Grundfos RCP-96 has Flow range: 0 - 27.5 U.S. GPM
According to Amazon spec sheet:http://www.amazon.com/Grundfos-RCP-96-UP515-55SFC-Recirculator-Timer/dp/B00128BJAO
Most tankless require .4 GPM to start burner and .25 GPM to maintain burner
Rinnai does not show C85e-1 so you will have to consult your manual to see minimum water flow requirement.http://www.rinnai.us/tankless-water-heater/
Sample manual from Rainnai mentions 'minimum flow rate' several times but doesn't give specific number. Yet promotion blurb on page 1 says "Ultra operates at a lower minimum flow rate."http://www.rinnai.us/documentation/downloads/U290-665x0200_Condensing_Manual_EN_FR_1-2010.pdf
Another rinnai manual mentions flow rate several times in troubleshoot section yet fails to define what that rate is:http://www.rinnai.us/documentation/downloads/U287-1833_VB_Series_R75LSi_R94LSi_R98LSi_Manual_EN_FR_EN_FR.pdf
It might seem that tankless promoters are CTA by failing to mention specific flow rate numbers.
I think tankless promotion is a definite overachiever, and vague flow rate is one tiny example.
It proves the necessity of reading whole manual and asking questions before buying a tankless.
There's another factor to consider:
All performance numbers are based on new products in ideal circumstance, and not based on a 4 year old product located in your home.
Your flow rate may vary, especially over time, and especially if water in your area is not crystal clear, and you are not diligent with correct water softener and filter.
Many factors can affect flow rates: water pressure, number of elbows, clogs in the line, sediment, size of pipe, aireators, water-saving shower heads, local water conservation policies, water well pressure, MUD district pressure issues, your home located near end of a water main, etc.
Read tankless efficiency vrs water softener http://waterheatertimer.org/Battelle_Final_Report.pdf
Image of tankless parts vrs tank partshttp://waterheatertimer.org/images/Compare-water-heater-parts.jpg
Bradford White tankless vrs tank side by side
Lime scale does not flush out of tankless
Tankless must have water conditions with less than 11 grains hardness
"Savings falls far short of a payback," 'without comparing service costs'http://www.pmengineer.com/Articles/Cover_Story/8cf9e86f7c298010VgnVCM100000f932a8c0____
Sediment clogs tankless pressure sensor without softener.