Samlex America STS-30 User Manual

Transfer
Switch
30 Amps

STS-30

Owner's
Manual

Please read this
manual BEFORE
operating your
transfer switch

OWNER'S MANUAL | Index

SECTION 1

Introduction .......................................................................... 3

SECTION 2

General information ............................................................. 5

SECTION 3

Installation .......................................................................... 6

SECTION 4

Troubleshooting ................................................................. 12

SECTION 5

Specications ..................................................................... 14

SECTION 6

Warranty ......................................................................... 15

2 | SAMLEX AMERICA INC.

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 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 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 gen­erator / inverter will get damaged. There is also a potential of re!

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 common­ly 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.

SECTION 1 | Introduction

Frequently, the total AC power requirement of all the system loads exceeds the camp­ground / RV park’s power inlet and consequently, requires the genset to power the
entire system.

Thus, there may be 3 types of AC power sources. Transfer switches are used to cong­ure switching of the AC power sources so that the priority of the AC sources is:

- Electric utility power

- Genset (generator)

- Inverter

SIZING OF TRANSFER SWITCH

Determining which circuits you will require during a power outage is the rst step in
selecting the proper backup generator / inverter and the transfer switch. Since most
home appliances operate intermittently, a 3000 watt generator / inverter and a 30 A
Transfer Switch can provide adequate power to circuits for the most common appli­ances, such as furnace, lights, refrigerator, freezer, microwave oven, and TV.

If your home has a deep well pump with up to 1 HP motor, a 5000 watt generator and
50 A Transfer Switch will be required to provide the starting capacity for the pump.
Larger wattage units can be selected for simultaneous starting and operation of multi­ple appliances.

TRANSFER SWITCH STS-30

Transfer Switch STS is designed for single phase operating voltage of 120 VAC, 60 Hz
and can handle input/ output current of up to 30 A or an Apparent Power of 3600
VA (Apparent Power = Volts X Amps. In this case: 120 V X 30 = 3600 VA). It consists of
a Transfer Relay (Fig. 2, R1) and a Relay Control PCB (Fig. 2, PCB1) for controlling the
operation of the Transfer Relay. Figs. 1 & 2 show the layout.

1. 15A power cord for
connection to inverter
(<1800 VA).

2. 15A, NEMA5-15P North
American plug

3. NEMA5-20R duplex
receptacle for battery
charger

4. ¾” cable clamp for shore
power cord / generator cord

5. Cable clamp for inverter
power cord

6. Grounding lug

7. Spare knockouts for ¾”
cable clamp. Additional ¾”
& 1” knockouts are provided
on the two other sides (not
shown).

4 | SAMLEX AMERICA INC.

4

3

7

6

5

Fig. 1 External view and layout

1

2

SECTION 2 | General Information

SW1

T5

T3

T7

T1

LED1

PCB1

T6

T4

R1

T8

T2

- R1: Transfer relay coil

- T1: Line "L", Common

- T2: Neutral "N", Common

- T3: Line "L1", NO (Normally open contact of transfer relay)

- T4: Neutral "N1", NO (Normally open contact of transfer relay)

- T5: Line "L2", NC (Normally closed contact of transfer relay)

- T6: Neutral "N2", NC (Normally closed contact of transfer relay)

- T7: (-) input for relay coil

- T8: (+) input for relay coil

- SW1: DIP Switch for enabling / disabling time delay for transfer
to generator

- OFF: Enabled - delay of 20 - 25 sec. (factory preset
condition)

- ON: Disabled - no delay

- LED1: Green LED - On when transfer relay coil R1 is energized

- PCB1: Printed Circuit Board for transfer relay control

Fig. 2 Internal layout of contacts of the transfer relay and the PCB for relay control

FEATURES

- Can be congured for transfer between Utility/Inverter or between Utility/Generator

- Multiple ¾” and 1” knockouts (7, Fig. 1) have been provided on all the sides for ease
of routing the input and output cables

- Consists of heavy duty 110 VDC, Double Pole Double Throw (DPDT) relay for switching
both the Line and Neutral. (R1, Fig 2)