There are commercially available units which use an VFD inverter to vary the speed of your pool pump, and although they provide great savings, being a DIY-er i wanted to have a go on my own, and try and simplify the whole unit.
I highly recommend checking out the commercial product from FUTURE WAVE, which can be purchased and applied to almost any pool pump for a large saving. www.futurewave.net.au/
The parts list for this project is quite simple:
1 x VFD with built in Programmable controller
1 x 1m power lead
If you get the exact unit i got, you can use the settings included here.
Step 1: Wiring and Programming
Firstly source your VFD.
I purchased this one from EBAY for a very reasonable price, high quality, good waranty.
Just search for VARIABLE FREQUENCY DRIVE INVERTER VFD 2HP 1.5KW
When it arrives, undo the packaging.and read the instructions to find the best method to hook up. I intended to install this for my parents, so i wanted to make it as simple to use as possible. I decided to use the inbuilt PLC operation to cycle through the modes, so there was nothing for them to adjust.
Connect up your power to the input terminals. Use an electrician to to this, mains wiring is dangerous! I used an extension cord, chopped in half, so i could plug the male end in where the pump was connected, and plug the pump into the female end. This will be different if you have a hard wired pump.
The first thing is to make the VFD start when it gets power ( as standard, they wait for a start signal ).
With this inverter you need to change
PD001, SOURCE OF RUN COMMAND, to 1 ( External ) and
PD044, Function for FOR input, to Run ( default is Forward direction, not used unless you also use reverse ),
Then bridge the FO R terminal to the D CM terminal ( as though you are continuously holding the run button ).
Thats the control wiring sorted
Other internal control changes:
PD007 change to 50 hz for MAIN speed, This is the default frequency that the inverter starts at ( we use 50 hz power in Australia )
PD080 change to 1 for 16 internal speed control
PD081 change to 1 for cycling run ( it cycles through the speeds you set and starts again when it gets to the end )
PD084 change to 3 sec ( ramp time when changing speeds )
PD086 change to 35hz ( our set SLOW SPEED. you can go slower if your pool still allows leaves to go back to the pickup )
PD101 change to 240 sec ( 4 minutes ). This is the time it runs at the MAIN speed
PD101 change to 6300 sec ( 1 hour 45 minutes ). This is the time running at SLOW SPEED. Maximum setting is 6500 sec
There are usually settings that need to be specified based on the exact motor you have. They are usually read off the metal plate on the motor.
The cycle with the above setup is:
Power on, ramp up to 50 hz, run at 50hz for 4 minutes, ramp down to 35 hz, run at 35 hz for 1 hour 45 minutes, ramp up to 50 hz, run at 50hz for 4 minutes.....etc
If power is interrupted, the cycle starts at the beginning again.
Step 2: Results of Operation $$$$$ SAVING!
I was surprised at the reduction in output current that resulted from running at 35hz.
Motor plugged into the wall 4.6 amps
Motor power at 35Hz 1.5 amps !!!!
Motor and inverter plugged into the wall 6.6 amps ( holy crap this inverter is wasting heaps of power )
Motor and inverter plugged in running at 35Hz, 3.5 amps
So the inverter is using an additional 2 amps! im a bit disappointed by this, and im going to look into why this is happening.
It could be that this inverter although is specified to run from single phase or 3 phase, is simply not efficient when running on single phase.
Never the less, it is still using much less power than it was, and this 1 amp, or 240 watts adds up.
at 20c / kWh, with the pump running 10hrs per day, its 50c/day saving. All up the inverter cost $120, so will pay back in 8 months
After 2 years the saving is $230.
Importantly, if i can work out why the damn inverter is wasting a couple of amps and prevent it, it will save 3 amps, or 750 watts. this means the savings are more than $500 per year and the payback is 3 months!
Either way it was an interesting experience!