IC20 + two speed pump = low flow error

[mcaswell]

Greetings all.

Our pool is nearing completion, but a problem has surfaced. When the pump (a 1hp Superflo two-speed) is operating on low speed, it's hit or miss as to whether or not the IC20 will function. Sometimes it works, but often the Easytouch panel (as well as the red light on the cell) will indicate a flow error. If I switch to high speed, it works fine, but when I go back to low speed, it will usually give the flow error within a few minutes (though sometimes it works on low speed for as long as an hour or two).

Backwashing the filter (sand) helps, but after a day or so (and maybe only a tiny increase in PSI) it's back to being unreliable.

I suspected the problem is related to how the cell is installed:

This pic was taken before the cell was installed... it's positioned in place of that horizontal section of PVC right after the filter. It just barely fits there, so there's an elbow immediately before and after the cell. I noticed in the manual that they suggest "for best flow sensing, provide at least 12"-18" of straight pipe in front of the cell inlet", which I clearly don't have. Presumably turbulence from the elbow is throwing off the flow sensor. I talked to the builder about replumbing it, which he sounded receptive to, but he spoke with his Pentair rep, who indicated that he didn't think it would help, as the pump on low speed wasn't going to provide enough flow regardless.

The suggested solution was to simply run the pump on high speed most of the time, which I am not happy at all with... the whole point of a two speed pump is to save energy by running it on low speed! But perhaps the rep is right... maybe this pump can't provide enough flow to consistently keep the cell happy. I just would have thought that I'd see more people complaining about this problem if that were the case, so I'm not convinced that turbulence from the 90 isn't to blame... if flow is otherwise just barely sufficient, the non-smooth flow coming off that elbow could be causing the flow sensor to not be closed all the time.

As you can see in the photo, there's no easy replumbing solution... adding several more elbows (to get to the space needed for the 12 - 18 inches of straight pipe) seems unavoidable. I think the person who originally plumbed it didn't realize that a SWG was going to be installed (that equipment had not yet arrived).

Another solution that I proposed was to swap out the pump for a variable speed (which is more expensive, of course)... that way, rather than run the two-speed pump on high, I could just increase the speed slightly until the SWG is kept happy.

Anyway, the short version... should a 1hp two-speed pump on low provide enough flow for a SWG, and how important is it to have that straight section of pipe before the cell?

--Michael

 

[JasonLion]

The IntelliChlor requires 20 GPM, which really isn't all that much. On most pools a 1 HP two speed should provide that much flow even on low speed. The actual flow rate you get varies tremendously depending on many many details of your setup. The plumbing on you equipment pad looks fairly good. That appears to be 2" pipe and there appear to be more than one pipe from the pad to the pool in each direction. Unless your pipes are smaller underground or much longer than average, I would expect you to be able to get 20 GPM on low speed. One other place to check is the return fittings. It might be that getting larger return fittings could help.

How much an elbow near the SWG affects the flow sensor is highly variable, depending on the exact placement of everything and how that affects the flow pattern inside the cell. In many cases it really doesn't have much effect, but now and then it can be an issue. It is difficult to say if that is really an issue here or not.

 

[mcaswell]

Hi Jason,

Thanks for the response (and, actually maybe I should have posted this in the Pumps forum, as it's more of a pump/plumbing question than a SWG question).

The plumbing is indeed 2" throughout (though I believe the return fittings are 1.5"). It's a ~12K gallon fiberglass pool with a tanning ledge. One of those return lines in the photo is for the pool returns (4 of them, though 1 of those has its own 2" line branched off near the pad), another goes to the ledge, and then there's a line for deck jets. The equipment pad is very close to the pool (maybe 6 - 8 ft., with the main drains and skimmer nearby on that side, though the plumbing for the returns goes around to the other side of the pool).

During the quote phase, I let myself be talked out of the Intelliflo, but I felt ok about that since I figured the two-speed pump would deliver most of the energy savings. But not having the ability to tweak the flow is coming back to haunt me now. My preference would be to keep the two-speed pump, but swapping out for a variable speed might be the most expedient way to resolve this problem.

--Michael

 

[JasonLion]

The returns will have 1.5" threaded pipe fitting with a return jet fitting of some kind screwed into that which will have an opening smaller than 1.5". The return jet nozzle is most likely to be 1/2" 3/4" or 1". If you have 1/2" nozzles, upgrading to larger nozzles would make a significant difference.

 

[jerryt]

I have an intelliflo pump and it was running at 15 gpm before I add my IC40 salt cell. So the salt cell would randomly give the no flow indicator light at 15 gpm. I had to bring the flow rate up to 19 gpm to get reliable operation of the salt cell. I contacted Pentair and they told me that the flow switch is set for 25 gpm and that it was NOT a problem for the cell to operate at flow rates below 25 gpm, except that the switch would not work. The cell requirement for 25 gpm is only for the flow switch operation, it is NOT for cooling or operation of the cell.

I see you have two options.
1) Modify the flow switch to operate reliable at a lower flow, like 15 gpm (remove the switch and increase the area of the head so more water press against it) or
2) By pass the flow switch and use a current sensing relay to switch the SWG on.
how-to-control-intellichlor-ic40-w-current-control-relay-t28298.html

I have added the current sensing relay to my set up as an added safe measure against the flow switch failing in the "ON" position, (this would be an explosion hazard).

