Cannot run A/C while at highway speeds

[scottandgaye]

This is long and I am sorry for that. But describing the setup and problem is necessary.

Here is my situation. First of all, this is a 2005 Hitchhiker II 32.5 UKTG fifth wheel. I have built a generator enclosure for our two Honda EU2000i generators and it is mounted on the rear of the trailer using the 2" hitch. This enclosure is well ventilated with ultra-high CFM radiator fans. The generators are paralleled and their output runs to an auto-switchover relay for switching between shore and generator power. The generators in this specific test are set with the economy mode set to OFF (they are running wide open). This is required for running the air conditioner. The air conditioner is original equipment and is a RV Products (AIRXCEL) 8535B676 model. This is a 15K BTU AC with heat pump. With this setup, I am able to start and run the air conditioner when the vehicle is stationery. In fact, it will run all day, cycling on and off as necessary, to maintain the temperature setting in the trailer. However, when I take it out on the highway, within minutes, both generators have gone into their overload state. No breakers inside the trailer have tripped. This is my dilemma. So, here are the things I have done to try to isolate the problem:

1) I have run the generators at full throttle for over 8 hours while coming back from our last trip. All breakers in the trailer were ON, but the AC control panel on the wall was set to OFF. The generators ran all day with no issues. Average highway speed was about 65 mph.

2) I have run this very same setup with the AC ON while driving around town. Slower speeds (45 mph max), but many stops, starts and turns. No issues. The AC runs just fine and the generators never go into overload.

3) I have turned every breaker in the trailer to OFF except for the AC and turned the wall control to on. Temperature was set to 60 degrees on the thermostat so that it would stay on the entire test and not cycle. I then took the unit out on the highway for 15 minutes. When I stopped, the generators were into overload, but, again, no breakers were tripped.

Conclusions:

It appears that this problem is NOT related to the generators nor their installation. It also does NOT appear to be an issue with the combination of the AC and other system(s) on the trailer pulling too much current. The AC will run all day as long as I don't move the trailer. It seems as though there is something going on with this model AC (or perhaps this unit specifically) that is causing a very high current draw when the trailer is going down the highway. The compressor should not be affected by wind, so I can only assume that one of the fans is potentially the culprit. Either the internal blower that blows the air in the ducts is getting stalled by a buildup of pressure inside the trailer while moving or the fan that pull air over the coils is getting stalled.

Has anyone encountered a similar situation? I know many people with motorhomes run their on-board generator and AC all the time while on the road. This should be no different. If someone has specifics on where to look in troubleshooting this, I would greatly appreciate it.

The primary reason for wanted to run the AC while on the road is to cool the trailer (we live in Texas) before we actually pull off for the night. Otherwise, it can take 2-3 hours before it is actually cool enough to go to bed, especially in the summer.

Any and all help/suggestions are appreciated!

Oh, and I am an electrical engineer, so I do have some knowledge of what I speak. But this has me baffled! I hope someone on here with experience in a similar situation can help!

Regards,

Scott
Allen, TX

[scottandgaye]

So, a partial update on the status of the investigation. While we were in Wyoming, one of the EU2000's started to burn considerably more oil than it should have. It was created a definite blue smoke screen when started every morning. So, on a business trip to Arizona, I came across an Onan 4kw Microquiet with only 290 hours on it. Had the guy start it up and run it under a load. Ran like a champ with no apparent oil usage. So, long story short, instead of trying to "fix" the EU2000 storage box I have to address a probable vacuum issue, I'm going to redesign the whole thing to handle the new Onan. Including sound isolation and vibration dampers. Plus, with a dedicated muffler, I plan to run the exhaust stack up the side of the rear stairs. This should eliminate any potential odors AND reduce some of the noise. My goal is going to be to get the noise level down to the point where you have to be within about 20'-30' of it before you even notice it. A lofty goal to be sure, but possibly doable. I'll keep everyone informed of my progress and may even be able to post some pictures. But, remember, we're staying comfortably in the high 90's to low 100's. May still be a while before I take this one on. Thanks for everyone's help. I think with the right setup, this will solve my problems. Plus, my wife can start it without ever leaving the trailer!

Scot

[JohnG3]

Ductape wrote:
More possibilities. Check fan rotation, is it pulling external air front to rear? If reversed pushing hot air out the front works fine until high speed airflow overcomes the fan, then you get high head pressure and high current.

If your trailer has a hump ahead of AC as many do then perhaps there's some sort of turbulence interfering with air flow through the coils st speed. Motorhomes are flat on top.

This sounds like the most likely answer to your problem. If the condenser is mounted in the front and the fan pushes the air to the front, when travelling at 60mph you have that speed of air movement pushing air into the AC unit. The condenser fan is now pushing against that incoming air causesing the fan motor to fight to overcome that incoming air. If the condenser is mounted in the rear, this should not be the issue.

[dclark1946]

I live just south of you in Richardson and have a couple of EU2000s that I store dry fuel wise. I could loan you one for testing if you want to try another generator. I only use these for power outages at home and carry a pair of EU1000s for our dry camping.

PM me if you are interested.

Dick

[gjcummings]

How old are the generators? I like Marcsbigfoot suggestion of float bowl issues. My EU2000i is ten years old and I just had to clean the carb - jets bowl etc. Check out YouTube. Prior to cleaning tough starting and stalling while under load after about 5 minutes...after cleaning carbs...zoom zoom zoom with one pull...as it should be. Check your plug also. Probably idle all day with bad plug but at speed (just had same problem with my outboard) ugh. Marcsbigfoot may be right as the brief hesitation causes the overload but not enough to stall out the gen then both gens go into overload.

