Variable-speed pump

[dalehileman]

The following link discloses persuasive evidence that slower circulation can radically cut power usage. Though the slower pump has to stay on longer, overall power drain is disproportionally reduced, as much as 90%. As the price of electricity creeps up, living on a fixed income I find the prospect appealing

http://www.youtube.com/watch?v=4dIz4R-1d2k

Thus a good and dear friend, an aerospace engineer who probably understands these matters better than I, strongly urges me to switch over. However several concerns arise which I'm hoping TFP can address:

1. I depend upon surface flow to slowly convey flotsam to the skimmer port. Would a slower pump not impede this action, requiring inordinate bouts of manual scooping

2. More critical, in an above-ground station my Polaris booster is connected at the output of the filter. Whether or not it is capable of self-priming I'm not sure, but I hesitate to experiment because if it sucks air it could self-destruct. Therefore I assume that pump speed would have to be adjusted to maintain at least a slight positive pressure at this juncture. So I am wondering if this consideration might not diminish any hoped saving of energy

3. Less critical but nonetheless a concern: For chlorination I depend on chlor-tabs tossed into the deep end but because recirculation takes place principally at the surface, wouldn't slower pumping concentrate FC at the bottom

Of course my Polaris does stir up the deep end but I am wondering if any bottom-to-top circulation it might provide would prove adequate

I hasten to explain about my controversial practice with the tabs. A high FC concentration near the surface drastically shortens the life of my solar cover, an important factor living on a fixed income so if I can prolong its life by just one season, in the time I hope to live I might save as much as $20,000 even discounting inflation. Of course the high concentration around a tab might eventually damage the fiberglass finish but I am depending on an occasional nudge by the Polaris to minimize the eventuality

Thank you guys for all your past and future help

 

[JasonLion]

Yes, variable speed pumps can save a lot of money. While savings of over 90% are possible in some cases, savings closer to 50% are much more common. Keep in mind that you need to balance out these saving against the increased up front cost of a variable speed pump. Depending on your electric rates, there may or may not be a net savings. Where I am, with electricity going for around $0.11/kwh, a variable speed pump is unlikely to ever payback the initial investment.

1) Skimmers sometimes work alright even at low flow rates, and sometimes they don't. If you are having problems with skimming the best thing is to turn up the pump speed for 15 minutes two or three times a day.

2) The main pump must be running when the booster pump is in use. Running the main pump on a very low speed is fine when the booster pump on.

3) Do you have a main drain? If so that will take care of maintaining good circulation. Likewise, if the Polaris is run every day, it will be sufficient to maintain circulation. If neither of those apply, you can again use short periods at a higher speed combined with a return pointing down to the bottom of the deep end, to keep the deep water circulating.

By the by, tossing trichlor tablets directly into the pool is a terrible idea. Long term that will damage the pool surface and cost far more to repair than an extra solar cover or two.

 

[dalehileman]

".....with electricity going for around $0.11/kwh, a variable speed pump is unlikely to ever payback the initial investment."

Here in Victor Valley, Ca my usage would probably fall into tier 3 or 4 where the rate is about two bits the kwh. Still I'm reluctant to proceed

"....with skimming the best thing is to turn up the pump speed for 15 minutes two or three times a day."

Thank you for that suggestion, somewhat of a surprise as I had assumed that changing speed would necessitate rewiring

"Running the main pump on a very low speed is fine when the booster pump on."

That's reassuring as I would have assumed a negative pressure at the input of the booster might somehow risk sucking in air

"Do you have a main drain? If so that will take care of maintaining good circulation."

Aha, thanks again, so that fixture at the bottom has a real function after all

"By the by, tossing trichlor tablets directly into the pool is a terrible idea."

Yes so I've been advised. Entrepreneurs attention, there's an obvious market for a tabs dispenser for instance that would sit at the deep end but would hold them a few inches from the bottom

Thank you once more Jason. Eager to hear from others with practical experience in these realms

 

[mas985]

I think Jason covered pretty much covered everything but recently I went through the same decision process as you. I am in CA with fairly high electrical rates and was running a 1 HP Northstar pump. I did a detailed cost benefit analysis and soon came to realize that since the Intelliflo had a fairly high up front cost for me due to interfacing with my controller, it would take close to 10 years before it was more cost effective than a 2 speed pump. Not only that, I was able to modify my 1 HP Northstar with a new impeller and motor and created a 1/2 HP 2 speed pump for about $130 (motor was off Craig's list) so this seemed like a no brainer to me. I may eventually go with a variable speed pump as they come down in cost and/or if I ever need to replace my controller because I think their main advantage is flexibility in optimizing energy savings and performance.

Anyway, in my sig, there is a link to a pool pump cost comparison thread & spreadsheet which allows you to directly compare the life costs of several pumps. You can enter the energy costs and the costs of the pumps plus run times for two different speeds. Scenario 2 is probably closest to your situation but you can modify any of them to suite your needs.

