Generator inlet receptacle installation on house

Power out? How about an inverter connected to your car?
kevm14
Posts: 14674
Joined: Wed Oct 23, 2013 10:28 pm

Re: Generator inlet receptacle installation on house

Post by kevm14 »

So for future reference I just took a few current measurements in my panel.

Oven preheating.
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About 12.5A on one line and 20.3A on the other line. My generator is rated for a max of 16.66A per line, steady state. I'm sure it could surge up to 20A and a little beyond (it has 20A breakers, and the breaker feeding the panel is 20A so anything over 20A is going to become breaker limited, for safety). So realistically, I could not preheat my oven even if I turned everything else off. My assessment is it would be pegging one line at 20A for several minutes on end and that's just a bit too far over the limit.

However, once the oven is preheated, the element duty cycle is pretty low and only rises to ~12.xA per line, with a brief spike to 17A that would probably be tolerable provided little else was running at the time.
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Now for more relevant news (because it's not worth attempting oven use....). My microwave draws more current than I expected, which explains why it seems to hard on the generator. That's because it pretty much pegs one line when it's running. Sigh. Microwaves are so inefficient.
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In the future I will have to pretty much make sure all loads on that line are off when running the microwave.

This is a good example of why you can't just add up watts of loads. Is it a 240V load? 120V? If 120V, which line (1 or 2)? Not to mention, the microwave is probably rated at 1000 or 1100 but that's cooking power I guess. It's actually drawing like 1950W. Again my gen is 4000W but that's nominally 2000W per line. So you can see why I say it would peg one line. Because that's exactly what it is doing.
kevm14
Posts: 14674
Joined: Wed Oct 23, 2013 10:28 pm

Re: Generator inlet receptacle installation on house

Post by kevm14 »

Finally got around to ordering two meters to monitor generator power loads.

https://www.amazon.com/dp/B08F1XBLH9/re ... SDTWMPHWEA

I got two of these. I actually had to order them separately because it was limited to qty 1. So I just placed two orders.

I will mount one in each box and I already have a spot next to my breaker panel that should be fine. This seems easy but there are multiple things to connect, and I may have to extend the current clamp wires.

The way I will hook it up I can't test anything until I am on the generator. It would have been slick to do what one guy in the Amazon reviews did which was hook up another pair of clamps to his main feed and switch between monitoring that and his generator. I guess I could still do that. The only reason I'd really want to monitor grid power is to better experiment with load balancing before the next outage.
kevm14
Posts: 14674
Joined: Wed Oct 23, 2013 10:28 pm

Re: Generator inlet receptacle installation on house

Post by kevm14 »

Note: Click on the sideways images and they'll load properly. Too lazy to fix at this time.

Decided to tackle this over the weekend and just finished up this evening. This stuff always seems simple but lots of little stuff takes time. I wouldn't be surprised if I had 4 hours into this. I was going to make video but I need to figure out a tripod. So I just have some pictures.

Other than some install pictures on Amazon I had no instructions other than the wiring (4 wires to each meter). So I just kind of planned my own thing and worked.

Theory of operation:
Each meter measures the voltage, current, power, power factor, frequency and energy usage of one line (120V). So using two I can measure both legs. The idea is to measure the specs of each leg of my generator output. I already know what loads are on each leg so now I can monitor load on each leg rather than rely on the single power meter on the generator (which does not tell you if one leg is beginning to overload, or even how close it is). This will be really cool and I can't wait for the next power outage so I can monitor things to my heart's content.

Install plan:
Basically the Amazon reviews showed a little plastic project box for each meter. In fact Amazon has a link that sells one meter with one plastic project box (they have other sizes, too). So I just bought two of those. Each box is independent and screwed to a piece of plywood next to my power panel. The wires come out of the back and come up and around to go into a knockout in the box, then up to the required end points. I could even connect the current probes (transformers) to any other wire in my box including the mains but as they are powered by my generator circuit this only works when that breaker is on, and realistically that means these units are only on when my generator is running. I could have hooked them up another way but I didn't. Anyway, simple in theory. Lots of stuff to do. Let's begin.