I do like the vortex/lack of O2 not allowing enough air for a bad air/fuel mixture causing the hesitation or drop in RPM causing the overload...

Can't wait for the solution

[wa8yxm]

This may sound like a strange question but....

When was the last time you CLEANED the condenser (Not to mention the evpaorator) on the A/C?

Also, I'm told heat pump units need much more power. possibly only in heat mode, Is it possible that is trying to engage due to a bump in the road flipping a relay's state?

[bshpilot]

time for an upgrade...and put these problems behind ya 😄

i for one appreciate you circling back & am interested to know how you end up resolving this problem.

[scottandgaye]

I really do appreciate everyone's suggestions. We just returned from a month in Wyoming and during the two days it took to get back, the temperatures in the trailer climbed into the 90s each day. The ability to cool it down prior to stopping for the evening would have been tremendously helpful.

That being said, we do not have any trips planned that will cause us to be out overnight on the road until next summer (we're not yet retired). As such, I plan to work on this over the next few weeks. However, it's close to 100 today in Dallas and only going to get worse.

The point of all of this is that I hate it when people come to these boards and ask questions, get good answers and then never come back with how they resolved their problem. I promise not to do that. But I am going to be stepping away from this thread for a while until I have a chance to work on the trailer again in the next few weeks. For those that have an interest in the outcome, I promise, I will update this thread with the results of my testing. If that testing results in a solution, I'll let everyone know that, too. Either way, I think that what I am trying to do would be helpful to other DIYers who may encounter a similar situation.

Thanks again and I hope to be checking back in on this thread soon!

[GordonThree]

scottandgaye wrote:

GordonThree wrote:
OP: your test #1 doesn't really prove anything, and you said it yourself. running the generators with no load is running the generators with no load.

I mentioned previously about putting a heavy load on the generators using space heaters. I can easily put 3-4 kw of load on with just the space heaters my wife has laying around. I would obviously want to secure them so that they do not tip over and start a larger problem. With a full (resistive) load, do you think that would potentially identify the generators as the culprit? If they still run fine with the heavier load, have I really ruled a vacuum builup out as an issue?

Sounds like a fine test to me... you'll want to make sure the heaters cycle on and off, like the AC would, so the generators have to handle starting a load while at speed, not just carrying one they started at a stand still.

Have the wife drive, and you can ride in back and switch the heaters off and on while at highway speed, toggle your main breaker, or the breakers the heaters are on, so they turn off and on at the same time.

[marcsbigfoot20b]

My guess would be that one of the generators is having trouble with the float bowl in the carburetor. Maybe bouncing down the road at speed is causing one generator or both to hesitate or bog for a second and then you get an overload.

Try shaking both gens or bouncing them up and down while stationary and running under load.

[NinerBikes]

Mount the generators up front, instead of in back, and take it for a drive. See if that fixes it. Or put whatever is in the 5'er that needs AC up front in the car cab while driving down the road, where the AC does work.

[scottandgaye]

So, to make sure I understand the generator vacuum issue, if the generator becomes "starved" of air due to a buildup in a vacuum at the rear of the trailer, it is conceivable that one (or both) of these generators is losing it's ability to supply the rated power? I would assume this behavior would be similar to operating these at a very (VERY) high altitude? So, an EU2000i that is being starved of air flow will "try" to supply the demanded power, but, being unable to, one (or both) will go into overload. As soon as one goes into overload, the second will for obvious reasons.

To be honest, I had not suspected a vacuum buildup at the rear of the trailer as a culprit. But I will now focus more on that. While that problem may cause me to completely redesign my enclosure, it is better than having to modify the AC unit to address a vacuum buildup there.

GordonThree wrote:
OP: your test #1 doesn't really prove anything, and you said it yourself. running the generators with no load is running the generators with no load.

I mentioned previously about putting a heavy load on the generators using space heaters. I can easily put 3-4 kw of load on with just the space heaters my wife has laying around. I would obviously want to secure them so that they do not tip over and start a larger problem. With a full (resistive) load, do you think that would potentially identify the generators as the culprit? If they still run fine with the heavier load, have I really ruled a vacuum builup out as an issue?

Ozlander wrote:
Drive slower. Problem solved.

I am assuming you are making this comment tongue in cheek. Driving slow enough to prevent this issue keeps me down around 45 mph. Probably not a good idea when the interstate speed limit is 75 mph. 65 puts me at enough risk.

bshpilot wrote:
run the generator full throttle (no load plugged in) - drive it and see if it stalls.

I think you and GordonThree are saying pretty much the same thing. Put it under a load without the AC and see what happens. Essentially, try to isolate the issue from the generators and the AC. Excellent suggestions.

Again, everyone on here has been very helpful and informative. I will see what I can do to rule one of these in or out as the culprit.

Scott

[bshpilot]

heres something to try -

run the generator full throttle (no load plugged in) - drive it and see if it stalls.

I only know of a couple of way that an engine would stall (no spark, not enough fuel or no air).
I realize that the generator will shut down from overload / too much load (but that why id like to see the load unplugged).

if the generator won't run (at speed down the highway) w/out load - then you've got a fuel or air delivery issue.

eco mode won't have enough fuel demand to really test the fuel air delivery/starvation.

[Ozlander]

Drive slower. Problem solved.

[GordonThree]

OP: your test #1 doesn't really prove anything, and you said it yourself. running the generators with no load is running the generators with no load.

They do not run "wide open" with no load, even if the eco switch is off, they run at a higher fixed rpm. the throttle and engine load is still low. As you add electrical load, the throttle opens more as engine load increases because the generator is harder to turn.

if there's a shortage of air (oxygen) due to a vacuum, it's not likely to affect the generators at idle, with the throttle mostly closed they don't need much air.