de-nature protein/enzymes.

[jimrod]

To keep the temperature in my mash ton at 150*  I pump the wort through a 50' coiled copper tube submerged in the hot liquor tank then back on top of the mash ton. This works great with a thermowell and a Ranco controller to keep the mash very close to target temperature.

If the hot liquor tank is too hot will it denature the protein/enzymes and interfere with conversion the my brew?
And is this the reason I've been getting poor efficiency?
What temperature should I use? What is the danger temperature?

[tschmidlin]

I would set the temp and flow rate to make sure the outlet temp from the heat exchanger is no more than 165F.  Lower is better, but lower takes longer for temp rises.  If you just want to maintain temp at 150F then I would think 155F would be fine.

[jimrod]

Is there a possibility of extracting tannins by recirculating too much?

[tschmidlin]

Not as long as your temp and pH remain in the proper range.

[mabrungard]

I agree with Tom excepting I will more strongly caution that the temperature of your wort at the heat exchanger outlet (or in the heat exchanger) should be no higher than your targeted mash temperature.  This will require that the wort system and mash tun be well insulated to reduce heat losses after the heat exchanger. 

I've got as many of the pipes and hoses in my system encased in that foam tube insulation for that reason.  This recommendation applies equally to RIMS brewers too.  Don't overheat your wort or you could see attenuation problems.  This comes from denaturing too many of the enzymes in the mash while you are heating and circulating.

The only time you would want the wort temperature to exceed your targeted mash temperature is when you're ramping the temperature up. 

[jimrod]

That is happening. 35 lb grain bill  for an 11 gal Porter and only 1.059 SG and 1.022 FG after 2 weeks. I'm lucky to hit 4.8 ABV.

I'll go Denny's route and add 30 oz of vanilla laced bourbon.

What do you think ?