Back feeding main panel breaker questions

[jimbo913]

First, I want to thank everyone on here for the help they provide. I belong to many forums but this one is hands down the best!

Planning to prepare my interlock back fed electric panel for a larger generator (hopefully an MEP-803A). Plan is to replace my existing 30A double pole back fed breaker with a larger one. Also will be purchasing a new RV 50A outside panel box to replace the 30A, and getting a 6' piece of 6/3 wire (with ground) to back feed my breaker from the outside panel.

Questions:
-Since the generator can run closer to 54A (not counting additional motor start capacity, which I don't think that would trip a breaker). Should I go with a 60A breaker or a 50A?
-I am guessing that the generator has its own breakers on each leg?
-Will the 50A outside receptacle handle the additional 4A assuming I ever surge it high enough to use it?

-The cord I was planning to use from the generator to the outside box is 10' of 50A RV cord, but I can use something else if recommended?


The backfeed breaker is in the lower left of my main panel and I have a 100A breaker on the right side that feeds my sub panel. I have listed below the circuits that I want to be able to run, and keep in mind they would never be ran at the same time and many have high starting amps but relatively low run amps.

Sub panel: 1, 3, 5, 6, 7, 6&8, 11, 10&12, 14, 16, 22 (2 ton AC compressor, 3/4HP well pump, 2 Bedrooms, Basement lights, garage outlets and microwave)
Main panel: 7&5, 13, 14&16, 17, 19, 20&21, 23, 25, 26, 30 (Lights, 1 bedroom, garage, water heater, sub panel breaker and a sprinkler pump). Basically I would be keeping everything on but 50A and 60A breakers.

Almost all the loads are on the right side of my main. The water heater (is only 600w running but takes 4800w to start it), then there is the sub panel, and the sprinkler pump that I hope never kicks on .

-So do I need to even out the loads with this configuration and if so what recommendations do you electrician types have? Also, all the lights in the house are florescent or led, and the basement only has a freezer in it. Besides start loads I doubt we will ever run more than 5kw-6kw for any serious length of time.

 

[jimbo913]

If I can run my second 2 ton A/C compressor, that would be awesome but I am not sure I can do that with an MEP-803 and have enough reserve power for other items? I did put hard start kits on the A/C compressors so the RLA of 54A should be much lower. They are on 20A circuits.

 

[Fredo Corleone]

You should never backfeed your panel linemen working on power outages could be hurt. A transfer switch the way to go.

 

[DieselAddict]

The breakers protect the conductors and by code you aren't allowed to install a breaker that exceeds your conductor rating. So if you are running 6ga copper then you have to use a 50a overload. To jump to a 60a you would have to use 4ga copper. That would also exclude you from using a 50a RV cord and 50a plugs. Everything will have to be rated for 60a. I doubt you would have any tripping issues with the 50a. I don't on my setup and I'm running a very similar configuration here.

You need to double check that cord and make sure how its set up. Many 50a RV cords are a combination of 30a 120v with a 20a 120v circuit inside and not a 50a 240v. That means it will be a combination of 10ga and 20ga wire which won't work in a 50a 240v setup. You'd melt it.

As far as load balance goes its hard to say how well it will be balanced. Obviously your 240v loads are balanced inherently except for the oddballs like a furnace with a 120v fan and a 240v compressor. That isn't very common though. The best thing is to take some measurements and see where you are. Setup a couple of scenarios such as light load and heavy load then measure it. You'll know for sure then.

 

[DieselAddict]

You should never backfeed your panel linemen working on power outages could be hurt. A transfer switch the way to go.

You should never backfeed a panel without an interlock. While backfeeding not the preferable method it is an accepted method.

 

[patracy]

Jimbo appears to have a interlock installed.

 

[Isaac-1]

I too would tend to say that an RV cord should work ok, just get your inlet/outlets set up correctly so that you never have live power to the exposed prongs. You might also consider a 50 amp twist lock (now being required for RV use in some states), google 50 amp California plug or outlet. Or if you really want to do it right, and money is not an object, upgrade to that 60 amp breaker, 4 ga wire, and a 60 amp pin and sleeve connector (the correct current one for 120/240 single phase is a 460P12W plug, which mates with other 460?12W connectors, bases, etc.) The 12 bit is the keying/color code for voltage. As to load balancing, it is hard to tell just looking at a panel, since alternating line sides are every other vertical slot, and many times the breaker sizing does not tell the actual load (many of those 15 amp breakers may be drawing less than 1 amp each, but are important because things like alarm clocks, or bathroom lights are connected to them).

