Pump Sizing Question

[BigDave]

Thanks to all of you, Mark I've been through most of the links in your sig - Thanks loads!
I'm going to try to estimate the static and dynamic head of my proposed system. I've emailed Hayward asking for pump curves for the 1 and 1.5 HP Power flow Matrix AG 2 speed pumps. Haven't heard back yet. It seems to me that the sweet spot would be a two speed pump with enough head on high to prime the solar and enough head on low to maintain the solar's flow rating (accounting for system dynamic head and psi required for vacuum check valve) and turn over the pool in eight hours (without the solar). Clearly this could all be achieved with a variable speed pump of sufficient capacity but those critters are pricey.
Does anyone knoe of a solar control system that will start a pump and run it on high to prime the panels and then on low (after staic head is returned).

[mas985]

You will have a hard time running a solar system on low speed of a two speed pump. In order to do that, you will need to plumb the vacuum release valve at a low elevation right above the pad. However, I would not recommend this as it will also the require the panels to run under a slight vacuum. Plus you will also lose efficiency running the panels at lower flow rates. With a two story house and recommended VRV placement (i.e. top of panels), you will need to run a pump at high speed or a variable at fairly high speed in order to keep the pressure up and the VRV closed. This is why I have such a low HP two speed pump. I use high speed for solar and low speed when I don't need solar.

[PoolDoc]

BigDave, if you get those charts, would you mail them to me?

I'm working on project that hopefully will be visible next spring, and will publish ALL of the pool info I've gotten over the uses, plus stuff I've found with Chem_Geek's help, plus all of HIS stuff he'll let me put up, plus all the chem MSDS I have, PLUS the old PacFab pump & hyrdraulics training manual (with the only detailed PacFab curves I've ever seen), etc.

My hope is it will be a reference we can all use to upgrade the information available to general pool users, by upgrading the information the 'answerers' have.

Already got the domain name, and with the advent of EPB Fiber here, bandwidth is no longer an issue. Which is a good thing, since the folder I have for that stuff is already almost a gigabyte, and I'm just getting started.

[BigDave]

Thanks Mark, that makes sense.
Does anyone know(knoe) of a solar control system that will switch the pump to high speed when calling for heat and back to low when it's not needed?

[mas985]

I think most controllers that control solar will switch to high speed by default. I know for sure that mine, AquaLogic, will definitely do that.

As for head curves, is the pump you are considering on this page?

The single speed and two speed versions will have the same head curve on high speed. Low speed is simply a scaled version. But looking at these pumps, I would like to see a little more flow rate at 50' of head. But you might ask the forum if anyone is using one of these pumps for a two story solar install. But if you want to be safe, I would go with an IG pump. Something like a 1 HP SuperPump, I know would work.

[BigDave]

Right now I'm trying to convice myself that a variable speed pump is the way to go. Install a flowmeter and set the pump to meet the flow requirements of filtration or the solar based on test and not "Wild Guess" estimate of piping / filtration / heat system in operation before being built.
cons:
Expensive
pros:
Potential to save on electricity ( I haven't calculated what it would take to break even on that )
Use only what we need to run the gear not use what the pump requires
Maintain optimal flow rate for each configuration
Can be adjusted as our needs change
Can self prime making it useable if we do get an IG
Keeps me from having to go through estimating the requirements of a system that doesn't yet exist and living with it later

Sounds like I'm taking myself into it.

[BigDave]

PoolDoc
I will send the curves if I get 'em. All I've gotten so far has been and auto answer email "We have recived your inquiry and will respond as soon as possible..."

[mas985]

Again, the head curves are on this web page if you don't want to wait for Hayward. It is a table under "Performance Data"

[BigDave]

I got that Mark and thank you very much. That table is partly what's pushing me toward Variable Speed - I'm not there yet, but trying to work my head around it.