JLD612 tuning help

[bkb]

I have a waste oil heater that im using these PIDs to control a heating element inside the burner. Going from a cold start (65'F) up to my setpoint (280) i have no issues. The problem is when the burner is still hot and it tries to start back up again. Lets say the block is 145'F i will notice the SSR is cycling very slow when it should be on solid trying to come up to temp. Then once the burner fires it cant maintain temp and will drop quick until i get smoked out by unburnt oil. I have 2 pids in different burners using very different settings but both have the same problem. I dont care about overshoot but dont want to undershoot more then 10 degrees. I need the pid to fire the ssr solid up to about 10' of set point then start to cycle, the cold oil and blower motor are working to cool the heater down quick. I am using the settings that come on the pid with great results when starting cold.

Any ideas???

[richiem]

No solution for you, but my hunch is that it's related to the temperature sensort and/or its location. The controller needs to be set for the type of sensor used, and I saw another post here where the person didn't know that the default is for a Pt100 sensor, and he was using a K thermocouple, and of course, there were problems... Check your default settings to be sure that they match your system. And be sure to provide feedback for the rest of us.

[bkb]

Both are using a K thermocouple and set up for such. The alluminum block is about 6'' long, 3/4 wide and 1'' tall with the k sensor mounted about 1'' infront of the cartridge heater that is pressed into the block.

[Tech_Marco]

How about a differential temperature control?
Say you want 145'F and fire it up when it drop to 140'F?

If that is OK, use Outy= 4. Note SSR will be disable but Relay 2 will be used to serve the controlling while the Relay 1 acts as alarm.

Above is wrong! Actually there is two Differential output Outy=3 and Outy=4
During Outy=3, J1,J2 serves as alarm and SSR differential control
While Outy=4, J1 serves as alarm, J2 serves as differntial control and SSR diabled

This is the latest features. Let me post the curve for you to view it. Just a minute...

PV = current temperature,
SV = target temperature,
HY = differential temp.

During RD= 0 (heating),
PV <= (SV-HY), Relay or SSR latched
PV => SV, Relay or SSR unlatched

[richiem]

OK, this is very cool! I look forward to seeing your new manual, Marco! Great features for many of the problems that have been posted here recently. Hope everyone sees this post.