Solar Panel System

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Allen G Myerson

Solar Panel System

Postby Allen G Myerson » Wed 06 Oct, 2010 19:07

mas985
But in fact, static head still exists and affects the pressure at the VRV but simply does not add to total head with respect to the pump.

I don't understand this statement. Why doesn't the static head add to the total head loss with respect to the pump?

I can see how it is offset by the water's potential energy if the head loss from the panels back to the pool is equal to or greater than the height. However, it is not offset if the head loss from the panels back to the pool is less than the height


chem geek
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Solar Panel System

Postby chem geek » Wed 06 Oct, 2010 21:39

I think he means that if there is enough flow restriction in the line from the closed VRV to the pool returns, then the static head on the way up cancels out the static head on the way down so doesn't factor into the calculation for total head. Of course, it does get factored in an indirect way since the amount of flow restriction one needs to prevent too much of a vacuum (technically lower than atmospheric pressure) that could collapse piping is based on the static head.

I wrote that in my earlier post as well. Mark wrote earlier that there are two scenarios: one where the VRV is open in which case you've got a split system with static head going up in addition to the dynamic head but a free-flow from the VRV down vs. a second scenario (the one described above) where the VRV remains closed in which case the static head is not used directly in the total head calculation (though as I pointed out above, to make the VRV remain closed one must have sufficient dynamic head loss from the VRV to the returns that is as large as the static head).
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mas985
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Solar Panel System

Postby mas985 » Thu 07 Oct, 2010 10:57

Sorry I wasn't clear and the statement is ambiguous. I just was being lazy. I probably should have written:

But in fact, static head still exists and affects the pressure at the VRV but simply does not add to total head with respect to the pump when the VRV remains closed. In many cases, when the pump is switched to low speed, there is not enough pressure to keep the VRV closed so the VRV will open and air will enter the plumbing increasing the net static head loss.


I was attempting to describe several posts I have read in the past where a pool owner with solar is thinking about switching to a two speed or variable speed pump and was asking if the solar would work ok on low speed. Sometimes, someone will respond that it should work ok because the static head is "cancelled" but of course they are making the mistake of ignoring the pressure at the VRV. So the VRV may or may not stay closed depending on the elevation of the VRV and the presssure in the plumbing.
Mark
Hydraulics 101 ; Pump and Pool Spreadsheets ; Pump Ed 101
18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, Solar Panels, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater
dabbstaylor
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Joined: Mon 05 Mar, 2012 22:51

Solar Panel System

Postby dabbstaylor » Tue 06 Mar, 2012 04:54

Hi there, I am new in new jersery and i want to install solar panel system at my home. I am here wondering for the best company from where i can buy solar panel in new jersery at reasonable rate. Please anyone here can suggest me.
John75

Solar Panel System

Postby John75 » Sat 10 Mar, 2012 20:10

Hi dabstaylor! Have you checked this guide to swimming pool heaters at www.indoorpoolguide.com/heating-systems

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