Load test results--a tale of 2 MEP-004A units

[1800 Diesel]

Conducted two load tests yesterday evening on 2 different MEP004As...On unit 1 I've completed the single phase mod, including the CT resistor installation; on unit 2 I've completed the single phase mod, but have not installed the CT resistors. Since I haven't finished my load bank (using water tank & HW elements), I've set up a breaker box (salvaged from our Katrina house in MS) with (10) 20-amp SP breakers & then connected 10 outlets (one per breaker). For each test I connected eight 1500-watt heaters running at full settings. For the unit 1 test, I also included a small compressor (HF 8 gallon model) plugged into the convenience outlet (which I believe connects from L3). For unit 2 test I did not connect the compressor, running only the eight heaters. Voltage on both units set at 120 each leg. 1st amp readings obtained from by AMPROBE reading on generator output lines.

Unit 1 results:

L1: 40 amps
L3: 39 amps

Percent load meter: 78%
AC ammeter load readings: L1: 85%
L3: 90%

Frequency, AC voltage, % power & AC ammeters % all stable during test.

**********************************************************

Unit 2 results:

L1: 39 amps
L3: 38 amps

Percent load meter: 100%
AC ammeter load readings: L1: 70-75%
L3: 60-70%

Freq meter fairly stable with slight variations 58.9-60.2 .
AC ammeter varied as noted by above values. The needle moved back & forth between the values noted.
AC voltmeter value varied slightly (119-121)

My biggest concern is the varying AC ammeter percent load swings. I need to look into meter adjustments in the TM (if there is anything) to determine if the zero-adjustment may be off. With no load on the bus, this generator's AC ammeter "bounces" during generator running from zero, up to 20 or 30%....

The other concern (more of a curiosity) is why eight 1500-watt heaters are not providing a 12 KW load. My assumption is that not all of the heaters are actually pulling the full 1.5 KW they're rated...

If anyone has any comments, please weigh in.

Thanks,

Kevin

 

[1800 Diesel]

Got into the TM last night and found a little info related to AC voltage fluctuations but nothing specific about ammeter fluctuations though they are connected. As to possible causes for voltage fluctuations the following causes were listed:

1. Loose electrical connections (didn't say where but I'll check all IWO gauges & meters and any other connections I can get to)

2. Defective Volt-Amp selector switch. (Only thing I can do here is swap out with a known good one or should I try contact cleaner or something else?)

3. Defective voltage adjust rheostat. (Same action as #2)

4. Defective AC Voltmeter (hoping this can apply to the %load ammeter too)

Next time I get into the machine I plan to monitor the amperage loads for a period of time with my new EXTECH meter and see if the value fluctuates the same as the on-board meter...

BTW, I have only looked through the Operator manual... have not checked the field & depot maint manuals...

Any other ideas, send me a note...still looking for causes/fixes for the fluctuating % load AC ammeter...thanks,

Kevin

 

[sewerzuk]

I have found defective meters FREQUENTLY. One of the first things I do when I am working on a "new to me" set is to verify voltage, frequency, and ammeter readings. It saves a lot of time troubleshooting. This may explain why the heaters are not providing the expected load.
As for the frequency meter movement, are you hearing a fluctuation in engine RPM?

 

[1800 Diesel]

I have found defective meters FREQUENTLY. One of the first things I do when I am working on a "new to me" set is to verify voltage, frequency, and ammeter readings. It saves a lot of time troubleshooting. This may explain why the heaters are not providing the expected load.
As for the frequency meter movement, are you hearing a fluctuation in engine RPM?

Morning Matt,

Thanks for the reply. (I think we're the only two on here that work on these models maybe??) I just did a connection check inside the unit and found all connections tight and just about to run another test. Also, once running, I'll try to adjust the meters and also will check voltage & amperage with my amprobe & also have a new EXTECH which also can do freq.

Standby for 20--30 mins or so...Thanks again!

