Another VS Pump purchase question - current pump just broke

[kcautodoc]

Hey all, I was servicing my old 1.5HP Pentair Ultra Flow pump this morning and the impeller broke. I also noticed the ground on the motor needed some parts to secure it better and then the gasket kit. I'm looking at $100 to $150 in money and I don't know how many hours of time to get this thing running again and then I still have a Watt guzzling pump running. I am now thinking about a VS pump and then see that the big recommendation is a 2 speed pump. I'd like a recommendation. I'm also confused about TDH. The VS pump data sheets show flow on the TDH vs GPM at certain RPM but it seems like at the lower speeds you would have zero flow if your TDH is over 20 or 30. The heater and sand filter require 55gpm and I have no idea what my TDH is but I'm guessing between 50-60. kWh cost is 0.10633 cents and I'm running the pump about 10 hr a day currently.

What size pump should I get?

Any Pump recommendations? I'm considering one of the Haywards or Pentairs (either Whisper or a VS)

Is the realized cost savings really that noticable?

I'm pretty upset about this whole ordeal since the pool is looking great and I've been SLAMing it for a while and now I'm going to be stagnate until this is fixed. Uggh!!! It's never ending.

Thanks,
Richard

Pool Description

20'x40' - 25,000 gal Gunite with 600 gal Spa
Output - Three 1.5" Lines to 3 Pool Jets, 1 Spa Jet, Spa Fountain Water Feature
Nirvana E140 - Requires 55gpm flow
Sand Filter - Requires 60gpm flow
Current pump is 1.5HP Pentair Ultra Flow
Chlorine Pump
BBB method
Partial Sun in North Florida with a Failing enclosure and too many pine trees around.

 

[mas985]

TDH is not a constant it is proportional to the square of the flow rate and the flow rate is directly proportional to the pump RPM. So when you 1/2 the speed, flow rate drops by 1/2 and TDH goes down by a factor of 1/4. There is an Intelliflo Curve in the link in my signature (Hydraulics 101) that shows how the head curve changes with RPM.

60 GPM for the sand filter is an upper limit not a lower limit. Slower is always better for filters.

As for the heater, the 55 GPM seems high. Most are usually lower than that so I would double check that. But in most cases, you will want to run the heater on high anyway. Do you heat the pool with the heater or just the spa?

This reference says 42-80 GPM which is reasonable for a heater: http://nirvanahp.com/wp-content/uploads/2012/04/NirvanaHP_TechnicalData.pdf

Do have only one pump that runs both the spa jets and the pool? If so, then you want the same size pump you have now just in a two speed version. If you like Pentair, the WFDS-6 or WFDS-28 would be a good choice.

I just noticed in your sig that is says 1 Spa Jet. Just one jet or did you mean one line to multiple jets?

 

[kcautodoc]

Thanks for the quick response. There is only one pump for both the spa and pool. The 55 was from the nirvana website but the flow indicator on the heat pump does have a range that bottoms out at 5psi. That 55 may be the middle of the flow range rather than the minimum but I will need to confirm that. The spa has one outlet from the pump that runs one jet in the spa, the pump has a second outlet that runs a water feature into the spa but is not used all that often. The spa can flow over into the pool but I try to keep this at a minimum because I am already adding acid on a regular basis and want to eliminate excessive aeration. The heater heats both the spa and pool. When we want to use the spa we close the pool valves to go directly to and from the spa and heat it to 100.

I hope I answered your questions.

- - - Updated - - -

I have no allegiance to Pentair and wouldn't mind a Haywood recommendation as well. It appears you are recommending a 2 speed vs a variable speed. Is that correct? If the 2 speed and VS were the same price would your recommendation be the same?

 

[kcautodoc]

Also, I guess I should add about the spa. There is a second pump, but it only runs the air jets and does not pump water through the heater or filter.

 

[mas985]

The second "pump" sounds like a blower, not a pump. Is it up higher at the end of the air vent pipe and looks kind of like this?

