Help with sizing a generator

[Smykowski]

I'm looking down the barrel of a complete remodel of our above ground pool, and I'm strongly leaning toward converting to salt as part of the process.

I understand that you should buy a system/cell that's double the rated size. However, my pool is approximately 25,000 gallons. In the case of a Circupool system, an RJ45 would be just about double. Other than the initial outlay, is there a downside to going as high as an RJ60?

 

[Jimrahbe]

Ski,

You can never go too big with a SWCG. But... Some SWCG's can only be adjusted in large increments, LIke 20%, 40%, etc.. Others in smaller increments.

If you buy a much larger cell then you need, it would be best to get one with smaller increments.

Thanks,

Jim R.

 

[Newdude]

Other than the initial outlay, is there a downside to going as high as an RJ60?

The upgrade maths work heavily in your favor. A 'too big' cell will fail electronically before the plates deplete, but the bigger cell only needs to last as long as the % of price increase.

Say, upsizing a 40k to 60k costs 20% more. If the 60k unit lasts 20% longer than the 40k unit, then it breaks even. If it goes the distance, it will last 50% longer. Effectively you'd be buying a 40k at full price and a 20k at 80% off.

 

[BDY]

One thing to think about - in your latitude you won’t run the cell very long in a season. Those of us in year round need to run the cell near the whole year. A greatly oversized cell for me may have more impact than for you as I have more hours per season to use it

If that makes sense …..

Food for thought

 

[Smykowski]

Thanks for the help so far. It never even crossed my mind that if you oversize too much, you could have runaway production.

Given your suggestions above, I want to determine two things. First, what is the cost per unit of chlorine for my pool, to assess whether or not the upfront cost is worth it. Second, what type of production does my pool need? I want to make sure that I’m not drastically under- or oversizing a generator for my pool, both from a % setting standpoint, and a total longevity standpoint.

Assumptions:
25,000 gallon pool
Average of 1.5ppm of FC per day
Bleach cost $4 per gallon ($5 on the high side)

 

[Smykowski]

First, the money….

Cost comparison (these figures represent the current upgrade sale at Discount Salt Pools)

RJ45 $1300 purchase price. Rated at 15000 hours (not sure if that’s realistic, so I’ll run numbers for 10K too). 2.0lb per day.
2.0lb per day = 9.6ppm per day
10000hrs=416 days
15000hrs=625 days
10K hr life = 416x9.6ppm=3993.6 ppm FC produced
$1300/3993.6= $0.326 /ppm
15K hr life = 625x9.6ppm=6000 ppm FC produced
$1300/6000= $0.217/ppm

RJ60 $1500 purchase price. Same hour rating. 3.1lb per day.
3.1lb/day = 15ppm /day
10000hr life = 6240ppm produced
$1500/6240= $0.24/ppm
15000hr life = 9375ppm produced
$1500/9375= $0.16/ppm

1 gal bleach =6ppm=$4= $0.67/ppm
1gal bleach = 6ppm =$5= $0.83/ppm

From a dollars and cents standpoint, in my case the SWG is a no brainer.

 

[Smykowski]

I have a two-speed pump that I run on low for approximately 10 hours a day. To ease the math a little bit, let’s assume 8 or 12 hours per day pump and SWG run time.

RJ45 produces 9.6ppm in 24hrs.
3.2ppm in 8 hours.
4.8ppm in 12 hours.
1.6ppm in 8 hours at 50%.
1.6ppm in 12 hours at 30%.

RJ60 produces 15ppm in 24 hours
5ppm in 8 hours.
7.5ppm in 12 hours.
1.5ppm in 8 hours at 30%.
1.5ppm in 12 hours at 20%.

These percentage settings seem reasonable.

Now for total longevity.

Assume pool season runs May 15 to Sept 15 (yeah, the northern latitudes suck. Only 4 months). That equates to 120 days of use.

RJ45 at 8 hour run time at 50% = 4 hour run time at 100%
4 hours per day x 120 days = 480 hours per year
10k life / 480 hours = 20.83 seasons
15K life /480 hours = 31.25 seasons

RJ60 at 8 hour run time at 30%= 2.67 hour run time at 100%
2.67 hours per day x 120 days = 320.4 hours per year
10k life/320.4 = 31.21 seasons
15k life / 320.4 = 46.82 seasons

I suppose those numbers shouldn’t be surprising given our short seasons.

Does all of this math look correct? And given the results, does this change any recommendations from before?

Is it possible that the cell could outlive the electronics if I got the RJ60?

Thanks again for all of your input.

 

[Smykowski]

Finally, even though the unit chlorine cost is way lower with an SWG, because of the length of my season and my already relatively low chlorine consumption, it looks like my payback times are ridiculously long.

At $4/gal, my yearly chlorine cost is about $120.
At $5/gal, my yearly chlorine cost is about $150.

So rough napkin math says that it would take 10 seasons before the SWG pays for itself.

In the end, I'm gonna be paying for the convenience.

Discuss.

 

[Newdude]

In the end, I'm gonna be paying for the convenience

If this is the *only* thing that comes from it, you will have a death grip on the SWG when I show up a couple of months later to take it away.

You'll likely save a ton in the long run, but the common theme from folks like you is their report back that they kick themselves for not doing it sooner.

@woodyp can tell you.

 

[Smykowski]

Ok, one more thing. I've done some searching, and it looks like the answer is to ignore the warning, but I have to ask....