 

[mcaswell]

The returns will have 1.5" threaded pipe fitting with a return jet fitting of some kind screwed into that which will have an opening smaller than 1.5". The return jet nozzle is most likely to be 1/2" 3/4" or 1". If you have 1/2" nozzles, upgrading to larger nozzles would make a significant difference.

Ah, got it. The eyeball fittings have a 3/4" opening. As an experiment, I removed all 4 of these, leaving just the plain 1.5" openings, but the flow light remained.

--Michael

 

[Bama Rambler]

Put your filter on recirc and see if that helps. One ½" pipe should be more than enough to get that pump to pump enough to satisfy the swcg.

 

[mcaswell]

I have an intelliflo pump and it was running at 15 gpm before I add my IC40 salt cell. So the salt cell would randomly give the no flow indicator light at 15 gpm. I had to bring the flow rate up to 19 gpm to get reliable operation of the salt cell. I contacted Pentair and they told me that the flow switch is set for 25 gpm and that it was NOT a problem for the cell to operate at flow rates below 25 gpm, except that the switch would not work. The cell requirement for 25 gpm is only for the flow switch operation, it is NOT for cooling or operation of the cell.

Hmmm... interesting. I'll certainly keep this in mind!

--Michael

 

[mcaswell]

Put your filter on recirc and see if that helps. One 1½" pipe should be more than enough to get that pump to pump enough to satisfy the swcg.

I can't try this now, as I just backwashed the filter again (called Pentair tech support, and they suggested I do a much longer rinse cycle than I had done previously, to fully clear out the laterals). As a result, it's working fine on low speed right now (as it did the past times I backwashed, at least for a day or so).

However, I did run it on recirc earlier in the week (at a time when the problem was occurring), and it did seem to do ok, though it's possible that I didn't let it run long enough (sometimes it takes 30 - 60 minutes or longer before the error happens).

Anyway, it seems like the pump is producing enough flow, but just barely... as soon as the filter gets just the slightest bit clogged, that's enough to make closing the flow switch unreliable (and the elbow right before the cell could be exacerbating this).

--Michael

 

[Razorback72727]

I certainly appreciate this thread.

We have an almost identical problem using a 1 HP Whipserflo two-speed motor with an IC20. On low the IC20 will randomly indicate low flow and its typically after a 30-60 minute run at low speed. Sometimes it will run all night and be fine, other times it happens within minutes.

Since I just ran across this thread, I haven't had a chance to check my return sizes. I also don't have the 12-18" of straight pipe before in inlet to the IC20.

Greg

 

[mcaswell]

So, yesterday I thoroughly backwashed and rinsed the filter. PSI (measured while pump is in high speed) was about 12 after the backwash, and the SWG seemed to run fine (let it run on low speed for several hours). Later, after vacuuming the pool, the PSI had risen to 13 (again, measured on high speed), and after running for a while on low speed, I did get the red flow light.

On recirc, flow light stays green.

So, with a perfectly clean filter (or on recirc), the flow is apparently just barely adequate to reliably close the flow switch. With just a little bit of resistance from the filter, however, it gets iffy. What remains to be seen is how much of an effect the lack of a straight section of pipe before the SWG is having. The Pentair tech support person I spoke with seemed to think that could be the cause of the problem, while the Pentair sales rep (the builder asked him to call me) indicated he didn't think that was an issue... he said the 1hp two-speed pump on low speed just wasn't capable of delivering enough flow through the SWG.

When I spoke with the builder again about it, he repeated his suggestion to simply run the pump on high speed more often (in other words, run it on high for around 4 hours a day with the SWG at 100%, which would generate the same amount of chlorine as 8 hours at 50%, then run it on low speed the rest of the day). I don't like that suggestion, for two reasons. First, it at least partially defeats the point of a two-speed pump... I want to run it on low speed for 10 - 12 hours a day, only using high speed when cleaning or when we're swimming. Second, I'd have to keep an extra close eye on chlorine levels, since the SWG does work in low speed some of the time, and with the SWG set to 100%, there's a good chance I could end up overchlorinating if the flow switch happens to be in a cooperative mood for several days (though wiring the SWG to a relay and setting up a schedule for it could alleviate this).

Replumbing the SWG (to include a straight run of pipe in front of it) could possibly fix the problem, but apparently he doesn't want to try that. I think a variable speed pump is an easy solution, but that would involve him taking the two-speed pump back, which apparently he doesn't want to do either... he insists that the Intelliflo would be a bad addition to my relatively small pool, since it is so powerful on high speed it would destroy the filter. I explained that I understood this, but that it would never be run on maximum speed. He also stated that during the Summer, you can't run primarily on low speed anyway (whether with a two-speed pump or the Intelliflo) even if the SWG was working, as this will cause the pool to "turn green".

Being new to swimming pools, I'm in no position to authoritatively argue against against someone with as much experience as him. But I do have common sense, and in the wealth of information I've read on these topics, I've seen nothing to indicate that you have to run on high speed most of the time when it's hot outside.

So, it looks like I'll be left to deal with this issue on my own after the build is complete.

--Michael