HERMS system Temp controll problem

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Jan 10, 2009
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Very briefly, I am building a brew system similar to a B3 1550. 3 tier, 3 low pressure propane burners controlled by solinoids. Currently using a 12 gallon cooler MT, 10 gallon HLT and a 15 gallon BK.

The control panel consists of 2 Ranco 1100 single stage ETC's and various switches to control the burners/pump by either the ETC's or operate manually. I currently at work an cannot post pics but will at my earliest opportunity.

Here is the problem I found during the preliminary tests.

While heating the HLT I set the ETC to say 170 deg F. Burners fire and the temp of the liquid rises. The problem is the liquid heats faster than the ETC can register. As a result, the volume of water gets to about 185 before the ETC reaches the 170 deg to shut the burner off. I have tried to "throttle" the burners down to perhaps slow the rate of rise to match the ETC and had closer but not accurate results.

I know that a PID controller might be the answer but since the investment in the ranco's have been made I hope to make it work. I might be able to increase the size of the HLT vessel to 15 gallons but not much bigger.

It seems that the Ranco 1100 is used on a lot of systems that I have researched. How does it perform in your system? Is there an adjustment for the "refresh" rate? (sorry I don't know the appropriate description) I.E can I speed up the ETC ability to sense temperature changes?

Any thoughts current users of the Ranco would be appeciated. Please point out anything obvious I am missing in my system.