:
the cells are usually rated at 100% output so if you run it at 50% the life will be longer
While totally true, I don't feel this captures what is really happening. Cell life time can be thought of as producing some fixed total amount of chlorine over the life of the cell. If you buy a cell that is twice as large, it will produce twice as much chlorine in it's lifetime. Since you will actually adjust it to produce chlorine at the same rate, the pools needs some constant amount of chlorine/day regardless of cell size, the twice as large cell will last twice as long.
it's not quite that simplistic, but at a high level - yeah

apart from production capacity, there are also other parameters that affect the life of it, like cell design, controller design, cell material, voltage/amps it's running at, water temp. etc.

plus if you are comparing between manufacturers it's really like comparing apples to oranges, as cell material will be different in most cases.

so if you take a large cell and run it at 50% it might last you twice as long from when it runs at 100%, or 1.5 times, or 3 times.
 

Strannik

TFP Expert
LifeTime Supporter
Jul 24, 2007
874
Brisbane, Australia
jeeman said:
So then, for a 15k gallon pool, is it safe to say that an SWG for 20k gallons can be run about 100% for 3 years, an SWG for 30k gallons can be run at 50% for roughly 5-6 years, and an SWG for 45k gallons can be run at 33% for roughly around 8-9 years? I'm guessing the math doesn't work like that? Probably more like an extra year for each 15k gallon jump in size?

Jeeman
i'd be speculating. see my reply to Jason above.

one thing i can say is that we had few occasions of customers bringing cells for replacement that lasted up to 12 years, with expected lifespan for those being 3 at the time they were made. so obviously they were doing something different to everyone else.
 

Strannik

TFP Expert
LifeTime Supporter
Jul 24, 2007
874
Brisbane, Australia
jparr said:
My CircuPool unit appears to be varying the voltage depending on the output percentage. The cloudiness of the water leaving the cell gets heavier when the output is set higher, and I have never seen it not producing chlorine even when set to 40%.
different manufacturers do it differently.

Autochlor RP/AC/Commercial range varies the voltage/amps applied to the cell, but SMC range cycles on and off at 100%
 

jeeman

Active member
Jun 3, 2010
31
So, I bought the Circupool RJ-45...now I am waiting for it to arrive. Where should I put it? In between the filter and the heater, or between the heater and the return? There is more pipe to play with between the filter and heater, but it's also higher (2.5 feet) off the ground....the heater to return has only about 5 feet to play with, but it's pretty near the ground.
 
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