bowsie1 wrote:

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Afternoon all. We are awaiting delivery of our new van, which has a Truma Avanti aircon. unit. The supplier has told us that a Honda 2.0kva inverter generator would suffice to operate it, providing no other 240 volt appliance is being used. This would be fine with us, as a 3kva is too big and bulky for ourselves to man-handle. As I would like to keep my wife happy, whilst travelling amongst the fish and muddies habitats ie., hot and humid, would anyone have any knowledge if this 2kva will be ok? Cheers Bowsie

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We have a Honda 2KVA, it runs the aircon (Dometic B3200) no problem at all, and will also run the fridge, TV, and the battery charger at the same time, although we run solar so we turn the charger off, we put the fridge on gas, and run the tv on 12 volt, saves the Gennie being loaded up.  One VERY important thing to get into the habit of doing.  When you pack up to move on, turn the aircon OFF.  If you don't and then you try to start the Gennie, it is trying to start with a load already applied before it has had a chance to get up and running.  Our aircon uses 7'5 amps, the Honda is rated for 10 amps, so as you can see there is a lot of draw on the Gennie on start up. 
If you look at the tech spec's of your aircon unit, that will give you the answer.  I believe that some aircons have a "soft start" which is like a stepper unit that increases the amp pull as the aircon starts up, so, initial useage MAY be 2amp, then 4amp, then 6amp.............. if you get my drift.  I just looked up the spec's, Aventa Comfort 4.2 Amp and the Aventa Eco 2.8 Amp, SO, a 2.0 KVA should be okay and give you a bit to play with.
Hope this helps.

Mark

Thanks Mark.We will purchase the honda 2kva, as so much more manageable.As we are getting solar fitted, I only wanted the gennie solely for aircon when required.This site is very useful and there is nothing more comforting speaking with people who have first hand knowledge.

Cheers,  Bowsie

Thanks D&. The specs you sent me actually made me aware that we were getting the Comfort unit as our paperwork only said truma unit.We are having a full rundown on the van shortly, so no doubt more questions will follow ...

Regards, Bowsie

D and D wrote:

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I hadn't looked at the current draw and confused the output with power usage. But now that I look I wonder how the unit can deliver 2400w output (Aventa comfort) from only a little over 1000w power input - never really understood electricity or electrically powered devices.

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ISTM that a 2kVA compressor would have more than enough capacity to power your aircon. Your Truma Aventa Comfort model draws 4.2A, so that is in fact around 1kVA from a 240VAC supply.

Frequently Asked Questions - Air Conditioners:
http://www.energyrating.gov.au/products-themes/cooling/air-conditioners/faq/

"How can the capacity output of an air conditioner be greater than the power input?"

"For air conditioners, the measure of energy efficiency is the Energy Efficiency Ratio (EER) for cooling and the Coefficient of Performance (COP) for heating. The EER and COP are defined as the capacity output divided by the power input. This is achieved by the use of a refrigeration heat pump which collects internal heat and moves it outside when in cooling mode, or collects ambient heat from outside and moves it inside when in heating mode. The apparent efficiency of heat pumps is high as they can move much more low grade energy in the form of heat than the electrical energy they require."

Star Rating Calculations:
http://www.energyrating.gov.au/products-themes/cooling/air-conditioners/star-rating/

"How can the Capacity Output be greater than the Power Input?"

"Refrigerative air conditioners (the only type covered by energy labelling in Australia and New Zealand -- evaporative units are not included) use a technique called the vapour compression cycle to "move" energy in the form of heat from one space to another. This is generally a very efficient process and the amount of low grade heat that can be moved is typically 3 to 5 times (or more) the energy required to run the compressor system. This ratio is called the Energy Efficiency Ratio (EER), used for cooling, or Coefficient of Performance (COP), for heating, and it is used as the basis for determining the star rating of an air conditioner (see below). A refrigeration heat pump collects internal heat and moves it outside when in cooling mode, or collects ambient heat from outside and moves it inside when in heating mode.

The efficiency of the system depends on the components used (their design and how well these are matched -- compressor, evaporator and condenser) and the temperature different between inside and outside (as the temperature different increases, the system becomes less efficient).

The system uses a refrigerant (which exists as a gas at low pressure and as a liquid under compression) which is compressed and liquefied, allowed to cool in a condenser, and then allowed to expand in a controlled way (through an expansion valve) to become a gas in an evaporator (the expansion is accompanied by a strong cooling effect). In this operation the condenser becomes warm and the evaporator to the condenser.

The principle is the same as used in a normal refrigerator which "moves" heat from the inside of refrigerator to the outside. In the case of an air conditioner when in cooling mode, the heat is removed from the room being cooled and pushed outside through the refrigeration system. Similarly, if the unit can operate in "reverse" (called heating mode or reverse cycle), the process runs backwards and the energy is collected from outside and moved inside to the room being heated. In most cases, air conditioners are more efficient when operating in heating mode as the energy used to compress the refrigerant can also contribute to the net heating output."

-- Edited by dorian on Friday 28th of June 2013 07:28:01 PM