Which pump do I choose of these two?

[Paulk]

[FONT=&quot]I’m looking to install an AG pool this spring, ~15,000 gallons. I’ve dozed the site and am ordering a pool soon. I’m looking at a DC VS pump that is 500 watts (2/3hp), or one that is 900 watts, (about 1.20 hp.) (I’m off the grid by the way!) The 500 watt pump, supposedly pumps maximum 4400 gallons per hour. I’m sure with 0 head. Max head is 50 feet. The pump of course will be below the surface of the water, but of course filters can and do restrict the flow, so the actual head will be something more than 0. I’m planning on running the pump basically whenever there is sun, which will be at least 8 hours a day. My understanding is that if I circulate the water in the pool once a day, I’m more than fine. 4 hours would be adequate, IF indeed I got 4,000 gallons per hour pumped. My question is what is the normal flow rate one might expect from such a pump IN a normal system? I’m leaning toward a cartridge filter system, and can maintain it and change it when needed, and will go for the largest filter I can, (less resistance), and I also intend to go to a swcg system. Thus I'll probably be running the pump more for CL generation that for debris removal I guess?[/FONT]
[FONT=&quot]I don’t know if this is enough information for someone to tell me if I need to go for the 900 watts or that the 500 is enough? [/FONT]
[FONT=&quot]There isn’t much difference in cost between the two pumps, but the difference is quite a bit when you start talking about the solar panels for the different pumps. So it would be “nice” if the 500 watt pump were adequate. I assume the fact that it is variable speed will help. [/FONT]
[FONT=&quot]Thanks for any advice. [/FONT]
[FONT=&quot]paul[/FONT]

 

[mknauss]

You had a previous thread discussing this subject:
Direct solar pumping

Did anything come from that?

I would think you want to go with the most powerful. As it is variable speed you only use what you need.

 

[Mayorb]

The 500W should be fine. Just make sure it will provide enough water flow to actuate the flow switch on your SWCG, which should be okay as long as you keep the filter from loading up. When in doubt, you can add an $9.00 floating clorinator to make sure pool is sanitized. Some pool pro's don't like them, but I depend upon them in my market because they sanitize 24/7 whether pumps are running or not.
Certainly, consider other opinions!
Good luck with it!

 

[Paulk]

Thanks Marty and Mayorb
Yes Marty, I had an earlier thread months back asking about Direct solar pumping. I suppose I could have added this to that, but this question isn't about whether or not to use direct pumps. That was decided. This was whether a 2/3 hp was adequate or did I need to go to 1.2 hp. I understand that it isn't a big deal cost wise to go for a larger hp when talking about AC. The cost differential is not great. But when you are talking about DC, it is because of the additional panel costs, plus additional installation charges, probably an extra $1500. IF a 500 watt motor can handle it, then great. So my question I guess is sort of asking how much reduction in flow does one expect normally in a system that has normally cleaned filters experience? Is the flow reduced by double from clean to dirty or what? I realize that one probably can't put any exact value, just asking for general case.
Thanks Mayorb, good point about the flow switch on the SWCG. I'm obviously NOT and expert. I'll try to be sure I'm covered. I'm open for sure to any opinions. The specs on the 500 watt pump indicate it would easily handle circulation, being ~75 gpm, but that of course is with no back pressure. The pump says max head at 50 ft. The 900 watt pump's values are only 92 gpm and 62f max head. Not huge difference, but it might be very significant. I'm willing to keep the filters well maintained, but if experts like you two feel I'm very close to the edge on the 500 watt pump, I'm ok with going to the bigger one.
thanks for any opinions.

 

[CJadamec]

If you are concerned about power usage the SWG is not the best option. As you have said you will need to run the pump longer to generate chlorine. A more energy efficient option would be a stenner pump and liquid chlorine or manually dosing with chlorine.

Can you link to the pump or post a pump curve? That would go a long way to picking a pump.