 

[1800 Diesel]

I have found defective meters FREQUENTLY. One of the first things I do when I am working on a "new to me" set is to verify voltage, frequency, and ammeter readings. It saves a lot of time troubleshooting. This may explain why the heaters are not providing the expected load.
As for the frequency meter movement, are you hearing a fluctuation in engine RPM?

Matt,

Completed two load tests this afternoon....results of 2nd test as follows (video to follow):

Load: QTY (9) 1500W heaters, with one connected to the convenience outlet. 4 each to L1 & 4 each to L3

Voltage readings: L1--123v L3--113.3v

Amp readings (via EXTECH MA220): L1--49.3 L3--33.4

% load readings: L1--near 100% L3--90%

% Power: 95%

After adjusting the meters a little, the variations seemed to decrease. (I did not touch the freq meter).

Note in the video that the freq meter is wandering a little, but not too much. On the other unit I'm working, the freq meter is rock sold--no movement. The other meters still wander back & forth a little (see video). In particular, the % power meter fluctuates quite a bit. When I check voltage amperage right at the output connections, there is no change in either voltage or amperage values--they're pretty much steady. With the digital meter (EXTECH), there is a slight (0.1 up or down) change in value but no far swings....same for voltage meter readings.

Of all data collected, my biggest concern or confusion is the different voltage readings measured at the output connections (L1= 123, L2=113.2) Phase-to-phase checks show pretty close to 240 or a little less. What would cause the two legs to show different voltages? BTW, this machine has been "single-phased" but I have not installed the resistors across the CT terminals. Doing that tonight...

Edit--SS wouldn't let me upload the video...will convert the file to something it likes & then upload...flash video file now uploaded, but it seems like it has to be downloaded prior to viewing...did I do that wrong?

 

[johnray13]

Conducted two load tests yesterday...For each test I connected eight 1500-watt heaters running at full settings...

Unit 2 results:

L1: 39 amps
L3: 38 amps

Percent load meter: 100%
AC ammeter load readings: L1: 70-75%
L3: 60-70%

Can you put the Amprobe on each heater wire (at the panel box)? You seem to be missing 23 amps somewhere.

 

[1800 Diesel]

Can you put the Amprobe on each heater wire (at the panel box)? You seem to be missing 23 amps somewhere.

I might be able to but the breaker panel is pretty crowded. We decided the other day that at least 2 of the heaters are probably only pulling half their rating. Might even be 3 of them...the old time milkhouse type and the wide ones that you can see the big zig-zag tungsten wires glowing red--they seem to pull heavier than the more modern heaters I have connected. I'll try to verify the loads on each feed line next time...all I've been doing is verifying the heaters are turned all the way up & each one is producing heat...another test done this afternoon too..those results posted...

Thanks,

Kevin

 

[sewerzuk]

I have seen main breakers with high resistance connections in them; you might fully load the generator and take voltages on both the input and output side of the breaker to see if it is the culprit. A loose or high resistance connection somewhere is dropping 10 volts (this is causing the heaters supplied by that "leg" to draw less power).

 

[1800 Diesel]

I have seen main breakers with high resistance connections in them; you might fully load the generator and take voltages on both the input and output side of the breaker to see if it is the culprit. A loose or high resistance connection somewhere is dropping 10 volts (this is causing the heaters supplied by that "leg" to draw less power).

Will check these connections next weekend. Off the grid for three days this week. I did notice the amber indicator light housing was quite hot last time I checked it, but didn't think to check if the toggle switch was also hot.

Any other components inside the control box worth checking?

Thanks

 

[sewerzuk]

Will check these connections next weekend. Off the grid for three days this week. I did notice the amber indicator light housing was quite hot last time I checked it, but didn't think to check if the toggle switch was also hot.

Any other components inside the control box worth checking?

Thanks

It isn't the toggle switch itself that you need to check; it is the main breaker assembly. The cables to L1-L3 pass through it; it is on the left side of the generator, near the voltage reconnection board.

 

[1800 Diesel]

.....As for the frequency meter movement, are you hearing a fluctuation in engine RPM?

