generator issues

[talltonsound]

my clients generac generator cranks but and runs properly, but after aprx. 20 seconds the lights start to dim slowly, as though someone is turning a rheostat off. throughout the whole house. anybody got any idea what this can be caused by? I've eliminated every thing i can think off......

 

[zbang]

Does the engine keep running at constant speed? Is it overloaded with the whole house on it (try with just a couple of lamps)? If the load is within spec, it could be the automatic voltage regulator (AVR).

Model # and actual load info would be useful here.

 

[JFletcher]

Welcome to the forum.

What series and kW is the generator? What voltage and frequency readings does it have on start-up? What is the load (amperage) on the generator, and how evenly are A and B legs loaded?

This is one of those instances where a short video that shows us exactly what is happening would be of help.

 

[Jraef]

You will have to post more details about the specific generator. For instance if it uses a voltage regulator that controls the field current of a synchronous alternator, you may have a failing regulator, a failing field current generator etc. etc. But there are several types of generators out there and several ways they regulate, or not, so all of the possible combinations can make for a long and arduous guessing game.

 

[petersonra]

Since you seem to have exhausted your expertise in this area perhaps it would be wise to bring in a generator technician who is familiar with this particular make and model of generator.

 

[goldstar]

Since you seem to have exhausted your expertise in this area perhaps it would be wise to bring in a generator technician who is familiar with this particular make and model of generator.

I agree, this is probably your best bet. I would start out by shutting off all the branch circuit breakers and then shut off the main inside the transfer panel to start the generator and then take the voltage readings as suggested. Then clip an amp probe on the at the feed to the breaker panel and then turn one breaker on at a time and see what the readings are on each phase. It's possible that there is a large enough current draw on a branch circuit(s) (maybe one or two refrigerators or freezers) coming on at the same time that's causing your problem. I'm guessing you used the Nexus load shedding module to interrupt the AC and other large amperage draw appliances.

If you don't find the answer then calling the generator tech is probably your best bet. When you find the answer please post it here. We'd all like to know in the event some of us experience the same issue.