complaints when using a hughes autoformer
I am looking at a used hughes autoformer. I know some parks rules say they are not allowed. Some parks we have been in, I have seen voltage at @ 102 to 104 with my a/c on. I would be using a PI 3o...
Forum Discussion
Dutch_12078 wrote:
I don't use an autoformer, nor have I run across a park to date where I needed one, but in those that prohibit them in their rules, I've found the predominate reasons are that they believe the devices somehow "steal" power, although I've never found a park manager or owner that could logically explain how that happens. The other reason has been possible liability insurance issues because the NEC prohibits the use of auto(trans)formers in RV's, which it does. I have inquired of the NFPA what the reasoning is behind the prohibition a couple of times, but I've never gotten a response.
The wording of that section in the NEC is none to clear, but I think the intent of the prohibition is only to have it applied to the convert. The overall section it's in deals with the interaction of the 12V system and the 120V system (I think the term is "separately derived systems" here, but it's been a bit since I read it). If so, it makes sense that they would want full galvanic isolation between the 12V side and the 120V side, which means the transformer in the converter can't be an autotransformer but instead needs isolated input and output lines. This avoids creating a ground fault on the AC side (connecting the neutral to the chassis ground via the 12V negative lead), among other difficulties.
Assuming that's the intent, they could have worded it a bit more specifically and clearly!
