PentAir SolarTouch 521592 vs. 521632

[Diver]

PentAir's brochure shows 2 types of the controls:

521592: SolarTouch Solar Control System with 3-Way Solar drain-down, valve actuator and 2 temp sensors (20' water, 40" solar) and
521632: SolarTouch Solar Control System with 3-Way Valve, valve actuator and 2 temp sensors (20' water, 40" solar)

The only difference is the valve and the first type is mentioned that it's a drain-down. Also on the spec page it mentions:

Solar valve automatically drains the solar collectors when pump shuts off

This is somewhat confusing to me. Can someone explain the "drain-down" feature of the valve? I feel that it would drain itself any way (towards the pool if there is a check valve between the T and the filter). I assume there is no check valve built in into the 3-way valve itself, is there?

Also, on somewhat unrelated note, I assume neither PentAir no Jandy check valves can be installed on vertical pipe, is that correct?

Thanks!

 

[Diver]

well,

i got some info from Pentair and can share it here. The drain-down valve has a small hole in a diverter that allows to drain water from the panel cold water intake side. Without it, the only path for water to drain is how water outlet and in some configurations it will not result in full drain.

come to think since the hot water outlet is typically on the high point of the panels, the only way for water to drain is thru cold intake and without drain-down 3 way valve it would not happen.

if a vacuum breaker is not at the highest point then some water will be siphoned thru the hot water outlet, but some might remain in the panels. this was actually discussed in details in this thread in deep end.

this drain down valve is discussed on this forum under "leaky valve" term..

 

[pooldv]

Yes, that is correct. There is a small hole that will allow the panels to drain when not in use. This will protect against a number of things; freezing, solar panels collapsing, remove weight from the roof when not in use, prevent overheating the water in the panels when not moving.

 

[Diver]

I was thinking that when solar is on that little hole will let some of the water bypass the solar and go directly to the pool. But Pentair rep said that it actually produces suction when the water goes by. I feel somewhat conflicted in that regard. I assume it could be a possible due to Bernoulli effect, but still I have doubts about it.

When solar is off, the opposite should happen - the hole should suck the air from the solar panels since it will open the vacuum breaker.

Unless, of course, that little hole is a valve itself, for example flapper/membrane style.

I was wondering if people who have solar with leaky 3valve see air being sucked in when solar is switched off??

 

[pooldv]

I ran my panels with a regular 3 way valve for a while at first, several months at least, before installing the solar valve with the pinhole. I did not notice any operational differences other than the panels draining down after the valve closes. It definitely does not suck in any air or cause any problems. Pretty sure it is just a pinhole, no flap or anything. I took the valve apart a couple of years ago but I don't remember for sure.

 

[Diver]

i received my solartouch controller and the diverter hole in the 3way valve is actually a valve itself. so there is a valve in a valve

the controller enclosure doesn't seem to be water proof. do people mount them outside as is?

 

[pooldv]

Hey, that is good to know. Yes, mine is mounted outside on the wall of the pool hut. Seems to be waterproof enough, been there a couple of years.

 

[gonefishin]

So, when looking at the two choices...is one preferred over the other? Living in the upper midwest should I pick one over the other...or is it a wash? One thought regarding water being in the solar panel is that it will be heavier...we get some unbelievable winds.

thanks!

 

[Diver]

So, when looking at the two choices...is one preferred over the other? Living in the upper midwest should I pick one over the other...or is it a wash? One thought regarding water being in the solar panel is that it will be heavier...we get some unbelievable winds.

thanks!

as far as i understand the leaky valve is the only option and without it the panels will stay full of water. i don't see how it would be beneficial under any circumstances..

i live in boston area and it gets very windy here with noreasters and such. the panels took the brunt of the winter without any problems. well, at least visually, i will find out in few months how they really survived their first winter...

 

[pooldv]

Agreed, it is widely advised that it is best for solar panels to drain down when not in use to avoid superheating the water and creating undue pressure on the panels and the plumbing. All solar panel installation instructions I have read say that the panels should be empty when not in use. My panels have been installed for 4+ years with no issues at all from known winds in excess of 50 mph and probably higher. We recently had to re-roof 3 of 5 buildings on the property due to hail, wind and thunderstorm damage. The two that didn't need re-roofing were a barn with Mueller metal roofing and the pool hut with the solar panels on them. Neither had any damage.