automatic dosing

amin36

In The Industry
Nov 24, 2017
79
shahsavar
Hi guys



Searching through the net i came across a video in which some one is installing their automatic dosing pump for both PH and chlorine control



Here it is:






A s you can see in 4:33 the injection valve for chlorine and ph are 20 centimeters away from each other.



I know that mixing liquid chlorine and muriatic acid at the same time would lead to chlorine gas which is deadly stuff and definetley she is following manufacturer instruction as you can see in 1:18.



Is it safe to do it like that?



It seems like this is how its done.i found the attached picture in the link below which is approved By PWTAG



Pool Water Treatment Advisory Group - Polyaluminium Chloride PAC Dosing





Thanks
 

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randytsuch

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Mar 29, 2008
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Los Angeles, Ca
Maybe the system is smart enough, or has some kind of interlock where only one of the pumps can run at a time.
So it won't let you inject chlorine and acid at the same time, and avoid your concern.

Since its a combined system, that would be pretty easy to do.

Randy
 

amin36

In The Industry
Nov 24, 2017
79
shahsavar
Randy

I asked the question below the video and someone from EPS(europe pool supplies)just answered like this :


EPS systems will never dose two chemicals at the same time to prevent mixing of chemicals.

So yes yo are correct

thanks
 

Dirk

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I have two of Pentair's auto dosing systems and my acid injection controller shuts down my chlorine system (SWG) as it doses acid. We recently had a conversation about this in another thread, and determined that a primary reason to avoid dosing acid during chlorine production had less to do about the chlorine gas issue and more to do about protecting the equipment. Either way, it's a bad idea to dose both at the same time. Systems that are designed to work together account for this. But it's a caution to those that build their own, separate dosing solutions to be aware of this potential problem and address it somehow...
 

randytsuch

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Mar 29, 2008
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I have two of Pentair's auto dosing systems and my acid injection controller shuts down my chlorine system (SWG) as it doses acid. We recently had a conversation about this in another thread, and determined that a primary reason to avoid dosing acid during chlorine production had less to do about the chlorine gas issue and more to do about protecting the equipment. Either way, it's a bad idea to dose both at the same time. Systems that are designed to work together account for this. But it's a caution to those that build their own, separate dosing solutions to be aware of this potential problem and address it somehow...
That may be a reason to not diy both a chlorine and acid dosing system.
I dose chlorine, and my fiberglass pool doesn't require enough acid to add an acid doser.

I trust software about 95% of the time, so I wouldn't depend on sw for the interlock.
It can be done in hardware, but would take a little effort, and depends how you are turning on/off your dosing pumps.
I use a smart plug to control my stenner pump, which would make it more difficult to solve if I did want to add an acid pump.

Randy
 

Dirk

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There are lots of DIY ways to build-in the protection. Seems to me a foolproof way would be to wire a common power supply to a double-throw relay, with each dosing pump wired to opposite sides of the relay, such that only one could be connected to the power supply at a time. There might be timers and other relays involved to get everything scheduled, but even if those went haywire and inadvertently called for both pumps at the same moment, only one would actually be energized by the power supply.

I think my Pentair setup is done by setting the SWG to zero output just before the acid pump is energized. It's probably reliable enough, but I wouldn't call that foolproof, because as you point out, somewhere in the mix is software/firmware and electronic signals that might get compromised somehow. A mechanical binary switch might fail, but it physically couldn't fail ON-ON.
 

MyAZPool

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Yup, this is definitely an important concern that should NOT be overlooked especially in the DIY realm. In the thread that @Dirk, references, this issue was thoroughly dissected and thanks to his input and some others, my DIY system will no longer allow for SWCG output during acid dosing.

I used to run the same system as he does but not long ago, I switched over to a DIY acid dosing system that gives me a few more "automation" options with less restrictions than I had before.
However, my current system now incorporates an enhanced "Chemical Priority Feature," that takes SWCG's into account as well - thanks to Dirk's input earlier on.

When the feature is activated, it will give acid dosing the “priority” and prevent chlorine production by a salt water chlorine generator (SWCG) if applicable. It does this by sending the correct command to the SWCG to affect a zero output until such time as the acid dosing event has ceased.

In other words, acid and liquid chlorine (or SWCG) dosing events CANNOT occur simultaneously.

Thanks!
r.
 
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Dirk

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r, can you link the thread we're both referencing. I couldn't find it...
 

