What is running on each leg of 50A service?

wagonmaster2 · 02-16-2008, 05:43 PM

On the Winnebago EMC when using 50A service, is it possible to tell which appliances are running on each leg of the 50A? I've often wondered if its possible to overload a circuit if running the clothes dryer, air conditioner/heat pump, microwave, coffee maker, toaster, and maybe a small electric heater or two at the same time. I've never had an occasion to run that much at one time but one never knows when it might have to happen. Using 30A service you know what current you are drawing but since we're not shown the draw on 50A are they assuming that no way can you exceed 50A on each leg?
Wagonmaster2

wagonmaster2 · 02-16-2008, 05:43 PM

On the Winnebago EMC when using 50A service, is it possible to tell which appliances are running on each leg of the 50A? I've often wondered if its possible to overload a circuit if running the clothes dryer, air conditioner/heat pump, microwave, coffee maker, toaster, and maybe a small electric heater or two at the same time. I've never had an occasion to run that much at one time but one never knows when it might have to happen. Using 30A service you know what current you are drawing but since we're not shown the draw on 50A are they assuming that no way can you exceed 50A on each leg?
Wagonmaster2

John_Canfield · 02-17-2008, 04:38 AM

The only way I know for sure is to look at your AC wiring diagram. I suppose it would be possible to overload one leg, but we have never managed to blow a breaker but we don't use a toaster or portable oven. We have used a portable heater, but no problems with that.

tderonne · 02-17-2008, 07:24 AM

Can't say that it's true for all, but ours only has the #2 A/C compressor on the second 50A leg.

Duner · 02-17-2008, 12:11 PM

I have 50 amp service in my '04 Winnie which is probably wired same as yours. But I have added the Progressive Industries Electrical Management System EMS-HW50C (surge, over/under voltage protection) and it shows the current on each leg. From what I observed, everything runs on L1, except L2 powers the electric water heater and heat pump compressor #2. I've looked at the schematics and the L1/L2 lines are shown going into a box symbol (without internal) detail and loads coming out which didn't help me understand the breakdown.

I've looked into this because I have a problem when running on the Onan generator and blowing L1 breaker in the generator box. This happens when the a/c is running and I use the microwave and the bat charger is pulling about 10 amps. I have to force off one of the loads. I wanted to redistribute the L1/L2 power but it is complicated by the Winnie EMS power shedding circuits. So I'm still in a quandary on this subject.

Happy Trails,
Duner

tderonne · 02-17-2008, 12:39 PM

We have a similar issue with the EMS not quite covering the way we use our systems. It's been a while, but I think when the A/C is running, we can't run the microwave. It can shut down the 2nd compressor, but not the first. I've thought about rewiring it such that it can shut off both compressors, that's what we do manually anyway. I looked into it more, but it was a long time ago. Seemed like it would be possible. (I forget what ours CAN shut down. I think the high speed indoor blower is what I was thinking could be changed to shut off the 1st A/C compressor.)

A good project for our trip to the Keys in a few weeks. We'll be on 30amp service, and I hope we'll need the A/C!

Tom N · 02-17-2008, 03:25 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tderonne:
We have a similar issue with the EMS not quite covering the way we use our systems. It's been a while, but I think when the A/C is running, we can't run the microwave. It can shut down the 2nd compressor, but not the first. I've thought about rewiring it such that it can shut off both compressors, that's what we do manually anyway. I looked into it more, but it was a long time ago. Seemed like it would be possible. (I forget what ours CAN shut down. I think the high speed indoor blower is what I was thinking could be changed to shut off the 1st A/C compressor.)

A good project for our trip to the Keys in a few weeks. We'll be on 30amp service, and I hope we'll need the A/C! </div></BLOCKQUOTE>

The EMS shedding sequence can be changed using a series of DIP switches. The DIP switches are located on the EMS Control Module board in your 120v breaker panel. Read your Intellitec EMS manual or call Intellitec.

