Onan OTCU-150

[hoghunter69]

Well the 35EK has been exercising weekly with load for about 30-40 minutes without issue. ATS cuts over and the kids don't even notice the TV flicker. Now that the weather has warmed, I've run the whole house including two 3 ton A/C's, electric range, electric oven and electric dryer simultaneously. You can hear the genset take a quick hit as units cycle on/off but it regains quickly. Fully loaded I see an even distribution across both legs between 30-40a.

In a previous post I mentioned the battery charger was not stable so I pulled the fuse and use a solar charger. The replacement clock is working perfect.

My recent outstanding issue is the test/normal/retransfer switch. It did not seem to work so I pulled the switch to figure it out. After a few tests with the OHM meter I filled the switch with electronic tuner cleaner and can now get the switch to kick on the genset but not get it to transfer load. WITH/WITHOUT LOAD is set to WITH on both EXERCISE and TEST.

All I have is the installation manual so I do not have any idea which relay should get energized when moved to TEST or schematics to see what connections are made/broken when in the test/normal/retransfer positions.

Anyone have an idea on how it should work or should I breakdown and buy a new switch. I want to be able to energize the genset and kick over to standby power in the event of bad weather.

[Gunny]

What do you mean the charger was not steady? Ammeter needle move around a lot? Assuming a stock charger, those were excellent chargers, if properly adjusted.

Does the switch (ATS) work properly for a power outage?

Test without load simply sends a start command to the genset. Test with load involves causing Source 1 voltage sensor in the Power Sentry to sense a loss of utility power. Watch that little red LED when you turn the key switch. There are timers involved, are you allowing sufficient time for them to do their thing? Again watch the red LEDs, this time in the middle card.

---------- Post added at 10:20 PM ---------- Previous post was at 10:17 PM ----------

Should be able to even use a remote SPST switch to remotely initiate an engine start and transfer if you want to go on generator power ahead of a storm. Goes on same terminal strip your start wires are landed.

[hoghunter69]

BC - could not get it to quit fluctuating wildly on a new battery no matter how minute I adjusted it.

ATS works great when simulating a power outage (cutting power at the service entrance). Waits my preset delay, kicks off the genset, transfers power. Flip the breaker, transfers power back, waits for the genset to cool down and powers off the unit.

When using the test/normal/retransfer switch, it ran 20 minutes without doing a transfer.

When I hit the switch, I get Source 1 Available, START GEN LED lights and retransfer complete is lit. Genset starts, Source 2 Available is lit along with Source 1. Transfer Timing never lights. Turning to RETRANSFER seems to have no effect. NORMAL causes the genset to shutdown after the preset retransfer timer has expired.

[EricWood]

You don't have a Signal Module hanging on the door do you?

Since you referenced having two switches for Load/No Load on your Power Sentry; looking at the board schematic with the dual switches, The key switch "test" position, and exerciser clock output, and the remote test input from TB2 on the switch mechanism ultimately end up at a common point on the mother board. One works, they all work. If one works, and not the other methods, problem likely outside the motherboard. If you can't get it to transfer without actually dumping power, may be your relay K18 on the mother board.

Do you have the manual? Let me know if you need it. Besides the diagrams, it show the schematics for the motherboards.

eric

[Billy J Shafer]

It will not transfer with Source one available. As Gunny said the test with load. Removes power from the source one control. I would guess bad board or an option may be causing the problem. But it is something you can get by with. Until you can find the problem. It will work on a power failure. As you know.

[hoghunter69]

Billy - this unit does not have signal module, phase balancer, or TB3 option. I believe the motherboard is 3953 (too lazy to get up and go look). I picked up copies of both the USER and SERVICE manuals to go along with the installation manual so I now have a clearer copy of the schematics and I printed them off on 11x17 paper.

I'll post the part numbers later as I have the manuals as a soft copy.

One test I have not tried is the remote start option by jumping across TB2-7/8. I want to run a 2 wire to a keyed switch on the 1st floor. Keyed switch will prevent accidental crank and keep me from going to the basement to initiate a start. If I can activate the genset via the remote test/area protect switch, then I can probably live without the remote/normal/transfer switch.

I'll start with K18 and see if it has dirty contacts.

[Gunny]

Key to it working (test with load) is that Source 1 LED. As Source 1 is the preferred source, the logic will not initiate a transfer.

Look closely at the key switch and wiring affecting this operation.

In my not so humble opinion, that is the best switch ever made and well worth the time and trouble to make it work correctly.

[hoghunter69]

OK - got it right. Little tuner cleaner in the with/without load switch worked back and forth a few times and it works correctly. Turned to test, ATS waited 15 seconds and fired up the genset. 30 seconds later it transferred the whole house from commercial to emergency power without a flicker.

However, when I went to check the voltage, frequency and ammeter, I noticed that voltage was only registering 90V and no amperage. I checked it on both legs and each read the same. The readings had been working correctly last week- 239v and 30a on each leg with the A/C's running. Nervous, I turned the switch to retransfer and the switch kicked over to commercial power instantly. So test/normal/retransfer switch is now fully functional.