 

[GrumpyDave]

Entrepreneurs attention, there's an obvious market for a tabs dispenser for instance that would sit at the deep end but would hold them a few inches from the bottom

Here ya go...

http://safensavepoolchemist.com/SunkenTreasure.html

 

[dalehileman]

mas, thank you for that link, clearly the cost comparisons are far beyond my earthly comprehension. You are to be congratulated for your determination

Dave thank you also. To think it took the Pool Establishment only 200 years to come up with this obvious approach to dispensing the tabs

 

[dalehileman]

Jason, afterthought:

"Running the main pump on a very low speed is fine when the booster pump on."

I assume then that any variable-speed pump at its lowest setting is capable of delivering at the output of even a fully-engorged sand filter a flow rate greater than that of a Polaris booster. Am I correct

 

[JasonLion]

Yes, a booster pump is a very low flow, high pressure, pump. Even a variable speed on it's slowest speed will still move more than enough water for the booster pump to work with.

 

[dalehileman]

Thank you once again Jason, another hurdle behind

So far one major drawback tending to discourage me is the possibility that a slower flow rate might require repeated daily manual scooping of flotsam

Still eager to hear from others having had actual experience in these matters

But meanwhile has anyone put to use a Sunken Treasure tab

Thanks again all

 

[ride525]

I haven't used the Sunken Treasure dispenser.

But the claims on the website make it sound pretty good. No chlorinators floating on the surface. And they claim one tab in their dispenser at the bottom would equal about five tabs in a floater. Think most folks with larger pools would order the two pak.

Jeff

 

[ride525]

Oh, and I just installed a VF pump two days ago. Even at the most optimal (for my pool system) flow rate of 23 GPM, there still is significant flow at the skimmer. I have solar cover on pool most of the time, so will inhibit surface flow, but the cover keeps a lot of leaves and dirt out.

Jeff

 

[dalehileman]

Ride thank you for that report. Out here in the Mojave Desert in the summertime we have to uncover the pool early in the morning else it overheats and so I am grateful for a significant surface current to carry flotsam into the skimmer

Please report later on the effect of the VF on your electric bill

 

[ride525]

I had a 1 hp pump, that I ran about 5 - 6 hours a day. So, less than one turnover for my pool (I guess about 2/3 of a turnover) . And it was using 1.6 kw. I estimated my power costs to be about $600 annually with that pump, and hours. My calculations are complicated a bit since I have PG&E with five tiers of rates.

It looks like the Intelliflo VF runs optimally on my pool at about 23 GPM. At about 0.25 kw, and 14 hours, I figure the annual cost for me to be about $100 with the VF. And the amount of water turned over should be higher with the VF in my calculations. I can cut this back some if I want, just making the pool size slightly smaller, and I can keep the same flows by cutting back the hours.

Jeff

 

[dalehileman]

Ride thank you again for those details. It would seem then that at least in your case the VF will pay for itself in a short time. Also am I right in guessing that you did all the work yourself as that factor might figure into the decision

 

[ride525]

Yes, I installed the pump myself.

I found it cheapest at Amazon, actually a reseller called Pool Supply Warehouse. Second order from them, first was a set of DE grids, which I received the next day. VF pool pump arrived pretty fast also, considering it came over 4th of July weekend.

Jeff

 

[dalehileman]

Again ride thank you for that excellent tip

What's a DE grid

 

[ride525]

DE grid is Diatomaceous Earth filter grid. Mine, and many others DE filters, have set of eight grids.

Oh, and many utility companies are giving rebates for variable speed pumps. Some, like the VS, may require a separate controller. The Intelliflo VS3050+SVRS and my Intelliflo VF do not require a separate controller. The rebate for me here in northern California is $100.

One final thing. My pool has simple requirements. No solar. No spa. No cleaner booster pumps. No water features. It just has an old Hayward Pool Vac, which seems to work fine on the skimmer suction line, even at the low 23 GPM setting. Not surprisingly, the Pool Vac, when connected, adds to the flow requirements, and the pump needs to work harder, it uses about 400 kw to keep the flow at 23 GPM when the Pool Vac is connectecd with 40+ feet of hose.

Jeff

 

[dalehileman]

jeff thank you again for your input. Wonder if you have noticed after installation of the VF whether flotsam is more likely to collect, requiring more frequent manual skimming

 

[ride525]

I have a solar cover on most of the time, so haven't noticed about additional skimming.

Jeff

 

[dalehileman]

Jeff I see, so you had mentioned.

I note you might consider the Sunken Treasure Cl dispenser but i am wondering if you had been using a surface dispenser whether you might have experienced fast deterioration of your solar cover as I did. With your lower flow rate I would imagine the problem would be exacerbated by a higher Cl concentration in that area