March 809 performance through HERMS coil

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.
Cheers!

I would start with your grain. When milled do you still have intact husks?

sennister said:

I would start with your grain. When milled do you still have intact husks?

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My mill gap hasn't changed and the crush leaves a good proportion of the husks intact. When I had the system setup as a RIMS System, the grain bed was set nicely because of a higher recirculation rate. I would have to throttle the recirculation valve back some to prevent over-compaction the grain bed.

My previous HERMS coil was 1/2" and 25 feet long. Flow was limited by resistance of the HERMS coil. I upgraded my pumps to the 815 impeller and it increased the pump output except when pumping thru the HERMS coil. My maximum flow was about 1.5 gal/min. I think 1.3 gal/min is about the maximum flow you will get thru a 50 foot X 1/2" coil. As long as your batch size is 15 gallons or less, you will have excellent control of your mash temp.

Thats good to know, Steve. I didn't realize the coil would restrict the flow rate that much.