The ATS must have sensed the correct voltage or it would not have lit the EMERGENCY available light or transferred to emergency power.

I took the access panel off to see if maybe the leads were laying funny and it was not getting a good read. They were where they have always been- dead center within the current transformers.

I was in a rush today playing Mr. Mom with the wife out of town. Tomorrow I will switch the main breaker off on the genset and meter the voltage on the supply side of the breaker. Don't want to take any chances of supplying low voltage to the ATS.

If I get 240 between L1-L2 and 120 between L3 and L1/L2, anyone have an idea of where to start on why the meters may be reading low?

[Billy J Shafer]

Low voltage to the switch will not hurt anything. It just wont do anything. If the source two available light is on. Your voltage should be within range. You may have a bad micro switch. Let me get my books out and do some reading.

[hoghunter69]

Billy - I am amazed at the effort you and others put into helping people on this site. I know I enjoy the wisdom you, Gunny, Eric, Kevin, et al have proved to me as well as the forum. I would not have gotten the unit up and running as quick without the insight.

[Gunny]

Use a good meter to verify your readings.

On the Daughter boards (voltage sensors) there are some adjustments, drop out, pick up and calibrate. Best to read the section on the manual a couple of times and understand the concept and have at it. I would adjust the source 2 to accept a fairly big range. Source 1 and Source 2 cards are interchangeable by the way should you need to swap them for trouble shooting.

A very handy feature of that switch is that you can manually operate it. Just use one hand and don't try to move both handles at the same time, do one than the other.

Does your switch have the meter option package? Nice looking but in my experience, not especially accurate, especially if dealer installed.

[Billy J Shafer]

We all try to help. I do it because I enjoy helping people out. I do agree with Gunny. That switch also called the OTIII was one of the best ever built. Gunny a Marine forgot one thing. Before you do a manual transfer turn the motor switch off. It can break your hand if it tries to go back. Good advice from a NAVY man.

[hoghunter69]

Thankfully I have never had to perform a manual transfer. When I am inside the switch - AUTO switch is set to off. I was inside one time and knew it was going to Xfer on its own- still scared the crap out of me when it flipped.

[hoghunter69]

No meter option - My model only has the exerciser clock (I had to replace), only the default undervoltage sensor, no alarm module, no phase balancer, no auto/manual switch.

[Gunny]

Like Billy, even though he's a sailor, help when I can. Feel that knowledge should be shared.

You have a motor disconnect switch, shuts off power to the motor so you can switch it manually without a fight.

First time I had my nose in a switch and it did its thing, startled me. After a whole lot through the years, doesn't bother me much any more, don't even flinch anymore.

Feel free to ask if you need help with that switch.

[Billy J Shafer]

First one I did was an old ASCO open bar switch. No Arc guards. At night. In a dark room when it switched. Big flash and a bang. Thought I had died. I think I jumped about three feet. Went to the bathroom after that.

[hoghunter69]

Well Billy I am stumped. I checked every connection inside the Detector to make sure no connections were loose or vermin had made a nest and the inside is almost dust free. Checked the leads through the current transformers again. Pulled the schematics and did not see anything that stood out as to why the voltage would read less than 100v on the meter while the ATS sensed 240v between legs (otherwise it should not have transferred).

Voltage meter gone bad?

[EricWood]

I was reading through other posts of yours...you have this unit set up for 240 single phase, correct?

If so, reference the attached picture. Those are the only applicable switch positions in single phase. The others will give you readings you may not be expecting, as Billy previously mentioned.

I'm presuming you were using the generator's voltage and ammeter instruments to observe the readings you posted. if you were on the three phase settings, yes L3 will show 120 volts, and there will be no amperage to read. It is very likely your meter is in need of recalibrating, if possible. (done with the screw adjust on the front of the meter, and an accurate handheld meter.) The jeweled movement wears in these from vibration, and can stick/become inaccurate.

eric

[hoghunter69]

Eric - the unit has been strapped for 240v 1ph and running without issue for several months. I checked the jumpers to make sure they were set for 1ph vs 3ph. No way they would have changed but I had to check.

Saturday I ran the rotary switch through all the positions to clean the contacts to see if that would make a difference. Tapped the meters to see if they were hung with no luck. Got nervous so I turned it off.

Thanks for the idea- I just took my little screwdriver I use with my analog Ohm meter to see how much I could move the needle. Was able to get it to move over a wide range. Wife and kids would probably get upset if I fired it up at 11:30 to see if it made any difference.

Plan this Saturday is to turn off the breaker at the genset and verify the voltage is 240v between L1-L2. If it is ok, then I'll flip the breaker back on, switch the house over to emergency with all the high use appliances on and see what the amp clamp shows on each leg at the breaker.

Hope it is something simple. 18 year old generator is bound to have a few quirks.

[Gunny]

CTs correctly oriented?

They should be marked with a white dot on one side. That dot should be oriented towards the source of the power. If not, swap the leads.

Be careful around CTs. If there is current flow, they will have an output. At full rated load they will try to put out 5 amps. What this means is with an open circuit, you may have more than a few hundred volts with a 5 amp potential.