Ike

 

[jimbo913]

Thanks DieselAddict.

I will just drop down to 50A breaker because 4A is not worth the added cost for 60A outlet and wire. Isn't the conductor rating also based on cable length? I am only going 5' inside with 6/3 and 10' on the outside and the RV cords are normally about 25-30' long. Thanks for the heads-up on the RV cords, I will make sure that all conductors are the same size before ever using one.

When you say to take measurement on the load, do you mean that once the larger Generator is hooked up, to check L1 and L2 on the control panel amp gauge or check it some other way?

 

[jimbo913]

As to load balancing, it is hard to tell just looking at a panel, since alternating line sides are every other vertical slot"

Ike

This is what I need to learn more about to have a better understanding. So it is not the right half and left half (even and odds) of each panel, but every other vertical slot? That makes sense now that I think about it... (and even seems obvious).

 

[jimbo913]

I took a look at an electrical panel bus online without any breakers in it and it makes sense now. If my understanding it correct, the 240V loads are automatically balanced since they use 1 of each leg. If I assign L1 and L2 to every other vertical slot and add them up, it looks very evenly balanced in the main. The 110V loads in the sub panel can't be added up in the same way as the main because I don't know if L1 and L2 are reversed when starting at one end of the panel and assigning L1 or L2 designations to each vertical row. However, the 110V loads are so small that it wouldn't make a difference which leg they were on. The microwave and the fridge are definitely on different legs and those are the largest 110V legs in the sub panel.

I think I got it now, and figured I would talk myself through it in case someone else comes along. Hopefully you pros can chime in if my new understanding is correct.

 

[Isaac-1]

Just keep in mind that when dealing with half height breakers (which I did not see in your boxes) that they can be plugged in so 2 single wides are on the same line, and a thin double wide will take up half of an L1 and an L2 slot.

 

[jimbo913]

Thanks. You learn something every day and sometimes more than one

 

[microjeep]

A quality 60 amp transfer switch is around $100 bucks, there is no way in he// I would install this without it! scenario; powers out, storming, raining like crazy, wife kids complaining about dark, DID YOU REMEMBER TO TURN THE MAIN BREAKER OFF? Best case outcome- the power comes back on and it trips the breaker. Worse case- cops, lawyers, funeral, lawsuit!

Took a better look at photo and saw mechanical interlock, that may satisfy code requirements but in the land of opportunist and lawyers don't if I would trust that in a court of law?

 

[DieselAddict]

A quality 60 amp transfer switch is around $100 bucks, there is no way in he// I would install this without it! scenario; powers out, storming, raining like crazy, wife kids complaining about dark, DID YOU REMEMBER TO TURN THE MAIN BREAKER OFF? Best case outcome- the power comes back on and it trips the breaker. Worse case- cops, lawyers, funeral, lawsuit!

I don't understand the comment in this context. Jim has an interlock that prevents both breakers from being turned on at the same time.

 

[Isaac-1]

I don't understand this comment either, as any transfer switch would need to be sized for the size of the main breaker going into the panel, not the 50 / 60 amp backfeed breaker. So probably 200-250 amp, not 60 amp which gets a bit more expensive. Either that or a sub panel would need to be wired in addition to that 60 amp transfer switch, which gets labor intensive as well. Now there are issues with interlock kits that do make them inferior to real double throw transfer switches. The two biggest problems with them is that they can easily be defeated by simply removing the front cover plate (some kits include special security screws for this reason), and perhaps more importantly a breaker is not a positive cut off device. It is possible for power to still be flowing through a breaker even with the switch in the tripped / off position if the contacts have welded themselves closed. I saw an example of this at a relatives house one weekend a year or two ago, the outlet for the refrigerator needed to be replaced, and the guy had turned off every breaker in the panel to locate it yet the light stayed on in the fridge, it would only go off if he flipped the main breaker, proof that it was being powered through that panel. Once the defective breaker was located and replaced it (along with the outlet), things went back to working as expected.

Ike

p.s. it is also important to know that regulations for interlock kits vary by location, and are even banned in some areas (I think the whole state of NJ), they are also often limited to being used with generators that are connected by way of disconnectable cords and not hard wired. (a distinction that makes no sense to me, but still it is there)

 

[DieselAddict]

Mechanical failures are a problem with breakers. One of the things done in industrial applications is to exercise breakers on a yearly basis and load test them every 5 years.

