Plumbing for Solar

[Lostuzer]

Edited to remove large font. JasonLion

I’d like to run this idea past all of you in hopes that if I’m making a mistake or there’s a better way you’ll let me know.

I’m ready for some solar collectors but don’t like the idea of the main pump being used as the only source for moving the heated water. My pump runs enough. The electric bills are proof.

I’ve come up with an idea which I believe would allow me to remain in control of the main pump; keeping my electrical costs down and not shortening the life of the motor.

With a kreepy krauly on a suction port plus two skimmers it’s a balancing act with no suction left for the main drain. I hardly ever use the main drain except when adding muriatic acid.

I believe I’d like to use the main drain line for an inlet to the filter as a feed for Pump B (when the main pump is not on).

With the main pump running the differential thermostat would control the opening of Valve A. Pump B and Valve B (normally closed) would not be allowed to operate.

With the main pump not running the differential thermostat would control Pump B and Valve B. Valve A would be closed.

Any help is appreciated!

Thanks,
Bob

 

[Bama Rambler]

My first question would be. How are you going to accomplish the control? A PLC would certainly do it or a custom controller, but most people aren't familiar with doing either of those.

It certainly looks like it'd work. I'd probably add a manual valve in the main drain line downstream of the check valve. I'd also move valve "B" to the other side of pump "B". You don't want to starve the suction side of a pump. While niether is good, it's better to deadhead a pump than starve the suction. Your graphic doesn't show how or where you plan on tying the discharge of the panels back into the pool. So I can't comment on that.


As a side note: using very large text in a post makes it hard to follow. I much prefer the standard size, that way there's not as much scrolling to read everything. Just a suggestion.

 

[lborne]

Have you thought about how you plan to operate this? When do you run the small pump? And if its on, what happens if the controller turns the main pump on?

IMHO, it seems like you are trying to solve a problem that you really could solve a much easier way. Why are you running your pump so much? Can't you just set it to run from at least 10am to 4 pm, which is the best time for the solar to work. Do you not get enough turn overs then?

The main pump is ideal for pushing the water through the filter and through the solar. I am willing to bet that your second smaller pump is still going to need to be fairly large - 3/4 HP at least. If it were me, I'd run my pump during peak sunlight times (10-4) and then maybe a bit more at night if needed.

 

[JohnT]

If pump B isn't nearly as large as a pool pump, it will have too little flow to get good efficiency out of the solar panels.

 

[mas985]

If pump B is more efficient than the main pump, why not just replace the main pump with pump B? The combination of the two pumps will certainly use more energy than simply repalcing the current pump with a more efficient pump or a two speed pump.

Also, there have been some studies which indicate that main drains are really not needed for proper circulation of the pool so I really don't think it is that important that you increase the flow rate in the main drains.

 

[Lostuzer]

The owner of the solar heating company http://www.splashsolar.com came over today. I threw out a few questions but didn’t delve into any of the particulars I’m posting about here.

The panel sample he had was very rigid, and smooth and flat on both sides, unlike what I saw pictured on his site (corrugated). I have a diagram to give you an idea of what it looked like. I was told they are made in Clearwater (just a few miles from me) by a company that’s been making panels since the 70’s.

For the t-stat, 12 4X12 panels, and a full installation I was quoted $4500 with a 10 year warrantee. I’ll ask if labor’s included in the warrantee the next time we talk. Remember this would be his typical install. Any comments?


Bama Rambler

My first question would be. How are you going to accomplish the control? A PLC would certainly do it or a custom controller, but most people aren't familiar with doing either of those.

After I come up with a workable model the controller will be the easy part. One of the few aspects of this I’m not intimidated with.

I'd probably add a manual valve in the main drain line downstream of the check valve

I’m sure there’s sound reasoning behind this suggestion but it eludes me.

I'd also move valve "B" to the other side of pump "B". You don't want to starve the suction side of a pump. While neither is good, it's better to deadhead a pump than starve the suction.

Good call! You Da Man! I would have never thunk of that. You might have saved me from having to by a new motor prematurely. I’ve got too much unnecessary stuff rattling around up there lately.

Even after having the devices trade places another consideration might the use of a delay to sequence the valve open before the pump turned on. Any thoughts?

…discharge of the panels back into the pool.

I figured running an open ended PVC line into the pool near a return port, for good distribution, might be ok. Or, if you’re talking about the draining of the panels after the pump turns off… I intend to forgo that unless I’m convinced there is a necessary reason for it.

lborne

Have you thought about how you plan to operate this? When do you run the small pump? And if it’s on, what happens if the controller turns the main pump on?

“With the main pump running the differential thermostat would control the opening of Valve A. Pump B and Valve B (normally closed) would not be allowed to operate.”

Can't you just set it to run from at least 10am to 4 pm, which is the best time for the solar to work? Do you not get enough turn overs then?

I get plenty of pool water turnover running from 1 to 4pm and the collectors will have to be mounted on a west facing roof.

I am willing to bet that your second smaller pump is still going to need to be fairly large - 3/4 HP at least.

. I haven't determined which size pump/motor would be needed. I was told a stand alone motor at 1HP would be more than plenty. I was hoping a 1/2 or, 3/4 at most, would work.