But being in Florida, I would avoid a VS for a couple of reasons. First, the electricity costs generally are not that high to warrant a VS. Second, FL gets a lot of lightning so you will definitely require a surge/lightning protection on the power system which can add quite a bit of cost. So for both these reasons, the economics of a VS just don't make sense. However, some people don't care about economics and are more interested in having the flexibility of a VS.

Also given you have only one spa jet, you can probably get away with a much smaller pump too if you want. For Pentair, a WFDS-3 or WFDS-24 would be sufficient. For Hayward, a TriStar SP32102EE or SP3210X152. Unfortunately, Hayward doesn't make a 3/4 FRHP two speed (TriStar) like Pentair does. So the Whisperflo will use a little less power than the TriStar because of this.

There are a couple smaller pumps that would work well too:

Pentair SuperFlo SF-N2-1A
Hayward MaxFlo XL SP2307X102 (Best efficiency out of all the pumps)

 

[kcautodoc]

I figured I'd just post a few pics. I do think that the spa "blower" is a pump and may be a temporary fix for me. Here is the setup. Non working pump on the left , disassembled. And, working "blower" pump on the right. The blower side sucks air from two vents at the spa deck and circulates it all the way around to the spa. The two intakes in the front are the skimmer and spa, in the back are the pool cleaner and main drain. Outputs to the spa and water feature in the front and to the pool in the rear.
View attachment 33538

The spa has five outlets, one jet for water and four air outlets from pump two (the almond one). You can also see the water feature in the center of the spa. The jet on the stair is for water and the two on the right and two more not seen are for air.
View attachment 33540

When you mention the "flexibility of a VS" what do you mean?

Here is the pool area. The pool equipment is on the far side of the picture around the corner. The electricity here is .106 per kWh so I don't know how that is high, low or average.
(whoops - exceeded my quota - I'll try to edit the pic a bit)


Do you still think the 3/4HP is enough?

Thanks,
Richard

- - - Updated - - -

View attachment 33541

 

[mas985]

The second pump is not a blower pump, it is another water pump that is used to drive the spa jets shown in the picture above. The way this works is water travels through a venturi tee which creates a partial vacuum and sucks in air which then mixes with the water. Both water and air then exit the jet and creates a pulsating water stream.

This is why I had the original question on the number of jets. It would be very unusual to have only one spa jet. But from the picture, I can tell you have multiple spa jets. Each of those outlets is a separate spa jet. My guess is that what you are calling a spa jet is actually just a normal return used for filtering and heating while the other outlets above the seats are the actual spa jets.

So basically you have a filter pump AND a spa jet pump.

This might help to understand how a spa jet works.

 

[kcautodoc]

I think that's exactly the case. So, now that you have a more clear picture of the setup do you think the 3/4hp is sufficient or should I go with the 1hp? Would you recommend any plumbing changes? And is there a post that explains the 'flexibility of the VS"?

Thanks for all the help. I'm a newbie for a reason.

Richard

 

[mas985]

There is no reason for a large pump so these should be more than enough pump for just filtering:

Pentair SuperFlo SF-N2-1A (~56 GPM high speed)
Hayward MaxFlo XL SP2307X102 (~51 GPM high speed)

Also, don't be fooled by pump label HP. It only has a loose relationship to flow rates and "power". I size pumps based upon flow rates, not HP ratings.

The flexibility of a VS is useful only when you have multiple high flow rate requirements (e.g. waterfall, slides, solar, spa, etc) run off a single pump. But in your case, the broken pump has only one job, filtering so only the smallest pump is required.

 

[kcautodoc]

Had a question about model numbers. I'm looking at the Pentair now. It seems like there are two different models numbers for the same unit. SF-N2-1A can be model number 340042 (on pentair website) and 346242 on most retail websites. Are these the same pump? I PM'd you with links since I'm not certain what the rules are for posting them.

 

[mas985]

340042 is the correct part# and I think the other part # is without unions but you should probably check with the seller.

 

[kcautodoc]

Purchased and installed. Gives just enough flow for the heat pump at high speed. Thanks for the help.

 

[timerguy]

Let's see what it looks like now!