AC tripping generator

[Mdk0420]

Hey all. I seem to be having some AC issues unfortunately. I ran some diagnostics but I haven't been able to figure out the problem.

I'm using a Westinghouse igen4500df generator. This should be more than enough to start an AC however it's hit or miss. Sometimes it starts up, other times it just hums until the generator trips its overload protection.

I've tested the resistance of my compressor coils and they show no resistance. My capacitors are very close to their ratings (both within 2%). Motor starter is on the low end kf its 43-52 rating at 43.8 but shouldn't be causing the issue if it's within range.

On the generator side I've ran a few test and need to run a bit more because I forgot some data. But what I have so far is here:

A successful startup did a draw of 28-30 amps.

An unsuccessful startup maxes out the generator at 48 amps but the voltage was down to 95v during the heavy draw period. After about 5 seconds it trips the overload

The generators low voltage goes all the way down to 55v on initial heavy draw and comes back to 95v in under a second and back to 120v or so within 2 seconds except when it has the unsuccessful start. It doesn't get passed 95v and 48 amps.

I'm measuring from the start of the generator line using true rms equipment so these voltages are probably lower at the compressor.

The fan motor spins freely. I did not check the refrigerant. It does get nice and cold when on.

I do want to get a soft start but I'm still baffled that a 4500 watt generator can't start a single AC system. I run my 15k BTU AC uni in my shed no problem.

Any suggestions on what else to look at? Is this somehow normal for a unit without a soft start? Are Westinghouse generators just junk?

[Mdk0420]

JBarca wrote:
Mdk,

You are welcome, and it sounds like you have everything up and going Great!


Now to your T-stat and what kind you have

Mdk0420 wrote:
Great stuff! That's exactly what I'm looking at lol. I had the 2 capacitor setup. I do not have a digital display like yours. Just a few switches that change from on, auto for fan control, temp control and a setting for cool, off and heat.

Opps...:S. OK, let's try this again.

The T-stat shown in this picture is the cream-colored rectangular-shaped bottom device that says, "Duo-Therm by Domitic". This vintage is the analog-style T stat that works with the analog control box. This control box requires a separate 12 VDC source run to the control box to operate the controls. The camper 12-volt DC system provides this. The 120 VAC is fed to that box, but it only powers the motors on the roof unit.


The digital display above the T-stat with the word (Acu-rite) is a 2, AAA battery-operated remote thermometer. I have the remote sensor inside the fridge to tell what temp the fridge is doing without opening the door. It is 34.7 F inside the refrigerator. The 70.4 F is the ambient temp in the room. This display has nothing to do with the AC unit or the furnace. LOL.... sorry about that; it just came along in the pic.

I hunted down a pic of the vintage before the analog control T-stat. This is called the "Bi-metal" system. This pic shows the T-stat that works with the Bi-metal control box. This bi-metal control box only had 120 VAC come to the control box up in the ceiling. An onboard transformer created the control voltage to work with the T-stat and power the control board to turn the relays on and off to control the roof unit. This system has no short cycle protection; you are supposed to wait and not fiddle with the on/off buttons or the temp slider. In automatic, the system takes care of itself. The two vintages of the system cannot interchange T stat or control boxes. They are specific to the technology of the time.


OK, now curious as I am "into" the Sunline brand of camper, what T stat is in your 2003 model year camper? And you know what month and year it was manufactured? This info is in the binder manual or the VIN tag on the front left outside of the camper if you can still read the tag. The model years rolled mid-year, sort of like the car industry.

Have a good campout,

John

I have the first duo therm one. I will try to see if I can find the manufacture date.

[trailer_newbe]

I think we are assuming the generator is running properly and delivering the power it should at full load. Unfortunately many generators have valves that are out of adjustment which limit the HP of the engine to something below what it was able to do when it was new. This in turn will cause the generator to fall short on lock-rotor and full load amps. You would be surprised how many generators can’t deliver what they are rated for. Additionally, the power module may not be delivering the needed voltage when the AC starts simply because something like an AVR or throttle governor is out of adjustment. I would load test the generator to insure it is actually performing as it should and if all that checks out then start looking at the AC unit.

[JBarca]

Mdk,

You are welcome, and it sounds like you have everything up and going Great!


Now to your T-stat and what kind you have

Mdk0420 wrote:
Great stuff! That's exactly what I'm looking at lol. I had the 2 capacitor setup. I do not have a digital display like yours. Just a few switches that change from on, auto for fan control, temp control and a setting for cool, off and heat.

