Intelliflo VS and Filter Pressure

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batterfierd

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Apr 14, 2013
21
Hello everyone, I'm a bit of a pool noob but I'm trying to pick up and learn as much as I can.

Just this past weekend, I installed a new Intelliflo VS pump to replace an aging single speed pump, and most everything works just fine. I seem to be having an issue with my heater, and I'm concerned it has to do with the bypass on it due to low flow rate.

When I use the Pentair spreadsheet to calculate flow rate, everything seems like it should be fine. I'm passing about 27gpm without the heater running during normal filter mode, and 45 when heating.

However, the pressure on my filter is very low. During the normal filter cycle at what should be 27gpm, the filter pressure gauge reads at around 2. Does this seem normal?

I should mention this is a mastertemp 400 heater and a Pentair DE filter, 48 sq.ft.

And here's what I'm seeing on the filter pressure gauge at various speeds:

Old Single Speed - 18psi
VS @ 1400rpm - 2psi
VS @ 2750rpm - 10psi
 
Welcome to TFP!

Yes, it is normal for the pressure to be lower at lower speeds. What this tells us is that your old pump was quite large, since it was moving more water than an IntelliFlo does at 2750 RPM.

Keeping in mind that flow rate estimates are just estimates unless you have quite a bit more information, your flow rate estimates look very reasonable.

What was the HP and model on your old pump?
 
My old pump wasn't that large. It was a Pentair Whisperflo 4, 1HP. I'm not sure how much water that would have been pushing, although I would like to know.

It seems a bit coincidental for my heater to have a problem just after I replaced the pump. I did have an issue with the bypass on the heater the second half of last year where the coil had to be replaced, but that was because the previous owner/pool company didn't keep the pH in check and it ruined the coil (or so I was told). I wouldn't think the same problem would come back so quickly.
 
The heater fires up, rattles and shakes the pipes, then shuts off. Then it tries again about 15 seconds later.

Also, not sure if this helps (or makes sense), but I ran through several speeds on my VS pump and inputted the numbers into the Intelliflo spreadsheet. The numbers I'm getting don't really seem to make sense to me. The 1000 rpm calculates higher than the 1200, and 3450 is lower than 2750. It's just making me question the accuracy of the sheet.

@1000 rpm - 148 watts, 37.31 gpm calculated
@1200 rpm - 176 watts, 28.28 gpm calculated
@1400 rpm - 250 watts, 40.17 gpm calculated
@1750 rpm - 426 watts, 53.16 gpm calculated
@2750 rpm - 1394 watts, 78.22 gpm calculated
@3450 rpm - 2325 watts, 69.80 gpm calculated
 
Just to follow up again, I've been watching the reading at 1000rpm for a little while now. It was reading in the higher 140s for wattage for awhile, then at 131 (bringing it to about 21 gpm, which makes more sense to me), next reading at 157 watts, then 163.

I'm not sure if it should be fluctuating this much.
 
Which version of the sheet are you using? The model's accuracy decreases rapidly with RPM so it is best to first calibrate at RPMs >2500 and then use the "Estimate" column for lower RPM valves. Also, you have to make sure the wattage stabilizes after changing RPM.
 
Thanks. Are either of these straight from Pentair, or is this info that individual dealers put together?

In any case, between the two versions, I'm only off 1-2 gpm on the estimates. I'm thinking that I might need to start focusing on the heater as the problem.

Before I do though, a couple of additional things I noticed. First, I'm testing out running the pump at 1000 rpm, and even though water is flowing, I can't visibly tell at the skimmer. I assume that means I either need to adjust something at the pool equipment or increase the rpm.

Second, also when running at 1000 rpm, the basket in the pump doesn't completely fill up with water. I assume that might be due to lower water flow and as it comes in it's just sending it out, but that seems like it might conflict with some of the gpm estimates from that spreadsheet. Not really sure what to expect though.
 

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I developed the spreadsheets based upon the manufacture's measurements. You can read about it here: pool-pump-energy-cost-comparison-t18378.html

When running at 1000 RPM, one thing to keep in mind is that the flow rate is probably around 20 GPM. That is not enough flow rate to notice in a skimmer and to purge air out of the pump basket. Full priming should occur on the higher speeds and the pump should not lose prime when the pump is off. If it does, then you have an air leak that should be fixed.
 
I'm not sure I understand completely. When you say full prime should occur, what should I expect to see as a result? Are you saying there should never be a large air gap in my pump basket? And I'm not even seeing light debris sucked into the skimmer, so I'm likely going to spin this up a bit higher either way. But if there's an air leak, I want to address it. The lid is on tight, so I'm not sure where else that would come from.
 
Full prime will have no air visible in the pump basket. At higher speeds this should be true after a few minutes. On lower speeds, sometimes a bubble does develop at the top of the pump basket (my 2-speed does this on low as well), but this is common and "normal". Switching back to higher speed should clear it out. The air bubble should NOT get larger when the pump is off (if it does, then you have a leak somewhere).

I have run on low for weeks with the large bubble in the pump ... never seemed to have air in the filter or in the pool, so it does not seem to be a problem.
 
At full prime, I see very, very small bubbles. At lower speeds, for example at 1600rpm, a larger air bubble forms (or sometimes two large ones). If I look closely, I see what appears to be very tiny air bubbles coming in through the intake of the pump. At 2500rpm, there is noticeable bubbling at the outlet in the pool itself. Is any of this normal?

I double checked my connectors at the pump, and re-applied pipe sealant to the thread, but I'm concerned that I have a small air leak in front of the pump. Does that sound plausible given the details here?
 
If you are constantly seeing small air bubbles moving around in the pump basket and even making it back to the pool, then that does sound like a suction leak somewhere to me.

How much straight pipe (and what diameter) do you have directly in front of the pump ... we have seen posts where having it too short caused problems.
 
I have 11 inch straight in front of the pump. I actually re-did what was there because there were several 45 degree bends with only 2in of straight pipe in front of the old pump. Long story short, the pipe coming out of the manifold from the ground was a bit tricky to work with as there was no pipe to attach directly onto. I had a small water leak there after installing the new pump, but took care of that. But that's the most likely place of an air leak in my mind. I think I'm going to redo it, but I'm going to need to get a pvc fitting saver. Without one, I'll have to cut into the pipes coming from the ground and redo the actuator as well. I haven't used a fitting saver before, but I hope it's as easy as it looks :)

Edit: Forgot to mention, 2 inch pipe.
 
Does the fitting saver slide into the pipe? If so that may not be a good idea as it would increase the suction head loss significantly and could cause more problems.

Posted from my Droid with Tapatalk ... sorry if my response is short ;)
 
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