There is a lot of anecdotal evidence for the failure rates of any pump. It is just big unknown which is why I started
this thread just to see if conventional wisdom was true.
Also, you can get an
Intelliflo VS (011018) for less than $900 and it has most of the features of the VF including timers which is all you need really.
One thing that can help is a cost benefit analysis to determine exactly when payback will occur. If it is less than the typical life of a pump, then it is all gravy after that.
So if I assume the following:
17k pool
0.5 turns/day in winter
1.5 turns/day in summer
1 turn average per year
25% on high speed
75% on low speed
Assume the same flow rate and run time for both pumps (sub optimal for the Intelliflo)
Average electrical cost of $0.30/kwh
Whisperflo WFDS-24 cost of $550
Intelliflo VS cost of $90 - $100 rebate = $800
Here is the lifetime costs after 60 months of operation:
Whisperflo WFDS-24 = $1779
Intelliflo VS = $2002
Even assuming that the Intelliflo has the same flow rates as the Whisperflo, the intelliflo will overtake the Whisperflo in about 5 years as being more cost effective than a two speed. After that it is a bonus.
Either a two speed or VS speed would be a good choice but the VF will take much longer to be cost effective (~10 years) than a two speed and it will never be more cost effective than the VS.