50 amp power switches to 30 amp

[Sky_Boss]

Originally Posted by jacwjames

A damaged cord could definitely contribute/cause your problem. Your cord has 4 wires, 2 wires are hot L1 & L2. Each leg provides 30 amp @ 120 volt but when combined provide for the 50 amp service. If one of these is intermittently loosing contact then your service will drop from 50 amp to 30 amp.

Checking the cord would be the best course of action now to confirm it has continuity.

Definitely check the cord, plug and connections all the way up the the automatic transfers switch.

However...maybe it was mistype or a pre-morning coffee posting (been there, done that) but...

50 amp service provides 50 amps @ 120V to L1 & L2 for a total of 100 amps.

If both L1 & L2 are performing properly the EMS would should show 50 Amps available and no information on current amps in use.

If one of the hot legs drops off because of bad connection in the cord/plug/power pedestal then one side could still be providing 50A on the other leg I admit I don't know what the EMS will display under that condition. My QUESS would be that it would show 30A available but could show up to 50A in use. Again...WILD GUESS!

If the common was damaged then I admit I'm not sure how that would play but not good for the entire electrical system as a whole.

[RVer402]

I was afraid you might say that - checking that cord and understanding what I find will definitely be problematic for me

Meanwhile, something of note re this issue: The EMS did its switch to 30 amp yesterday and stayed like that till this morning when I turned on electric furnace. When I turned it on, the amps of course flip all around when the fan comes on and it is in the process of starting, and then when the furnace itself kicks in (the bigger sound that puts out the heat in case I'm not using the correct terminology) EMS immediately jumps to 50 and stays there until when ever it seemingly randomly jumps back to 30 again. I have noticed that same scenario any time it is showing 30 and I turn on the electric furnace. Would that give any clue as to which may be more likely, e.g. the EMS circuit board versus wiring issue at the damaged cord? Maybe it doesn't help at all as far as giving direction, but just thought I'd throw it out there.

Later today I hope to be able to accomplish my diagnostic project about the inverter issue and if not then definitely in the morning. I am working around some other things but that is my next priority. I am convinced now that that issue is a matter of education and thus understanding limitations and it would be so awesome to put one longstanding issue to rest. Once I have done that I will call the EMS place and/or possibly check cord (tho very nervous about checking cord), etc and see if can make some progress with the EMS matter.

[TQ60]

Go and get a voltmeter and short extension cord.

Set meter to ac volts and check your outlets as they should measure 120 or so.

Now plug cord into any outlet and measure between the narrow hole in the cord and narrow hole in other outlets.

You will see either zero or 240.

This is when you have 50 amp.

Make not of the outlets used when you find a 240 reading.

Next time 30 amp is indicated remeasure.

If still 240 then still 50 amp power so possible issue with ems but still could be loose wire.

If 120 then you lost a leg and are 30 amp and your system may be working arround it.

A bad cord surely will do what you have.

[RVer402]

Thanks so much for all the thoughts and instruction. Back to the separate inverter "issue" for this post and then forward with the EMS issue.

Big Big Thanks Sky Boss!! I completed the project you outlined and all is well and I have a much better understanding now!! It only took about a year and a half to get to this point and a lot of frustration - for no reason!! Thank You for taking the time!! Maybe you could give some instruction to some mechanics out there! After you initially posted that outline for me, I was pretty certain I knew how it was going to turn out as I had had the realization a few days ago that the frig was playing a role. Then you explained about the breaker panel that's related to the inverter, etc. Light bulbs at that point started to go off in my mind! Understanding and knowledge makes a heap of difference!! For the past few days I have been turning off the frig before using hair dryer or mic/oven and have had no tripping issues. That additionally to me confirms my findings. In the past the inverter tripping has not been 100% of the time so I guess it could still happen but I don't think so. It has been steady for several days that way without tripping. Since it doesn't happen every time I think it has to do with the power surges in the frig when it is running harder, etc and when those coincide with also having mic/oven on or with hair dryer, that's when I guess it goes over the 30 amps. In thinking back to some of the specific occurrences that I remember very well, I think it has more commonly occurred with the mic/oven when running the oven and it is in preheat stage which I assume is taking more power than it does once it gets to correct heat. Had one day where I was trying to cook something in oven and it tripped four or five times in preheat stage and then once to temperature it didn't trip again. All of this correlates in my mind with the findings today. I think the best thing to do is to continue to turn off the frig whenever using the microwave/oven or hair dryer. Also, we normally use propane for the frig and only using electric right now while hubby is away as I can't drive the rig and need to conserve the propane. Once this is done we will be back to propane and it shouldn't be an issue. We WERE using electric on a regular basis prior to a few months ago at the time we had so many problems with this before, so once again the scenario fits the findings. Forgive my wordiness here, but THANK YOU again! This is one "issue" we can put to rest!! Thanks to all and big thanks to Sky Boss for your excellent play by play instructions!

