If your chamber is failing to Heat or Cool, please use the following FAQ, Troubleshooting Guide to help you.
Watlow PM Love Controller
What is a limit controller?
Limit controllers act as a safety measure to prevent the chamber from going above temperatures that may damage your test products or the internal machinery of the chamber. If the temperature goes above the limit the controller is set to, it will cut off power to the rest of the chamber and keep it turned off until the temperature falls below the limit again. Chambers with a Watlow PM limit controller will have a lower limit as well that serves the same function if the temperature goes below that.
By factory default the limits will be set to about 10 degrees above/below the operating range of the chamber (ie, a chamber that goes to 180C will have a default high limit of 190C) but you can feel free to set a narrower limit range if that works better for your testing needs. The instructions below go through how to check what limit(s) your controller is set to and how to change it if needed:
Watlow EZ-Zone PM
Viewing High and Low Limits on the Watlow PM
The PM limit controller has four main menu screens that can be cycled through by pressing the green button on the front of the controller, two of these screens will be for the high and low limits. Examples of both screens are pictured below; the low limit menu will be the screen with “LL.S1” displayed in green at the bottom and the high limit will display “Lh.S1” at the bottom. The number displayed in red on both of these menus will be the temperature that particular limit is set to; if you need to change either of those limits you can do it by changing the red number to the new limit with the arrow keys and pressing the green button to save it.
Troubleshooting Alarms and Errors
You can determine whether the PM controller is in an alarm/error state by consulting its main menu screen (the screen that displays the chamber temperature reading in red); a controller in an alarm state will display FAIL in green at the bottom of this screen as pictured below, otherwise this screen will display SAFE at the bottom.
This controller most commonly enters a fail state if the chamber’s temperature is above the high limit or below the low limit, if that’s the case then you can either adjust the limits accordingly or wait for the chamber’s temperature to fall back into the limit range.
If the controller has a separate error causing it to enter a fail state, the controller screen will alternate between its menu screen and a screen displaying Attn and the error type like the one pictured below.
For a full list of all the error message displays and what they indicate, consult page 21 of the EZ-Zone manual linked here: EZ-Zone PM Manual
Love Evco Controller
Setting the high limit
If your chamber does not have a Watlow EZ-Zone PM limit controller, it most likely has a Love Evco limit controller in place. Unlike the EZ-Zone, this controller model only has a high limit. To set the high limit, simply press the “Set” button on the front of the controller and use the arrow buttons to adjust the limit setting as needed. As a default, the limit will be set to about 10 degrees higher than the chamber’s maximum operating temperature.
Troubleshooting the Controller
If the controller enters an alarm state, an error symbol will appear on the main display along with an error message like in the picture below. If the chamber temperature is reading higher than the Evco’s high limit, the Out1 reading in the top left will stop being illuminated. If that’s the case, either adjust the limit accordingly or wait for the chamber temperature to fall below the high limit.
If the controller has a separate error causing it to enter a fail state, the controller screen will alternate between its menu screen and a screen displaying Attn and the error type like the one pictured below.
For a full list of the Evco’s error displays and what they indicate, consult the manual linked here: Love Evco Limit Manual
Locking/Unlocking the Controller
The Evco controller has an additional feature that allows you to lock the controller, if this happens the entire chamber will stop running until the controller is unlocked again so it’s something to check for if the limit controller is stopping the chamber from running but isn’t displaying any error messages. To lock or unlock the controller, hold the Set button and the down arrow button together for two seconds; the controller will display “Loc” if it’s being locked and “UnL” if it’s being unlocked.
For additional assistance, please reach out to AES’ support or service team. You can reach us by phone at 978-772-0022 and by email at support@associatedenvironmentalsystems.com