What Are Distance Limits On Moving Solar Heated Water To A Pool Or Natural Gas To A Gas Pool Heater?

[PeterP]

I have a 16' x 36' pool located down a 45 degree hillside approximately 200' from a rooftop where solar panels could be located. It is also a little more than 200' and downhill from my gas meter to the pool house where a natural gas heater could be located. One solar contractor proposes 12 Heliocol 4' x 4.5' solar panels with a Pentair Intelliflo variable 4 speed pump to move water up the hill in 2" black solar pipe, through the panels and back down to the pool. A second contractor says the distance is too far for effective solar heating. The second contractor also thinks the distance is too far for natural gas flow, unless a separate 2" dedicated gas line from the meter is used. Please share any information on these issues.

[quantumchromodynamics]

Run the water through 3-inch PVC both ways.

Run the gas line as a two-stage line. A smaller 3/4 or 1-inch diameter line can be run at high pressure into a second stage regulator near the pump house and then from the second stage regulator into the heater. Call your HVAC people to get an estimate on this. They should have no trouble at all.

1) How high is the roof, above the pool water level, that the solar panels will be located on?

2) What is the design flow rate required for the proper operation of the solar panels? Minimum? Maximum?

3) What will be the BTU requirements for the Natural gas heater?

[quantumchromodynamics]

One solar contractor proposes 12 Heliocol 4' x 4.5' solar panels

It doesn't seem that Heliocol makes a 4' x 4.5' panel. They have a 4' x 10.5', is that the one you mean? That one takes 4 gpm. The 4' x 12.5' takes 5 gpm. Therefore, 12 would take 48 gpm or 60 gpm. Although 48 to 60 gpm is not a lot, I think that 3-inch PVC would be best because of the 200 foot run both way equals a total of 400+ feet of pipe. A smaller diameter pipe would have too much head loss. Head loss is determined by the pipe length, pipe diameter, speed of the water, drag coefficient, surface area of the pipe in contact with the water and other factors such as 45 or 90 degree turns etc.

Assuming 60 gpm at 400 feet of pipe length:

2.0" pipe equals a head loss of 24 to 34.53 feet of water or 10.4 to 15 psi. Velocity = 6.13 feet per second

2.5" pipe equals a head loss of 10 to 11.67 feet of water or 4.33 to 5.0 psi. Velocity = 3.92 feet per second.

3.0" pipe equals a head loss of 3.6 to 4.8 feet of water or 1.56 to 2.1 psi. Velocity = 2.72 feet per second.

As you can see, going to a larger pipe will allow you to meet your flow requirements without excessive head loss. A 2-inch pipe is definitely too small. A 2.5-inch pipe would be acceptable, but not ideal, for 48 gpm. A three-inch pipe will allow the pump to run much more efficiently and you will save a lot of money on electricity.

I believe that the height of the building needs to be added to the head loss because the head loss is not offset by the water coming back down due to a vacuum breaker being used on the solar panels to prevent collapse of the panels due to vacuum.

If there were no vacuum breaker the height of the building would be taken out of the equation because the water coming back down would offset the water going up. Add the height of the building to the head loss that the pump needs to overcome. Add 5 feet of head for the solar panels.

Assuming a 12-foot tall building:

12 foot for the building + 5 feet for the solar panels + 5 feet for the pipe + 5 feet miscellaneous = 27 feet of head (11.7 psi)

If you are just adding a booster pump to be used only when you want to use the solar panels, a 1.0 H.P pump is much cheaper and can deliver about 65 GPM at 30 feet of head. I don't see why you should need an expensive variable speed pump when you only need one speed.

However, if you want to use just one pump for your system, then the Intelliflo would be a good choice so that you can tune the exact flow that you want.

Where will the pump get its water supply?

What are your current pump and filter specifications?

http://www.heliocol.com/residential/technical.html

http://www.engineeringtoolbox.com/hazen-wi...ater-d_797.html

http://www.engineeringtoolbox.com/pressure...ipes-d_404.html

[quantumchromodynamics]

I think that PVC schedule 40 can be used up to 140 degrees Fahrenheit.

What will the maximum water temperature coming out of the solar panels be?

If the temperature will be at or near 140 F, then you could use schedule 80 CPVC as shown here:

http://www.charlottepipe.com/Default.aspx?...mp;type=PVCCPVC

"CPVC Schedule 80 pipe and Schedule 80 fittings system is intended for pressure applications where the operating temperature will not exceed 200 ° F."