Don't think I ever answered this question, but I can detect no engine RPM changes--seems steady as she goes....

 

[1800 Diesel]

It isn't the toggle switch itself that you need to check; it is the main breaker assembly. The cables to L1-L3 pass through it; it is on the left side of the generator, near the voltage reconnection board.

Roger that...looking at the TM now...thanks....

 

[1800 Diesel]

I have seen main breakers with high resistance connections in them; you might fully load the generator and take voltages on both the input and output side of the breaker to see if it is the culprit. A loose or high resistance connection somewhere is dropping 10 volts (this is causing the heaters supplied by that "leg" to draw less power).

Conducted another test this afternoon--data & results as follows:

Load: QTY (6) 1.5 KW heaters distributed between L1 & L3

Board readings:

L1-- 75%

L2-- 75%

% Power-- 75-80% (needle fluctuating)

Frequency-- 60hz (+/- 0.1hz needle fluctuating a little)

*************************************************

Voltage readings at main circuit breaker:

Terminals numbered from outside to inside, 1st set taken on recon board side, 2nd set taken on output terminal side...

1--120.1

2--122.5

3--126.6


1--120.1

2--122.6

3--126.6

Amp readings from output lines:

L1-- 37.80 amps

L3-- 35.5 amps

From this data, it seems we can conclude the problem is not due to the main breaker contacts, since the values are essentially identical....so that leaves what? Voltage regulator assembly? Anything else??

 

[sewerzuk]

That's strange...in post #5, L3 was lower than L1. Now, L3 is higher than L1. What is different? Do you have your load bank hooked up the same?
All of your voltage readings are taken with your digital voltmeter, correct? Do you see the fluctuations in voltage and frequency on your digital voltmeter as well as the sets meters, or are the fluctuations only happening on the set's meters?
Do the fluctuations seem to happen in tandem with each other (do all the meters move together)?

You are correct...as long as you took your voltage readings across the main breaker with the set under load, it appears to be working properly.

Without being in front of the generator, it is kind of hard to troubleshoot! I have had sets that had "bouncy" meters...just old parts acting like...old parts. It is strange to see ALL of your meters moving around. Loose ground? Bad connection in the control cubicle? Loose connection in one of the generator's 12 leads and/or and of the cables going to the load terminals?

 

[1800 Diesel]

That's strange...in post #5, L3 was lower than L1. Now, L3 is higher than L1. What is different? Do you have your load bank hooked up the same?

Answer--With all the rain we've been getting around here, I have to disconnect/store all my heaters after each test. For this most recent test I just plugged in the 6 heaters & then load up the generator. If the percentages vary too much between L1 & L3, I shift one or more heaters until the percentage value for each phase is about the same. So, yes the actual arrangement/hookup for this test was different from #5 post. WRT the voltages changing, I'm not sure about the relative position of L1 & L3 on the main breaker. Since the wires are bundled/wrapped after they come off the breaker terminals, heading over to the main output terminals, I am not certain which cable matches to L1 or L3. That's why I described the numbering as "outside to inside" and "recon board side"... In other words, the 1,2, 3 numbers for the voltage readings are just sequential values taken from the closest (to the door opening) towards the center of the generator. I haven't had a chance to look at the wiring diagram to see if it will help identify each wire IWO the main breaker. I assume I can do this using an ohmmeter (with genset not running).


All of your voltage readings are taken with your digital voltmeter, correct?

Answer--Yes, all readings taken with EXTECH MA220...(I know it's not a fluke, but it's all I can afford.)


Do you see the fluctuations in voltage and frequency on your digital voltmeter as well as the sets meters, or are the fluctuations only happening on the set's meters?

Answer--Voltage & freq readings are stable with the digital meter; the fluctuations occur on the set's meters.


Do the fluctuations seem to happen in tandem with each other (do all the meters move together)

Answer--I believe they may be occurring together, but I need to watch for this to confirm. Weather permitting, I'll attempt another load test this afternoon.


You are correct...as long as you took your voltage readings across the main breaker with the set under load, it appears to be working properly.

