Inteliflo VF- solar and heliocol

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dykes26

dykes26

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Aug 17, 2009
185
Ok- We originally wanted the VF for energy purposes. Then we find out that the VF has issues with solar backpressure, thus they (pentair) reccomend the VS for solar pools.

Our solar guy says that their solar shouldnt be an issue with back pressure as they do not have the small holes that most solar has- he wnt as far as saying they are they only panel right now that works with the VF.

opinions-prior experience-help?
 
dykes26 said:
Ok- We originally wanted the VF for energy purposes. Then we find out that the VF has issues with solar backpressure, thus they (pentair) reccomend the VS for solar pools.

Our solar guy says that their solar shouldnt be an issue with back pressure as they do not have the small holes that most solar has- he wnt as far as saying they are they only panel right now that works with the VF.

opinions-prior experience-help?
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I can only provide an opinion. It's possible that the solar representative is correct, but it sounds like sales-talk. Why risk it? Pentair recommends the VS pump. Go with their recommendation.
 
From what I understand, the issue is not the back pressure from the solar panels but the VF auto flow rate adjustment. When panels are installed on a two story roof, the varying pressure when priming the panels causes the auto flow rate adjustment loop to fail and it shuts off the pump. This doesn't always happen but can happen.

When switching to solar, the panels must be primed and the pressure can change quite a bit while this is occuring so the VF will be adjusting the flow rates to match (VF always assumes static conditions). The biggest problems can occur for installations on two story houses. However, for solar installations on the ground or on one story roofs, there seems to be less of an issue with this.

Note too that with the VF or VS, higher flow rates are required to both prime the panels as well as keep the heat transfer efficiency up so either way, you will be losing some energy efficiency with solar.
 
I assume that is per panel and not total flow. And I also assume that you have more than one panel. How many? Also, what is the total sq-ft of the panels?
 
dykes26 said:
sorry- 8 panels- 400 sq ft. - single story about a 12 foot rise.
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5 GPM per panel sounds about right although probably a minimum so you will need at least 40 GPM.

As to the speed needed for that, it depends on the head loss of the plumbing with the solar. But my guess is around 1400-1800 RPM. Once installed, it should be easier to narrow down but if you go with a VS, you might want to consider a flow meter.
 
Flow meters are installed in a section of straight pipe 28" long for 2" pipe and 35" long for 2.5" pipe. Few pads have that much straight pipe but if you do, that will be the most accurate solution. However, if you don't have a piece of pipe that long and straight, then you might want to go with the estimation method which uses your filter pressure to determine flow rate. But really, if your close, that is good enough. Knowledge of your exact flow rate is interesting but not really necessary.

If you are only measuring flow rate for the solar panels, then another method is to measure the water temp before and after solar and shoot for something less than a 5 degree difference. Since you have a SWG, this is pretty easy to do. The water temp is measured before the solar and since the SWG is installed after the solar, the internal temperature sensor will give you water temperature after solar. Adjust the flow rate until you get at most 5 degrees temperature difference on a fairly hot day. Solar panel efficiency will increase with lower temperature difference but this will also lower the pump efficiency so there is a trade off.
 

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I am getting conflicting information from Pentair as to whether or not the VF can operate with solar heating mounted on 2-story. Has anyone got the VF working with solar or should I go with the SVRS? Thank you.

Richard
30,000 Gal. In ground
AutoPilot Total Control
Solar Heating
Water feature
 
I think the reason that you are getting conflicting information is that sometimes it works and sometimes it doesn't. As some have posted, it seems to work fine in a one story installation but priming on a two story installation requires twice the pressure for priming the panels so I think this is the primary problem. So there is a chance that you wouldn't have any problems but if you want to avoid any problems then go with the VS or SVRS.

What was the primary reason for the VF anyway?

Once calibrated, a VS can be set to any flow rate just like the VF, it just isn't set directly but via the speed. Pentair may even give you the calibration tables it uses to convert the flow rate setting into a speed settings. This should be the same for both pumps. Its a long shot but it doesn't hurt to ask. I can also provide a calibration table of sorts based upon some of the published information that I have. It would use the RPM and power to look up GPM.

I haven't been totally sold on the VF concept myself. The VF has a control loop which forces the pump to keep the same flow rate which can be a good or bad thing. Anytime a pump will speed up automatically when there is extra head loss, sometimes unintended, it can cause problems. I would think that this would not be desirable for filters as well when they start to get dirty. I would prefer that the flow rate decreases as the filter gets dirty instead of the pump trying to force the same amount of water through.

If I ever replace my pump, I would probably go with the VS because of this and of course I have a two story solar system.
 
Mark:

Thank you for the reply. Very helpful. The only reason I was looking at the VF is because of the "scheduling features" (built-in automation). However, while the VS does not seem to have the VF features, the SVRS seems to do the same things with a comparable LCD display. What do you think about going with the SVRS?
 
Here is a simple spreadsheet which will allow you to do the conversion from RPM and Watts to GPM. Although I'm not sure how accurate it is since I haven't had the opportunity to do any verification but it matches the data points in the California Energy Commission data but that is only 4 points.

The Calc tab allows you to enter Watts and RPM to calculate GPM.

The Table tab is just a large lookup table if you want to take it with you.

See here for the spreadsheet.
 
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