G'day all:

I came across a passing reference to a possible limit value in the Energy Management System software for maximum current or power draw that caught my attention.  I can't remember which forum I found this on, but it raised a very interesting point.

The writer mentioned something about the Energy Management Systems in general (any brand) using this pre-programmed limit value in determining when to start shedding loads.  He really couldn't comment further on this point.  This is a very important issue if you want to install, and actually use, a larger capacity generator set with an Energy Management System that may be set up to have an industry standard 5.5kw gen set.

The Grand Design 394M/395M toy hauler with three AC units is a power hungry unit to start with.  If I install a residential Whirlpool 120VAC refrigerator, cloths washer and gas dryer, i'm honestly going to need to install a larger capacity generator set.  I want to install the Onan 7.0kw gen set instead of the standard Onan 5.5kw set.

If the Energy Management Systems are generally set up with particular values for each system to use to determine when to start shedding loads, it could be possible that the additional power may not be available no matter how much more power is actually available from the generator.  That might present an issue.

Does anyone out there know if the Energy Management System in your specific RV must, or even can, be changed to allow more power draw before reaching limits that cause the system to go into the load shedding mode, if, in fact, my understanding is correct?  Does the vendor have to do this, or can your builder do this?  Or perhaps there is a "Settings" sub-routine that allows the user to enter certain values?  I would not allow the user to do this, if it were up to me, because these systems operate as electrical protection devices and certainly should only be set up by someone that knows the specific electrical system installation.  But that's just me.

I have other feelers out in an attempt to answer these questions definitively, but have not received any replies as of yet.  This certainly is something that needs to be learned by anyone that is thinking about larger capacity generator sets.  If there are limits set with industry standard values that cannot be changed, the extra cost involved is a waste of money.  It does not seem reasonable to me to put limit values in the program that cannot be changed, at least by the builder, since they install larger capacity gen sets in other RVs that likely have the same, or similar management software.

Lost in the ether on this one,

Dave

-- Edited by Dave MW on Monday 21st of January 2019 10:37:05 AM

I know exactly what you mean, Bill.  With my background working on radar sets, I have learned to be absolutely anal about watching power distribution within systems.  But the average RV buyer may not have had a background in system electronics.  But there may be someone out there that knows these management systems that could shine some light on this.

The problem may come from being limited to a pre-set list of values not allowing you to manage any capacity above the pre-set industry standard values.

My mother-in-laws 2014 Winnebago Sightseer, a 50AMP motorhome, has an Energy Management System that does not get in the way on 50AMP at all. In fact I did not realize she had one for over a year. It seems to detect if she is on 30AMP or 50AMP automatically and the 50AMP can be wired in phase (not code), since she was using a cheater box to use two 30AMPs at one of her daughter's places.

Edit: This is a cheater box - https://www.pplmotorhomes.com/parts/electrical-plumbing-lp-gas/rv-electrical-systems-and-accessories/adapters/rv-cheater-box_55-7031 .  In case you didn't know they existed.  She mostly uses it with 2 30AMPs.  You can't use it with a GFCI circuit.