IntelliFlo VSF - More Power with Colder Water?

[DB-Cooper]

I have a pool that was filled April 2020. Shortly after filling, I recorded the power usage at various flow levels of the pump. That's one nice angle about the VSF, it adjusts RPM to a set flow point.

Fast forward, and I've noticed the RPM and power usage (which I would think are related) has increased substantially to provide the same flow. What I can't make sense of is if I change to RPM settings, the before/current measurements make no sense as the same RPM produces less GPM but also less power. It seems to have recently gotten worse as water and air temps have decreased. Here's that data, I'll comment about one incident that is likely a contributor shortly after. As I provide this today, yesterday was 10-15F colder (air temp) and the same 30 GPM test was using over 700W.

When new:
30 GPM = 1,945 RPM = 404 Watts
2,750 RPM = 55 GPM = 1,215 Watts

Now:
30 GPM = 2,394 RPM = 676 Watts
2,750 RPM = 38 GPM = 1,043 Watts

Now with Filter Bypass (Recirc Mode)
30 GPM = 1,950 RPM = 410 Watts
2,750 RPM = 53 GPM = 1,196 Watts

Possibly contributing factors include:
1. Updated firmware a couple weeks ago to the Sept 2020 release. However, I noticed power usage was up prior to this.

2. Pehaps more restriction would cause more amperage to spin the same RPM, that would explain why the same RPM is producing less flow, but not sure why it's be less flow and less power for the same RPM.

3. Definitely contributor is, around June 10, I had to have some coping reinstalled. The crew that did this ended up filling my pool/spa with concrete dust as they had to grind the old adhesive down and make a smooth concrete platform to reapply the coping. It was a tedious 2-3 day chore to get this cleared up which included lots of pump time, draining the spa into the pool and then refilling from the pool. The robot helped tremendously, lots of brushing but astonishingly to me water got back to crystal clear quite easily (I really thought we were in drain/fill territory as a new pool owner). I immediately back-washed and obviously the water was dirty, but it ran clear reasonably quick after backwashing and rinsing about 5 times. I've since back-washed maybe 4 times. My pool otherwise stays SUPER clean as it's above ground and effectively above the trees. Lots of robot, daily scooping up of the few leaves/insects that get in there, etc. Unfortunately, I didn't record a pre-concrete-incident filter starting pressure as I never thought to record that. Since the incident, after back-washing, starting pressure has stayed at 18psi @ 2750 RPM. It literally doesn't go up at all given the pool stays quite clean. Maybe it's gone up 1 psi in two months. Each time I backwash, I never have to adjust the pressure dial since the pressure hasn't changed after the backwash. Reminding again, I don't recall my starting pressure before the concrete incident.

Every pool is different, I really wish I knew my starting pressure on the brand new filter. It's worth noting my pool equipment is on a higher elevation than my pool by a fairly notable amount 8' vertically higher than top of water, 16'+ from bottom drains to pump. Priming the pump the first time was quite an effort.

I'm going to do a full filter breakdown to rule out that (well my pool builder is since he made the concrete mess), clearly the filter adds pressure and requires the pump to work harder, but I'd think even in full bypass, it should outperform (less power) a brand new filter. I'll report back after, but considering things really haven't changed in the last month except it getting much colder, it seems the RPM and power usage has been going up in concert with colder air/water.

Pictures attached of equipment location to pool and some concrete cleanup pictures:

 

[Jimrahbe]

DB,

Sounds to me like your filter is getting dirty.. As the filter gets dirty the pump has to work harder to force the same amount of GPM through it.

Thanks,

Jim R.

 

[DB-Cooper]

Thanks Jim! Yeah I definitely think that's the case. I'm not sure it's getting dirtier, I think it got dirty that one time.

I did some more testing today, I remember switching some return configurations around after doing my initial measurement. I closed my spa return (in favor of spillover schedule) and closed my bubbler returns on the shelf. I did this to increase pressure to the returns I was using for aeration fountains to combat high Summer water temperatures. Opening those returns up actually reduced RPM and power by about 10%.

I'll report back here after the filter breakdown.

 

[JamesW]

Put the system in Service mode and go to the pump keypad to see what the system pressure is at different flow rates.

 

[JamesW]

Unfortunately, I didn't record a pre-concrete-incident filter starting pressure as I never thought to record that. Since the incident, after back-washing, starting pressure has stayed at 18psi @ 2750 RPM.

The pressure is excessive, which is probably due to the concrete dust. A full breakdown and thorough cleaning is indicated.

It's also possible that the cell and/or heater are scaled from the concrete dust.

Check the cell and clean if necessary.