Now can move back to EMS and will do so below in another post.

[RVer402]

As for the EMS, several have shared thoughts, etc. and I do appreciate all.

As to voltmeter, we do have one, I have personally never used one as hubby has done that and he is not here currently. The one that is on board currently is an analog one as he has the digital one. No idea if I can do that but willing to try to learn.

I wish I knew how long this issue has been occurring. It was quite a while before we really tuned in to the EMS panel, so it could have been occurring from day one for all we know. I noticed it consciously for the first time more than a month ago and I tend to think I would have noticed at some point much prior to that but can't say for certain. Would it make sense that if it only started occurring more recently that it would be less likely for it to be related to the "damaged" shore power cord? Just seems to me if related to that it would have been occurring from the time it was damaged which was before we owned the rig, but I may be wrong. ALSO, as stated I can't say for sure that that wasn't the case - I'm just tending to think that. Nothing is simple of course!!

I am going to start by calling the company - thank you again, Jim. I will give them the info and see what their thoughts are as far as possibilities and possible diagnostics and go from there. I will post back after that.

Once again, thanks to all! What a wonderful group of helpful folks!

[TQ60]

Please post a good photo of your volt meter and someone here will give you very detailed instructions on how to use it.

Not difficult by any means

[RVer402]

Re the EMS I called M&M and they are away right now until Thursday of next week so I will need to wait on making that call. Meanwhile as I may try using the voltmeter and checking some things suggested here if I can figure it all out. As suggested I am going to attach a pic of one I currently have available. I will be reading the booklet but I am all ears for any instruction and recommendations. We will see what I can do. Also going to include pics of the cord etc. Though the attaching page looks to allow to attach up to four at once, I have only been able to make one per post stick so I might wind up with pics in their own posts.

Thanks again!

[TQ60]

Basic operation is simple but first some general safety.

With your meter only change the setting while BOTH leads are not touching anything just to avoid crossing a wrong place.

Next be careful to not touch the shiny parts of the probes with your fingers.

DC is direct current or anything battery powered.

AC is alternating current or anything that connects to shore power.

Last is range.

If you know the value you expect select next larger one and if you do not know select largest one.

So for measuring battery charging voltage you select DC because it is battery then next select a number larger than 14 in the DC area.

Now lol at the scales and locate the scale with DC and the number on the selector.

Connect probes to the battery or whatever is being measured and then read the number from the scale.

Real basic directions.

You can Google analog voltmeter use and operation for much more detailed tips and instructions too.

[Ray,IN]

Originally Posted by D Lindy

Not being the brightest bulb in the box, but my first though was that you might have a loose connection on one of the legs of your 50AMP wiring at the circuit breaker box or at the transfer switch. Just a thought for what it might be worth.

I agree. My Progressive system will not display 50A service, it will display anything less.

[Lt Dan]

Originally Posted by Knightab

I am not so sure that isn't the correct way for it to work. Perhaps when using 30 amps or less it just defaults to that but the minute you use 31 or more amps it pops up 50 amps. Have you noticed if it is only showing 50 amps when pulling more than 30?

No, that is the way it's supposed to work. When it senses only 120v it will display the amperage draw. When it senses 240v (120v on each leg) it does not show amperage draw at all.