I'd run my pump during peak sunlight times (10-4) and then maybe a bit more at night if needed.

I’ve never ran my pump at night. All of this last winter up until now I’ve ran it 3 hours a day and the pool looks great. But it’s still cold.

mas985

If pump B is more efficient than the main pump, why not just replace the main pump with pump B?

Pump B would not be more efficient it would be less energy consuming by being smaller.

The combination of the two pumps will certainly use more energy than simply replacing the current pump with a more efficient pump or a two speed pump.

You might have missed the point. I'm trying to maximize my heated water circulation and use a smaller less energy consuming pump to do it. Why run a 1 1/2HP pump when a 1/2HP pump will work just as well. I would like to get a more efficient main pump but that’s on down the road. Compared to what I have now I believe it would pay for it’s self in about 2 years but forking out that much money would also continue my feelings of wanting to prolong its life by not running it any more than necessary.

Also, there have been some studies which indicate that main drains are really not needed for proper circulation of the pool so I really don't think it is that important that you increase the flow rate in the main drains.

I always figured what I lacked by not using the main drain could be partially be made up for with the Kreepy. After the two skimmers and Kreepy there’s nothing left for the main drain.

Simply put:

I would like the panels to always have water in them.

When the water in the panels is hot enough (4 deg. above pool temp.) and the temperature setting on the t-stat, e.g. 82 deg., is not satisfied I want that water to dump into the pool whether or not the main pump is on.

I’m trying to accomplish a couple of things here. One would be to prolong the life of my existing pump/motor, keep the power bill down, and provide hot water as quickly as possible.

Thanks for any and all help,
Bob

 

[JohnT]

I'd be willing to bet that what you are planning is going to be significantly less efficient for heating than just running your main pump during the peak solar period, and that your electrical savings will be just about negligible.

You don't want to leave water in the panels without circulation. The water can quickly exceed the safe temperature for many panels and cause panel damage. Solar systems are designed to drain the panels when there is no demand for heat.

 

[duraleigh]

What software did you use to draw that amazing diagram? It's the best I've seen on this forum!

 

[JasonLion]

+1 on letting the panels drain down when not in use.

 

[Bama Rambler]

I'd probably add a manual valve in the main drain line downstream of the check valve
I’m sure there’s sound reasoning behind this suggestion but it eludes me.

I'd add it in case you ever had a problem with that check valve you could isolate it and stop from pumping water back through the main drain bypassing the system. It'd also allow you to work on it with the system running if you ever needed to.

 

[mas985]

Lostuzer,

I think you missed my point. Pump B is more efficient simply because it is a smaller pump. Smaller pumps generally will have a higher gallons/watt-hr capability making them more efficient. So pump B will be able to turnover the pool using less energy than the main pump. So my main point is why would you ever want/need to run the main pump? Why not simply use the single more efficient pump all the time?

Also, with your setup, when you run Pump B alone, the filter will be under suction instead of pressure. I don't believe that they were designed to work that way and could be a problem.

I still think you would be better off to simply replace your main pump with a lower HP pump and maybe even a two speed. This will give you considerable amount of energy savings and you probably won't need to replace the pump in the future. In fact, if you want to make it real easy, replace the motor and impeller on your current pump and downsize it. No plumbing changes required.

 

[Lostuzer]

JohnT

I'd be willing to bet that what you are planning is going to be significantly less efficient for heating than just running your main pump during the peak solar period, and that your electrical savings will be just about negligible.

My usable solar periods should be much longer than my scheduled filtration periods of 3 or 4 hours. Plus I have to consider that the swimming crowd here doesn’t like Kreepy moving around during the afternoon swim times, which is my peak solar period.

You don't want to leave water in the panels without circulation. The water can quickly exceed the safe temperature for many panels and cause panel damage. Solar systems are designed to drain the panels when there is no demand for heat.

I need to get my head wrapped around this. Will a panel with water in it get hotter than a panel without? Maybe the idea of having the panels constantly filled with water is not one of my greatest ideas. I thought the contractor mentioned this feature in context of being damage prevention in the event of a freeze. The contractor would have to approve any modifications to his typical installation in order to meet the requirements for the warrantee. I plan on having the contractor do any install mods. He said he had the same system (materials) with some of his own modifications. I’ll get with him and have him show or explain what he’s doing different than the typical install.

Bama Rambler

I'd add it in case you ever had a problem with that check valve you could isolate it and stop from pumping water back through the main drain bypassing the system. It'd also allow you to work on it with the system running if you ever needed to.

That is good advice. I’ll incorporate that into the next diagram I make.

mas985

I think you missed my point. Pump B is more efficient simply because it is a smaller pump. Smaller pumps generally will have a higher gallons/watt-hr capability making them more efficient.

I sorry I don’t know enough to respond to this statement intelligently.

So pump B will be able to turnover the pool using less energy than the main pump. So my main point is why would you ever want/need to run the main pump? Why not simply use the single more efficient pump all the time?

My existing pump barely applies enough negative pressure for two skimmers and the satisfactory operation of the Kreepy Krauly. I wouldn’t think a smaller rating pump would suffice.

