Dialing in VS Pump RPMs when running solar

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Q

QingGuy

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Mar 22, 2015
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Las Vegas NV
Starting to run solar I had installed back in March on a daily basis and I wonder, how to dial in my VS Pump speed. Installers set it for 2,620 RPM and it's running fine, however, if possible I'd like to dial it down to just above where it needs to be (I'm assuming it's less than where they set it). Is there any way to gauge minimum speed on a case by case basis? I read something about bubbles; if you see bubbles increase speed. Any other methods?

I run my skimmers/floor drain at 1,150 btw and this give me nice action in the skimmers.
 
Clean filter thoroughly. Back speed off until you get champagne bubbles. Then add 200 rpm to account for the filter getting dirty. An experienced installer with the right check valve can tell if flow is adequate by looking at the flapper. The bubble method works well in practice also.

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They're not paying your electric bill! I'd never tell my client a standard speed. Every pool is different. 2,000 - 2,400 works for most pools, but we use a panel with very low flow resistance.

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We've got the same pump. I used to run my solar at 1950 rpm but I upped it to 2100 rpm last fall. The bottom header is about 7' above the pump and upper is 9ish feet. If you can easily get to the panels to feel them when they are running, check to see if they are cool to the touch. And you don't want the water from the returns to be "too hot". Warmish is good.
 
pooldv said:
We've got the same pump. I used to run my solar at 1950 rpm but I upped it to 2100 rpm last fall. The bottom header is about 7' above the pump and upper is 9ish feet. If you can easily get to the panels to feel them when they are running, check to see if they are cool to the touch. And you don't want the water from the returns to be "too hot". Warmish is good.
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Height doesn't have as much effect as you might think. The water has to come back down, which creates somewhat of a siphon effect. As long as the vacuum relief stays closed, the extra height has a much smaller effect than the feet of head from extra lift.

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Except the water will "boil" if there's no pressure from the pump but maybe these heights aren't enough. IIR it is 32 feet when you have to go submersible for a well pump as you can't draw it up higher than actual that. Maybe Mark will chime in.

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So champagne bubbles are what I want? At 2,620 I didn't have any, I bumped it down to 2,200 and I have them. I felt the water in front of one of the returns and there's a strong flow, however, I can't feel much heat. When I turned it on this morning at 10:00 a.m. to when it turned off at 5:00 p.m. my temperature rose from 60 degrees to 66 (outside temp got to 78 today).

While running solar I run the bottom drains and two skimmers open 100%. I assume this is a good setup. Can I run my suction vac while running my solar?
 
QingGuy said:
So champagne bubbles are what I want? At 2,620 I didn't have any, I bumped it down to 2,200 and I have them. I felt the water in front of one of the returns and there's a strong flow, however, I can't feel much heat. When I turned it on this morning at 10:00 a.m. to when it turned off at 5:00 p.m. my temperature rose from 60 degrees to 66 (outside temp got to 78 today).

While running solar I run the bottom drains and two skimmers open 100%. I assume this is a good setup. Can I run my suction vac while running my solar?
Click to expand...
You want no bubbles after the air is purged. There are a lot of factors. The panel brand/type makes a pretty big difference. I don't know what panels you have, but some brands will require higher flow rates. The location of the VRV can also be a factor.

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FLPoolDIY said:
FloridaSolarPro, Can you explain more about the VRV location?
I recently moved mine to the lower head so I could reduce my RPM to 2350.
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The VRV should really be at the highest point, but if the manufacturer allows it in their installation manual, it can be located elsewhere like you suggest. If you do place it on the lower header, I suggest placing it as close as possible to the return line, i.e. at the opposite end from the feed. This is usually only necessary if your pool has exceptionally low back pressure (resistance) on the pool return lines. It also depends on the design of the VRV and how much positive pressure it takes to reliably close it.

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The closer to the pump the VRV is located, the lower the RPM the pump can operate and still keep the VRV closed. So those that want to operate at the lowest RPM possible can locate the VRV on the supply side of the solar panels as close to the pump as possible. However, it is not advisable to install the VRV lower than about 6' above the pump to avoid water coming out of the VRV when opening. In addition, there are some issues to take into account with a low VRV height. Specifically, if the solar valve turns off but the pump remains running at the same RPM, water can heat up in the panels so that when the pump does shut off, it can create a very high vacuum within the lines and although rare, it may collapse the piping and/or panels because the PVC is softened due to the heat. To avoid this, it is important that the pump ramps down RPM (or shuts off) when solar turns off such that there is not enough pressure to hold the water in the panels (i.e. VRV can open). This can only be accomplished with a solar controller that supports it. The point I am trying to make here is that it is possible to run solar this way although some thought has to be put in to selecting both the VRV height and pump RPM settings to mitigate the risk. Also, make sure you don't void the panel warranty doing this.
 
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The VRV is closed by the water pressure when the solar valve opens and the pump pressurizes the solar array. The higher the valve the more pressure it takes to close it. Then when the solar valve closes the VRV opens to allow the solar panels to drain back through the pinhole in the solar valve so the panels remain empty when not in use, so the water doesn't overheat.
 
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