The sensor coil shown below with the neutral lead going through it in the breaker panel in a 50 amp conversion is what controls the EMS. When it senses return current on the neutral lead, then it knows that you are on a 120v 30 amp connection. If there is no current on the neutral lead as there would be in a 240v connection, then it knows you are on a 50 amp connection.

As mentioned above, a loose connection or a faulty main breaker could be causing the load on one leg to fail causing the sensor to read a current and default to 30 amp. There will be two circuit breakers, probably labeled Main breaker, one for each leg of the 240v 50 amp panel. As stated earlier, one of those two or one of the other circuit breakers could be loose or faulty causing the change in power status.

[HHIDan]

Originally Posted by Lt Dan

The sensor coil shown below with the neutral lead going through it in the breaker panel in a 50 amp conversion is what controls the EMS. When it senses return current on the neutral lead, then it knows that you are on a 120v 30 amp connection. If there is no current on the neutral lead as there would be in a 240v connection, then it knows you are on a 50 amp connection.

I believe this is not how it works...
The EMS checks the voltages on the two breakers that control the first two loads to shed. Easy to test for yourself, turn a breaker off for Shed Load 1 and you will see it will display 30. I found this out by accident as I turned off the breaker for Engine block heater...

[Sky_Boss]

Originally Posted by HHIDan

I believe this is not how it works...
The EMS checks the voltages on the two breakers that control the first two loads to shed. Easy to test for yourself, turn a breaker off for Shed Load 1 and you will see it will display 30. I found this out by accident as I turned off the breaker for Engine block heater...

100% Correct.

I just tested something...

I turned off the breaker for my block heater (load 1) and then fired up both heat pumps a dryer and a couple other items. With my Progressive Industries remote read out I monitored L1 & L2. The is what I found...

1. EMS showed 30 amp service.

2. EMS showed the amps in use as the difference between L1 & L2. As an example, My PI showed 20A on L1, 15A on L2 and displayed 5A in use.

3. Nothing got shed even though I was up to 35A.

I'm not sure that would do the same if there was a physical loss of a leg such as might be the case for a faulty power cord or pedestal. I just found it interesting.

[HHIDan]

If you lost a Leg then only half your main panel would receive power (from the other Leg).

The EMS would report 30 Amps but half the stuff in the RV would not work.

This is why I asked the OP earlier if there was any thing in her RV that did not work and I believe she said everything seemed to work. Because of this, I would conclude that her problem is likely with the EMS board. I would check the 12 volts that powers the EMS board, might be a problem with batteries??

[RVer402]

Hi to all,

I have been busy and must admit I'm a bit nervous about taking on the voltmeter just yet. I will have more time first of week and may or may not take it on then. Meanwhile a couple things...

I haven't tried to digest all the stuff about checking various things with voltmeter and possible scenarios etc, but I am tending to think it might be the EMS board. And HHIDan it's interesting that you bring up the question of some possible relation to the batteries. Also to verify as mentioned before, I have not noticed that anything is not working when it shows 30. I haven't tested it per se and I may need to do that specifically but I have had no indication of that. Also, when showing 30 and I turn on electric heat it consistently goes back to showing 50 when the furnace burner or whatever it is kicks in. It shows the amps moving all around when fan starts and when the big furnace sound starts it goes immediately to 50 every time.

Batteries - another big topic and I don't want to divert off the EMS here but just to say if this could be impacted by a battery issue - the house batteries are bad and need to be replaced. Since we are done for the season after May we were going to address that when we return in the fall, but just FYI that there is definitely a battery issue aside from this in case it has any potential bearing on the EMS issue.

There has also been discussion that this may also be normal operation and I can't exclude that since I can't say with certainty that this hasn't been occurring all along. We were clueless on the EMS panel for a long time...

I am still tending to wait till Thursday and chat with the M&M folks before doing much exploring with the voltmeter but I am going to at least try to educate myself a bit on using it meanwhile. Also thinking next time EMS is showing 30 I should test various things to try to confirm everything does work at those times. Reasonable plan?

Many continuing thanks to all!!