MEP-803A wiring into the home

[CapePrep]

I am not sure this is helpful, but I feel there are a lot of "Handy" guys on here that will get this and use it. I have taken my electric panel cover off. I have a clamp on amprobe that I attach to each leg coming in. I then go(usually by myself!) and start to go back and forth from the panel to an appliance. I turn on the stove top, write it down, start the clothes dryer, right that down. Come up with a few different scenarios of what would be running under certain circumstances, i.e. the oven going while drying clothes and wanting a cup of coffee. Turn on a few lights,etc.. Right down all of this and see what kind of actual numbers you have on the amprobe on each leg and go from there. This doesn't help with your voltage drop, but gives you real amperage draw as opposed to trying to read each appliance data tag, accounting for age, etc. This should get you closer to what you need. Hope this helps.

 

[Guyfang]

What we do on the construction site is to clamp an amp meter on each leg, and let it record the next 24 hours, (or longer) data. If you meter only records the highest reading, that's helpful also. At least you know what peak is.

 

[jaxbill]

I am not sure this is helpful, but I feel there are a lot of "Handy" guys on here that will get this and use it. I have taken my electric panel cover off. I have a clamp on amprobe that I attach to each leg coming in. I then go(usually by myself!) and start to go back and forth from the panel to an appliance. I turn on the stove top, write it down, start the clothes dryer, right that down. Come up with a few different scenarios of what would be running under certain circumstances, i.e. the oven going while drying clothes and wanting a cup of coffee. Turn on a few lights,etc.. Right down all of this and see what kind of actual numbers you have on the amprobe on each leg and go from there. This doesn't help with your voltage drop, but gives you real amperage draw as opposed to trying to read each appliance data tag, accounting for age, etc. This should get you closer to what you need. Hope this helps.

I second that idea. Guessing really doesn't work. Everyone should do what you're describing.

I hate to admit it but I started doing what you described and got lazy after awhile but discovered something really helpful. I bought this thing called the Sense Monitor so I could continuously monitor my usage. It only puts CTs on the main utility feeds but their back-end system (via wifi to the internet) tries to detect individual devices.

From that point, it records 24x7 usage and adds it all up into kWh for folks worried tracking utility costs. It caught my heat pump (not the air handler), water heater, oven, sewage pump, a couple of lights, wash machine, dryer, and microwave. Everything else shows up as "Other" or special category called "Always On". Even if it doesn't detect stuff, you can still turn a device on/off and watch the main meter (on your phone app/website) jump up and down. You just have to do the math. Sense helped me a lot. I know exactly how much current I need from a generator after watching it for six weeks.

Edit - pictures from the app. First shows my "power meter" a little bit ago. Shows all loads. You can see the heat pump starting (and get the measurement) and what it added to my overall draw when it was running. The 2nd picture is the heat pump itself. Again, shows the peak in the top left for that time period and the load after started. It's tough for the pictures to do it justice. You have to interact with the app to get useful data. I use this when on gen power (non-MEP) to keep an eye on usage. I also uploaded a device level page (my water heater).

 

[Ranger Danger]

Let's assume I know nothing about electrical (not much of an assumption!!). Given a specific load and a specific distance, would it be ok to oversize a supply wire. Say a known load and distance calls for a #4 wire, would it be better to run a #2 instead? The only drawback I can come up with is cost.

 

[jaxbill]

Let's assume I know nothing about electrical (not much of an assumption!!). Given a specific load and a specific distance, would it be ok to oversize a supply wire. Say a known load and distance calls for a #4 wire, would it be better to run a #2 instead? The only drawback I can come up with is cost.

I don't know the highest amount of current it can generate. 52 A is the highest I've seen someone mention. IMHO, if you're using a back fed breaker, the safest bet is to use wire to support the rating of that breaker. So, 50A or 60 A are the two logical choices. Making the wiring match the breaker seems logical.

 

[Farmitall]

Let's assume I know nothing about electrical (not much of an assumption!!). Given a specific load and a specific distance, would it be ok to oversize a supply wire. Say a known load and distance calls for a #4 wire, would it be better to run a #2 instead? The only drawback I can come up with is cost.

You can't over size a supply conductor.

 

[Farmitall]

I don't know the highest amount of current it can generate. 52 A is the highest I've seen someone mention. IMHO, if you're using a back fed breaker, the safest bet is to use wire to support the rating of that breaker. So, 50A or 60 A are the two logical choices. Making the wiring match the breaker seems logical.

