Strange amp readings - 2000 Vantare H 3-45

[D Lowe]

The coach is set up to run 2 A/C's on each leg. Sometimes it will be pulling about 35 amps per leg which seems about normal. Other times it will show 50+ amps on one leg and 0 amps or close to 0 on the other leg. At that point I have to shut down one A/C or it will for sure blow a circuit breaker. I never know when it is going to be normal. Sometimes it will stay OK for days and other times it may be abnormal from the moment I turn on the A/C's. When it is abnormal it will still be showing all the amps on one leg even when I turn all the A/C's off. Any ideas what is going on?
D Lowe, 2000 Vantare H 3-45, 2 slides

[Mark3101]

Where are you seeing this? On an inverter panel, or a dedicated voltmeter? I don't see how you can get a load to jump to another leg without something shorting out. Are you having any other issues with your electric systems?

[Jon Wehrenberg]

D,

All our coaches should be set up so if we have four AC units they are split between the 2 120V legs. Your amp draw with all four ACs on at about 35 amps per leg is what I would expect to see.

I think your coach has all of the electric circuits going through the inverters instead of just certain dedicated circuits. Is it possible one of the inverters is dropping off line? I am just guessing because I cannot think of any reason why only one leg would start carrying all of the load and the other leg none of the load.

[nrhareiner]

When you are seeing the amp draw being uneven, is one inverter bank showing the amber light indicating not in float charge mode, while the other bank showing 2 green lights? If yes then check and see if one inverter is reading float charge with inverter amp reading a negative 9-15, and the other leg reading a charge rate at the same value on the positive end of the scale. Then check amount each leg load versus input and that may get you the answer as to what real draw from pedestal is looking like. Hope this helps.

[D Lowe]

Yes. one inverter will be in bulk charge and the other is in float just as you describe. I will check as you suggest. Are you suspecting an inverter is causing this?

[D Lowe]

Just returned from the coach after reading these posts. I've been in Prevosts for a long time but I'm still learning things, some of it that I knew in the past & had forgotten. I realized this bus has a manual switch to bypass the inverters. When I did that and turned on all 4 A/C's I was only pulling between 28 & 30 amps on each leg which is what I consider very normal. I've owned this bus 4 years and I don't believe the house batteries have been changed in that time. I believe that I have some bad house batteries because when I bypassed the inverters one inverter immediately showed to be in float charge and the other one was in bulk even though it had just before switching been in float also. Am I on the right track?

[D Lowe]

I'm beginning to lean toward thinking this way. The inverter doesn't seem to be dropping off line but it doesn't seem to be carrying the load. This is giving me some ideas to try.

[D Lowe]

I'm seeing it on the inverter panel in the coach. I have a dedicated voltmeter but haven't tried that yet. I don't believe anything is shorting out. This is the most serious issue I'm seeing but I don't think my electrical system is acting just right. Another response I received suggests it may be an inverter problem and I'm leaning that way myself. I don't fully understand the system in the Vantare but I think everything goes thru the inverters.

[BenC]

When one inverter goes to "float charge" the float voltage that inverter wants to see 26.6vdc at it's input, while the inverter that is still in "bulk charge" wants to maintain battery voltage at 28.6vdc. If the loads are great enough downstream of the inverter in float, it will start inverting to drop the battery voltage to 26.6 while the other inverter ramps up its charge rate in an attempt to maintain the bulk and "absorption" voltage of 28.6vdc. This is normal, and always occurs at the end of the charge cycle, but usually only lasts for a few hours UNLESS you have bad batteries or extremely high load on the inverters, both of which are the most common situation that prevents the one in bulk from "finishing up" its charge cycle and dropping to float with the other inverter.