Inverter Open Ground

[Aquanuts]

The first symptom of my problem is that my 700W Cook Power Microwave trips my 1.5kW/3kW Ames PSW Inverter. An amp clamp reveals that the microwave draws about 8 to 10 amps. The trip occurs each time the magnetron kicks on.

When I plug a GFCI circuit tester into the output jack of the inverter it indicates Open Ground. My (-) of the 24VDC is tied to trailer chassis and my AC neutral is not bonded to the chassis but will have a bond provided by the shore power panel. I have an isolation relay that will allow shore power/generator to power all AC circuits when external power is applied and the inverter powers AC when no external power is available. AC grounds are all tied together and bonded to the trailer chassis and are not switched by the shore power relay. The inverter chassis is tied to trailer chassis.

Am I doing this wrong or is there a problem in the inverter?

 

[Cheap 4-life]

The first symptom of my problem is that my 700W Cook Power Microwave trips my 1.5kW/3kW Ames PSW Inverter. An amp clamp reveals that the microwave draws about 8 to 10 amps. The trip occurs each time the magnetron kicks on.

When I plug a GFCI circuit tester into the output jack of the inverter it indicates Open Ground. My (-) of the 24VDC is tied to trailer chassis and my AC neutral is not bonded to the chassis but will have a bond provided by the shore power panel. I have an isolation relay that will allow shore power/generator to power all AC circuits when external power is applied and the inverter powers AC when no external power is available. AC grounds are all tied together and bonded to the trailer chassis and are not switched by the shore power relay. The inverter chassis is tied to trailer chassis.

Am I doing this wrong or is there a problem in the inverter?

I’ve read on here somewhere that the inverters neutral needs to be bonded to ground. Some use relays to do it so that the inverter neutral isn’t bonded to ground when grid/shore power is present

 

[Aquanuts]

I guess I could add that the inverter powers the refrigerator, AirCon unit and other AC needs (not at the same time).

 

[Aquanuts]

I’ve read on here somewhere that the inverters neutral needs to be bonded to ground. Some use relays to do it so that the inverter neutral isn’t bonded to ground when grid/shore power is present

I was reading a post by FilterGuy but it seemed to vary by make, unless I read that wrong. Unfortunatly the schematic for the Ames is a well kept secret. Thanks for the reply though. I'll read that thread again.

 

[time2roll]

Usually an inverter trips off due to overload or low input voltage. It would seem the rating is sufficient. Have you monitored the voltage on the input terminals to the inverter as you switch on the microwave?

 

[Bud Martin]

Does your clamp on DC Amp meter have peak current capture capability? Does Ames have error code? It sounds like it is overloaded.

 

[Aquanuts]

Usually an inverter trips off due to overload or low input voltage. It would seem the rating is sufficient. Have you monitored the voltage on the input terminals to the inverter as you switch on the microwave?

I have not checked that. I'll do it.

 

[Aquanuts]

Does your clamp on DC Amp meter have peak current capture capability? Does Ames have error code? It sounds like it is overloaded.

I agree, but was trying to see if anyone thought I was doing something wrong. It could be that the inverter is just not big enough, even though it seems like it should be. On the meter, it does have capture but I'm not sure if its fast enough. 2k counts. Klein Tools 1020U-A2. Be nice to have a scope.

 

[Bud Martin]

I do not think you are doing anything wrong, I think it is an overload condition.
BTW, what the model of the AMES Inverter?
BTW, searching for 'Klein Tools 1020U-A2' but nothing for that model comes up.

 

[Aquanuts]

I do not think you are doing anything wrong, I think it is an overload condition.
BTW, what the model of the AMES Inverter?
BTW, searching for 'Klein Tools 1020U-A2' but nothing for that model comes up.

PWRI1150024S is the Ames P/N. 24v 1500/3000W. The # on the Klein must have been the s/n. The model is CL120. It says 2000 count on it so it would seem fast enough but I'm not capturing a high spike.

Gonna try taking it apart to see if there is a loose ground wire. Then a Jumper from neutral to ground on the inverter supply to the shore power relay. If those don't work, time to buy a bigger inverter.

 

[12VoltInstalls]

What size and length are your inverter cables?

 

[rcrracer]

It might be due to poor power factor. Plug a approximately 700 watt or greater device in like a hair dryer or heat gun and see if that works OK.

 

[Bud Martin]

The 2000 count spec of the meter has nothing to do with capability of capturing fast transient of the signal.
Count means the maximum value that can be displayed.

Meaning of "count" on digital multimeters? | FAQ | Hioki

www.hioki.com

In your post #1:"An amp clamp reveals that the microwave draws about 8 to 10 amps" that current is already exceed the 700W rating of the microwave, 120VAC x 10A = 1200VA (due to micro wave is not pure resistive load so PF comes into play), so it is probably higher than that if your meter is fast enough to capture surge.

 

[Whinny]

Probably 700 cooking watts look at the rating plate inside the micro door for running watts.......

 

[mikefitz]

700W Cook Power Microwave trips my 1.5kW/3kW Ames PSW Inverter.

Check out the DC side of the inverter, ( volt drops , poor connections, undersized cable, battery limit).
What is the maximum DC current into the inverter, voltage at the terminals?
Is there a battery BMS current limit?
It does not sound like a ground fault. I think the Ames inverter is not neutral to earth bonded inside the inverter ( or can be configured so), the subject was discussed on the forum , a search may find.

Try the inverter on similar high loads, at a guess the peak microwave power will be around 1300 watts.

Mike

 

[Aquanuts]

The 2000 count spec of the meter has nothing to do with capability of capturing fast transient of the signal.
Count means the maximum value that can be displayed.

Meaning of "count" on digital multimeters? | FAQ | Hioki

www.hioki.com

In your post #1:"An amp clamp reveals that the microwave draws about 8 to 10 amps" that current is already exceed the 700W rating of the microwave, 120VAC x 10A = 1200VA (due to micro wave is not pure resistive load so PF comes into play), so it is probably higher than that if your meter is fast enough to capture surge.

Yes, the 700W is cooking power. The power consumption is greater. As you have pointed out, the meter may not be fast enough to capture the current surge, thanks.

 

[Aquanuts]

What size and length are your inverter cables?

The battery bank is 6 ea 12v 200Ah AGM configured as 3 24v series pairs, in parallel. They are tied together and connected to a bus bar and from the bus bar through a breaker (150A) to the inverter. The wire is #4 multi-strand copper. The length of wire connecting each of the three parallel[ circuits to the bus bar is 18'. The length of the wire to the inverter is 7'.

 

[Diysolar123]

in order to read inrush current you need a meter with that specific capability...fyi, they are pricey such as the fluke 370 series or better ($600+)

 

[Aquanuts]

in order to read inrush current you need a meter with that specific capability...fyi, they are pricey such as the fluke 370 series or better ($600+)

Yea, probably not on my list of near future purchases. Just gonna have to guess at this one.

 

[Colonel.lp]

If your microwave is drawing 10amps, that's about 1400w draw including inefficiencies. Surge could be 4200w to 5600w at startup. If other stuff runs fine from the inverter then id say it's underpowered. Is it pure sine? What size are your cables to the inverter from battery and how long?