Opps...:S. OK, let's try this again.

The T-stat shown in this picture is the cream-colored rectangular-shaped bottom device that says, "Duo-Therm by Domitic". This vintage is the analog-style T stat that works with the analog control box. This control box requires a separate 12 VDC source run to the control box to operate the controls. The camper 12-volt DC system provides this. The 120 VAC is fed to that box, but it only powers the motors on the roof unit.


The digital display above the T-stat with the word (Acu-rite) is a 2, AAA battery-operated remote thermometer. I have the remote sensor inside the fridge to tell what temp the fridge is doing without opening the door. It is 34.7 F inside the refrigerator. The 70.4 F is the ambient temp in the room. This display has nothing to do with the AC unit or the furnace. LOL.... sorry about that; it just came along in the pic.

I hunted down a pic of the vintage before the analog control T-stat. This is called the "Bi-metal" system. This pic shows the T-stat that works with the Bi-metal control box. This bi-metal control box only had 120 VAC come to the control box up in the ceiling. An onboard transformer created the control voltage to work with the T-stat and power the control board to turn the relays on and off to control the roof unit. This system has no short cycle protection; you are supposed to wait and not fiddle with the on/off buttons or the temp slider. In automatic, the system takes care of itself. The two vintages of the system cannot interchange T stat or control boxes. They are specific to the technology of the time.


OK, now curious as I am "into" the Sunline brand of camper, what T stat is in your 2003 model year camper? And you know what month and year it was manufactured? This info is in the binder manual or the VIN tag on the front left outside of the camper if you can still read the tag. The model years rolled mid-year, sort of like the car industry.

Have a good campout,

John

[Mdk0420]

Great stuff! That's exactly what I'm looking at lol. I had the 2 capacitor setup. I do not have a digital display like yours. Just a few switches that change from on, auto for fan control, temp control and a setting for cool, off and heat.

I got the soft start done correctly and everything is working smoothly now. I now am drawing between 13.5-16amps on the tests I did with a voltage drop only down to 114v. The surge is much lighter now. Even tested it while running the microwave and it still started up.

The other plus on the soft starter is that the micro air that you recommended has a built in 3 minute cycle period so it cannot short cycle my AC anymore either. If I try it just gets an error and then clears after 3 minutes and starts up again (was trying to force a short cycle but doesn't work so the 16amp draw was all I was able to get now).

Note that this was without the battery installed still but because the surge is less, there's still a possibility that the battery being hooked up would help keep the control unit functioning since it would have a good 12v connection. When the surge hits I wouldn't be surprised if it dropped down to under 10v on the DC side.

Unfortunately I already had things apart before testing the battery theory but now that my voltage drops aren't crazy that isn't something I can test without hooking all the old start components back up lol.

Thank you for the recommendation on the soft starter! Worked great and in the end it seems to of solved all of my issues.

[JBarca]

Hi Mdk4020,

I'll respond here in your generator post, so it ties together better.

Here are a few things to help explain the older Brisk Air controls that apply to your 2002 AC system. There are three main parts to the AC system in controls.

1. The roof unit. This is what is in the roof itself. The roof unit has fan and compressor motors, motor capacitors, and a wiring harness with a 6-wire white plastic plug into a control box inside the camper. That is the extent of the controls on the roof. There are no contactors or other control devices up on the roof to start or stop the motors. Motor control comes from the control box.

Look like this. The silver junction box houses the capacitors.


Inside the capacitor junction box. NOTE: pending the age and vintage of the roof unit, you may or may not have 2 capacitors in this box.


The wiring diagram from the side of the capacitor box


NOTE: The little black capacitor is called out at "COMP STARTER" on that wiring diag. This extra smaller capacitor is not always used, it helps the compressor get started by boosting the start voltage as that vintage compressor needs the extra help.

The other capacitor is a split capacitor, part of it for the fan, the other part for the compressor the Mfd ratings are different for each part. This split capacitor comes in a few shapes, round and sometimes white or silver or oval again pending the vintage. Here is the top of a round silver one.



2. The control box, is a silver metal box inside the camper up in the ceiling where the air intake grill is and the mesh filter. This box is where the fan and motor contactors (relays) are located on a PC board. The 6 wire white plug from the roof unit plugs into this box.

