MEP-003A bonding concern/issue

[pwatkins87]

I am switching 2 MEP 003A's form being SDS's to non SDS setups. I disconnected the neutral bonding cable. and just to be safe I checked continuity between the Neutral Lug on the connection board and the ground lug and I am still measuring a very high resistance of 2. 672 M ohms. My question is, is this standard and just resistance being read through a gauge or transformer in the control panel or is there a bigger issue such as a chaffed/chewed wire or failing component?

I am concerned because I am running the two units mounted together on a fuel trailer that are now feeding two separate panels that have a shared neutral and ground and both panels are bonded. I cant afford to create a bonded neutral at the generator since they are mounted together and share a ground through the fuel trailer frame. If something were to become unbalanced or go wrong with the house wiring, I don't want to have a voltage back feed situation at the generator through the other generators neutral if they are still bonded for some reason.

Attached is a picture of the meter reading.

Thanks for any and all help!
PW

 

[peapvp]

2.6 Meg Ohms is pretty high. How many Meg Ohms do you think it should be with the connection between chassis and N removed, since you are asking this question?

 

[pwatkins87]

I honestly don't know. I am still learning the intricacies of these units. What I do know is on almost all civilian units when unbonded there is no continuity between Neutral and Ground, so I guess that is what I was expecting on the MEP-003A.

I am asking as a CYA so I don't burn up any of the control panels or worse lock up a gen head and motor.

 

[peapvp]

I honestly don't know. I am still learning the intricacies of these units. What I do know is on almost all civilian units when unbonded there is no continuity between N and G, so I guess that is what I was expecting on the MEP003A.

I am asking as a CYA so I don't burn up any of the control panels or worse lock up a gen head and motor.

2.6 Meg Ohm with bonding removed is basically any type of moisture from humidity etc between the stator coils and the Genhead housing / chassis

this reading probably would be much higher when measured after the Genset ran for 8 hours with a 80% load and the genhead had a chance to completely dry out.

 

[peapvp]

One add on as bonus for today:

Fluke defines CONTINUITY as follows:


What is continuity?
Electrical
Continuity is the presence of a complete path for current flow. A closed switch that is operational, for example, has continuity.
A continuity test is a quick check to see if a circuit is open or closed. Only a closed, complete circuit (one that is switched ON) has continuity.
During a continuity test, a digital multimeter sends a small current through the circuit to measure resistance in the circuit.
A meter with a continuity beeper briefly sounds off when it detects a closed circuit. The level of resistance needed to trigger the beeper varies by meter, but most will indicate continuity with a measurement between 0-50 ohms.

Link to Fluke Website

so, 2.6 Meg Ohm is not Continuity, but a very very high Resistance.

Since the N is the connection of 3 coils in a Wye scheme, it has normally 0 Volt potential to earth ground when not connected in a fully functioning and balanced three phase system.

As humidity (condensation) builds up on the stator windings then we will get some very high resistance readings like in this case.

 

[2Pbfeet]

I am switching 2 MEP 003A's form being SDS's to non SDS setups. I disconnected the neutral bonding cable. and just to be safe I checked continuity between the Neutral Lug on the connection board and the ground lug and I am still measuring a very high resistance of 2. 672 M ohms. My question is, is this standard and just resistance being read through a gauge or transformer in the control panel or is there a bigger issue such as a chaffed/chewed wire or failing component?

I am concerned because I am running the two units mounted together on a fuel trailer that are now feeding two separate panels that have a shared neutral and ground and both panels are bonded. I cant afford to create a bonded neutral at the generator since they are mounted together and share a ground through the fuel trailer frame. If something were to become unbalanced or go wrong with the house wiring, I don't want to have a voltage back feed situation at the generator through the other generators neutral if they are still bonded for some reason.

Attached is a picture of the meter reading.

Thanks for any and all help!
PW

Just for a little extra perspective, Ohm's law, and all that, V=IR, or I=V/R.
So with 240V, and 2.6 million ohms, the current flow would be 0.0923 milliamperes. Per Fluke, above that's not continuity.

All the best,

2Pbfeet