I'm sure someone out there has experience with the performance of a march 809 pump recirculating sweet wort through a HERMS coil mounted in a HLT. I just rebuilt my propane based keggle RIMS system into an all electric HERMS system like Kal's Electric Brewery.
I'm running two March 809-c pumps in the system. The recirculation goes from the pump (approximately 1' below the MLT valve) into the HERMS coil in the HLT. The coil is a 50'-1/2" SS coil. The output of the coil is to either a silicon return hose, or a sparge arm made from copper. Both methods generate a flow rate of approximately 1.3 gal/min.
Does this flow rate reduce the effectiveness of the grain bed? I ran a test batch of an ordinary bitter, and was getting grain particles throughout the sparge, but it was hard to tell if it was due to a loose grain bed, or my feeble attempts to controlling the runoff rate into the boil kettle. I'm sure the second go-around will be much smoother.
I'm also wondering if I get the larger 815 impeller that Morebeer sells, and retrofit the original impellers, if that would increase the flow rate.
Thanks for anyone's 2 cents and I'll post pictures of the setup soon.