"What we want to do is tie solar in where the pressure is lower than the height..."

[Diver]

"What we want to do is tie solar in where the pressure is lower than the height..."

Hi!

I’m reading “The Marriage of a Solar Heater and a Swimming Pool's Mechanical and Plumbing System” at h2otsun.com web site and I’m a bit confused about their statement:

“If we tie solar in where the pressure is lower than the height of the collectors then we can do a conventional solar installation in which case the collectors drain down at least somewhat when solar is off.”

I believe that when a panel is fully primed, there is no static head, just the dynamic head. In other words the pump doesn’t have to work to get the water to the highest point of the panel, since water going down balances that out. So pressure being lower than the height of the panel would still allow for the flow if the pressure is lower than dynamic head.

What I don’t get is how the water would get initially to the highest point of the panel and close the vacuum breaker if “the pressure is lower than the height of the collectors”?

Am I being slow here?

 

[mas985]

Re: "What we want to do is tie solar in where the pressure is lower than the height..

This can happen with low speed of a two or VS pump. First, you need to prime on high speed and the switch to low speed after priming so a controller must support this action and not all do. Second, on low speed pressure drops so if there is a VRV on the panels at a high elevation, it will open and prime will be lost. But you can lower the VRV to a position on the supply side of the panels such that it remains closed on low speed.

However, almost any pump will prime solar on high speed on a two story roof so that should rarely be an issue.

 

[Diver]

Re: "What we want to do is tie solar in where the pressure is lower than the height..

Mark,

Thank you for chiming in. I do agree with what you said, it just seems that they brought it in a very different context that didn't make sense to me. They seem to talk about regular 1 speed pumping.

Anyway, thank again, I'm all set on this issue now

 

[mas985]

Re: "What we want to do is tie solar in where the pressure is lower than the height..

It could be an issue with high speed if you tie in after a lot of head loss where pressure is lower but normally solar is tied in after the filter and is usually plenty of pressure there.

Sent from my SM-G900V using Tapatalk

 

[Diver]

Re: "What we want to do is tie solar in where the pressure is lower than the height..

but they actually advising to tie at the point where pressure is lower under normal circumstances:

What we want to do is tie solar in where the pressure is lower than the height of the collectors...

that's what i don't understand. if you one does what they suggest, it seems that the panels will never prime.