I have a manual transfer switch that was installed approximately 10+ years ago that is rated 5000 Watt and 20 amp max input. The old generator died and was replaced with a Generac GP5500 / 6875 model. Twistlock outlet from generator states 120/240 vac - 30 amp. Wiring to transfer switch is 10 - 3 w/ground - approximately 60 foot run. Transfer switch has 6 - single pole 15 amp circuits with two connected together for well pump. Others are for fridge, furnace and lights. Should this transfer switch be upgraded or is it safe to operate?

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    What makes you say the transfer switch is only 20A? That seems awfully low. Also, those types are hokey and overpriced, don't replace with another of that kind... Ask us how to do it much more elegantly, with a subpanel from a much higher quality maker - for 1/3 the price. – Harper - Reinstate Monica Jan 5 '19 at 22:27
  • What type of inlet is wired to the transfer switch at present? – ThreePhaseEel Jan 5 '19 at 23:16
  • Not sure what you mean by inlet , but, at generator Is a 4 prong twistlock plug , then approximately 60 feet of 10 /3 with ground to another 4 prong plug at transfer switch. Label on side of switch box says 20 amp input max. 5000 Watt . MFG is Connecticut Electric. – JCalvin Jan 6 '19 at 2:42
  • @JohnDowst an "inlet" is the opposite of a receptacle outlet -- it mounts into a box and has prongs on it, accepting a socket that's been fitted to a cord – ThreePhaseEel Jan 6 '19 at 15:41

From the information you have given out on your last comment "maximum 5000W" the answer would be that you need to replace the transfer switch to match the new generator.

Your old transfer switch (xfrs) has a max rating of 5000W and you new generator actually has a surge wattage of 6875W which is considerably more than the existing xfrs rating. We are not taking into consideration what is connected to your current system. It's a matter of how much the generator can provide. In short you size generators to provider a certain amount of power. You use what's connected to calculate the required size not the other way around.

Good luck

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  • Thanks to all who schooled me regarding this question. It sounds like it weighs heavily on the amount of wattage . Time to call in a licensed electrician. – JCalvin Jan 6 '19 at 19:49

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