2021 Isata 3 / Onan QD3200 Gen Overload

sdbruin · 04-11-2021, 07:43 PM

So we had the new Isata 3 out this past week and encountered an issue with the QD3200 diesel gen shutting down with an "Overload" condition displayed on the panel, after about 10-15 minutes of running. Prior to the shut down we had been running the standard Coleman AirXcel A/C and also recharging batteries with the converter from dry camping. Effectively, it appears running both the A/C and requiring a charge on the house batteries triggers the generator to max out and shut itself down. I was able to replicate this repeatedly in our driveway today, so this rules out the heat, altitude and fuel levels as factors. Running the A/C or converter independently do not cause the shutdown; just when they are run together they cause the issue consistently.

Some further datapoints, the Victron BMV is showing roughly 60A/770W being pushed into the batteries from the converter. The AirXcel Mach 10 AC (model 45054-8792) is the 15000BTU model, and the spec says 14.2 amps on cool. The batteries are 100AH Battleborns and the stock converter has the activated dip switch for LiFePO.

OK -- So why on earth is the gen shutting down?

My first thought is that it could be a bad AC start capacitor?
Other possibilities, a bad inverter on the gen, bad converter ... or maybe the gen really is underpowered to do both charging + AC.

Love any others input on this.

JLeising · 04-12-2021, 12:04 AM

A guess - something else is drawing significant 120 volt power. My first guess would be the water heater. On my 2012 MBS I turn off the water heater circuit breaker when using both the A/C and the microwave (forces the water heater to use propane). Refrigerator would be another possibility.

Rich.M · 04-12-2021, 04:52 AM

We have the QD 3200 generator in our unit. Our ac is the Dometic Brisk 12,000 BTU. No problem running ac ,charging and even a brief microwave on generator all together. I always have refrigerator on gas and hot water electric off on generator. I do recall having to add an additional hard start capacitor ( Dometic option) that was not included from the factory. The 15000 AC could not be ordered with QD 3200 in 2015 model year due to power requirements. Those Lithium batteries draw much higher charge rates and I have seen some forum reports of electric only refrigerators putting more demand on that generator. Try everything switched to gas, ac fan on low and cross your fingers, use a meter that can read amps and check converter and ac. Even if the numbers add up on paper consider additional capacitor or one of the soft start kits for ac. Good Luck

Bill Davis · 04-12-2021, 05:17 AM

Just for future posters, the I 3 has a propane only water heater and 2 way fridge.
My guess is something is drawing on the system besides the A/C and converter. If the OP has the inverter turned on their maybe something else plugged in to the 120 volt circuit putting it over the top. In the older Isata3s the fridge plug was not connected to the inverter. I don’t know about the new ones. If the fridge will run off the inverter and it’s set on auto that could be the problem. I believe on auto will always default to 120 volts.

sdbruin · 04-12-2021, 09:54 AM

Thanks all, I think you all might be on to something about a draw happening that I'm not aware of. Bill is spot on - the I3 has a Truma on demand propane heater, so that can't be drawing anything. The 2-way fridge was also off yesterday when I recreated the issue. The inverter was on (cannot shut off when connected to shore power or gen), but to my knowledge nothing connected. (When the gen is off I can measure the pull from the battery with the inverter on, and its minimal). @Rich, when I pulled the cover off of the Coleman AC I did see a pretty sizeable capacitor already installed from the factory, but that leads me to believe perhaps it might be faulty. Agree, as well, I'm going to do some measuring of the numbers coming off of the shore power plug, and watch it over the 20 minutes or so when the AC cycles, perhaps the capacitor isn't building up enough juice between cycles and causing a spike in demand. Will post back if I find out more. The good news is I have a 4-month wait nearly over for a dealer service appointment!

Travler · 04-12-2021, 11:18 AM

By your numbers you are pulling about 20.4 amps from the generator. The full load is rated at about 26.7 amps. So you are pulling about 77% of capacity. If you do have anything else pulling then you are getting close. The other thing to look at is if the breaker is tripping when the AC starts. That may be taking it over the limit. You may be able to get past this by adding a soft start to the AC. Just one idea to get around the issue.

**bclemens** · 04-13-2021, 10:20 AM

Yes remember, the diesel gen is only a 3.2kw. The LP gen is 3.7. The Diesel gen has always been a little taxed vs. the 4.0 gas or 3.7 LP so we have to be careful on what A/C we run. The Dometic would trip the diesel every time.., and it wasn't power, but harmonics between the two. It was weird...it was never near capacity but the A/C created issues.

Have you tried turning down the charge %? The lithium charger can push some amps.

sdbruin · 04-13-2021, 10:28 AM

Thanks BC. Thats kind of what I assumed, but I'm ~900W away from hitting spec limit, and at 68 degrees and sea level this isn't asking a whole lot. I do wonder if adding a soft start module would smooth out the peak amp requirements so both can run. (*my unit has the coleman mach 10 vs Dometic, probably the same issue, made maybe slightly worse by the 15k btu unit vs 12.5).

Does the PD unit have a way for me to turn down the charge beyond the default lithium dip switch?

**bclemens** · 04-13-2021, 11:02 AM

Quote:

Originally Posted by sdbruin

Thanks BC. Thats kind of what I assumed, but I'm ~900W away from hitting spec limit, and at 68 degrees and sea level this isn't asking a whole lot. I do wonder if adding a soft start module would smooth out the peak amp requirements so both can run. (*my unit has the coleman mach 10 vs Dometic, probably the same issue, made maybe slightly worse by the 15k btu unit vs 12.5).

Does the PD unit have a way for me to turn down the charge beyond the default lithium dip switch?

I thought there was a setting in the Firefly that could allow that...but I could be thinking of the big trucks.

The Dometic would draw less and still cause issues...I just know that the problem existed for some reason and this makes me think of that. Atwood was the first that I KNEW did not cause that imbalance and Coleman Mach was the other. The Atwood's had their own issues that seem to have since been corrected, but the Coleman Mach is just a better interface for Firefly.

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