Recirculating Mash Question

[Hamaki]

I bought a $20 ebay pump and rigged up a temporary HERMS (IC in my HLT)for my last batch to try to counter the tendency for mash temps to fall several degrees in my poorly insulated keggle MLT. In the past I started a degree or two above target and added boiling water once or twice during the mash as needed to bump up the temp, trying to average around my target mash temp.

I followed the recommendation of a guy with a RIMS setup & March pump by doing the recirc by laying the hose on top of the grainbed (no sparge arm). Checking temps in several locations in the mash I found four to five degrees difference between areas near the hose and those with little influence by the recirc flow. It was a fairly stiff mash with little free liquid covering the grain. I stirred several times during the mash to try to even temps out but I don't like having to retrieve the hose every time to lay back atop the bed and the recreation of hot spots & cool spots concerns me. I didn't measure flow rate but estimate that the pump was putting out maybe a quart a minute in this arrangement.

Is the variable temp within the bed during mash not a big deal as long as the "average" temp is on target? Would a sparge arm or similar means of distributing the inflow improve temp uniformity? Should I just go with a higher water:grain ratio in the mash? Bigger pump?

 

[atoughram]

I dont know any way to keep the temperatures from stratifying except to constantly stir the mash - which I've never done - and have efficiencies from 75-80% with all malt beers. So, give it a try, I'm sure it will be fine.

One other thing - my mashes are pretty soupy, 1.35qt/lb of grain. When I do a temperature raise, it usually takes 15-20 minutes for the bottom of the mash tun to approximately equal the temperature of the top of the mash tun with constant circulation. I have a thermometer in the outlet of the MLT and the outlet of the RIMS tube.

 

[Hamaki]

Thanks, atoughram. My efficiency with the current setup has routinely been 80 - 82% till this last batch, which dropped to about 76. I think part of this might be because I didn't stir as frequently or as thoroughly as usual because the hose was in the way. I was thinking that once any dough balls were dealt with the recirc should keep things moving for good conversion & extraction.

My water:grain ratio was just over 1.5:1 but with a significant volume below the false bottom there was virtually no free liquid over the grain bed during the mash. I'm not ready to spring for a sparge arm or a big boy's pump just yet so I think I'll run it a bit soupier next time to see if the free flow of liquid over the grain surface improves temp uniformity across the bed.