Pump power w/ different impellers, 2-speed vs VS w/ solar

[haz]

I just installed Heliocol solar panels. Although I can hear/feel the solar on in the pipes beyond the valve (in addition to seeing my iAqualink tell me it's on and seeing to control valve turned on), but it's not heating enough. My pump is a fairly new 2-speed:
Jandy Zodiac FloPro FHPM 2.0-2.

I had replaced the impeller with a 0.75 HP impeller to try to get better energy efficiency. However now that the solar doesn't seem to be working right, I think I am probably not getting optimal flow to the solar panels. I asked the installer if it seemed the flow was OK, since I read here by feeling the panels you can tell if they're getting to hot and not absorbing heat due to too slow flow rate. Anyway, I don't think my installers evaluated that aspect. Anyway, the installer's suggestion was for me to switch the impeller back to 2.0 HP.

So while doing so, I decided to see what kind of energy savings I was getting with the smaller impeller. Results with clamp amp meter: 240 volts. Amps:
0.75 HP impeller: 3.0 in low-speed, 5.25 in high-speed
2.0 HP impeller: 3.2 in low-speed, 8.8 in high-speed

Seems like less savings than I would expect if I swapped a 2.0 HP pump for a 0.75 HP one. Especially less than 10% difference in low-speed.

My first thought before measuring was that if it worked with the original impeller I should try replacing it w/ a 1.0 HP impeller. However maybe I'm not getting the efficiencies of lower HP by just replacing the impellers.

So my questions are:
1. Does this seem unusual?
2. If going back to the original impeller fixes the problem, should I consider getting a variable speed pump, or replacing my pump with a 1.5 or 1.0 HP 2-speed pump?
Should I

 

[Isaac-1]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

Lets take a step or two back here and look at the problem, does all or just part of you flow divert through the solar panels? If all of the flow is through the panels then when the sun is out and the panels are operating is the return water noticeably warmer than the rest of the pool water, by how much?

Ike

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

Only part of the flow is through solar. I know there is a pipe from the pump thru the filter. That splits and looks like it has flow going to SWG and back to return, another fork directly back to the return, and some up to solar.

I can't tell if the water is warmer on the return as it is on the bottom of the pool and I'm not home during the day. I can try to see during the weekend.

 

[mas985]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

How high are you panels? What is the filter pressure while the panels are engaged?

I run mine with 1/2 HP impeller on a two story roof so unless your roof is really high, a 3/4 HP should work fine. However, you may need to redirect more of the flow through the panels. Does the split have a valve?

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

the panels are 23' above pool level and 25' above ground/pump level. I will check the filter pressure and whether there's a valve on the split (if there is, it was one that was already there between the the split to the SWG and rest of the return.

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

Does there need to be a valve that controls flow either to solar or to the rest of the water outflow (in my case, the line to the SWG and another that bypasses the SWG and goes straight to return)? It seems like there ought to be, given that water will flow through the point of least resistance, and if it can easily go through the pipes to the SWG and direct return, there will be little pressure up the solar, no?

 

[mas985]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

Yes, there is usually a solar valve that is right after the filter or after a check valve after the filter. This controls the solar flow from zero to 100%. In many cases it is automated. Can you post a picture of your pad equipment?

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

OK, looked at it. There is a a fork after the filter. One fork has a valve, and after that is a split to the SWG and it looks like a bypass straight to the return. The other fork goes to the solar pipes. That has an automated valve.

By the way, I told the company owner that the pool was staying in the 87-88 degree range w/ the solar on, even though it was running in solar mode all day since I put the temp higher than that. He told me that was normal, but there was 90+ temperature and sunny those days. Who is right? I've turned the solar off the last few days, and the day temps have been 85, reading up to 86 for a short period.

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

See photo of solar valve

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

Also, in terms of the pool temp, I think it's gotten a little cooler over the last week or so, so I think the slight drop in pool temp is largely because of that and not too much because the solar heater is off.

 

[Isaac-1]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

I am starting to suspect installation / flow problem with your solar panels. Given your layout with partial panel bypass, if it were mine I would install a flow meter on the line going from the automatic valve to the solar panels, this would let you confirm flow and optimize it for your panels by partly closing the flow valve on the solar bypass (assuming that is the manual valve in the photo). Dave sells a flow meter at TFTestkits.net that would be just about perfect for this application and should be an easy 10-20 minute splice in installation.

Ike

 

[mas985]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

How about a picture of the entire equipment pad?

You mentioned another split ahead of or after the solar valve?