Dirk

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To be clear, that double-throw relay idea I just mentioned referred to a setup with two Stenner-like injections systems, one pump for chlorine, one pump for acid. It wouldn't be used for an acid pump and SWG setup. Something more like what @MyAZPool just described is needed because you can't readily power an SWG on and off, as they have a lengthy startup process (Pentair's do, anyway).
 
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MyAZPool

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r, can you link the thread we're both referencing. I couldn't find it...
@Dirk
Yea, it was difficult for me to find as well. Mainly coz I think the two of us might have been a bit guilty of some "hijacking". :p
Oh well, the thread certainly served a great purpose lol...
Here we go...
 
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Dirk

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Yah, I knew I wouldn't find it by title, and I can't seem to make good use of the search engine here... Thx. Bookmarked.
 

Dirk

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@amin36, if you're interested, one of our resident experts, @JoyfulNoise, explains why you need to separate acid injection and SWG chlorine production. While his explanation applies to pumping acid into an active SWG, I think the first of the two reasons might also apply to the "two pump" injection system as well. Matt will hopefully correct me if I'm mistaken about that.

So why should an SWG turn off when acid is being injected? Well, again it's a little complicated but there are two very good reasons to do so. The first is based on the chemistry above. You really don't want to run a chlorine generator in a low pH environment or else all you will do is create a lot of undissolved chlorine gas that will bubble out of your returns. Chlorine gas leaving the water will cause the pH to skyrocket and this is what is termed as the "short pipe effect". The other MORE IMPORTANT reason to not inject a strong mineral acid while generating is that you will strip off the transition metal catalyst from the plates by doing so. The TM catalyst normally forms a conductive oxide layer on it's surface that allows it to aid in the formation of chlorine gas. Acids will strip away that oxide which is why I always suggest to NOT use strong acids to clean the cell. However, when the cell is running, the anode will continuously regenerate that TM oxide layer from the freshly exposed TM so, in effect, a constant stream of highly acidic water will continuously strip away the catalyst layer when the cell is electrochemically generating chlorine. Normal pool water at a pH in the 7's does not do this or does so at such a low rate that you would have a hard time measuring it. Drop the pH while the cell is running and you will increase that dissolution rate rapidly and completely hose your SWG plates.
 

JoyfulNoise

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The biggest concern for a binary chemical feeder (acid and liquid chlorine) is not so much dosing at the same time or too close together but a failure of the circulation pump and failures of the interlocks that turn off the chemical feeder pumps when there is no circulation. Most commercial pool chemical accidents happen when the system is unattended and interlocks fail. This results in the dangerous mixing of acids and chlorine. The result would be a large concentration of chlorine gas buildup which would an extreme health hazard.
 
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Dirk

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I'm not quite sure what you were asking about regarding your link to "Polyaluminium Chloride PAC Dosing." We don't recommend flocculants, and you wouldn't inject chlorine or acid before the filter. (Not quite sure why they would recommend introducing flocculants before the filter either, but that's irrelevant.)

If you were just referring to the part of that diagram that shows:

filter --> heater --> acid injection --> chlorine injection or SWG --> pool

then yes, that is the generally accepted order. It's what Pentair recommends. That's how I've got my setup configured.


Regarding Matt's comments: some of the "interlocks" (as he calls them) would be:

- wiring the injection systems' power source to the same timer or relay that energizes the filter pump, so that the injections can't occur unless there is also power applied to the filter pump,

- the relay or circuit that @MyAZPool and I described that prevents the two pumps from running at the same time,

- and a flow switch mounted in the plumbing that senses when water is actually moving through the pipes, which would complete the circuit to the injection pump(s).

My IntelliChlor and IntellipH combo has all those. I think MyAZPool's DIY system does, too.

One member here once described an event where her acid pump got stuck ON and emptied her entire acid reservoir into her pool. I know my setup has a sudo prevention for that, in that it only allows so much acid to be dispensed at a time. But I'm not sure how robust that is. Not sure how MyAZPool's system handles that.

I'm somewhat covered for that in another way. My SWG doesn't have the chlorine-producing capacity to overdose my swimming pool (unless it ran unbridled for a week or more, which I would notice long before then). And my acid reservoir doesn't hold more than a couple gallons of acid at any given time, usually quite a bit less, which also is not going to cause any great harm to anything.

There is a thread here that tells the story of a commercial pool's chlorine system that malfunctioned and overdosed the pool with some large amount of chlorine, and injured some young swimmers before anyone noticed what was wrong with the pool. I would say the primary safeguard for that potential danger is not building a system that holds a dangerous amount of either chemical. That way, even the worst malfunction can't really do any harm. I wouldn't be comfortable, for example, with the tanks used in the systems some of our members built, that hold 15 or 30 gallons of chlorine...
 
