The Balboa GS Series control pack comes in many different models such as GS500, 

GS501, 510, 511, 514, 520, 523 and so on. You can also get them in a Duplex (Z), Serial Standard (SZ) or Deluxe (DZ). This can often be confusing to know what panel to pair up or what circuit board to fit.

When identifying a correct panel to fit with the board, look at the full name of the panel. If it is ends with an S, i.e. VL700S, this panel works with any Balboa PCB ending in S or SZ.

Panels ending in D, i.e. VL801D, works with PCB's ending in D or DZ.

Panels with no end lettering i.e. VL200, VL240 are Duplex panels and work with all PCB's ending in Z or no lettering at all i.e. GS500 or GS500Z. Beware that this is different on OEM licensed equipment and it is better to ask our advice.

When you need to replace a PCB, the most common mistake is to look on the green printed board and see "GS500" printed on it and assume that is what you need. This same back board is used for every model in the GS range. The board only becomes different with the number of relays, plug ports, wiring and software chip.

To ensure you are searching for the right part, look on the side of the transformer to find a 5-digit number beginning with "5". Always note the full serial number and full part name to have the best chance of sourcing the correct replacement part - first time.