Without being in front of the generator, it is kind of hard to troubleshoot! I have had sets that had "bouncy" meters...just old parts acting like...old parts. It is strange to see ALL of your meters moving around. Loose ground? Bad connection in the control cubicle? Loose connection in one of the generator's 12 leads and/or and of the cables going to the load terminals?

Reply comments--I had previously checked all connections inside the cubicle, but will now connect a separate ground lead to each of the "offending" meters. The main copper ground rod & copper wire is securely connected and driven into the earth. Previously had checked terminal connections at main breaker, but now will loosen, clean and reconnect. Not sure about where the 12 leads actually connect to the generator head itself....are these soldered connections or threaded lugs? Are they accessible without doing a major dis-assembly?

Thanks for keeping tabs on this effort. Appreciate your assist!

 

[1800 Diesel]

That's strange...in post #5, L3 was lower than L1. Now, L3 is higher than L1. What is different? Do you have your load bank hooked up the same?
All of your voltage readings are taken with your digital voltmeter, correct? Do you see the fluctuations in voltage and frequency on your digital voltmeter as well as the sets meters, or are the fluctuations only happening on the set's meters?
Do the fluctuations seem to happen in tandem with each other (do all the meters move together)?

You are correct...as long as you took your voltage readings across the main breaker with the set under load, it appears to be working properly.

Without being in front of the generator, it is kind of hard to troubleshoot! I have had sets that had "bouncy" meters...just old parts acting like...old parts. It is strange to see ALL of your meters moving around. Loose ground? Bad connection in the control cubicle? Loose connection in one of the generator's 12 leads and/or and of the cables going to the load terminals?

Did a quick test right before dark today with (9) heaters. Didn't record the gauge board meters since I'm trying to focus on the voltage differential between L1 & L3. First I believe in the last set of readings I must have reversed the data from L1 to L3. I mistakenly listed the L1 as L3. In other words, post #5 was correct. Since L0 is the lowest terminal I believe I assumed the uppermost terminal was L3, which of course it isn't. Anyway, for this test I noticed something I hadn't picked up on before. With the main breaker closed and with no load the two phases are nearly the same voltage (L1=117.5v & L3=117.1v)...After applying the loads, (L1 51 amps & L3 45 amps) the voltages were as follows: L1=124.8v & L3=L3=117.4v

After loads were removed I adjusted the voltage for a phase-to-phase reading close to 240v and the phase readings showed 120.2v for L1 & 119.7v for L3.

Prior to starting the generator, I found one loose connection on the parallel switch and three loose wires (recently pushed through the pins but not soldered) on the air filter light. I soldered these three wires and I also tightened the loose wire on the parallel switch. Obviously I don't think this effort made any difference but wanted to mention them anyway.

So for now, the voltage difference between the two phases seems to increase with the generator under load and the difference goes to less than 1/2 volt with no load....the mystery continues..no solution yet...

 

[Triple Jim]

Sewerzuk is obviously the experienced one for this, but I don't think this small voltage difference is an indication of a problem. It's probably an artifact of the zig-zag configuration.

 

[1800 Diesel]

Sewerzuk is obviously the experienced one for this, but I don't think this small voltage difference is an indication of a problem. It's probably an artifact of the zig-zag configuration.

That would be my wish, but I have another MEP4 right next to this one (also rewired for single phase) & the L1/L3 voltages are identical. I've about decided to surrender and just run this one the way it is. Since I can adjust the voltage for one to be about 124 & the other to be about 116--or whatever it ends up as long as the phase-to-phase is 240 volts, then I'll still be within the + or - 8% of 120v or well within the allowable range for electric appliances or electronics.

But I still am curious what's causing the differential. Thanks for weighing in....we still might get to the bottom of it yet...

 

[Triple Jim]

I'll be listening for the answer. 116V and 124V are actually only 3-1/3% away from 120V.

 

[s011883]

Have you tried swapping out your voltage regulator box and seeing if that makes any difference on your load test. This would be another item that you could cross off your list.