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Frequently Asked Questions
What decision does this device make?
When to leave one source for another.
It monitors voltage and frequency.
It calls the generator to start.
It accepts the supply when stable.
And it returns the load afterwards.
Open or closed transition?
Open breaks before it makes.
The load sees a brief interruption.
Closed parallels the sources momentarily.
The load sees nothing at all.
But the network operator must agree to it.
Should the neutral be switched?
It depends where the system is earthed.
A switched neutral moves that reference.
An unswitched one keeps a common path.
The wrong choice circulates current.
And trips earth protection mysteriously.
How long is the changeover?
Seconds, dominated by the engine.
Detection takes a moment.
Starting and settling takes longer.
The switch itself is fast.
Sensitive loads still need a battery system.
Why does it need exercising?
Because it sits idle for months.
Mechanisms stiffen and contacts oxidise.
Control settings drift out of memory.
One real operation is what it gets.
Scheduled tests find what inspection cannot.
Does it transfer back on its own?
Normally yes, after a delay.
The delay confirms the supply is genuinely back.
It avoids chasing an unstable network.
A cooldown run follows.
Manual return is an option on some sites.
What is sized here besides current?
The withstand during a fault.
The switch must survive until something clears.
Motor loads impose inrush too.
So does a large transformer.
Rating for steady load alone is not enough.