Generator Automatic Transfer Switch

Old 11-29-02, 01:00 PM
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Generator Automatic Transfer Switch

Any advice on how to troubleshoot an automatic transfer switch for my standby generator (Dayton3W057C) would be appreciated. It is a 40 Amp, 4 pole switch. It failed to transfer the load with our last power outage. I was able to jump the wires to get the load transferred but this was not really convenient. I priced a new transfer switch contactor $673! I wonder if there is a way to determine if the switch is at fault or if a relay or auxiliary switch is at fault. Is it possible to open the switch up and clean it out? I can describe how I jumped the generator voltage to the load if that will help troubleshoot. There are four terminals on the top of the switch, the two outer have the line in(L1, L3) attached, the two center have the load (T1, T3) attached. On the bottom of the switch are four more terminals, the outer two have jumper cables to the terminals with the load and the inner two have the generator(G1, G3) voltage. I moved the jumper cables over to the G1 and G3 terminals and the load was transferred. When power was restored the generator shut down but the load was not transferred back until I removed the jumper cables from the G1 and G3 terminals.
Old 11-29-02, 02:01 PM
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Did the generator start by itself and the load didn't transfer or did nothing happen at all?
Old 11-29-02, 05:14 PM
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The jumpers that you refer to, are they power conductors (#8awg or so), or control conductors (#14 awg or so).
Tell us more about the sequence of operation. Is there a test button on the unit that will auto start the gen and auto transfer the load? What happened and what didn't happen. Also, is there a web link you can give to the model switch you have.
Old 11-29-02, 06:22 PM
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Definitely power conductors not control wires.

Normal Test Scenario: When the engine is started in the "check" position, the engine will start and the generator will produce normal voltage. The transfer prevent contact(normally closed on the Start/Stop Relay) prevents the generator voltage from energizing the load transfer contactor coil. The load is not interupted by any normal "exercise" mode. The generator will not carry the load unless the commercial service is interrupted or the main circuit breaker is turned off.

Normal Transfer of Load Sequence with power failure
1. Stop/Start Relay coil is de-energized
2. The SSR NC contacts close to apply a ground signal to
a. the gas solenoid through the closed contacts of the overcranking relay
b. the starting system is also controlled by the ground signal from the SSR contact and the OCR. This ground passes through the normally closed contacts of the stop cranking relay which will open to interrupt the cranking when the engine starts.
c. the ground is also applied to the timing element (heater coil) of the overcranking relay to begin the cranking interval timing.
3. the gas solenoid valve opens to allow fuel to the engine
4. the engine cranks and starts
5. When the engine starts, the generator voltage rises as it approaches operating speed. The generator voltage energizes the Stop Cranking Relay Coil. This opens the SCR normally closed contacts to:
a disconnect the engine starting circuit
b disconnect the overcranking relay timing element timer
6 A set of N.O. contacts on the SCR and a transfer delay relay (TDR) allow the engine to reach full speed for 20-45 seconds before the generator voltage is applied to actuate the transfer switch contactor.
7. The TDR is a thermal timing device that begins timing when the generator voltage(115V) is applied to the TDR heater coil through the NC contacts of an auxillary switch mounted on the transfer contactor. After timing out, the TDR contacts close to apply power to the transfer switch contactor coil.
8. when energized, the transfer switch contactor opens the line contacts and closes the generator contacts to apply generator power to the load.
9 the NO contacts of the Aux. switch close to lock up the contactor coil
10 the NC contacts of the Aux. switch open to de-energize the control ground signal on the TDR heater element.

This is nearly verbatim from the Operating Instructions...There is more for the transfer back when power is restored.

When our power went out the generator started, there was 240V between G1 and G3 and nothing on any of the other posts. After I moved the power jumpers to the G1 and G3 posts there was no voltage at L1 and L3 (no back feed).

I have not found any other sources for information. The part number is 61694 Description is Contactor 4 P.D.T. @ 40 amps (ATS) If you know of any please let me know.

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