4 | SAMLEX AMERICA INC.
SECTION 2 | General Information
2.1 FUNCTION OF A TRANSFER SWITCH
In case of failure of the main AC power source like the Grid power, it is desirable to
switch the critical AC loads to a standby / back up AC power source like a Generator
or an Inverter. The switching action should ensure that only one AC power source is
connected to the AC loads at any one time and that the Grid power and the Generator /
Inverter output power are never connected in parallel but remain isolated
The electrical loads cannot be connected in parallel with the Generator / Inverter and
Grid power at the same time. This will cause the following damage and safety hazards:
- The Grid line voltage is normally "stepped down" by a transformer before entering
the home / RV park / campground. The transformer will work in reverse when
voltage is sent through it in the opposite direction and will "step up" the voltage
fed back into it. If the Grid power is interrupted (say the feeder section upstream is
switched off by workers for repairs), the Generator / Inverter will feed voltage back
into the Grid power lines, this voltage will be stepped up by the transformer and
will electrocute the workers that come into contact with the Grid lines.
- If the Grid power and the Generator / Inverter are alive at the same time, the Grid
power will be fed back into the Generator / Inverter and the Generator / Inverter
will get damaged. There is also a potential of re!
2.2 APPLICATION OF TRANSFER SWITCH IN HOMES
By installing a Transfer Switch near your Main Breaker Panel and connecting a Gen-
erator / Inverter to the Transfer Switch, you can run selected circuits from your Main
Breaker Panel for appliances such as a furnace, well pump, sump pump, refrigerator,
television, computer, printer or lighting circuit during a power outage, depending on
the capacity of your Generator / Inverter.
2.3 APPLICATION OF TRANSFER SWITCH IN RECREATIONAL VEHICLES (RVS)
RVs have both a 12 VDC House or Domestic System and a 120 VAC System. The DC
System commonly provides power for area lighting, stereo, water pumping and other
loads requiring relatively small amounts of power. The 120 VAC System powers larger
loads like microwave ovens, hot water heaters, washer /dryer, coffee machines, hair
dryers, space heaters, heating and air-conditioning (HVAC) and convenience outlets that
supply power to audio, video and entertainment systems. The domestic refrigerator
is commonly supplied by both the 12 VDC and the 120 VAC Systems and sometimes
alternatively by propane.
Inverters are also used to provide AC power for dry camping where AC Grid power is not
available or in cases where gensets are not permitted due to noise restrictions. Typically,
the Inverter only supplies AC devices that are the highest priority such as microwave,
entertainment and convenience outlets. It is not practical to run loads like hot water
heaters and HVAC systems from Inverters that are ultimately powered from batteries.