 

[Paulk]

Hi Chuck, thanks.
I very much appreciate your response. As Marty mentioned earlier, I DID have a thread about Solar pumps. I didn't get a lot of replies, as I find, most folks of course don't bother going solar on their pumps, as there really aren't a lot of options that are easily found. Being off the grid, I did a fair amount of sleuthing around and did find more than a couple. Sorry to make the reply long, but just want to make it understood. A pump of say 1 hp, going a fair amount of a day, (let's say 12 hours?) will draw a fair amount of power. Let's say minimum of something like 9000 watts, over that 12 hours, or maybe 75 am-hours? Not a lot of AC, but for a battery system, that is a significant amount of power. My system could handle that, most days, not a problem, (though could NOT handle that for 24 hours for sure). The problems come fast and furious on cloudy days. If it were cloudy all day, (happens often) then not much power is generated. IF no one was there and could turn off the power usage, that would draw down batteries and potentially really harm batteries. (my current battery pack of two large batteries cost a little over $5,000. So needless to say, no ones wants to damage batteries by overdrawing them. I run my normal water pumps (lorentz submersibles) off DC direct. That is, when the sun shines, they run. When it doesn't, they don't. NO batteries, no problems. Run it that way for 20 years. Virtually all of my normal power comes from Solar. WHEN I am there, and need more, sure I can kick on a generator, but I'm only there part time.
As to a SWSG. This I understand, or was led to believe, was a much smaller user of power? Something more in the neighborhood of 70 watts? IF so, then I'm not SO concerned about it's power usage. I suppose I COULD run that directly off my power net. But I've also heard, but yet to talk to anyone that knows, that the normal swcg is actually DC and it is close to 27V. (perfect voltage to run off a panel, so tempting) I'm going to call Hayward or someone else this week and attempt to ascertain that. I suspect that they won't LOVE my just running it directly off DC direct, but I might still do that. So I burn up a cell or two once in a while? The nice thing of running it directly off a dedicated panel is the it would then basically only run when the pump was running. I realize it might not be that simple, and might have to change my mind on that, but I'm pretty convinced that I SHOULD go direct on the pump itself. I'm just trying to figure out WHICH pump I need. As I said before, going with the larger pump will add about $1500 for the extra panels. STILL, even if I have to go to the 900 watt, DC direct seems to be the best option.
I DID originally consider just going with Chlorine and a stenner pump. Maybe that IS the best way, but again, I HAVE energy, and I'm not totally against using it, If it was just running some system that used 100 watts or so, 8 hours a day, that is not a problem. I can't conceive of there being 5 days in a row out here without full charging by the sun ONE of those days. Hope that makes sense?
As to the pump curve. Thanks. Yes, Looking at the JP17, (500 watt) and the JP21, (900 watts) both below.
Again, sorry to post so much back up information, just trying to make it clear.
regards
paul

- - - Updated - - -

Seems that I can't currently get the pdf of the pump curve to post. Let me see if I can get it some other way.

 

[Paulk]

Chuck, couldn't seem to get the PDF to save here, so hopefully taking a picture of it, and I can figure out how to post a picture.

 

[Paulk]

Hopefully the above file can be read Chuck.

 

[bizzle]

One way to address a pump running when clouds are blocking the sun would be to use a photovoltaic sensor or other type of controller to keep the pump from running when it's not sunny enough to generate power for the pump. I read through your posts but I may have missed something because they are more difficult to read than I'm used to due to the formatting, but one thing to keep in mind is that you don't want the salt cell running without the pump so you'll need to configure your system with that limitation in mind.

In my newly installed 3HP Pentair Variable Speed pump, it shows that when it's at 1100 RPMs it's using roughly 167 watts. I think 1500 was close to double that. I don't know if that information can help you, but I'm using somewhere around 4Kw in a 24 hour period of continuously running and even if I had to run it around 1500 RPMs I'd still be under or right around the 9K you're worried about using (and that's running it at an unnecessary 24/7 but I haven't dialed everything in yet).

 

[CJadamec]

Based on the pump curves you should be ok with the JP-17 15/500 pump. It looks like it will do around 40gpm @ 30ft of head. That's what your average run of the mill small pool pump should do. As long as you have a basic system this will be fine. If you plan on adding solar water heater panels at some point this pump might not have enough power. The JP 21 is a much better choice if you think solar water panels are on the horizon.

As for the SWG. The power used by the SWG isn't worth considering when compared to the pump that has to be running for it to work. The main reason I said to go with the liquid chlorine is that you can get away with running your pump for as little as 30 min a day. After 30 min of run time any chemicals you add to the pool should be fully mixed and any additional time you run the pump is really just for skimming the surface.

Bizzle makes a good point if you have an inverter that will put out 110v or 220v AC power @ 60hz. I would recommend a superflo over an intelliflo in your case because you don't need a big pump or have automation. The superflo will also run off either 110v or 220v. These pumps use less wattagea @1100-175000rpm, than your DC powered pump at full speed, and move more water against more head. Case in point I can run my solar heater panels @1900 rpm which uses right around 500watts. I can run my heat pump at 1400rpm which uses 150 watts. Don't let the size of regular pool equipment scare you off, for what you are planning on spending on that DC pump you can probably get an inverter (if you don't already have one) and a superflo pump. Gets parts and servicing your pump down the road will be much cheaper and easier. You have plenty of power available to run one of these pumps if you are considering those DC pumps. With an inverter powered AC pump you will get a lot more pump for your money and it should take less energy to run. Just some food for thought.

