Energy Management Load Indication

[LewF]

On our 2009 Camelot the IntelliTec energy management system control panel does not indicate the load current when the generator is providing power. The manual and our experience with our 2007 Endeavor tells us it should. Anyone have a similar system and can tell us if you see load current indicated when your generator is running?

I want to know how much load I am putting on our 10kw generator so that I don't run it with too light a load - bad idea for diesels. I guess I will eventually figure out the load of the various systems on the coach and can then estimate by what's turned on but I think the IntelliTec panel should be able to tell me directly. Thanks for the help.

Lew

[BigSkyBob]

Hi Lew. My 2008 Camelot displays the current load on the EMS panel when the generator is delivering the power. But I have often wondered why it doesn't when connected to shore power. There are several relays behind that panel that control the display so perhaps the problem lies there.

[Luv2go]

Has your generator output always been this way? If not, something has gone wrong, otherwise here's a possible explanation:

Short answer:
It was designed that way.

Long answer:
Normal 50A service is 120/240V, i.e. there is 120V from one each line to neutral and 240V across both lines (this is why it is so important to make sure the pedestal neutral is good before hooking up).

The Intellitec EMS measures current with a CT (current transformer) on the Neutral line. With 120/240V service, the neutral current is equal to the difference in currents supplied by each line, so it is not a true indication of current being drawn by the coach. That's why the EMS does not display it. It senses line-to line and shuts off the current display when it senses 240V.

Why did Intellitec choose to do it this way? IMHO cost and design simplicity. There is another EMS mfr (don't remember exactly who) which uses 2 CT's which allows load current to be displayed for all conditions.

So if your generator is set up to produce 120/240V the EMS cannot display the current. It is very possible that your generator was set up this way on purpose because of wiring issues (10KW at 120V = 83+A which is requires larger wire than the 6ga used for your typical 50A service). Your Endeavour may have had a smaller generator which they could wire for 120V only.

Can you rewire your 10KW generator to produce 120V only and make the EMS display? Probably, but if you're not careful you'll be going over the current rating of your Neutral wiring in the EMS. If rewired for 120V only in a way to protect the 50A neutral wire, you'll only get 6000W out of your 10,000W generator.

Stewart

[ShapeShifter]

Quote:

Originally Posted by Luv2go Short answer: It was designed that way.

Stewart, I think you have it 100% correct.

My 2007 Endeavor does show the current when running the generator. It's an 8kW generator, wired up in dual 120 volt mode, so that that the neutral can have up to 66 amps on it. In my case, the neutral wire from the generator through the transfer switch and all the way up to the breaker box is oversize to handle the extra load that this arrangement provides.

But with a 10kW generator, the 83 amps the neutral could carry would indeed require a very heavy wire, so it is quite reasonable to think that they wired the generator up in 120/240 volt mode. Because Intellitec is too cheap to put in more than one current transformer, there would be no current readout in that case (just like when on 50A shore power.)

Anecdotal evidence that I've heard from others is that 8kW and smaller RV generators are usually 120 only, while 10kW and larger are usually 120/240. The neutral wire size is likely the driving factor behind this.

[tquarles]

It could also be, as was explained to me by a service writer, that when plugged into 50 amp service, there should be no load shedding because everything built into the RV can be powered simultaneously, so the load-shedding system is shut down, but when running on my generator(7.5kw), also 240 v, but only 35 amps, it shows the current because it may need to load shed. (The 7.5 kw generator can't be wired as 110v, because that would require a 70a breaker in the load center as the main supply breaker, which isn't there - there is a dual-leg 35a breaker on the generator feeding through the transfer switch to the same dual-leg 50a breaker as shore power)
With your generator at 10kw, you likewise can power everything in the rig without load-shedding.
I agree it would be nice to have the display (I'd like it when on shore power sometimes, just for curiosity), but it appears they configure the rigs to shut it off if the load-shedding circuits aren't going to be doing anything.

[ShapeShifter]

Quote:

Originally Posted by tquarles It could also be, as was explained to me by a service writer, that when plugged into 50 amp service, there should be no load shedding because everything built into the RV can be powered simultaneously, so the load-shedding system is shut down, but when running on my generator(7.5kw), also 240 v, but only 35 amps, it shows the current because it may need to load shed. (The 7.5 kw generator can't be wired as 110v, because that would require a 70a breaker in the load center as the main supply breaker, which isn't there - there is a dual-leg 35a breaker on the generator feeding through the transfer switch to the same dual-leg 50a breaker as shore power)

Your rig may be the exception to the rule, but if you look closely, and take some voltage measurements, I'm willing to bet reality is a little different than what you wrote.

Have you looked at the wiring diagram for the 50 Amp Intellitec system? If you do, you will see that it has only a single current sensor, which is on the neutral wire.

With a 240 volt supply (two hots in opposite phase) the neutral wire carries the DIFFERENCE of the current on the two hot lines. That means that the single sensor cannot reliably tell you the total current for a 240 volt source. I believe that's the real reason there is no current display on 50 amp shore power. (Because load shedding is not needed is likely the reason that Intellitec didn't spend the money to add a second current sensor.)

With a 120 volt supply (two hots in phase) the neutral wire carries the SUM of the current in the two hot lines. That means the single sensor can reliably tell you the total current in the two 120 volt hots. It also means that the Intellitec system has the information it needs to do load shedding.

Now, you say your 7.5 kW generator is 240 volts. But you also say that the Intellitec panel shows you the current while running your generator. The panel is incapable of showing the current for a 240 volt source. If you look closely, I think you will see that your generator has two 120 volt outputs of about 31 Amps each. Those two outputs are connected to the two hot legs feeding your main breaker panel. That may sound like a 240 volt hookup, but measure the voltage between the two hot legs, and I'll bet you don't measure any voltage. That's because the two hot legs are in phase with each other, meaning that the neutral can carry up to about 62 amps, which is what the Intellitec panel is measuring. If you look, I'll bet that you find that the cables between the generator and the transfer switch, and between the transfer switch and the breaker box, both have an oversize neutral to carry that extra current.

You say this can't be because you don't have a 70 amp breaker. You don't need it because you have two 35 amp breakers on the generator, which are feeding two halves of a double pole 50 amp main breaker, and returning on an oversize neutral. I do believe that you don't have a 70 amp 120 volt generator, nor do you have a 35 amp 240 volt generator -- instead, you have a generator with two 31 amp 120 volt outputs that are in phase with each other. (Take a look at your generator specs, either on a ratings plate or your generator owner manual -- I'll bet it doesn't say 120/240 volts, but simply says 120 volts.)

You say the reason the panel doesn't display current is because it doesn't need to shed loads. I say the reason is because it can't display 240 volt current (and the reason it can't is because it doesn't need to do it.) I admit that's some fine nuances of semantics. But the rest of it (your generator supplying 120 or 240 volts) is a more significant difference, and has some important ramifications. Check it out, I think you're going to be surprised.