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

Here's a picture of the pipes. From the filter, there's a right turn to a manual valve followed by a split - one pipe off the split going to the SWG and the other going I think to the return.

The left turn off the filter you can see going to the automated solar valve and up to the panels. The solar return has a red manual valve - I guess that would be to reduce the flow through the solar?

You can see a bypass connection between the solar input and return. That gets closed when the automatic valve opens the pipes to go into solar mode.

By the way, it seems that the filter pressure is 12 PSI regardless of whether solar is on or not (with the pump in high-speed).

Does it definitely seem that something is wrong? It shouldn't be that 450 ft2 of solar with an uninhibited SE exposure should just raise the temperature on sunny days at most a few degrees above what the pool would be on its own? In South Florida, the temp should be able to go above 87 degrees or so, no?

 

[mas985]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

That is a really odd way to plumb for solar.

In order to "turn on" solar with that plumbing, you need to turn off the valve that is by the filter exit as well as turn on the solar valve. If you leave the manual valve in the off position all the time, it should work but there is still a check valve missing right after the filter. I believe the manual valve was meant to be a bypass but it is not meant to be fully on, only partially on. With solar engaged, slowly turn that valve off until the panels start to purge (you will here it) and then turn it a little more. Filter pressure should rise by 3-4 PSI.

There are a couple different ways to plumb solar and here is an example of a better way:

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

Here's a picture of what looks like probably is a check valve right underneath the automated 3-way valve. It says on it "1/2 lb. spring". So if this is one, wouldn't that make my setup like what you have in that diagram? If there is a problem, I can have the solar installers do what i need (add a flow meter, change the piping, etc.) - I haven't paid more than the deposit since I thought it wasn't working.

So you're suggesting that I slowly close the valve after the split from the filter that after splits to go to the SWG and also straight to return? Would that not create more pressure that I wouldn't want when the pool is running in non-solar mode? If so, would you suggest and is there a way to put an automated valve that partially shuts that valve the amount needed to force the right flow of water up the panels?

So if I measure the amount to shut that valve based on the sound of purging panels, no need to bother w/ a flow meter then?

 

[mas985]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

Here's a picture of what looks like probably is a check valve right underneath the automated 3-way valve. It says on it "1/2 lb. spring". So if this is one, wouldn't that make my setup like what you have in that diagram? If there is a problem, I can have the solar installers do what i need (add a flow meter, change the piping, etc.) - I haven't paid more than the deposit since I thought it wasn't working.

Yea I missed the check valve in the first picture. The configuration is not ideal but it will work if the manual valve is set right. I am not a big fan of that type of check valve. It is better than some but they do add a lot of head loss. The flapper style are much better.

So you're suggesting that I slowly close the valve after the split from the filter that after splits to go to the SWG and also straight to return? Would that not create more pressure that I wouldn't want when the pool is running in non-solar mode? If so, would you suggest and is there a way to put an automated valve that partially shuts that valve the amount needed to force the right flow of water up the panels?

It won't create that much extra pressure when solar is off because there are still two paths around the manual valve. The main flow will go through the solar valve, bypass the panels in that short connector pipe and go directly to the return pipe that then tees back into the main pipe right after the manual valve. There is a little more head loss doing it this way than a more direct approach.

The other problem with the way the installer did it is that the return pipe will back fill when solar is off so the panels may sit with water in them and heat up. This can cause issues when the pump shuts off and the very hot water drains back through the PVC and it softens the PVC. This is more of an issue in very hot climates. Again if you look at the picture I posted, there is usually a check valve on the return side so this doesn't happen.

So if I measure the amount to shut that valve based on the sound of purging panels, no need to bother w/ a flow meter then?

Not really. Usually a 3-4 PSI rise is usually a good indicator. Also, I can give you a rough estimate of flow rate vs PSI by the panel size. What is the panel ength (flow direction) and width? Also what is the feed pipe diameter and length going to and from the panels?

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

Ok, I see that the water should flow thought the short connector pipe if the solar valve is off. However in my setup, it doesn't flow back past the manual valve or return anywhere I see. By the way, I have a second pump on my system for a water feature, and the pipes tie in on the inflow and return valves. There is also a gas heater with 2" pipes, and the pipes go into the ground so I can't see where they come from at the pool equipment, which is a few ft away.

Before the solar installation, there was a 2" pipe off the main pump that you see off to the left in the picture, which went on its own into the ground. They hooked the solar 2" pipes into and back into that pipe. To the right off the pump is the manual valve, followed by a split. One end goes into a 2" pipe into the ground near where the pipe now coming off of the solar pipes go into the ground. To other end goes to the SWG, which goes into pipes split w/ electric valves marked pool and spa return, along w/ the return from the water feature pump.

