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Caymanedge · 06-06-2023, 08:10 PM

Having issues with my Onan QD8000 in my Journey.
Runs fine, shows 66amps on power panel, but blows the circuit breaker on generator if load gets above like 20amp. I can run one AC fine, but when second one kicks in it trips the breaker. I can swap them and get the same result so there doesn’t appear to be an issue with the AC units. Any ideas?

2004Horizon · 06-06-2023, 08:23 PM

First guess, open your ATS box and torque your lugs. (With power disconnected.)

Second, and follow up recommendation, open your circuit panel and torque your lugs.

Note: There is a torque, but frankly, with a lot of force, you can't over-torque with a 9" screwdriver, unless you possess the strength of a 30 year old (still).

The point is that if you can put 1/8+ turns on the lugs, then you maybe overheating at this connection point.

It worth a shot and it's free. It's also a good think to do as preventative maintenance every 8 years or so.

===

If this is not the problem, my guess, and this is very likely, is it possible you have never Tuned-up your basement AC? ...Have you?

That said, and you have not, then my guess is your AC hard-start-capacitor (and motor starter (aka PTCR)) needs to be replaced.

You should also measure and replace your run capacitors too! Plus these are cheap on Amazon.

What is possible, IMO, is that you are getting a much higher "in-rush" current when you start your AC compressors; and your power panel can't pick it up, because you need a clamp meter designed to measure "in-rush" and I'm sure your power panel will not.

That said, your basement or roof AC is talking you to you you better listen unless you want a compressor in your AC to fail? Fortunately, the cost to DIY a run compactor is cheap and almost anyone can do it if you take pictures and keep track of the wires so you don't mix-up where they go.

2004Horizon · 06-06-2023, 08:28 PM

As for your ATS, if you visibly inspect it and see any thing burnt inside, that's a good signal your lugs are lose and it's a 50/50 chance tightening them will fix your problem for free.

If you need to replace your ATS, make 100A ATS (in today's market) or one you are SURE can handle the 70A neutral your generator demands. Me... I would buy a used Parallax 5070 over any new ATS that uses Chinese contactors, but that's another discussion for another time.

This 70A requirement is because your Onan is rated for 2-35A wires, which to my knowledge is only specified on the QD7500 and QD8000. I.e., you have 2-Neutral-White Wires going to your ATS. So your new ATS need to handle 2-neutral wires. And any RV tech that tells you different is setting up for a fire down the road, potentially!

Just be mindful, an ATS that advertises 50A service may not be what you need. This is why you may need to buy a 100A-ATS box, because they don't make "true 70A-neutral" ATS boxes like they used to.

And I'm going to assume you have a Parallax ATS-5070 like the ones in the diagram below. And if you are really good, you can rebuild or repair your ATS easily, but finding those old 8-Pin Contactors is not easy; and these things are rivetted in place. So you have to deal with that. But if your bridge-rectifier is bad, then you can replace that easily. (Of course, you need to find other posts that talk to this.)

Let's hope you just need to tighten your lugs!

Message to all: If you have never torqued down your ATS and circuit panel lugs, after 15 years, you may be living on borrowed time!

Caymanedge · 06-06-2023, 08:32 PM

Good deal, thank you!

TandW · 06-07-2023, 06:10 AM

Do you have a red dot temperature gun? Next time you run the genny, try to take aim at the troublesome breaker. I'll bet it's failing or has a loose connection. The breaker should be at the same temp as it's surroundings, until it gets close to max rating.

Caymanedge · 06-07-2023, 07:33 PM

No luck so far. 100amp ATS is fairly new and all the lugs are tight. Power panel lugs are tight as well. All fluids filled up.
Both AC units have soft starts and I am currently running them on a 30amp power feed so it’s not an issue in the rig.
I do not have a temp gauge but I am suspecting it is the breaker. 8 spike t9 Cummins and it’s available for $150. Going to try and get a temp gauge before I spend that money.
Thanks for the help.

2004Horizon · 06-08-2023, 11:15 AM

Sorry. Thought you were were working with a basement AC.

Good idea to rule out a weak breaker. Is the breaker one of the 2-35A breakers on the generator?

If so, let us know if you can switch the neutral wires to see if your "good" breaker trips after you do this. If not, then it's not a bad breaker.

shootist · 06-08-2023, 11:20 AM

Quote:

Originally Posted by Caymanedge

Having issues with my Onan QD8000 in my Journey.
Runs fine, shows 66amps on power panel, but blows the circuit breaker on generator if load gets above like 20amp. I can run one AC fine, but when second one kicks in it trips the breaker. I can swap them and get the same result so there doesn’t appear to be an issue with the AC units. Any ideas?

Breakers are a bimetal spring. They go bad all the time. Next time you run the gen check the breaker that blows for heating up. Your finger on the face of it will suffice. The two breakers can be tied together with a bar so both will trip. But if so one should be hotter than the other

Caymanedge · 06-08-2023, 11:47 AM

Grabbed an IR. Thermometer this morning. Will try and check it later today. Cummins gave me the new breaker number, 2P 35 $143…320-1875-01

Caymanedge · 06-08-2023, 11:50 AM

Forgot to mention. When I checked the oil the yellow end to the dipstick came off….so I picked up some hi-temp JB Weld….

shootist · 06-08-2023, 11:56 AM

Quote:

Originally Posted by Caymanedge

Grabbed an IR. Thermometer this morning. Will try and check it later today. Cummins gave me the new breaker number, 2P 35 $143…320-1875-01

Does blue seas make a breaker that will fit. That is out of this world pricing

https://www.bluesea.com/products/cat...rcuit_Breakers

Blueseas makes top quality stuff, onan/ cummins is chinese for the most part.

Caymanedge · 06-10-2023, 05:33 AM

So I finally got a chance to do some testing. Circuit breaker sat at an ambient 75d, fired up the generator and after a few minutes running only moved up a degree or two. Then I engaged one AC and the breaker temp rose to 78d. After 10min I engaged the second AC and after 5min it only rose to 80d. It ran longer than previously when the breaker would trip with no signs of overheating issues and it never tripped.

When it failed previously the ambient temp was much higher, like 87. Might have played a factor but hard to imagine it would move it that much. Research shows the breaker could function normally up to 130d.

I will test it again tomorrow when at a location to better run these tests.

Thanks for the input.

shootist · 06-10-2023, 10:39 AM

Quote:

Originally Posted by Caymanedge

So I finally got a chance to do some testing. Circuit breaker sat at an ambient 75d, fired up the generator and after a few minutes running only moved up a degree or two. Then I engaged one AC and the breaker temp rose to 78d. After 10min I engaged the second AC and after 5min it only rose to 80d. It ran longer than previously when the breaker would trip with no signs of overheating issues and it never tripped.

When it failed previously the ambient temp was much higher, like 87. Might have played a factor but hard to imagine it would move it that much. Research shows the breaker could function normally up to 130d.

I will test it again tomorrow when at a location to better run these tests.

Thanks for the input.

You are not measuring the actual bimetallic spring.

twinboat · 06-10-2023, 10:47 AM

First, where are you reading 66 amps from your generator ?
Amps are a measurement of current being drawn not available.

Then you say the amps are reading 20 for 1 A/C. Even that's a bit high, unless you have other things going.