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Posted on RV.net - December 12, 2009 by Larry Cad

RVIA Show, Louisville KY, Tiffin Energy Management System

One of the questions I received before the show was regarding details on the Tiffin EMS or energy management system.  I tracked down Mr. Bob Tiffin at the show who very cleverly shunted me off to Mr. George Cepynsky of Precision Circuits Inc. for the detailed information. 

The Tiffin energy management system is a very cleverly designed and implemented collection of components which work together to benefit the motorhome owner.  It does more than your run-of-the-mill EMS because it connects all the potential energy sources together and uses all sources in an intelligent manner to operate your motorhome’s electrical devices. 

A typical EMS will at the least, monitor energy usage and will shed loads if the programmed current limit is reached.  As an example, if a 50 amp rated motorhome is plugged into a 30 amp source, and if you are using your microwave while the air conditioner is on, you may overload the 30 amp circuit.  If you have an EMS, the EMS may shut off the A/C temporarily until the microwave is finished, then reconnect the A/C.  This same concept can be extended to several loads and the system can operate in a way that you, the user, may not even know it is happening, thus disrupting your life in the RV as little as possible. 

The EMS in Tiffin motorhomes takes this concept several steps further by using an intelligent connection to the available Magnum inverter/charger installed in the coach.  Synergy simply defined, means that the whole is greater than the sum of the individual parts.  By combining the EMS designed and supplied by Precision Circuits Inc. of Lisle Ill, with the Magnum inverter, this intelligent EMS can do more than either one by itself.

 Consider this example; your motorhome is plugged into a 30 amp service and you are running you’re A/C, and your microwave.  Your motorhome is pulling about 24 amps from the power pole at the campground.  Right about this time your spouse decides to dry her hair.  With no EMS, you stand a good chance of tripping a breaker.  With a simple EMS, the system will cut the power to the A/C temporarily to allow the hair dryer to run. However, with the system in Tiffin motorhomes, the EMS controller senses that you are approaching the limit of the shore power, and sends a signal to the Magnum inverter to turn on to begin supplying additional power to the coach.  In this case, an 1800 watt inverter can supply about 15 amps, which is enough to keep all three appliances going.  We all understand this is only a temporary boost, depending on the battery charge, but it should be sufficient to get through this high energy usage situation.  When energy usage goes down to a sufficiently low level, and when power is available, the Magnum is told to begin recharging the batteries to prepare for the next power usage surge. 

By the way, the EMS is also capable of temporarily lowering the battery charge level to allow the power being used for battery charging to be sent elsewhere in the coach, to be used for other purposes.  Let’s consider the above example where the A/C is on, and you decide to use the microwave.  However, right at that moment, the Magnum charger is bulk charging your batteries to the tune of 100 amps DC.  This equates to 10 amps from the AC line, or about 1/3 of the available current.  When you turn on the microwave, the EMS senses that you are too close to the 30 amp limit and tells the Magnum to slow down on the charge rate for a while, until the microwave goes offline and then instructs the charger to resume full charge levels. 

The system monitors the incoming line voltage and adjusts to either a 50 amp or a 30 amp service and requires manual setting for a 20 amp service.  Some say it isn’t necessary to have an EMS when you have a 50 amp service and normally this is true.  However, with larger motorhomes, and with dark colored full body paint, many newer coaches are being equipped with 3 air conditioners.  With the EMS installed, you are able to run all three units, and still have power left to operate other electrical devices such as a residential style refrigerator, or the ever present hair dryer. 

The system obviously has the ability to shed loads when it is necessary to remain within the available power, but one nice feature of this function is that the EMS remembers what the actual load was before it was shed.  With that knowledge, the system can continuously monitor actual usage and then determine when it is safe to reapply the previously shed load. 

Finally, the EMS takes into account that you also have a generator on board, operates the EMS based on the generator capacity, and provides a very nice sequence start for your electrical loads, allowing the generator to warm up without dumping your total load onto the generator all at once.  One other advantage of this system is that the coach manufacturer has the option of installing a slightly smaller generator set into the RV without limiting your life style as an RVer.  This can lower the cost of the coach, decrease the weight and possibly provide better fuel mileage and less generator fuel consumption, advantages that are desirable in a “green” world. 

The EMS system components, supplied by Precision Circuits include a proprietary circuit breaker panel with separate spaces for breakers being supplied by the Magnum inverter as well as the necessary current monitoring components and connection points for shed control.  The system is configured by the factory to provide maximum utility for the coach owner, based on what electrical devices are installed by the RV manufacturer.

I think it is very important to know that this equipment is manufactured in the good ole United States of America, something that is very hard to find these days.

 Due to the complexity of the installation process, the Precision Circuits EMS is not being offered as an aftermarket retrofit so your choice is to dream of that day coming sometime, or go out and buy a new motorhome that uses the system from the factory.

You can view the system brochure by following this link.

http://precisioncircuitsinc.com/Brochures/0010020000PowerControlBrochure080507.pdf (this links has been removed - for more information we suggest: Tiffin Motorhomes, alternative link found on Precision Circuits website.)



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