12.5 cents per day
 

Yep, with my new settings on the VFD pool pump we're down to 12.5 cents per day.

1000 RPM for 16.5 hours @ 54 Watts = .891 kWh
2400 RPM for 2.5 hours @ 350 Watts = .875 kwh
1.766 kWh @ $0.071/kwh = $0.125 per day

Taking into account rounding, I'm down to $46 per year for the stupid pool pump. Before, I was running a 1hp pump 14 hours a day

1 hp with a 1.86 SF = 1379.5 Watts
@ 14 hours per day = 19.3 kwh/day = $1.37/day or $500 per year

Now if only I could do something about the pool cleaner boost pump, which uses 1035 Watts for 2 hours a day...

Need to swap our main pump for a VFD.

In other pool related news, the water temperature hit 93F...

With the solar cover on, ours hit 90 degrees.....a little warmer than I like it, but allows midnight skinnydips with the wife, so it's all good !

Yeah? With whose wife?

Yours of coarse !

Ha!

Guy walks into the bar. Sees an age-appropriate hottie all alone...

My pool hit 80* today....felt like a sauna.

There are concerns about VFDs now starting to come to light that deal with eddy current creation in motor bearings and other components. This probably isn't a huge deal for a residential pool pump and the fixes are supposedly relatively straightforward (grounding rings, non-conductive bearings, things like that) but in some applications it can be a huge deal. I'm running into this now involving exhaust AHU fans serving a critical lab building.

VFDs are generally a good technology but there are quirks related to using them that aren't readily obvious or fully understood by many engineers (ask your EE if he or she has reviewed or commissioned a harmonics study for whatever facility they intend to install them in before doing so - if they look at you like you have three heads, run away). Also make sure that any pumps and motors are specifically rated as VFD compatible so you can get a warranty later if there's an issue and not end up potentially buying them twice.

Ahh, the joys of new high-tech stuff in buildings...

When working for a large manufacturer of centrifugal water chillers there were problems with the rotor discharging a stored electrical charge through the steel ball bearings to the bearing race on the back end of the motor on VFD machines. Eventually the bearings would degrade and start to rumble.

The fix was to remove the defective bearings at the back end and install ceramic bearing sets. Also the back bearing cover plate was re designed to allow the installation of a grounding brush on the end of the motor shaft. Was kind of crude but it worked.

Most motors that are installed for VSD/VFD are designed for the purpose. Not that it prevents all failures.

VFD's cause all sorts of nasty harmonics. I think they are a plague on mankind. I've had to have power companies re-route electrical feeders to some of the facilities I have done work at to get away from harmonics caused by other facilities that have a,bunch of these lousy things and screw up the power grid for everybody.

JR

Hey Redbeard,

At 1,000 rpm, how many HP is the motor making? And how much at 2,400 rpm?

Thank you very much!

I need to hire an egghead electrician to do the math on our refrigeration equipment. But if it messes up my WiFi I get to kick him in the nuts, right?

sooo confused!!!

I wanted a new "intelligent" pool pump and figured I might save $100 per month. I understood it to be variable speed. I have a very large pool, and lo and behold before I got around to pulling the trigger on an upgrade my 2hp pump seized up and died.

So, I was no longer worried about payback periods etc. Installed it was approx $1800, and I think I got a rebate from Edison.

That was two trouble free years ago. Not sure if this is what a VFD is, but it's been a no brainer.

And by my calcs I did save about $100 per month.

I replaced our pool pump with a variable speed (Pentair IntelliFlow) model and saw a minimal savings in my power bill. I didn't run numbers prior but I do know that I'm getting raked over the coals on electricity costs - $.25645 kWh. Ran some AC last month and I'm at $500/month for a small 3bd/2ba home. Yep I also have insulation issues that I am still working on too. Sorry for hijack.

Wow, you are getting raked. In AZ our cost is about .1341

Why aren't pool pumps directly hooked up to a set of solar panels? Seems to make sense, you have to run them most in the sunny time of the year.

I don't miss having a pool one bit. It was a great experience for everyone involved. I can buy a hell of a family health club membership, including competition pool access, for just the electricity and water bill I used to have.

G

Red - great study!

Take a look at this. I used to do energy use surveys and here is how I calculated it. Was this OK?


Record Amps:
For 3 Phase 460 or 480 Volt, Average Brown, Orange, Yellow Legs
For 3 Phase 208 or 230 Volt, Average Black, Red, Blue Legs

What are the Volts: (Typically 3 Phase, 460)

Determine the Power Correction Factor.
Unless a Power Factor is determined, a value between 0.85 (older or larger motors >2hp) and 0.91 (newer or smaller motors <2hp) is acceptable.

Calculate kVA in Order to Determine
kWatt Usage:
kVA = Volts X (Averaged Amps X 1.732) / 1000

Convert kVA to kWatt
kWatt = kVA X Power Correction Factor

Annual Hours of Operation for Motor
Daily Hrs X Days per Wk X Wks per Yr
(8 hour shift, 5 days/wk, 50 wk's/yr = 2000 hours)
(24 hour shift, 7 days/wk, 52 wk's/yr = 8736 hours)

kWatt Hour Rate
National Average is $0.06 kW-hr

Calculated Annual
Energy Costs
(kWatt X Hours of Operation X kWatt $Rate)

Not sure where you are in So Cal, but in San Diego, the new two tier rates are outrageous!

Up to 384 kWh, $0.19, beyond 384 kWh, $0.395, so I expect your savings are about right.

A 2hp Ecostar Pump can be bought for just under $1000. If you had a pool company install it, I would suspect your pricing is about right.

We actually threw 6 bags of ice in the 96 degree pool to cool it down a bit last month.....melted in about three minutes. Probably got it down to 95.5!