That's ok as long as you are keeping within 50 feet from the generator to the house panel. Once you start going beyond 50' you start incurring a voltage drop and that drop can only be dealt with by going to a larger circular mil wire. And even that might be pushing it in some cases.

On another note: If you are back feeding lets say a dryer plug that is wired with #10/3 or 4 and that run of 10/3 is 40 feet from the dryer back to the house panel. If you used another 50 feet of 10/3 to back feed that dryer plug from the generator now you have a total of 90 feet of 10/3 cable from your emergency generator to the house panel. NOT GOOD.

Even if you fed the panel from the genset to the back feed dryer plug with #2, you still have that 40 feet of #10/3 to contend with in the supply path. Your weak link is that 10/3. You would have to shed loads at the panel by disabling breakers so you do not/cannot exceed the current capacity of that 10/3 wire(which has now become your emergency panel feed).

A 50 amp rated range outlet would be a safer backfeed point and even that has limitations depending on what devices will be drawing off of it from its location back to the panel.

Now, add in the fridge, the well pump, sump pump, AC unit, lights, furnace blower, et al and you can quickly see how the loads tax the feed.

When you are feeding a panel from the street, it is usually fed with adequate sized cable to accommodate total load of the house and usually any additional loads within reason unless its a very old low amperage service to begin with. It is then distributed with appropriate sized wire point to point for each device fed. The dryer takes 10/3, the electric stove takes #8 or #6 depending on the size of the stove, the furnace takes X, the well pump takes X, the sump pump takes X

The whole supply circuit is only as good as its weakest link. The closer you can backfeed the panel and the larger the wire size you can use in any situation, the better off you are.

Back feeding can be done but it must be done with caution as to what the total draw is down the line at the panel. You will have to shed loads so you don't exceed the current capacity of the smallest cable in the feed circuit.

 

[Zed254]

I went with a 70amp breaker on my generator feed (MEP803A). The 803 puts out 52 amps and my electrician said we needed a 20 or 25% buffer. The only thing I could find on the net that explains what he was taking about is here. https://www.hunker.com/12291117/how-to-size-a-circuit-breaker

If we follow hunker's advice and our 803 is generating 52 amps we'll need a 65 amp breaker: 125% x 52 = 65amps.

I believe the ampacity of the 6/4 SOOW cable I used for single phase power (2 conductors hot) is bumped up above 55amps because the ground and neutral conductor should not be carrying many amps. Attached ampacity chart only shows 6/3 and it shows 55amps.

http://www.southwire.com/ProductCat...e&token=282&desc=Viper+Rubber+Type+SOOW+Black

Am I missing something if I stay within 50 feet?

 

[Farmitall]

I went with a 70amp breaker on my generator feed (MEP803A). The 803 puts out 52 amps and my electrician said we needed a 20 or 25% buffer. The only thing I could find on the net that explains what he was taking about is here. https://www.hunker.com/12291117/how-to-size-a-circuit-breaker

If we follow hunker's advice and our 803 is generating 52 amps we'll need a 65 amp breaker: 125% x 52 = 65amps.

I believe the ampacity of the 6/4 SOOW cable I used for single phase power (2 conductors hot) is bumped up above 55amps because the ground and neutral conductor should not be carrying many amps. Attached ampacity chart only shows 6/3 and it shows 55amps.

http://www.southwire.com/ProductCat...e&token=282&desc=Viper+Rubber+Type+SOOW+Black

Am I missing something if I stay within 50 feet?

Are you feeding the panel directly or are you backfeeding through another outlet?


My point above is, if you are back feeding through a stove or dryer outlet to energize the two busses in the panel(giving you 240v in two 120v legs), you are limited to/in the current capacity of the wire that runs from the panel to that outlet.

If you feed the panel directly from the generator using a conductor size that will carry the total load of all the devices in the house you are good. If not, your total current draw is limited by the size of the smallest wire in the feed path to the panel.

 

[jaxbill]

Are you feeding the panel directly or are you backfeeding through another outlet?


My point above is, if you are back feeding through a stove or dryer outlet to energize the two busses in the panel(giving you 240v in two 120v legs), you are limited to/in the current capacity of the wire that runs from the panel to that outlet.

If you feed the panel directly from the generator using a conductor size that will carry the total load of all the devices in the house you are good. If not, your total current draw is limited by the size of the smallest wire in the feed path to the panel.

I’m using a dedicated breaker with an interlock. New wiring to match the breaker.

 

[Farmitall]

I’m using a dedicated breaker with an interlock. New wiring to match the breaker.

