Pool pumps suck...

Re: Pool pumps suck...

I have an Pentair pump as well, These are VFD based pumps and do operated at less wattage than the older 2HP counterparts. The flow rates are acceptable. I have mine only running about 4 hours a day and is adequate to floor clean the pool with some light brushing occasionally. The real key to these would be to have the programmable controller installed so the pump can run full force for a short period of time to do skimming and in floor cleaning and then set back to low flow mode for filtering and stirring for a longer period.

In the hot AZ sun and water temps in the 90's, stirring is critical to keep an algae bloom from occurring. While I don't have a salt water system, the length of pump run is directly proportional to that sanitizing systems effectiveness, this would be ideal for the low flow mode of these pumps. I have found that a one step oversize from the manufacturers recommendation diatomaceous earth (DE) filter system is superior to any other method of filtration. It lowers the pumps filter resistance. It is then pretty clear when a backwash of the filter is needed just from the sound of the pump motor straining. It also scrubs the water to a crystal clear consistency.

On my previous 2HP pump with a sand filter I struggled all summer with the pool to keep in nice, while having to use large doses of chlorine to hold the algae at bay. It got to the point of several 24 hour runs per season with large does of shock. I have not had to do that once this season since the change out.

Re: Pool pumps suck...

Solar Guppy wrote: »

... The VFD units do use less energy, but its because they pump less water.

Another option that is half the cost is a 2-speed motor, run at low-speed for filtering, high speed when your running the pool vacuum or other accessories

...The VFD are nice, but one can get the same savings by just using an appropriately sized pump for 1/4 the cost

I just went through this exercise for my pool.

My single speed 2.2 THP filter pump motor stopped working due to old age. It was pumping at about 70 gpm at 3450 rpm at about 1900 Watts. I was running it 6 hrs/day, resulting in turning over about 85% of the 30 Kgal (the size of my pool) each day. Total annual kWh was thus about 4200. At 12¢/kWh, that's $500 annual operating cost.

Knowing that with a 2 speed motor, running at 1/2 the speed I was running at, for twice as long as I was running, this would result in filtering the same amount of water each day, but at 1/4 the energy (kWh), I purchased an AO Smith E-Plus Premium Efficiency 2 speed motor. The 2.2 THP model is B2983. Lo speed is spec'd at 0.28 THP.

Now I'm running the existing filter pump's new motor in Lo speed, which is half speed, 1725 rpm, giving me about 35 gpm. Lo speed runs at 330 Watts. I've doubled the time the pump runs in order to filter the same amount of water, to 12 hours. New daily energy cost is about 4 kWh/day, which is about 1450 kWh annually. At 12¢, that's a new operating cost of about $170 to filter the same amount of water.

Net savings is about $330 annually.

Thinking that I needed to wait until my single speed pump broke before replacing it with a 2 speed pump in order to make the pay back reasonable, that's what I did. I now see that if the pump itself is in fine shape, the economics of 2 speed motors are so compelling I could have outright replaced a perfectly working single speed motor and still have a payback period of about 1.2 years ($400 / $330). Wish I hadn't waited.

Parenthetically, I did look at VFD technology pumps. And indeed their efficiency is even better (about 30% more efficient than induction motors). But the cost, at least here in Dallas, for VFD pumps is very high ($900+, not including installation). My electric rate just isn't high enough to make the investment worthwhile.

Best regards,

Bill

Re: Pool pumps suck...

BB. wrote: »

... energy savings with the VFD is the use of Permanent Magnet Motors (typically synchronous) vs Induction Motors (probably accounts for the extra costs too).

The VFD technology motors are 30% more efficient than induction due in part to 3 things: permanent magnet generated field, optimized power frequency as a function of rpm, and construction efficiency techniques also used in induction motors advertised as 'hi efficiency.'

The economics for VFD motors improves if you can replace more than one single speed motor with a VFD motor. I.e the VFD motor serves as the filter motor, the spa motor, the waterfall motor, etc. Unlike a 2 speed motor, the VFD can be set to many different speed settings to serve whatever function is needed.

The expense of a VFD pool pump also comes from the marketing strategy (Pentair in particular) of including a control/timer system as part of the pump. This way you don't have to spend more money to install an automation controller for the various functions you want the VFD pump to do (i.e., setting up a schedule for different speeds for filtering, cleaning, waterfall action, etc.) can all be done with the electronics on the VFD pump). The marketing strategy is make it so it's just one purchase - the pump - that can universally be dropped in without other (equipment) expense.

In actuality, when you purchase a VFD pump (particularly Pentair), more than likely you're in essence purchasing a control (timer) system too. If you already have a controller (i.e. Jandy's AquaLink), then you're purchasing duplicate capability with the motor. There are exceptions to this strategy (i.e. VFD motors with external, 'hanging-on-the-wall' electronics). But for the most part, if you just walk into a retail pool store, what's offered for VFD pumps is units with the control (timer) capability included.

The advertising for VFD pumps is pretty slick. Often the baseline compared to is running the old single speed motor 24 hr/ day, and thus cutting the time down to just one turnover of water, with the efficiency of a VFD, makes for "$1000 or more savings each year."

Interesting also, if you just casually walk into big name pool retail outlets, odds are excellent they won't have 2-speed motors 'in stock' (you can order them though). In stock inventory is limited to single and VFD motors. The reason there's no 2-speeds in stock is you need further investment for a control system (generally). It's interesting to note that the common pool owner doesn't have a control system. Or at least there's not enough owners with a control system to warrant stocking 2 speed motors.

Probably the biggest 'rap' against VFD pumps, other than cost, is warranty. Most offer just a 1 year warranty, standard like the single speed units. The big name VFD pumps, like Pentair, also don't make any piece part replaceable. If something goes wrong with the built in timer / controller, you have to replace the whole motor portion of the pump. At retail in particular, not inexpensive.

I think there's little debate that VFD pumps are impressive for their versatility and for the operating cost. But unless your kWh cost is 20¢ or more, you're going to need the VFD pump purchase to hold up for a number of years to just break even.

Best regards,

Bill

Re: Pool pumps suck...

a0128958,
i believe one of the other moderators merged bmet's question to this thread on pools.

bmet,
i wouldn't use too much of it if at all for it is corrosive. just like chlorine it'll turn your hair lighter and not 1 hair at a time either.:roll:

Re: question on types of chemicals

There is also a salt-based chlorination system you could look into. From what I've read most of the salt is removed before the flow re-enters the pool so its not like swimming in the sea. Chlorine products are still produced by the system, but not the type that irritates eyes and has a strong chlorine smell.

http://en.wikipedia.org/wiki/Salt_water_chlorination