ICP Furnace Showing 80% Limit Fault
December 8, 2025
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Most gas furnaces have several safety limits, main limits, roll-outs, 80%’s will have a DSS (Daft Safety Switch) These safety
Have you ever noticed that (inside the software) some User Interfaces (UI) have serial numbers listed, and some don’t? Why is that and where are they? This article will show you exactly where to find those missing serial numbers on both locked and unlocked screens.
For starters, where can serial numbers be found?
Typically, the Model/Serial numbers of communicating systems can be found in the UI in two locations: 1 in the unlocked screens and 1 in the hidden service screens.
*If you do not know how to make the white hat turn green, please refer to the UI install manual for this information*
When communication equipment is made, the original control boards (in them from the factory) have a model and serial number loaded into them. This way, when you install the equipment, you can see the model and serial numbers for all the equipment through the UI. However, only the original factory board can contain the serial number! If the original board is removed, then a “Service Board” would have to be installed in its place.
Service Boards, they look identical to the original board. These boards drive the equipment 100% the same as the original; the only thing different is they do not have a serial number encrypted into the software. When these boards are installed, they will rely on being told what their model number is by: model plug, selection of a model number on the screen, or use of a dip switch. This is all dependent on which and what type of unit the board is going on.
So, to sum all this up: If you look in the UI and a serial number is not listed for a unit, this means that it is not the original control board in it because it has been changed.
Disclaimer: The technical statements, information and recommendations contained herein are believed to be accurate as of the date hereof, but Mingledorff’s does not make representations or warranties, express or implied, as to its accuracy, its completeness, or the results to be obtained. The information is being provided for informational purposes only and is intended for use by persons having adequate skill and expertise regarding the proper selection, use and application of the products and recommendations and at their own risk and discretion.
Most gas furnaces have several safety limits, main limits, roll-outs, 80%’s will have a DSS (Daft Safety Switch) These safety
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