-Tom

wagonmaster2 · 02-17-2008, 04:41 PM

Since the EMS doesn't show any draw on 50A, you'd think Winnebago could furnish this to all customers with 50A service in their coach. They wired the coach, so it should be a simple matter to tell us what is running on each one. And without all the complicated wiring schematics.
Wagonmaster2
2004 Meridian 36G

tderonne · 02-17-2008, 05:04 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Tom N:
The EMS shedding sequence can be changed using a series of DIP switches. The DIP switches are located on the EMS Control Module board in your 120v breaker panel. Read your Intellitec EMS manual or call Intellitec.

-Tom </div></BLOCKQUOTE>

It's not the sequence I need to change. I need to change what it can shut down. It's been while but I think mine can shut down the #2 A/C compressor, the water heater, fridge, and the high speed indoor blower. With everything turned off that the EMS can turn off, the #1 A/C and microwave will draw more than 20 amps. Doesn't take much more plugged in or turned on to use more than 30.

Tom N · 02-18-2008, 06:20 AM

Most Winnebago motorhomes run the second AC or the #2 compressor, for a basement AC unit, off the 50amp L2. The auto transfer switch send L2 to the second AC or #2 compressor when plugged into 50amp service.

The L1 50amps powers the remainder of the coach.

When plugged into 30amp service L2 will have no power and L1 will have 30amps. The EMS will decide if there is sufficient power, from the 30amp L1, to power the second AC or the #2 compressor.

The Intellitec EMS manual shows a pictorial diagram of both 30 and 50 amp connections.

-Tom

wagonmaster2 · 02-18-2008, 04:26 PM

Thanks Tom N - that's simple enough. Golly, you'd think they'd run more on the L2 leg than just one compressor, but I've never had any problems while on 50A so maybe they know what they are doing. Used to think I'd never want a coach with 50A and have to drag around that big heavy cord, but after using 50A service its really hard to be limited to only 30A shore service.
Wagonmaster2
2004 Itasca Meridian 36G

Tom N · 02-18-2008, 04:47 PM

50amp is actually 2 - 50amp circuits so 100amps is available. As opposed to a single 30 amp circuit.

Many older homes only have 100amp service.

-Tom

DancinCampers · 02-18-2008, 05:18 PM

Tom, I'm not sure about L2 not having power when a 50amp coach is plugged into 30 amps. I think the dogbone puts power on both L1 and L2. Otherwise there would be no reason to have the EMS turn off the #2 compressor or hwh, items on L2. But I could be wrong. I think the diagrams in the book show 30 v 50 amp installations, not 30amp operation on a 50amp install. You have peaked my interest and I plan to look them over next time I'm in the coach.

The EMS board has 4 relays, if my memory serves me right. Two of them are 120V, to control the refer & hot water heater. The other two are 12V to control the #2 compressor and hi speed fan.

I think the EMS is designed as it is with a purpose. The thermostat controlls both compressors (the time delay sequences) when in the cooling mode. If you had the EMS control both of them, it would be possible that both compressors would try to start under pressure. This would cause the internal overloads to trip, or the 30amp pole breaker to trip or the coach 20amp circuits to trip, or worse. With the EMS only controlling the #2 compressor, this shouldn't normally happen, as the tstat won't call for it unless the #1 is already up and running.

You could rewire it to control #1 compressor, then just turn off the #2 compressor breaker when on 30amp, and run on one compressor only. But I'm not sure how this would affect operation on the generator, as one leg of it feeds L2.

It may be better to install 2 small on/off switchs on your EMS remote panel, then control the compressors manually, but then when you restart them you become the tstat time delay interface.

Just don't let the smoke out of the wires, not good.

