Modulating Auto Draw-off

[TapTapTap]

Looking again, the H2O I have has a 2" butterfly valve behind a 2" spout.
A good feature for smaller rigs as in my 2x6 - is the ability to have it open less than 100% when it calls for a draw. I'm set at 50% when wide open.

That's what I recall and my concern was that too much syrup would set between the valve and the syrup pan with a 2" or even 1.5" valve/pipe. So I decided to stay with my current un-modulating system. I'm able to still adjust the full-on flow with another manual ball valve just ahead of the autovalve.

Ken

[Bricklayer]

I currently have the CDL modulating draw off.
Pretty happy with it.
I originally had built my own copy of the CDL one for last season and had some issues with it. So I purchased the controller unit from CDL.
It acts the same way as the home made one does.
So I’ve come to the conclusion that being wood fired and having a modulating auto draw has its issues.
I fire by firebox temperature and not time. This seems to keep the boil somewhat steady. But even opening the door and loading for the 15 seconds it’s open drops the temp of the syrup pan. The auto draw controller senses this and adjusts accordingly and saves the data and expects that the change will be the same next time. So I find that it’s not a true modulating drawnoff because the PID is in relearning mode every time it gets close to drawnoff temp. I assume that on an oil rig with a constant temperature that it would work a whole lot better.
I still get constant draw offs and no big spikes in temperature like I did with my open close auto draw off I had before. It keeps the draw offs small and steady. I think this would be the case with all modulating draw offs on all wood fired rigs with a fluctuating boil temp because the PID has to know how much to open the valve to affect the temp of the syrup amd for how long. When you have a fluctuating temp of fire controlling the boil it changes with every fire minute by minute.
Having the butterfly valve and the belimo controller like almost all modulating draw offs have is the best worry free part of it. After struggling with open close ball valves and nitre build up clogging them for years I would never go back to anything but a butterfly valve for a draw off. Never had it clog or fail on me. The belimo controllers are strong enough to close the valve no matter how much nitre is flowing through them. 2” valve is what I have on my 30” x 10” evaporator. I have it set at a little over 1/2 to open fully. And never had a problem. Having it fully open at 2” full bore while running I would Probley have a heart attack watching the levels.

[johnallin]

That's what I recall and my concern was that too much syrup would set between the valve and the syrup pan with a 2" or even 1.5" valve/pipe. So I decided to stay with my current un-modulating system. I'm able to still adjust the full-on flow with another manual ball valve just ahead of the autovalve.

Ken

Not home to check right now, but pretty sure my Revolution pan is 1" pipe off the boxes. The H2O connects from the 1" to the 2" with a TriClamp fitting.
I don't think there's really any more syrup sitting in the pipe than before but could be wrong.