Before starting this test go to the breaker panel and feel each breaker with the back of your hand. Make note of any that feel warm. If any feel HOT that breaker may have a problem.

Here is a procedure you should do once a year - Turn OFF the main breaker then check to make sure the power is off EVERYWHERE in the house. If you find power somewhere this means that the MAIN breaker has fused contacts. Replace it IMMEDIATELY. After you have verified there is no power in the house flip EVERY breaker in the panel OFF and ON a 4-5 times. Make sure all the switches move as they should. Leave them all in the OFF position.

Flip the MAIN breaker ON and OFF 4-5 times leaving it in the ON position. Check again to make sure the power is off EVERYWHERE in the house. If you find power somewhere this means one of the OFF breakers has fused contacts. Replace it IMMEDIATELY.

Turn on all the lights, ceiling fans, and other loads that can come on safely when you turn on the breakers. The idea here is you need some load on them for the next test if possible. A halogen work light or two is great for this.

Go down the panel and flip each breaker on one at a time. Listen for any signs of arcing (buzz or sizzling sound) when you turn on the breaker. Make sure the handle on the breaker moves correctly and doesn't feel squishy when it reaches the ON position. If any of the breakers make such a sound or don't feel right when you turn it on replace it.

One of the main reasons for doing this is to clean the contacts on the breakers. When you flip it on and off you will cause the contacts to rub together and brush off any dirt that might be there. You'll also find out if any of the breakers are fused. Something simple like this could prevent someone from being hurt or prevent your house from suffering an electrical fire. Its well worth a half hour of your time.

Edit - should have read it once more before hitting post.

 

[steelandcanvas]

Mechanical failures are a problem with breakers. One of the things done in industrial applications is to exercise breakers on a yearly basis and load test them every 5 years.

Before starting this test go to the breaker panel and feel each breaker with the back of your hand. Make note of any that feel warm. If any feel HOT that breaker may have a problem.

Here is a procedure you should do once a year - Turn OFF the main breaker then check to make sure the power is off EVERYWHERE in the house. If you find power somewhere this means that the MAIN breaker has fused contacts. Replace it IMMEDIATELY. After you have verified there is no power in the house flip EVERY breaker in the panel OFF and ON a 4-5 times. Make sure all the switches move as they should. Leave them all in the OFF position.

Flip the MAIN breaker ON and OFF 4-5 times leaving it in the ON position. Check again to make sure the power is off EVERYWHERE in the house. If you find power somewhere this means one of the OFF breakers has fused contacts. Replace it IMMEDIATELY.

Turn on all the lights, ceiling fans, and other loads that can come on safely when you turn on the breakers. The idea here is you need some load on them for the next test if possible. A halogen work light or two is great for this.

Go down the panel and flip each breaker on one at a time. Listen for any signs of arcing (buzz or sizzling sound) when you turn on the breaker. Make sure the handle on the breaker moves correctly and doesn't feel squishy when it reaches the ON position. If any of the breakers make such a sound or don't feel right when you turn it on replace it.

One of the main reasons for doing this is to clean the contacts on the breakers. When you flip it on and off you will cause the contacts to rub together and brush off any dirt that might be there. You'll also find out if any of the breakers are fused. Something simple like this could prevent someone from being hurt or prevent your house from suffering an electrical fire. Its well worth a half hour of your time.

Edit - should have read it once more before hitting post.

All excellent suggestions, good post!

 

[DieselAddict]

Took a better look at photo and saw mechanical interlock, that may satisfy code requirements but in the land of opportunist and lawyers don't if I would trust that in a court of law?

I agree 100% that a doubled ended transfer switch is far safer.

 

[microjeep]

First and foremost i would like to apologize for posting while asleep. woke up this morning read this and had Y2K flashbacks. Installed dozens turned down many more. Really wish I had documented some of the "ways to save money" I heard. In my OPINION the only proper way is to add a transfer switch AND sub panel, (just assumed this was in the mix because there were 2 panel photos?). What it cost is what it cost? Again my opinion and that's all it is. Your house your family your call.

 

[k10greene]

You should definitely using a 60A breaker so that you have a safety margin. Whenever I figure a load I never max out a breaker 100% that just leads to problems and doing the same job twice. Rule of thumb I try to only use 90% capacity on the breaker. If conditions ever change you're going to have problems with an undersized breaker. Transfer switch is also proper I just installed one in my bosses house for his generator. It saves liability and other potential headaches.