On a lighter note, maybe a smaller microwave

(The devil made me do it

)

Route 66 · 02-19-2008, 03:28 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I think the dogbone puts power on both L1 and L2. </div></BLOCKQUOTE>

You are correct.

tderonne · 02-19-2008, 05:55 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DancinCampers:

The EMS board has 4 relays, if my memory serves me right. Two of them are 120V, to control the refer & hot water heater. The other two are 12V to control the #2 compressor and hi speed fan.

I think the EMS is designed as it is with a purpose. The thermostat controlls both compressors (the time delay sequences) when in the cooling mode. If you had the EMS control both of them, it would be possible that both compressors would try to start under pressure. This would cause the internal overloads to trip, or the 30amp pole breaker to trip or the coach 20amp circuits to trip, or worse. With the EMS only controlling the #2 compressor, this shouldn't normally happen, as the tstat won't call for it unless the #1 is already up and running.

You could rewire it to control #1 compressor, then just turn off the #2 compressor breaker when on 30amp, and run on one compressor only. But I'm not sure how this would affect operation on the generator, as one leg of it feeds L2.

It may be better to install 2 small on/off switchs on your EMS remote panel, then control the compressors manually, but then when you restart them you become the tstat time delay interface.

Just don't let the smoke out of the wires, not good.

On a lighter note, maybe a smaller microwave

(The devil made me do it

) </div></BLOCKQUOTE>

Excellent analysis Dan. As I said, I haven't put too much thought into it yet. As for adding a switch for the compressors. Got that in the form of a thermostat. That's what we do now. Go turn off the AC and run the microwave. Might not be a way to make the EMS cover us when we want AC and the micro on 20 amps. AC alone is pushing it. More noodling...gotta look where the #2 compressor is turned off, figured it was just like the thermostat and the delay would still be there? Perfect project for a day with nothing better to do next month.

DancinCampers · 02-19-2008, 06:59 PM

Tim,

The #1 comp control wire (Y1) goes directly from the tstat to the basement unit. The #2 comp control wire (Y2) is routed thru the 12V NC relay on the EMS control board, then to the basement unit. I don't think the EMS unit has any delays built in, but there may be one on the basement PC board.

My EMS control board is located inside my 120VAC breaker panel.

The path for the HI SPEED blower is a little different, it goes thru the EMS control board, but when the EMS takes it out of the circuit, the control voltage is placed on the LO SPEED wire going to the basement unit.

ctcamper · 02-20-2008, 01:46 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">50amp is actually 2 - 50amp circuits so 100amps is available. As opposed to a single 30 amp circuit. </div></BLOCKQUOTE>

That is 50 amps available at 240 volts or 100 amps available at 120 volts (50 amp per leg) and shared neutral.

SCVJeff · 02-20-2008, 04:10 PM

So, how do it know that it's getting 50A or dog-boned 30A service? Is this single phase 110VAC on 50A breakers, or 220 split?

Dave and Cris · 02-27-2008, 06:17 PM

I wanted to second the comment about getting used to 50A service and more load on the L2 leg. After two months on the road, we just plugged into a 30A service for the first time in a long while. I had the elec heat (heat pump) on and when the wife started using the microwave, the power management system started shutting down things. I have a hunch they designed the a/c compressors to be on dedicated circuits because of the AMP surge when they first start up.

DancinCampers · 02-28-2008, 06:41 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I have a hunch they designed the a/c compressors to be on dedicated circuits because of the AMP surge when they first start up. </div></BLOCKQUOTE>
When the basement air is working properly, the compressors and outdoor blower motor are all sequenced by time delays to reduce amp surge. I think the real reason the #2 compressor is on L2 circuit is because of the generator. My genset has 2 breakers, a 30AMP (which I think is L1, and a 20Amp (which I think is L2). I think L1 & L2 are separate circuits on 50Amp & GenSet power, but when on 30Amp shore power are in reality just 2 extension cords plugged into 1 30Amp outlet.

Jeff, the EMS manual outlines how it knows the difference, I believe it can tell the phasing of the L1 & L2 lines. It can tell when on gen power by the B+ voltage from the genset.