Question about Generac HTSN100A 100Amp HTS 1ph 120/240V Automatic Transfer Switch

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On a power failure switch will transfer to generator when commercial power is restored the switch will not transfer back and the generator cuts off leaving the building without power.

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Sounds like a problem with the H-100 controller. Contact Generac to get support.

Posted on Aug 27, 2010


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1 Answer

HOW DO I install a 3 phase generater to an mcc to automatically change over to generater power in the event of a mains power failure?

You would need a three phase automatic transfer switch.

Your local electric company usually requires you the have these automatic transfer switches install by a license electrician.

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Why wont my transfer switch change back to utilities position when the power is restored?

It depends on the brand of switch and generator. A Generac has its brains in the generator control board, others in the switch, what brand of switch please?

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Coils on transfer switch got fried when utility came back what could have caused this

possible failure of a relay. contact generac,sometimes they will accomodate you with new parts

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I have a Briggs & Stratton Automatic Home Generator 7 kW, Model# 40301. I had it installed by an electrician. Who also installed Briggs & Stratton Transfer Switch 50 Amp. The problem is the...

It sounds like the mains sense wire is disconected from the control panel or the run wire is not being cut by the aux contact on the transfer switch.
Is the transfer switch manual or motorised?

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Generator Transfer Problem

There isn't much you can do with servicing the generator set or transfer switch unless you've got lots of experience in diagnoising semi-conductors and electronic components.

Depending on the age of the system, it would be benificial to have a qualified service tech take a look at it.

As an electrician, I've installed several back up generator sets in homes for customers and have had a few of these automatic transfer switches with intermittent operation issues. Sometimes it's the switch and other times it's the Generator that is causing the problems.

Hope this helps, and best regards!

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2 Answers

Transfer switch will not switch back to utility

The transfer switch should transfer back to utility within about 30 sec. after utility is restored. While waiting for the transfer switch to switch back to utility volatge. Check for DC volatge across wires 23 and 194 in the transfer switch, if you have battery voltage(12-13.5 VDC) then you you probably have a stuck relay on the PC board in the generator. The board needs to be replaced. If you don't have battery voltage across these terminals then your problem is actually in the transfer switch.

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Generac 4456 does not start on power loss

I install and work on these everyday. If you hooked up the transfer switch you probable have a control wire wrong. check the utility power sense wire. That lets it no when to start in auto. it could be a relay or fuses. or a control board.

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Prblem with ASCO ATS

This could be part of the normal behavior of the ATS. Many ATS are set up to allow the switch mechanism to sit in the "neutral" position for a time delay (as much as a minute) so that things like large motors, pumps, etc to wind down so that they don't get powered up at full speed. Here is how I would troubleshoot your ATS:

1) With the Commercial power on and the ATS in Normal, start the generator and make sure that the power at the Emergency terminals of the ATS is the correct voltage and frequency, if this is a 3 phase system also make sure that the phasing matches the commercial power side.

2) Turn the generator off, make sure it's in off not auto. Turn the commercial power off. Then manually operate the ATS transfer mechanism (there is usually a little handle for this), check continuity of the poles of the transfer mechanism to make sure that it's really making and breaking contacts where it's supposed to. While you're doing this you need to check the limit switches at both sides of the transfer mechanism, These switches are how the ATS controller "knows" what state the mechanism is in, they sometimes get out of mechanical adjustment and on rare occasions break and have to be replaced.

3) Once you've satisfied yourself that the transfer mechanism is operating correctly, set it to the Normal position and turn the commercial power on. Switch the generator into Auto so that the system is in it's Automatic mode. Find the manual for the ATS if possible and locate and record all of the adjustable time delays, I often write down the time values we want inside the door of the ATS.

4) With your stopwatch or sweep second hand wristwatch at the ready, start the Test function of the ATS and time out the various operating states as the system goes thru them. In general your ATS should do something like this:

a) You hit the test function, the system simulates a Commercial outage and begins a transfer sequence. On many systems there is an adjustable time that the Commercial power has to remain off for anything to happen, this is Time Delay Start.

b) The ATS closes the contact that tells the generator to start. Then it waits until it sees correct power at the Emergency terminals of the transfer mechanism. When correct Emergency power is available, the ATS controller fires the transfer mechanism to put it into its neutral position. After an adjustable time delay (Time Delay Neutral), the controller fires the mechanism again to put it into Emergency position. Some mechanisms aren't designed to do this "stopping in the middle" feature and so there is only the one action by the controller to get from Commercial to Emergency position, it's also worth noting that on mechanisms that can stay in the neutral position the delay could be 0 so the switch will transition as fast as it can.

c) The system is now suppling the load from the generator. Some ATS require you to interact with the test at this point to get back to the Automatic mode, read the fine manual. In any case there will be a delay from the time the ATS detects correct power at the Normal terminals until it starts the sequence to get back to Auto, this delay is called Time Delay Emergency to Normal. You want this time to be just long enough to keep from making false transfers, but not so long that you waste fuel, most places are something like 15 - 30 minutes.

d) If there was a delay in the neutral position going to Emergency, there ought to be one coming back to Normal. Keep in mind that this delay isn't about the source of power, it's about the load.

e) Once the switch is in the Normal position, the ATS should keep the generator running for a time (Time Delay Cooldown), to allow the prime mover (engine) to return to a safe to shut down condition. On small air cooled engines this can be 0, on very large diesel engines it can be as much as 30 minutes.

f) The system is back in Automatic mode waiting for a power fail.

5) If the ATS can perform a transfer test as above correctly, it should be able to operate just the same way during a real outage. One can and should be able to demonstrate this by operating a disconnect (switch, breaker, etc) at the Commercial power side of the ATS.

If your ATS doesn't pass the transfer test as above, look for (in order of probability)
Incorrect power from the generator.
Broken or missadjusted limit switches in the transfer mechanism.
A mechanically broken transfer mechanism.
A bad controller in the ATS.


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1 Answer

Generac Guardian 15kW Generator

That sounds just about right, if the relay contacts get welded together it sometimes takes out the driver on the printed circuit board. As you found out, 12vdc from 23 to 194 makes the transfer switch move to the Generator position, relay not energized makes the ATS move to the Normal position.

You can make a nice test function by installing a 10 amp contact switch in series with either the N1 or N2 terminals. When the switch is open the generator thinks the Normal power has failed.


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