Modulating Auto Draw-off

[bmbmkr]

Thank you for the reply. Good info. The bracket keeps the Belimo in place so that it doesn't just spin around while trying to open the valve?


BW

[Bricklayer]

Yes. It connects to the bottom of the belimo and bolts to the valve.

[bmbmkr]

Yes. It connects to the bottom of the belimo and bolts to the valve.

Good deal, if you get a chance, could I get a photo or link when you get a chance?

[JPGraphX2]

Anyone could share PID parameters?

Thanks
JP

[Bricklayer]

For some reason I can’t post pictures. Is the site not allowing pictures to be attached to posts anymore ? I have a wiring diagram that I have been trying to post.

Here are the parameters that should work.
I have not had the time to fully test mine on the evaporator yet but it seems to work and modulate the valve.

INTY = P100
OUTY = 1
COTY = 4-20 ma
RD = 1 ( cooling )
OT = 2
HY = 0.1 ( this means it will go .1 degrees higher then your set temperature before it starts to open valve )

[Bricklayer]

Finally I’ve been able to get it all set up and put together 100%.
Noticed a few problems with this setup.
There are 1000’s of different settings on this PID but it seems like for what we want to do with it there isn’t an optimum setting without using autotune while making syrup. The PID is basically trying to keep your temp at your drawnoff temp. It calculates how long it takes to heat, cool down , and tons of other things while the evap is running and temp is fluctuating up and down. So if it sees a temp spike say when your heating it up to temp it may open the valve a bit to slow down the temp rise and test how the system will react. Can’t turn that off in settings.
I’ve dialed in the settings very close to where they need to be. But I think to be able to dial it in properly it needs to be run on an evaporator that’s boiling sap and making syrup and Auto tuned to that
I’m just testing it on the evaporator with water. So it’s not giving the same results as sap would. And every evaporator is different on how the temp drops in the syrup pan once a bunch of syrup is drawn off. The goal with a modulating valve is to slowly modulate the valve to keep the temp as close to drawnoff temp as possible and not spike to high. And also you don’t want the valve to open to 100% to fast and drawnoff all the syrup and flood the pan with fresh sap from the flue pan and drop temp way down. Then your basically batch boiling in your syrup pan.
The settings I have now with boiling water will start to open valve at the set temp. Then open it as the temp rises a bit but it won’t start to close untill the temp is below the drawnoff temp. So the temp of the syrup pan will drop way down and a bunch of not syrup will be drawn off. So just trying to get that setting right.
I think some of it has to do with the belimo valve speed of opening and closing being pretty slow. So just gotta figure out the closing settings on the PID. I’ve adjusted my belimo to only open about 3/4 of the way. So the actual time the valve takes to open and close is reduced. I also adjusted the butterfly valve and the belimo to be not fully closed 100%. Just enough to stop the flow of water while it’s boiling. Hard. This decreases the time the valve takes to open by about 5-6 seconds. It’s adjustable by the screw stops on the belimo valve. Basically the butterfly flapper is hitting the gasket but not that final pop to seat it in the middle of the gasket. Obviously this is going to differ with every valve. So that would need to be adjusted for whatever evap your using it on.

[cbmapleguy]

Hi, Do you have a better quality picture of the wiring? I built an auto drawoff a few yrs ago but looking to add a modulating valve to it.

Cheers!