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amin36

In The Industry
Nov 24, 2017
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Dirk

PAC is used here as a cougulant not a flocculant trapping attracted suspended particles in the filter.
The second thing you mentioned " We don't recommend flocculants ",i do not agree.flocculants are pretty much effective at removing phosphates, pathogens and other undesirable particles and even reducing combined chlorine as well
 

Dirk

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You are free to do as you like in your pool, of course, but we don't generally advise the use of flocculants, reducing phosphates, or reducing pathogens with methods other than maintaining the correct FC level for your CYA level. And I only diverted to addressing your last post because this is your thread. These topics and assertions are way off course from your original post.

I'm sure there are specialty cases where flocculants might be used, or it's desirable to reduce phosphates, but those are not among our go-to methods of pool care. And we don't stray too far from those. On top of which I'm not any sort of expert in either one of those processes, but we certainly do have folks here that are, if you'd care to engage with them on these topics. I can call their attention to this thread, if you like, or you can start a new thread to discuss your ideas, and they will likely spot it and offer some thoughts.

But just to give you a fair warning, this forum is not for debating different methods of pool water maintenance. It's for teaching a very specific method, which is TFPC (Trouble Free Pool Care). So alternate methods, wether they work or not, are not explored here to any great degree, because we don't want to confuse folks that are new to TFP or new to pool care.
 
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amin36

In The Industry
Nov 24, 2017
79
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@Dirk
I understood that here people do not like discussion of phosphate.so i am not talking about this any more.
Actually just startred reading previous posts

" . We recently had a conversation about this in another thread, and determined that a primary reason to avoid dosing acid during chlorine production had less to do about the chlorine gas issue and more to do about protecting the equipment. "

would you please link this thread?

" @amin36, if you're interested, one of our resident experts, @JoyfulNoise, explains why you need to separate acid injection and SWG chlorine production. While his explanation applies to pumping acid into an active SWG, I think the first of the two reasons might also apply to the "two pump" injection system as well. Matt will hopefully correct me if I'm mistaken about that. "
"

Regarding Matt's comments: some of the "interlocks" (as he calls them) would be:

- wiring the injection systems' power source to the same timer or relay that energizes the filter pump, so that the injections can't occur unless there is also power applied to the filter pump,

- the relay or circuit that @MyAZPool and I described that prevents the two pumps from running at the same time,

- and a flow switch mounted in the plumbing that senses when water is actually moving through the pipes, which would complete the circuit to the injection pump(s).

My IntelliChlor and IntellipH combo has all those. I think MyAZPool's DIY system does, too.

One member here once described an event where her acid pump got stuck ON and emptied her entire acid reservoir into her pool. I know my setup has a sudo prevention for that, in that it only allows so much acid to be dispensed at a time. But I'm not sure how robust that is. Not sure how MyAZPool's system handles that.

I'm somewhat covered for that in another way. My SWG doesn't have the chlorine-producing capacity to overdose my swimming pool (unless it ran unbridled for a week or more, which I would notice long before then). And my acid reservoir doesn't hold more than a couple gallons of acid at any given time, usually quite a bit less, which also is not going to cause any great harm to anything.

There is a thread here that tells the story of a commercial pool's chlorine system that malfunctioned and overdosed the pool with some large amount of chlorine, and injured some young swimmers before anyone noticed what was wrong with the pool. I would say the primary safeguard for that potential danger is not building a system that holds a dangerous amount of either chemical. That way, even the worst malfunction can't really do any harm. I wouldn't be comfortable, for example, with the tanks used in the systems some of our members built, that hold 15 or 30 gallons of chlorine..."



Thank you very much.great information (y)
 
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amin36

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Nov 24, 2017
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shahsavar
Another concern i have is that chlorine must be added to pool water at least 30 minutes after acid injection.do automation systems take that into consideration?
 

Dirk

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Another concern i have is that chlorine must be added to pool water at least 30 minutes after acid injection.do automation systems take that into consideration?
Mine doesn't. During SWG chlorine production, my IntellipH sets the SWG to 0 output and injects immediately, then restores SWG function immediately after.

For the DIYers that have added acid injection to their Stenner chlorine pump systems, I don't know how they handle that.

From post #10, above. The discussion we were having about pumping acid into an active SWG was a hijack in the middle of this seemingly unrelated thread:

 
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