 

[DB-Cooper]

Put the system in Service mode and go to the pump keypad to see what the system pressure is at different flow rates.

Thanks, I was unaware of that reading/function. Based on my reading this isn't a pressure sensor it's deduced effectively from RPM, Watts and Flow which is similar to my reporting. I set it to Mode 3, 2350 rpm, 32 GPM and it read 18 PSI. Again, not having a baseline here not sure what it should read, but definitely thinking my filter is adding unnecessary restriction. Hoping to get the filter breakdown done in the next week.

 

[JamesW]

Since your equipment is 8 feet higher than the pool, the filter gauge will be about 14 feet above the surface of the water. That means that you have to add about 6 psi to the reading to get the actual filter pressure. That puts the actual filter pressure at about 24 psi, which is excessive for the reported flow rates.

Concrete dust is horrible for filters. Definitely need to do a full breakdown and cleaning.

 

[DB-Cooper]

Since your equipment is 8 feet higher than the pool, the filter gauge will be about 14 feet above the surface of the water. That means that you have to add about 6 psi to the reading to get the actual filter pressure. That puts the actual filter pressure at about 24 psi, which is excessive for the reported flow rates.

Concrete dust is horrible for filters. Definitely need to do a full breakdown and cleaning.

Thanks! I will say it was amazing to see the spa drain, then refill it from the filtered water that was cloudy and seeing it crystal clear. It's amazing how well the filter works, but yeah that concretes got to go somewhere

When I said 8 feet higher, I was sort of eyeballing it from filter height. What's the formula for height that you're using? My guess is it's more like 10' in total, but good to know.

 

[JamesW]

Gauge height above the water divided by 2.31 = the extra psi needed to add to the gauge to know the actual filter pressure.
10/2.31 = 4.3 psi + 18 = 22.3 psi total.

 

[mas985]

In the first picture, the equipment appears to be only a few inches above the pool deck.

 

[DB-Cooper]

In the first picture, the equipment appears to be only a few inches above the pool deck.

Wide angle and optical illusion. It's six standard steps just to get base where the pipes come out of the ground, then a couple more feet for the raised surface. Here's a picture from the other angle:

 

[DB-Cooper]

Also, yesterday I did some testing. Water temp was 46F and when I turned on the pump to start the hot-tub, 3450rpm was yielding only 42 GPM. After some heatup, it rose to 50 GPM. I also tested 40 GPM when it was cold versus warm and the pump became much more efficient, going from 1800W down to <1200W to maintain 40 GPM. It wasn't linear, somewhere around 70F it basically reached its max efficiency.

I'm waiting for some new concrete/masonry work to complete this week then doing the tear down, but the cold water temps have been affecting my efficiency.

 

[DB-Cooper]

Ok, update post. Did the filter breakdown. It was quite dirty, didn't backwash before, hard to tell what's DE versus concrete powder bound to DE, but here's the scientific testing of water at 50F:

When new (water temp of maybe 80F):
30 GPM = 1,945 RPM = 404 Watts
2,750 RPM = 55 GPM = 1,215 Watts

When I made original post with uncleaned filter:
30 GPM = 2,394 RPM = 676 Watts
2,750 RPM = 38 GPM = 1,043 Watts

Dirty with Filter Bypass (Recirc Mode)
30 GPM = 1,950 RPM = 410 Watts
2,750 RPM = 53 GPM = 1,196 Watts

After Breakdown and Recharge (water temp of 50F):
30 GPM = 1,999 RPM = 430 Watts
2,750 RPM = 50 GPM = 1,168 Watts

So I'm pretty close to new again. As stated, I do think the colder water plays some role, but saving almost 250W during my low pump speed mode is pretty substantial. My starting pressure at 2,750 RPM went down ~3 PSI, I expected more there, but the flow/watts report back confirms success.

Here are pics of the filter right when I took it out before cleaning:

 

[JamesW]

DE filters are very good at filtering out small particles. But, that means that they can get clogged quickly if the water gets anything substantial in it.

You should not need more than about 20 gpm most of the time.

I would set the system to run at 20 gpm and only ramp up to 40 gpm when the heater turns on.

 

[DB-Cooper]

DE filters are very good at filtering out small particles. But, that means that they can get clogged quickly if the water gets anything substantial in it.

You should not need more than about 20 gpm most of the time.

I would set the system to run at 20 gpm and only ramp up to 40 gpm when the heater turns on.

I run at 30gpm as I think that’s what IC60 requires. I bump to 40gpm when I heat. 20 I think is too low for a chlorinator.

 

[JamesW]

20 I think is too low for a chlorinator.

Adjust until the flow switch closes and then add 100 to 200 rpm for margin.