Solar Systems- 2" vs 1 1/2" Header?

Hi All,
While we're undergoing some pretty heavy pool-deck renovations, we'll be upgrading the pipes of our 20,000 gallon inground concrete pool to 2" PVC (up from 1 1/4"!). We're also planning to add solar, and have started researching all the options/ suppliers.
We have two "burning" questions at this point:

1) Are there solar panels that have 2" headers, rather than 1 1/2"? It would seem that the additional flow would make a big difference, but maybe we're oversimplifying? If it helps, the location of the panels would be installed just 8-12 ft above the pool pump, which is a 3/4 HP Hayward (may need upgrade to 1 HP, I believe), and the total run of the heater circuit (from filter to returns) is about 40 ft.

2) Has anyone tried to increase the solar heating efficiency by enclosing the panels, even partially, in glass? I've seen solar rail systems that seem pretty simple (I'm relatively handy) to adapt to an enclosure. I'm also thinking this would help reduce or eliminate wind factors, since the wind off the Bay at night could take a lot of heat away before the water returns to the pool.

Hoping to figure this piece out before the plumbing gets too far underway, b/c the contractor spec'd 1 1/2" pressure-side pipes (after 2" vacuum side) unless we deem something else is necessary.

I can tell you that the Fafco solar bear mats are usually advertised as having 2" headers but they actually take a 1-1/2" NPT fitting which works out OK for me as I am using 1-1/2" hose but if you want to use 2" pipe then you would have to get an adapter. I wonder if the 2" measurement refers to the diameter of pipe used for the header - that would seem about right.

I don't know how much you would improve efficiency by encasing the mat in glass. The mats are normally cool to the touch as the heat is being transferred to the water passing through it so I wouldn't think the wind would have a big effect as long as the sun is shining. If you want to keep from losing heat at night then maybe you should consider either bypassing the solar heater once you lose sun exposure or set your pump to run only during the sunny part of the day (meeting the 2x volume circulation time).

I would ask the contractor why he chose 1-1/2" on the pressure side.

Peter

Peter

My Solar Industries panels are 2". Their standard panels are 1 1/2". I wanted 2" because my pool was plumbed that way and we have a long way to go to the panels (130' from the pump).

A very reputable installer I spoke with initially wanted to put in 1 1/2" ("we do all of them that way"). When I insisted on 2", he called Solar Industries and they recommended 2" for our installation. To his credit, the installer was very gracious and basically said that you learn something new every day.

Cost was the same. I think the real difference only comes if you had enough panels to "use up" the 44gpm of 1 1/2" pipe. From what I remember, most panels can handle 4 to 10 gpm per panel (4' wide - one way, not u-turn type). So that means that if you are planning on 4 or less panels, 1 1/2" is fine, between 4 and 8 or so it is a toss up, 8 or more will really benefit from 2" pipe. (I have 8 4 x 14 panels). All of this depends on how much flow you push through the panels. The more flow (without stressing the panels), the better (see other threads on solar efficiency).

Thanks so much for the tips!
Peter, my case was exactly like tphaggerty's. The contractor said "Unless there's a specific need for 2", we'll be doing 1 1/2" pipe on the return end." So I was just sizing up that need. It looks like 1 1/2" should be ok, since we'll have at most 6-8 panels with good sun. 2" pipe may be overkill for our size pool/panels, but might come in handy if we choose to divert return water to a water feature (a growing interest as we re-design things!), which would also run during daylight hours.
I think we need to take some time to digest this info here & all else we've received so far & go back to the design table for a few days. This is really helpful, so thanks for taking the time!

An update: We've decided to go with 2" pipes throughout, both for solar as well as suction & pressure sides. In addition, we were able to find a local seller for 2" Fafco solar panels. The contractor agrees that it might be a bit of overkill on the pipe size, but that the improved flow rates should make several aspects of the pool run more efficiently (faster turn-over, better heating, better filtering), especially with a 2-speed pump.
Thanks again for the input!