 

[Paulk]

Thanks VERY much Bizzle and Chuck. All very good points. Yes, I do have inverters of course, and yes, I have 220 and 110, all 60 hz. I suppose you are right about a PV sensor that might indeed save my system if it is cloudy for too long. Just being off the grid makes one VERY careful about potential energy drains.
Of particular interest were your actual wattage uses on your pumps. Very good to know. I'll have to digest this now a bit, but I think I probably will go with an AC version of a SWCG, obviously a lot easier. As of this point, I'll probably continue to consider going with the DC pump, but I'll have to consider that. I now have enough information thanks to the forum, to make a pretty good decision. All good food for thought. I'll talk to my neighbor who is a solar engineer also. (but not a swimming pool expert)
Bizzel, sorry about the formatting. Old habits die hard perhaps. Again, thanks for the actual figures on a lot of the stuff. This is why the forum is so helpful.

paul

 

[bizzle]

Why do you prefer the DC pump for this application?

One thing to keep in mind is that if you decide to go with an AC SWCG you'll need to figure out how to sync the AC SWCG and DC pump. The SWG isn't supposed to run without the pump running so it seems that the pump and SWG should be wired together.

 

[Paulk]

Thanks Bizzle
I do understand I need to wire the SWCG in such that it is not going without the pump. That can be done, but yep, will need a bit of figuring out. If I couldn't, I guess I'd have to run a different way.
As to why I like DC pumps? DC motors are great motors. They used to be too expensive, but now they are much cheaper. Brushless motors also are even better. AC motors are not bad, (3 phase are great). DC motors are naturally VS, AC motors are not, unless they are 3 phase. I admit my desire to run a PV direct motor is probably somewhat over cautious, given the amounts of power that you two have said is typical, but again, if I run DC direct I have NO worries about my main system, worries that I might mess up batteries. YES, one could go and put in some panels, then put in a dedicated inverter for the pump, but that would definitely mean more panels, more expense. All AC motors have a significant inrush current needed to start them. 5x8 TIMES the operating current. (you can get around that if you are dealing with 3 phase, with a VFD, but we aren't talking that here). DC motors do not have that limitation. So running a DC motor I basically just have to do about a 30% overage and I'm fine. Again, probably just being overly cautious from past experience. Again, thanks so much. I'll come back in a few months and hopefully be able to say it all is working well. Or say I wish I'd done it differently.

pk

 

[CJadamec]

Actually we are talking about a VFD with the modern vs motors. My pump is definitely a soft start VFD it takes about 5 seconds to get up to speed. All of the pentair VS pumps use permanent magnet motors.

As much fun as DC voltage speed control is, Frequency speed control has a ton of advantages.

As for protecting your batteries your inverters should already be doing that job. The inverter should limit any excessive inrush current demands on the battery.

Anywho don't for get to size you wires properly for the low DC voltage you are running at.

 

[Paulk]

I'm not an electrician, but my understanding is, basically all 3 phase motors are variable speed, thru, as you say, varying frequency. Basically single phase AC motors are NOT variable speed. So, not saying that this is what is going on, but if it is a variable speed motor, in general, it is either 3 phase, or it is a DC motor. So with a VFD, yep, you can make that 3 phase motor variable speed. Also 3 phase motors are MUCH simpler in their mechanics than single phase, and last MUCH longer. Lots of DC motors of course have soft start too. I have a pretty good sized wood shop at my ranch and all the larger motors are 3 phase, and yep, soft start and thus the inrush is not so bad. It is interesting how so much of this stuff is changing. Yes, Frequency speed control is great, unless you are trying to do more than about 25% or less of the full speed. Then you get a lot less torque.
Re the protection of batteries, that is what they would like you to think. Yep, the inverters do do a bit of that, but not particularly well. You have to keep an eye on it.
Yep, DC you have to have much larger wires for supply, DC is not really great to move long distance. Again, thanks Chuck. I am still thinking it over. We'll see. At least now I have a bit more knowledge about the actual demand on the pump.

best
paul

 

[CJadamec]

Your assumptions on 3 phase motors is a little bit off. Every AC motor is variable speed with a frequency drive. AC motor speed for any AC motor is directly linked to the frequency of the AC power it is supplied with. The basic construction and principles of operation are the same with in both single and 3phase motors. Single phase motors can suffer from a lack of starting torque which is often overcome with the addition of a starting capacitor. There is nothing to support your statement that single phase motors are more complicated than 3 phase. If anything the opposite is true, because 3ph motors have triple the number of windings in them.