My Hayward heater says it's not approved for salt water pools. I'm replacing a skimmer because of a leak, and the warning that came with it says "Attention: Disregard any statements in any literature that may state that the use of a Chlorine salt generating system is approved, it is not! The use of any type of Chlorine Salt Generating System on your pool will render your warranty coverage null and void. The use of such systems causes premature rusting and corrosion of all metal parts that are not a manufacturing defect."

What's the deal? And if all of these pools are not approved for salt water, are there products that specifically are approved for salt water?

(And yes, I understand that the use of liquid bleach for the last 10 years probably means I already have a salt pool and don't know it. )

 

[Smykowski]

Bump?

 

[proavia]

If your heater isn't approved for salt pool, you better uninstall it now - as every chlorine pool is a salt pool.
Adding liquid or solid forms of chlorine also add salt.
If you test your current salt content, you may be surprised at the measurement.

Nah - your heater should be fine as long as you maintain TFP recommended levels.
Salt levels in a pool are about 3000-3500 ppm. Ocean water is about 35,000 ppm.

 

[Newdude]

How old is the heater ? I'm thinking it's outdated literature from the early stages. Hayward has been making SWGs (safe for its own equipment) from the get-go. But there was some misinformation out there at the very start.

 

[Mdragger88]

If you’re pool is already 10yrs old any warranty is likely now in it’s prorated phase anyway which is generally not very favorable so basically useless. The same line of thought applies to the heater as well. Do you know what it’s components are made of?
The parts of the pool where salt water actually touches (top rails) would be my main concern personally depending upon their material.
I am also curious of your current salinity level so when you find out let us know!
I’m considering collecting data for a completely unscientific study similar to the D.R. Millionaire study except, you know, with regular people who unknowingly already have salt pools and didn’t think it was possible “Everyday Salt Pools”
but seriously, as for the roi on a swg there are some things to consider, when this pool has lived it’s life do you plan to replace it? If not you may perhaps consider one of the universal circupool models. Ul40 or UL55.
They are highly adjustable, affordable & offer a basic well known design. It is debatable if one will live as long as the units you have compared

 

[Smykowski]

How old is the heater ? I'm thinking it's outdated literature from the early stages. Hayward has been making SWGs (safe for its own equipment) from the get-go. But there was some misinformation out there at the very start.

Heater is likely from 2006.

If you’re pool is already 10yrs old any warranty is likely now in it’s prorated phase anyway which is generally not very favorable so basically useless. The same line of thought applies to the heater as well. Do you know what it’s components are made of?
The parts of the pool where salt water actually touches (top rails) would be my main concern personally depending upon their material.
I am also curious of your current salinity level so when you find out let us know!
I’m considering collecting data for a completely unscientific study similar to the D.R. Millionaire study except, you know, with regular people who unknowingly already have salt pools and didn’t think it was possible “Everyday Salt Pools”
but seriously, as for the roi on a swg there are some things to consider, when this pool has lived it’s life do you plan to replace it? If not you may perhaps consider one of the universal circupool models. Ul40 or UL55.
They are highly adjustable, affordable & offer a basic well known design. It is debatable if one will live as long as the units you have compared

Current pool is not the issue. We are likely going to be replacing it, and the components we're using (skimmer and return fittings) specifically have the warning I copied above.

And yes, I think it might be time to run a salt test just to see where I'm at.

 

[Mdragger88]

Another economical option is the pureline line from inyo - the warranty for them is not as advantageous as the Circupool choices but the price reflects this. I purchased a pureline t15 replacement cell for an old aquarite I aquired mainly because their output was higher than the other options (i have a 26K gal pool in the south) & who knows how long the old controller will live. I also don’t have much faith that my pool will live on 10 more years for reasons other than salt.

 

[Mdragger88]

Heater is likely from 2006.

That’s no spring chicken - it’s living on borrowed time. When it goes if you choose to replace it then just go with a “salt friendly” model.

Current pool is not the issue. We are likely going to be replacing it, and the components we're using (skimmer and return fittings) specifically have the warning I copied above.

That’s a crazy warning because they’re plastic right?? I can’t see how salt would affect that other than cheap stainless screws for the skimmer which will rust whether there’s salt or not.

There are so many salt friendly choices for pools now with resin components & supposedly extra wall coatings.
If I were to replace today I would go with an Aurora as it is completely resin, walls & all. It wasn’t out yet when I bought my current pool.
Hopefully by the time that replacement happens for me there will be more completely resin options available.

 

[Smykowski]

That’s no spring chicken - it’s living on borrowed time. When it goes if you choose to replace it then just go with a “salt friendly” model.

That’s a crazy warning because they’re plastic right?? I can’t see how salt would affect that other than cheap stainless screws for the skimmer which will rust whether there’s salt or not.

There are so many salt friendly choices for pools now with resin components & supposedly extra wall coatings.
If I were to replace today I would go with an Aurora as it is completely resin, walls & all. It wasn’t out yet when I bought my current pool.
Hopefully by the time that replacement happens for me there will be more completely resin options available.

Yeah, I found that hilarious too. The only components that are metal are the screws, and they look like they're stainless.

 

[Smykowski]

Interesting results.

I ran a salt test, and came up with 1200ppm.

This is after a 25% drain and fill (in order to attempt to fix my leaks). This implies a 1600ppm salt level prior to the drain. I was expecting higher.

 

[Newdude]

It's early in the season. You drained to close last year and picked up some spring rain as well.