Newsletter Archive

Hot Weather Products

Now that spring is upon us, fridges become the hot selling item (or should I say cool)! Trying to predict the power consumption is a good challenge because of several factors:

• efficiency of the fridge (insulation thickness, compressor efficiency etc)
• efficiency of the inverter (if 230V powered)
• ambient temperature
• usage pattern
• inside temperature

In general terms a fridge will use 5% more energy for every 1 degree C it is run colder inside. So if your mate runs his fridge 5 degrees C colder than yours, he'll use some 25% more power. Our testing shows that a typical 230 V fridge uses 2-3 times more power than a 12/24 V equivalent once you add in the inverter losses. The good news is that we can now supply fridges with 'CARE 30' refrigerant which is some 20% more efficient than R134a. It is a flammable gas, however only some 50-60 grams would be required in a standard fridge.

The other cool items applicable to summer are fans. Ceiling fans are the most popular form of cooling. However 12/24 V ones are very expensive and are somewhat disappointing in their performance - ie they don't spin very fast! We normally recommend 230V units but they run very noisy on modified square wave inverters and some feel they soon burn out. So we strongly suggest using them in conjunction with a sine wave inverter. The ceiling fans in our offices use 11 W on slow speed, 24 W on medium and 52 W on the fastest speed (measured on the AC side) or between 2 and 6 amps at 12 V.

Automotive fans use 2-3 A at 12 volts but I find them a bit noisy and obtrusive. My favourite are the 120 mm extractor fans which are actually sold as cooling fans for computers etc. They draw 200-400 mA at 12 V. They are quiet and of good quality and are effective as a 'personal' fan on your desk or over your bed.

Refrigerative air conditioners are very power hungry drawing at least 700 W and more. We'd normally only recommend their use on large diesel hybrid systems.

How much power?

We often get asked about FAX machines. While they might use 100 W or so when transmitting and receiving, the big drain is when they are on standby for long periods - ie 8-24 hours a day. Our Ricoh 500 unit drew an average of 7.34 W over a 3 week period. If you cannot 'afford' this power drain we suggest you only switch it on during office hours or perhaps only when it is actually needed. Another alternative I've seen used by remote missions/schools etc is to print on their letterhead "FAX on between XX and XX hours only".