Samlex America STS-30 - Manual (Page 3)

2 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 3
SecTIOn 1 | Introduction
Function oF a tranSFer Switch
In case of failure of the main AC power source like the electric utility power, it is desir-
able to switch the critical AC loads to a standby / back up AC power source like a genera-
tor 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 electric utility 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
electric utility power at the same time. This will cause the following damage and safety
hazards:
- The electric utility 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 electric utility power is interrupted (say the feeder
section upstream is switched off by workers for repairs), the generator / inverter
will feed voltage back into the electric utility power lines, this voltage will be
stepped up by the transformer and will electrocute the workers that come into
contact with the utility lines.
- If the electric utility power and the generator / inverter are alive at the same time,
the electric utility power will be fed back into the generator/ inverter and the gen-
erator / inverter will get damaged. There is also a potential of fire!
application oF tranSFer Switch in homeS
by installing a transfer switch at your breaker box and connecting a generator/inverter
to the transfer switch, you can run selected circuits 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.
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 common-
ly supplied by both the 12 VDC and the 120 VAC system and sometimes alternatively by
propane.
Inverters are also used to provide AC power for dry camping where AC shore 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.