My mother in law recently replaced her 4 burner Frigidaire range and is often popping her breaker when she is cooking for a large party – ie 4 burners going and oven.
I checked the specs for the range and they suggest a 50A breaker. The electrical circuit however is a 40A breaker. The cable is a cu Phillips NMD7 8/3 Nylon 900 300V. The run is about 40-50ft, not in conduit – parts are in unfinished ceiling, other parts behind acoustic tile. But either way, plenty of ventilation.
From what I've read,I can put a 50A breaker on a 8/3 THHN cable but I don't see that rating (THHN) printed anywhere.
Is the NMD7 nylon 900 THHN? Or does it need to be specifically indicated? What does the 900 stand for?
Is the only choice to have a new 6/3 cable run?
Best Answer
In Canada, NMD 8/3 is allowed for up to a 40A circuit, NMD 6/3 is required for 50 A (Actually NMD 6/3 has an ampacity up to 55A, but try to find a 55A breaker…). Sorry, Eric.
Additional info: You may find some ampacity tables that list NMD8/3 as having an ampacity of 55A, but these tables assume a 90˚C conductor temp, and the code says you need to use the 75˚C ampacity when connecting to terminals rated to 75˚C, which includes all domestic circuit breakers and the NEMA 14-50 receptacles used for ranges and stoves.