Also, with your setup, when you run Pump B alone, the filter will be under suction instead of pressure. I don't believe that they were designed to work that way and could be a problem.

This is one consideration I had not taken into account. If your assumption is correct then maybe I should not feed pump B thru the filter and maybe get a smaller, maybe replaceable cartridge small pool rated, filter and completely isolate the solar system from the existing filtration system all together.

I still think you would be better off to simply replace your main pump with a lower HP pump and maybe even a two speed. This will give you considerable amount of energy savings and you probably won't need to replace the pump in the future. In fact, if you want to make it real easy, replace the motor and impeller on your current pump and downsize it. No plumbing changes required.

As per above: I need all of the suction I have now.

Thanks again for all the advice,
Bob

 

[JasonLion]

My existing pump barely applies enough negative pressure for two skimmers and the satisfactory operation of the Kreepy Krauly. I wouldn’t think a smaller rating pump would suffice.

I find this surprising. What size pump do you have now? I would expect most 1 HP or larger pumps to be able to handle your setup without problems (unless something is wrong).

 

[PoolGuyNJ]

Having multiple pumps on a single set of suction plumbing is a NO-NO, even if it doesn't exceed the flow rates for what is there unless it's over twice the needs of the two combined. The reason is if someone puts a larger pump on, it throws what ever safety margin out the window.

If this pool was built last year, it was built to VGB specifications. If there is a SVRS systems in place, you may run into additional operational issues, depending on the unit used.

I strongly recommend reconsidering this idea and stick with a single pump.

Scott

 

[Lostuzer]

JasonLion
I find this surprising. What size pump do you have now? I would expect most 1 HP or larger pumps to be able to handle your setup without problems (unless something is wrong).

Thanks for your speculation. We bought the house a year ago. The pool is about 10 years old and the pump I believe is the original. I’ve been meaning to tear it down and replace the bearings because I don’t believe it’s as quiet as it should be. When I do this I’ll see the impeller and if it needs replacing, and as a result, gives me more flow I’d be happy. After your comment I’m going to push this up on my to-do list

The facts are:
Last April I opened the filter (48sq.ft. DE) and thoroughly cleaned it. The filter material seemed supple enough so I didn’t believe it to be limed up. With both the skimmers and main drain wide open, and 5 lbs. of fresh DE in the filter, it registered 14 lbs. of pressure on the gauge.

PoolGuyNJ
Having multiple pumps on a single set of suction plumbing is a NO-NO, even if it doesn't exceed the flow rates for what is there unless it's over twice the needs of the two combined. The reason is if someone puts a larger pump on, it throws what ever safety margin out the window.

Never would the pumps be allowed to run at the same time but the more I think about it I might just “…completely isolate the solar system from the existing filtration system all together.”

If this pool was built last year, it was built to VGB specifications. If there is a SVRS system in place, you may run into additional operational issues, depending on the unit used.

We have an anti-entrapment cover. We don’t have a SVRS.

 

[mas985]

Without filtering, there is a good chance you might get debris stuck in the panels which would be difficult to clear and would reduce efficiency. Eventually, the whole panel might plug up.

 

[Lostuzer]

Without filtering, there is a good chance you might get debris stuck in the panels which would be difficult to clear and would reduce efficiency. Eventually, the whole panel might plug up.

Thanks for the good advice but I've already thought of that.
"...get a smaller, maybe replaceable cartridge small pool rated, filter..."

When I saw a sample of the panel I realized how easy it would be to clog up. A roly poly bug is big enough to block one of the channels.

As a starting point I've been looking for smaller cartridge filters on ebay.

 

[Lostuzer]

Maybe I’m missing something here. Would someone please comment on the possible problems of allowing the panels to always remain filled with water? It seems to me that if they were always filled, the ability of the panels to produce warmed water would be greater; especially if I had a pump (auxiliary) that was actuated by the temperature differential thermostat.

I thought the drain down was an antifreeze feature. It only got below freezing 3 nights this last winter and it was one of the coldest I’ve seen. During these colder times I’d have the panels drained and inoperable anyway.

Thanks,
Bob

 

[mas985]

The primary reason for draining the panels is because of freeze protection. However, a little known problem, probably because it doesn't happen all that often, is that with water left in the panels and with the pump off during the day, the water can become super heated and soften the PVC piping connected to the panels. And because the panels are under suction when the pump is off, because of the elevation, the pipe has the potential to collapse. Again, probably does not occur too often but I talked with an installer in the central valley once, where it gets really hot, and he said that they had a few cases of this happening. So I would say that draining panels helps prevent both freezing and melting.

As for the panels being more efficient because the water stays in them when they are off, I don't think that will add that much more heat then if they were empty. Water comes out hot either way but that is not really what heats a pool. It is the continual addition of BTUs over the course of the day and higher flow rates that increase heat transfer.

 

[Lostuzer]

...water can become super heated and soften the PVC piping connected to the panels

Now, that makes sense. Thank you for your wise words. The panel sample I looked at seemed pretty beefy, but I had not taken into consideration the possibility of damaging the connecting PVC. Back to the drawing board.

Thanks,
Bob