Directly to the panel or through a backfeed outlet like a dryer or stove outlet? That's the key point.

If you are feeding the panel directly at the panel that's ok. If not then you are still current limited to the size of the wire that goes to the panel from your backfeed point.

You will also still be limited by the size of the conductor used from generator to panel(directly fed) and the length of that run. If it exceeds a certain distance you will be introducing a voltage drop. That drop will cause higher currents to be drawn because of lower supply voltage.

Your panel is normally fed from the mains by a very large conductor/s that does not introduce any voltage sag/drop and will supply as much current as needed up to the limits of the main breaker rating.
When you substitute that feed with a smaller conductor, you limit both your current draw capabilities and possibly introduce a voltage drop or sag because of the smaller feed conductor size coming in from a long run of cable from the generator.

I hope this is making sense in layman's terms.

You can't push or pull more current through a wire than the wire is safely capable of carrying.

 

[CapePrep]

Guy, Do you have any information on what type of meter you used that recorded usage? I have been on the inter webs looking and most systems seem very expensive. I would think in todays technology, there would be something that could be easily stored and either reviewed on meter or downloaded. Interested to hear what you used.

What we do on the construction site is to clamp an amp meter on each leg, and let it record the next 24 hours, (or longer) data. If you meter only records the highest reading, that's helpful also. At least you know what peak is.

 

[Zed254]

I used a dedicated circuit to backfeed my panel through one of those connectors that force you to turn the breaker box off before you can throw the 70 amp generator breaker. My electrician wired it to handle the 70 amp breaker. BUT I am using 50 amp 'California Standard' connectors from generator to house: so these two connectors become the limiting factor in my generator circuit.

 

[Guyfang]

Guy, Do you have any information on what type of meter you used that recorded usage? I have been on the inter webs looking and most systems seem very expensive. I would think in todays technology, there would be something that could be easily stored and either reviewed on meter or downloaded. Interested to hear what you used.

John Fluke hand held clamp style meter is all I can remember now. We had a USB cable to a laptop. Hook all three up, turn it on, and come back later to get it. If I make a trip to work in the next few days, will look at what model it was. I am still hacking and coughing my lungs up. Its -6 Celsius right now and next week supposed to go to -20.

 

[Zed254]

. Its -6 Celsius right now and next week supposed to go to -20.

You be paying your dues for all those spring and summer evenings in the beer gardens drinking that awesome German brew!!! Get well soon and Prost!!

 

[Farmitall]

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I don't post much in this arena. Its not what I know best. Too many other smart guys out there, so I just don't do it.

So, why am I here? Well, I follow everything generator wise, just to be able to do just this. At the end of the day, the whole thing rotates around You need to consider total current requirement. Everyone repeats it, over and over again, but not everyone "Gets it".

Everything about a house hook up hinges on this fact. Everything. Its the very first thing anyone tosses out in these threads. You simply can not figure gen set size, wire size AND length, hook up gear, safety gear and on and on, until you figure TOTAL current requirement. And then toss on a SAFETY SWAG!!! As has been mentioned, its not good to operate on the edge of the envelope.

Why don't you guys set down and write something for new guys. A guide to this many legged animal, "House Hook Up made simple, 101".

Guy, I'm working with a real piece of crap computer right now. When I get better computer capabilities I will do just that and include diagrams as well and hopefully get some of the people who don't understand what's involved to be able to get a better picture of things "electrical".

 

[Guyfang]

Sharing is what makes this a better forum!! Heck, I may one day get a handle on this stuff.

 

[jaxbill]

John Fluke hand held clamp style meter is all I can remember now. We had a USB cable to a laptop. Hook all three up, turn it on, and come back later to get it. If I make a trip to work in the next few days, will look at what model it was. I am still hacking and coughing my lungs up. Its -6 Celsius right now and next week supposed to go to -20.

That's a nice Fluke. I never saw one with a computer hookup. I made the mistake of buying the cheapest Fluke and it can't even remember/recall the peak current. And I think that was still around $100.

 

[Hard Head]

https://wiki.ezvid.com/best-electricity-usage-monitors

I use the efergy. It gives the daily average but you can watch peaks. I would like a better one but 300 is too much for a monitoring system

 

[69birdman]

So what's the consensus, what's the best 803a hook up to home, mobile & fixed 0 to 50' from home , 50' to 100'. Surely someone has some time logged, what's worked for our experienced owners. I have 38' total of 6/4 from lugs to 50amp breaker. Should I up the breaker to 60?