ATS AP4450 doesn't deliver power when switched to source B

[dnll]

Title. When on source A, power is delivered to all outlets, but when on source B, no power is delivered to the outlets. The ATS is on in either case, I can connect to the NMC just fine and don't see any errors or anything. I tried swapping the sources from the 2 different circuits and it's always source B that is problematic no matter where it's plugged in.

Any insight on what/where to look for would be appreciated.

[Teken]

A couple of questions come to mind as to the operational state of the ATS. 

LCD: What does the LCD indicate as to the voltage & frequency? Both should display 120 VAC / 60 Hz. If not you have to identify where the input fault is such as at the outlet, power cord, internal ATS PSU.

LED: When the ATS is transferred to source B. Does the LED show the normal flow of power?

Transfer: When you press the front A, B, AB source button does it work and is there a sound when engaged? There will always be a very distinct (thunk) sound when the primary source is selected.

Logs: What does the error logs show in terms of errors, line condition, operational status? Anytime you unplug a source input the logs will declare a fault and unsync state.

NMS: If this unit is monitored by a Network Monitoring System (NMS) it should indicate the DC power supply voltage, hardware state, etc. What are they as this will narrow down the issues.

At the most basic level if the ATS was unplugged. As soon as you apply power to any input plug there will be a distinct (thunk) indicating power is applied and the relays are engaged. If you do not hear any sound when power is applied to (Source A / B) there is an obvious electrical / mechanical fault.

If you do hear the thunk sound this indicates the ATS does see input power. So the next step is to determine if the electrical circuit is operating as expected. 

As noted up above the front panel has a manual button to select between the sources. If this doesn’t work you have narrowed down the problem as the selector. That can be the button is faulty so you can use the web interface to select the source.

If the web interface also doesn’t allow the source to be selected you’ve isolated to the control system. If however the ATS does allow you to change the source you should see and hear that change. If you don’t hear anything but the face and UI show a change of source.

You have narrowed the problem to a hardware issue which normally indicates failed relays.

These relays can be replaced by a qualified repair facility without too much hassle.

Let me know what you observe! 👍

[dpierce4776]

I have run into a similar issue with the AP77xx line. Mainly in the 120 volt series as the AP4450 is. After talking with tech support and some testing and trouble shooting with electrical engineers on units giving issue. This is what I have found.

The switching mechanism that switches between input A and input B on the ATS is two pieces of metal each attached to the hot and neutral output wires, that are attached to an electromagnet. The way it is supposed to work is unit powers the electromagnet in a negative charge with the desired selected input charged positive first and then charges the secondary side up. This is why as @Teken said you should hear a "Thump" when one side loses power for whatever reason. the magnetic forces attract each other since the primary side as now lost its charge the now only positive charged side pulls the negatively charged switching mechanism to it. When power is restored to the primary side the ATS monitors the power from that side then positively charges that side and removes the charge from the other sides electromagnet to make the switching mechanism stich back to that side.

I say all that to say this I have seen times that:

1. In a quick power flicker the switching mechanism gets stuck in the middle and no power is going to the output of the ATS.

2. The programing of the ATS gets "confused" for lack of a better term and does not de-energize one side causing switching mechanism to be "stuck" to one side so long as the ATS has any power to it.

3. in some (very rare) cases if dirt or debris gets in or there is a lot of power flickering or surges the switching mechanism can melt or hot and become welded to one side of the input.

You can try doing this to resolve your issue if either #1 or #2 are the case which 99.9% of the time with issues like yours. Remove power from both inputs to the ATS. wait at least 30 seconds to 1 minute for the ATS and its capacitors to completely drain their charge. That also drains the electromagnet of its charge. Then plug in the side that was not working before. If that works then try plugging in the other input to the ATS and see if it will switch to that side as well as back and forth. Remember just selecting a "primary" side will not be instantaneous. It will take a few seconds to switch, as the ATS makes sure that power is "OK". But if you pull the power cord out of its power source it should be instantaneous as no "checking" is done then. Although I do not recommend that method.

If the ATS still does not output power from the B side then it is most likely welded and you need to replace it

[dnll]

Thank you for your help. Since I have 2 units (one of them working perfectly) I should be able to hear the difference about the "thump". I will comment back once I have time to do some additional testing.