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You should be able to get the filter from your dealer. How do you know the heater kicks off? If, it is turning off, it sounds like dealer did not change jumper.
Sounds exactly like they didn't set the jumper.One question- Do you have a 60 amp GFI breaker on this spa, or a 50? Reason I'm asking is that you don't say which in your original post, and I'm wondering if the installer noticed your breaker sized at 50, and left the jumper that way. It's just a guess, and may well be wrong- but if you do have a 50 amp breaker, that may explain it. If you have a 60 amp breaker, then the dealer probably just missed it. Sorry I don't have the jumper setting to check- I'd ask your dealer about that unless you are very comfortable rooting around with the circuit board on your spa. My theory for Sundance not putting the part numbers in the owners manual is that they just tell you to get your filters at the dealer, who should have the correct ones for your spa. Them giving you a part number would make it just a hair easier to get a filter from source that isn't a Sundance dealer. I have a Sundance, and when I get filters at my dealer, it's easy to just pick out the correct one from the shelf- they don't have part numbers displayed on the filters on on the shelf.