Do they have to connect the solar return to go to the pipes past the split and go towards the SWG?

So I should tell them to replace their check valve with something like:
Ok, I see that the water should flo...w.globalindustrial.com/p/plumb ... 7AodKkgAIQ[/url]

and tell them because the kind they installed contributes too much head loss?

In terms of back fill, I do live in hot climate (South Florida), so that's a concern. Now there's that manual red valve they installed on the solar return. Should I tell them to replace that with a flow valve above (before) a flapper-style check valve to solve that issue? Do I want/need a manual valve like the red valve they inserted? Don't know what that would be for.

Not really. Usually a 3-4 PSI rise is usually a good indicator. Also, I can give you a rough estimate of flow rate vs PSI by the panel size. What is the panel length (flow direction) and width? Also what is the feed pipe diameter and length going to and from the panels?

2" pipes. Nine 12.5' high x 4' wide panels = 50 ft2/panel = 450 ft2 of panel.

I just closed the valve to turn up the PSI by 3. Even if I turned it up more, I don't hear any more flow through the valves. The installer claimed (before I changed the impeller back to 2 HP from what I'd downgrade to 0.75 HP) that he felt water flowing through the panels on the roof.

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

Here are a couple of views of the entire system. The gas heater is off to the right, with just 2" PVC coming from and back to underground.

Note that the pump seen closer (on left) in this pic is the larger water feature pump. The further (right) one is the one that goes to the solar and SWG.

 

[mas985]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

This is the type of check valve you should use:

http://www.zodiacpoolsystems.com/Produc ... Valve.aspx

And a check valve should be installed on the solar return near the ball valve. Although, you don't have to remove the ball the valve. Another good option where you can get a flow meter with a check valve is this:

http://tftestkits.net/FloVis-Flow-Meter ... r-p74.html


Next, 3 PSI rise should be enough. Just make sure that the SWG is getting enough flow to activate.

Also, you should be able to feel a slight water temperature difference out of the return. A properly working solar system will have return water than is around 3-4 degrees warmer than the incoming water.

Another way to make sure the panels are working properly is to feel the panel surface, only if you are comfortable getting on the roof. If the panels are cool to the touch, the panels have enough flow rate. If the panels are hot, then they probably do not have enough flow rate.

 

[haz]

Re: Pump power w/ different impellers, 2-speed vs VS w/ sola

This is the type of check valve you should use:

http://www.zodiacpoolsystems.com/Produc ... Valve.aspx

Thanks, I'll have it installed.

And a check valve should be installed on the solar return near the ball valve. Although, you don't have to remove the ball the valve. Another good option where you can get a flow meter with a check valve is this:

http://tftestkits.net/FloVis-Flow-Meter ... r-p74.html

Thanks. I will order the FloVis meter. Should it be installed after (below) the short connector pipe on the return (on the left in my pics)? I figure it should so I can measure flow even with solar off.

And with this meter, I don't need a separate check valve on the return side, correct?

By the way, is there a purpose of the red manual valve they installed on the return before the short connector pipe?

Next, 3 PSI rise should be enough. Just make sure that the SWG is getting enough flow to activate.

How can I tell if the SWG is getting enough flow? I assume it won't turn on if not.

Also, you should be able to feel a slight water temperature difference out of the return. A properly working solar system will have return water than is around 3-4 degrees warmer than the incoming water.

Another way to make sure the panels are working properly is to feel the panel surface, only if you are comfortable getting on the roof. If the panels are cool to the touch, the panels have enough flow rate. If the panels are hot, then they probably do not have enough flow rate.

Today was a high of 87 degrees. The pool temp was around 84 at 11:30 am today when I closed the manual valve enough to raise the filter by 3 PSI, and an hour after sunset the pool reads 83 degrees. I will try raising it to 4 PSI above baseline for tomorrow to see if that makes it work. I have never felt what to me seems like warmer water out of the return. The roof is 25' high - too high for me to go up. The installer tech said he could "feel the water going through the pump" w/ the downgraded 0.75 HP impeller (I've switched back to 2.0 HP at their request when I said it wasn't working), but I don't think the tech knew the concept of feeling the temp on the panels to see if the flow is right.

Now you mentioned previously that the current piping should return the solar flow past the manual valve on the fork after the pump (to the right in the pic) opposite the flow to solar? Maybe where the water flow after solar goes now is to the gas heater, so we wouldn't want to reduce that flow? Or should I ask them to redirect some of the piping?

Thanks for all of your help with this.