The person at the drawing board drawing a contactor has one question in his head: let the circuit work. Which make, which series, he either does not know, or does not want to know, at that moment. The part number becomes a question that falls onto the purchasing desk when the drawing is done: what is the number of this contactor?
The person at the purchasing desk does not know the circuit. He cannot, and it is not his job either. He has the BOM in his hand; every row in it is an order. The row says "Contactor -K1, qty 4" and the number is empty, so the person placing the order either guesses or calls the drafter. A guess means ordering the wrong part. Calling the drafter happens every time, and it takes minutes every time.
Is the part number in the drawing or in the table
The answer to this question decides the rest of the work. If the part number is kept in the table, the drawing and the table are two separate worlds. The contactor in the drawing is a symbol, the one in the table is a row. Nobody guarantees that they belong to each other. The project goes on, the contactor in the drawing changes, the row in the table keeps the old number. The order goes out with the old number.
In EupCAD the device data is part of the drawing. When you put a contactor on the page, the record for that device is also created in the project: tag, name, type, maker, part number, rating. The mark in the drawing is tied to that record; the record lives in the project file. You enter the number where you see it; there is no separate spreadsheet to search.
The BOM is grouped by part number
A row in a BOM is a part. If the same number is used three times in a project, the BOM has one row, quantity three. That is the point of the BOM being a purchasing document: if the number is the same, the part is the same, and the quantity is summed.
That summing working correctly requires every device to have the right number. EupCAD's BOM groups the devices by part number and maker. Four contactors with the same number are one row, quantity four.
How a device without a number shows up in the BOM
Honesty is required here. Devices without a number cannot be melted into a single "no number" row; that is a piece of information the person placing the order does not have. In EupCAD, devices with an empty part number stay as separate rows under their own names and are marked "(no part)".
That marking is not a favour; it is a warning. It means "the part in this row cannot be ordered, fill in the number". The row without a number stays visible in the BOM; it sits there until it is noticed and filled in. It is not deleted or hidden.
The maker column: one number, two makers
A part number does not define a part on its own; it defines it together with its maker. Two different makers using the same number range is rare but not impossible; if the order goes out on a number without a maker, the part that arrives can be the wrong maker's. If the same number is a part of two makers, the person at the purchasing desk does not know which one to order.
That is why the grouping in the BOM is done on number and maker together. If a project uses the same number from two makers, the BOM has two rows, each with its own maker. The maker column decides the order on its own.
The device list: the raw data behind the BOM
The BOM is grouped data; the raw data is the device list. The device list shows every device in the project on one row: tag, name, function text, type, page, maker, part number, rating. The device list says how many devices a row in the BOM corresponds to.
This list is part of the delivery package. The maintenance crew answers the question "how many of this part are there in this panel, and where are they?" in the device list. The BOM answers "how many am I ordering?"; the device list answers "how many were used, and where?".
The function text: the eye of the person reading the number
Next to the part number in the device data, a function text is entered: "main drive motor", "air compressor contactor", "smoke detector supply". This text helps the person at the purchasing desk read the number.
The number is the maker's data; the function text is the project's data. Two different points of view. The number answers "which part is this?"; the function text answers "what does this part do?". The person at the purchasing desk converting the number into an order verifies, with the function text, what that part does in the panel.
In EupCAD the function text is also visible in the drawing, next to the device. The person at the drawing board sees the answer to "what is this contactor for?" in the drawing.
The rule check counts the missing data
EupCAD's rule check inspects whether every device tag in the drawing has a device behind it. It gives findings at two levels.
If there is no device record at all, the report shows "Warning: -K1: no device record". This says that the symbol in the drawing has no data counterpart; the device has not been entered.
If the device record exists but the part number is empty, it shows "Info: -K1: order number empty". This says the device is in the drawing but its data for purchasing is incomplete.
Look at it numerically: if three numbers are missing on a panel with fifty devices, those three rows are at the top of the report. You do not go through the fifty devices one by one; the report has counted the gaps for you.
The rating: the data sitting next to the number
A part number alone is not enough; there is a rating next to it. A contactor being "16A" or "25A" decides the order. EupCAD's device data carries this field too; it is visible in the BOM and in the drawing.
This serves two purposes. First, the person at the purchasing desk does not have to ask "16A or 25A?". Second, the rule check can verify protection compatibility: when comparing the motor's current with the thermal breaker's range, these values have to come from the drawing data. A protection check cannot be done on a value based on a guess.
The last look before ordering
Before ordering materials for a panel, the "(no part)" rows in the BOM have to be zero. That is not a check the person at the purchasing desk does; it is a check the person at the drawing board has to do, before the order.
In EupCAD this check is the BOM itself. The rows without a number are marked; when there are no marked rows left, the BOM is in an orderable state. The order goes out from a clean document.