Here's another approach using only two relays (one light-duty, one heavy-duty) - it may serve as a useful starting point for the TS.

 

I have used a Kill-A-Watt meter with several backup generators and they do just fine. While I have not used inductive loads I have used calibrated resistive loads and not seen any difference between my residential AC mains supply and backup generator. This includes my first old beater Coleman 5.0 KW surge and 4.0 KW run generator powered by a Briggs and Stratton 8.0 HP generator which actually puts out a pretty clean sine wave as well as my large backup generator. The forum has a pretty good article on THD. ELY the ICE man is in the link.
As to capacitive dividers and the forum? They are discouraged because there is no isolation betweens the mains voltage and load. They are not a "good idea" especially for a beginner so their use is discouraged. Well actually their use is a prohibited subject in forum discussion as a matter of general safety.

Ron

The early Ki-a-watt meters used a capacitive dropping scheme and a zener shunt regulator that was not able to handle the much higher current that some generators caused with their high harmonic content. I believe that the design was altered to handle more harmonics without damage.

 

The early Ki-a-watt meters used a capacitive dropping scheme and a zener shunt regulator that was not able to handle the much higher current that some generators caused with their high harmonic content. I believe that the design was altered to handle more harmonics without damage.

At one point I had two of those things, one is still new in box. Somewhere under piles of assorted junk they ley. What I really need is a dumpster. Years ago I was involved with a computer hardware test forum. I helped them with designs for PSU load banks. In return I got free hardware. Anyway the one Kill-A-Watt I had I started using on everything I had just out of curiosity. Long story and I really don't want to drag things more off topic. Maybe later today I'll shoot you a PM (Private Message) my scheme. Damn things worked good and mention of them had me looking for the ones I have.

Ron

 

OK, Rr, Back to the topic. The TS has mentioned keeping the size small, but some dimensions would be handy. The standard socket for an 8-pin plug in relay is not small at all, nor cheap. The big plus with those is the plastic housing that keeps the hot parts covered. So how much room does the TS actually have for a relay ????

 

OK, Rr, Back to the topic. The TS has mentioned keeping the size small, but some dimensions would be handy. The standard socket for an 8-pin plug in relay is not small at all, nor cheap. The big plus with those is the plastic housing that keeps the hot parts covered. So how much room does the TS actually have for a relay ????

Beats me and we both suggested a SSR and they make them with 120 VAC control voltage. Typically 3 to 32 volt DC control and 90 to 280 VAC control. I figure the thread starter has more than enough choices to work from that everyone contributed. Not sure where the ball is but I don't see it in my court. Want a relay? I'll suggest a relay, want a SSR I will suggest a SSR. Don't give me a budget? You are on your own.

Ron