The problem up until the last 2 decades or so is the technology needed to make a VFD drive was very expensive and large. As with all things technology based VFD drives have gotten smaller, cheaper, and better performing.

I don't really follow your torque argument. If the drive and motor are designed for it you can get full torque from the motor all the way down to zero speed. I can show you a lot of AC powered cranes to prove my point going back to the 70's.

That's not really the point tho. The concerns you are expressing about speed control and AC motors just aren't existent anymore with the equipment that is available today.

So as for your batteries you have not only the first set of inverters controlling current you also have a second line inverter in the VFD drive controlling current to the pump motor. Assuming you have sized your battery bank and primary inverter correctly the amount of shock loading the batteries experience should be next to none. In reality the direct DC motor you are planning on getting will probably have a higher and more abrupt starting current than a VFD driven soft start AC motor.

I'm not saying I'm against the idea of the DC pumps you are looking at, I just don't see them as the best fit for your situation. Where you are located and the equipment you already have makes for a much stronger argument to not re-invent the wheel so to speak. An off the shelf easy to get AC powered pump with a huge dealer network and parts availability for decades to come is a huge plus next to a pump that is only available on the internet and the primary consumers of it are in other countries. On top of all that a superflo VS is a, less expensive and better performing pump, that uses less energy at low rpms than the DC pumps you are looking at.

 

[Paulk]

Thanks for taking the time to give me a long answer. Interesting, I am on another woodworking forum and there are lots of electrical engineers on that forum and while I may well be misunderstanding, I did not know that single phase motors were able to be variable speed with such a drive. Perhaps so. I'll try to check that out. Yes, VFD's are a lot less expensive than they used to be, certainly for smaller say 3 hp and less they are inexpensive now. What you say makes a fair amount of sense about repairability even though it seems that a lot of the pool manufacturers are not particularly trying to make great equipment, more just inexpensive equipment, (but that is generally what the market demands)
As to the torque, perhaps I'm not using the right terminology. But for sure my experience and the EE guys, (a few of them are professors of EE) say that you can't take a motor down, say you are working with a lathe, take the speed down to 1/4, I think that you go to 15 HZ, then you might well get the speed, BUT you get no power, that is, you can stop the rotation with your hand easily. I've done exactly that and yep, can't use it to turn a bowl anymore.
But not arguing that, I'm not an expert at that. My actual field was hi tech materials for outdoor equipment and clothing, pretty far from the present topic.
again, thanks.
paul

 

[CJadamec]

Keep in mind I'm talking about industrial equipment that a small wood working shop isn't going to have hanging around. An AC drive system like that is till an expensive item to develop torque like that at low speeds. In reality these types of drive systems stop being AC systems at low speed. That's because AC power becomes DC power when you remove the frequency. So with the right equipment you can blur the traditional lines. They may be EE's but the world or motors and technology is very wide and ever changing. I can say for certain that in my experience these drive and motor systems are out there. I work on them every day.

As for single phase being single speed it goes down to the fundamentals of how they work. AC motor speed as I have said is governed by the frequency of the AC power. A 60Hz motor will spin slower when connected to 50Hz power.

That's the fundamental principle behind VFD's (variable frequency drives). A VFD basically works like this. It takes incoming AC power and rectifies it to DC power at the same incoming voltage. It then takes the DC power and inverts it back to AC power but the inverter is capable of controlling the Frequency of the output power to the motor. It doesn't matter how many phases are in the motor it has no choice but to respond to the frequency changes but changing speed. There is more that goes into it but that's the basics.

In the world of water pumps though it really doesn't matter. You need virtually zero torque to spin the impeller of a centrifugal water pump. Max torque on the motor in a water pump is going to develop at the point you hit both peak pressure and flow in the system. In a water system that is nowhere near the bottom end of the motor speed.

As for what the pool equipment people are making for the top brands I would have to say I disagree with you statement that they aren't trying to make great equipment. My pump is built solidly and has worked flawlessly since I took it out of the box. I've seen cheap tools and equipment and had the opportunity to work with a huge range of quality. I can say with out a doubt that the pump I own was built to last for a long time with a tremendous attention to design and detail. You get what you pay for with equipment. If you buy cheap you will get cheap. If you don't do your homework somebody is going to sell you something cheap for the price of something good.