NOTE: There are a few versions of this control box. This picture is from the older analog T stat system.




At this point, we (nor you) know if you are on the analog or the bi-metal control box. Those are the 2 main types of control boxes; they are wired a little differently and have different control power sources.

The analog control uses 12 VDC from the camper DC system to power up the control board.

The bi-metal controls use 120 VAC to run a transformer on the control box board to create the control voltage to run the AC controls.

Your 2002 camper might be on either of those 2 control boxes. Ideally, you understand what you have for now and future troubleshooting.

3. The T stat. The T stat sends signals to the control box to run the roof unit or not. There are other features the T stat does, but again the analog T stat and the bi-metal T stat are different. We need to know which you have.

This pic is of the analog T stat.


Behind the cover of the T stat





The above is more to help you understand how the 3 main parts of the AC controls work. There is more going on with the T stat, the furnace interlocks, and possibly why your genny is having issues, but I need to know if you are on the analog control or the bi-metal.

Each main control part has different part numbers. The roof unit you posted the model number for is only the roof unit. The roof unit works with many different control systems.

The control box has its own part number, and so does the T stat.

I can tell which vintage you have by the looks of the T stat. Please post a pic of your T stat. . If it is like the T stat above in my pic, you are on the analog system. The bi-metal system looks very different. I do not have a pic handy of that T stat.

Now to your Micor air. I'm not sure if you sorted out your wiring issue yet. Here are a few big-picture things.

Here is your wiring diagram from the other post
https://gcdnb.pbrd.co/images/muahNFRxR0uK.jpg

When going with the Micor air, you have to abandon the small black capacitor called COMP STARTER on the wiring diagram.

The color codes can be confusing. These pics from my last Micro Air install may help. This is a newer Dometic Brisk air unit, but the roof unit wiring should align with yours.

Here is the blue compressor tie-in that is calling out. I used a black wire to extend the Micro air black wire


The Micro air (MA) cable casing is gray; it shows the brown (MA)-to-white (DOM)from the compressor (must be the white from the compressor) and black (my wire)-to-black (MA) connections and the red (MA) plugs into the capacitor red, and the white MA with the yellow connection hood also plugs into the capacitor.






Here is a link to my Flickr photo site with more pic of the micro air install, which may help.
https://www.flickr.com/photos/camper-johnb/albums/72177720307672421

The Micro air needs the first 5 starts to work right to train (learn) the unit how to optimize the starting profile. There are instructions on how to do this on a genny. See page 26 in the Micro Air instructions. https://www.micro-air.com/support-documents/installation_resources/EasyStart_364_Installation_Guide_...

Since you had a few messed up starts on the first 5 starts, I'm unsure how to reset the starts. And I'm unsure how the soft-start will react to those messed-up first starts. You may have to call them on Monday on how to reset the learning process to get the system optimized.

I hope this helps, and please let me know about your T stat; I can explain the rest of the AC controls for the future once I know which you have if you want.

Let us know how it goes.

John

[Mdk0420]

JBarca wrote:

Bobbo wrote:
The thermostat SHOULD prevent short cycling.

Assuming Mdk4020 is still on his original older Dometic control board, and T stat from 2002/2003, he might still be on the older bi-metal controls T stats. The mechanical and bi-metal T-stats were not smart enough to create a timing function to prevent short cycling. The older analog T stat may also have had the issue.

Even a new non-ducted AC with mechanical controls has the short-cycle ability issue.

When the electronic T stats came to be, many of them had the compressor timer to prevent short cycling.

The AC unit is original from what I can tell. I did not look into the thermostat however the unit is dated for 2002. I know for sure that I can short cycle it manually just by flipping it to off and then back to cold. I don't know if there is any logic for when the AC shuts off automatically though. I'm not familiar with these systems at all.

[JBarca]

Bobbo wrote:
The thermostat SHOULD prevent short cycling.

Assuming Mdk4020 is still on his original older Dometic control board, and T stat from 2002/2003, he might still be on the older bi-metal controls T stats. The mechanical and bi-metal T-stats were not smart enough to create a timing function to prevent short cycling. The older analog T stat may also have had the issue.

Even a new non-ducted AC with mechanical controls has the short-cycle ability issue.

When the electronic T stats came to be, many of them had the compressor timer to prevent short cycling.

