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3_tons's avatar
3_tons
Explorer III
Jul 01, 2021

An Odd ATS Situation…

I rarely camp while on-grid, so my plan is to install an ATS Switch in such a way that the dominate position (normally shore power) would be reassigned to the honda 2200 generator, and the generator position (the middle terminals) would be reassigned to my sine-wave inverter…

The problem I’m encountering is that while I can read 119vac at the inverter’s output, when I connect this output to the middle ATS terminals (normally assigned to generator…), the relay contacts fail to actuate, and the readout is about 30’ish VAC -this whether the remaining 4 terminals are connected or not…

If I disconnect the inverter wires from these two generator terminals, then do a voltage check, the inverter line voltage is restored to 119VAC…

If I connect the inverter up to the dominant shore power terminals, all is fine and the air conditioner runs perfectly, as the contactor relay is at rest in it’s normally closed (default) shore power position…

Upon first glance, this issue (due to the strange voltage reading) seems somehow related to the contactor’s wound coil (per the strange low voltage reading) however (as an experiment) if I connect shore power to this same contactor (normally assigned to generator) the relay works perfectly and the air conditioner kicks on…

At this point my wee pea-brain is starting to get flummoxed :) lol …

3 tons

Upon edit, I should also add that when I connect the inverter up to what’s normally the generator terminals, (as previously stated ) the contactor fails to respond, BUT if I push against the contacts (using an insulated prod) to properly open the contactor, the air conditioner starts-up perfectly…Kinda crazy why the contactor responds to (opens up to accommodate) shore power but not to the sine wave inverter…
  • Does the inverter have some sort of load sensing/auto turn off/auto idle feature? Maybe the transfer switch coil isn't enough of a load to trigger the inverter to produce (full) power.
  • 3_tons's avatar
    3_tons
    Explorer III
    time2roll wrote:
    3 tons wrote:
    when I connect this output to the middle ATS terminals (normally assigned to generator…),
    Middle? Are you sure that is not the output? Input is usually top or bottom, left or right.

    Have a picture or a model number?


    From the perspective of north to south (per the diagram inside the cover plate) the upper terminals go to the main (or in my case repurposed for the air conditioner), while the bottom terminals are for shore power (in my case, the Honda genny), while the middle terminals are for the generator (in my case, repurposed for the inverter)…If I manually push the contactor with an insulated prod) the air conditioner energizes perfectly…

    So, I unplugged the time delay circuit board and the relay voltage rose from 32vac to 118vac (great news!!), however the contactor is still not responding to the inverter…. If I substitute shore power for the inverter (at these same middle terminals) the contactor acts and responds appropriately….For some strange reason the contactor sees a difference between the very robust sine wave inverter vs shore power at these same middle terminals….Sounds crazy!!

    FWIW, it’s a go power 30a ATS….I spoke to a retired electrical engineer and he too was baffled…

    3 tons
  • 3 tons wrote:
    when I connect this output to the middle ATS terminals (normally assigned to generator…),
    Middle? Are you sure that is not the output? Input is usually top or bottom, left or right.

    Have a picture or a model number?
  • Call me. I can talk better than I can type.
    I am an electrical engineer and can help you over the phone.
  • And is the inverter a MSW or PSW type?

    The inverter output may not be recognized or common as required by the ATS.
  • My first thought was a floating ground.

    Are the three grounds bonded together?

    Are the inverters neutral and ground bonded?

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