Install details:
Just trace the back side of the meter onto the front cover of the box.
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To cut I sort of cobbled together an approach. Drill the 4 corners. Then drill them a bit larger. I should have drilled them large enough for my scroll saw but since I didn't I used a Dremel to start cutting. Then the scroll saw did a nice job on the soft plastic. Sort of trim it up with the scroll saw and get rid of the rough edges. Eventually the monitors will just snap firmly into place like they were meant to go there.
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Then the current probe wires needed to be extended. They are way too short as it comes. I just used some general hookup wire that I had laying around. Strip, twist, solder, heat shrink. Again, easy, but with measuring and stuff it still took a bit. Came out nice.
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The next part was a lot more tedious. First I chose a mounting location for the boxes. I drilled 9/32" (maybe?) hole in the back for the wires. Then a small pilot and screwed them directly to the plywood with two cabinet screws each. Then it was time to run some wires into the box.

Like I said I knocked out a hole in the bottom and I did have a 3/4" wire clamp in stock so that was good. I ran the signal wires up first. Then I set the transformers aside because power would be more tricky.

Both monitors want neutral so that wasn't too bad. For wire I just split a 14/2 bundle and pulled out the black and white wires. White for neutral. I ran that up to the neutral connections and found one for each wire and screwed them in. For the hot I WAS going to just jam a second wire into the breaker but then I realized the proper thing to do would be to use a wire nut to join the power feed to the existing generator feed wire and then use a single wire into each leg of the breaker. This was annoying. But I made it work. Just cut the generator wire, strip back, reinsert the stub into the breaker. Get a suitable wire nut. Connect all 3. Sounds easy but I was joining two 10ga wires and a 14ga so...it required some brute force. Hopefully everything is twisted up well and connected.

Then simply snap each transformer onto the little stub. This was tight but I made it work.
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Then run the wires into the boxes. I hooked up one monitor at this point and flipped the gen breaker on to power it. Worked!!
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Tonight I hooked up the second and finished the install. It won't see any current because it's reading the generator feed. Nothing's happening on those until I actually connect the generator (and power goes the other way).
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Nice. But there's a bit of a wire nest. Need to do something with that.
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Ended up doing this. Just used some coax wire clips and each bundle is for one meter, 4 wires each. Not great but I don't think this will give me any issues. May not be code without the outer insulation and if I had planned better I would have kept the outer insulation for the part that is outside of a box. But whatever.
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All done! Or was I?

Went upstairs to have dinner. Put something in the toaster, and ate my dinner. Toaster dinged, and when I got up, the toaster (and my bread) was cold!! WTF! Turns out half the outlets in the kitchen were dead. Oh good lord. Went downstairs. What did I find? This.
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This conductor feeds those outlets and it broke off right at the breaker. How? Well I was pushing some wires back into the box before I put the cover on. I must have inadvertently pressed right on that wire and it broke off. It sucked running stuff up from the bottom but that's how I chose to do it. It's hard to work behind stiff solid conductor wires but just be careful what you press on (and obviously careful what you touch).


Anyway, all is well. Outlets are back. Everything is good. Now I just need a power outage to test my meters!
Fast_Ed
Posts: 547
Joined: Wed Oct 23, 2013 9:45 pm

Re: Generator inlet receptacle installation on house

Post by Fast_Ed »

Wow, thats a cool addition to the generator setup. The project boxes are a nice touch.

Funny how those old wires can be just fine for decades.. but just an afternoon of mashing them into each other and they're done.
kevm14
Posts: 14674
Joined: Wed Oct 23, 2013 10:28 pm

Re: Generator inlet receptacle installation on house

Post by kevm14 »

It's worse than you think. That circuit was new for the kitchen and goes into a new GFCI breaker. Well....I guess I don't know if the wire was reused (they added circuits but may have reused some). Maybe it was.
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