[Mdk0420]

I got my soft start but I am having install issues. If you have any insight there, here is the link: https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/30394528/p/1.cfm

It did not solve my issue but its quite possible I got wiring messed up or I'm not doing something correctly. Now the soft start trips with a "Stall" error instead of my generator tripping lol.

I did not run any additional metering tests because it was getting late. I hooked the soft start on, gave it a few runs to try it and it just made my problems worse for the time being because now instead of a chance the generator trips, the soft start has the "Stall" error 100% of the time.

As far as the short cycling goes I'm not sure what protections are on this unit. I did get the model number to it though. It is a Dometic Duo Therm 59516.331 AC unit. It is 13.5k BTUs. Not a very big unit. Whenever I short cycle I do it on purpose shutting down the unit then starting it back up after about 15-30 seconds.

Also note that I did NOT test the 12v battery theory yet. That could still very well be an issue of it forcing a short cycle if the inverter is cutting the thermostat on and off. This will be another thing I test out this weekend. Trips in a week so gotta figure it all out by then lol

[Bobbo]

The thermostat SHOULD prevent short cycling. Short cycling is GUARANTEED to really spike the amperage draw.

[Mdk0420]

I'm fairly sure I had the battery in the on position when I tried it off shore. I'll have to double check that test because that does sort of make sense. The way I recreate the issue is by short cycling it. If I turn it off and back on within a minute or so it will trip almost every time. So if the DC circuit cuts off supply to the AC and then sends power again from the surge it would short cycle it as well.

My soft start gets here today so I'll update on if that solves the issue and include the battery in on the test.

[Galvanizd]

For the OP . Here is a some info that might help with the 12volt idea. from above. This guy is pretty good. The entire video is excellent info and offers great stuff, At about 2:15 , he addresses what MIGHT be your problem. At any rate , might be a good place to start

https://www.youtube.com/watch?v=ooPAwYEKbUE

[bucky]

Kudos to the OP for doing all they could to solve a problem rather than the norm on the interwebs of just throwing out a vague request for help.

[JBarca]

Galvanizd wrote:

Mdk0420 wrote:

valhalla360 wrote:
Shouldn't need a soft start with a 4500w generator. My best guess is the water heater is on electric and the battery is low so the charger is putting out max charge...that may be enough to push it over the edge.

The 12v battery is disconnected. I have it charging for when we go on our vacation in 2 weeks.

The hot water heater is off. I don't think mine has an electric option but I have no load amps of a few miliamps even if it did. I've always operated my hot water from a button on my control panel and it runs propane to heat it up but that switch is off

You need to reconnect your 12 volt. You need both to properly operate the ac unit. Power to the ac unit is provided by generator or shore power. 12 volt power is needed to tel the ac unit what to do. Might be part of the problem .

Galvanizd, This is a good thought.

This is something to rule out; yes, connect the battery and try again. We didn't get a confirmation if this Sunline was using a Centurion or an American Enterprises power converter. In 2003, Sunline stopped using the Centurion and went to the American 60 amp 12-volt power converter. I know that the American can run OK without a battery attached, but I'm not sure about the Centurion.

But, the battery will act as a capacitor on the 12 VDC side. Actually, it will run the AC unit control board all by itself. Now here is the but, the Dometic analog control board uses a 12-volt DC relay as a starter for both the fan and a separate one for the compressor. If, by chance, the 120 AC power flickers or goes low volts, the power converter may stumble and drop the 12 VDC control low enough that the control board flickers the relays while trying to start the compressor. The generator will not like that flicker of the AC power during this high surge spike. Having a battery in place will supply a constant 12 VDC regardless of the power converter dips. This is all theory, but it could happen. The best way to rule it out is to put the battery in and try it.

For sure, let us know how this battery test goes.

John

[Galvanizd]

Mdk0420 wrote:

valhalla360 wrote:
Shouldn't need a soft start with a 4500w generator. My best guess is the water heater is on electric and the battery is low so the charger is putting out max charge...that may be enough to push it over the edge.

The 12v battery is disconnected. I have it charging for when we go on our vacation in 2 weeks.

The hot water heater is off. I don't think mine has an electric option but I have no load amps of a few miliamps even if it did. I've always operated my hot water from a button on my control panel and it runs propane to heat it up but that switch is off

You need to reconnect your 12 volt. You need both to properly operate the ac unit. Power to the ac unit is provided by generator or shore power. 12 volt power is needed to tel the ac unit what to do. Might be part of the problem .