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Old 06-13-2019, 04:01 PM   #21
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Originally Posted by BurntAsphalt View Post
Mike,
I just installed an easy-start on our 2011 AI. I "trained" it on shore power and it worked fine. When I ran it for the first time with the on board generator, the compressor came on after a short time and I had cool air blowing. I left to do something else for a few minutes and when I returned the compressor had shut off with the fan still going (and still warm in the coach). I shut it off and waited 5 minutes and it worked when I turned it on again. The compressor came on but did not shut off like before (but I only let it run about 10 minutes the second round). I need to let it run for an hour to see if the compressor acts up again. Like was mentioned before, I hope it just needs to learn how to run the compressor on the gen set. It will be very inconvenient if retraining is needed every time the power source differs.
Interesting! This is very similar to what I'm experiencing.

Today I ran the A/C using a rented Honda EU2000i generator, as recommended by Micro-Air for troubleshooting. It ran fine, but since I had to plug generator into normal shore power plug the Mini-PCS (Power Control System) treated this external generator as an external shore power source.

But during other A/C testing today using the installed Onan LP generator it would only run compressor for 4 minutes before it shut down. Five minutes later it started the compressor again, as designed, but almost immediately shut down again. Then I turned off all circuit breakers except the main and A/C breakers. This disables the Mini-PCS. The A/C then ran for over 5 minutes without issues on generator. I shut it down myself with the thermostat. It was very cool here today, only 65degF. I'll try running it longer when it warms up again in a few days.

I suspect the Mini-PCS is interfering with running the A/C on the generator. I had some trouble with this before I installed the EasyStart. Before installing the EasyStart the A/C would pull about 40A momentarily on compressor start, then the Mini-PCS would just dump the whole load and initiate a restart delay of 2 minutes. Then I would disables the Mini-PCS and A/C ran OK.

Now with the EasyStart installed the Mini-PCS keeps the power on the coach, but just stops the compress and fan keeps running. The Mini-PCS gets an input from the generator so it knows when on generator power and is designed to prevent overloading the generator. I've seen as high as 19A on the Mini-PCS display just before it shut down the compressor. This is likely close to the cutoff designed into the Mini-PCS to prevent generator overload.

A few days ago I ran another test, that Micro-Air recommended, removing the A/C cover and opening the EasyStart control box checking for the error LED indicators that light up when the compressor is shut down on generator. I got the indication that the power was interrupted. That could only have been done by the Mini-PCS as the generator kept running fine and continued to power the coach.

More testing to come.

BTW - A/C runs fine on shore power.
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Old 06-13-2019, 04:23 PM   #22
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Originally Posted by Boxster1971 View Post
I suspect the Mini-PCS is interfering with running the A/C on the generator. I had some trouble with this before I installed the EasyStart. Before installing the EasyStart the A/C would pull about 40A momentarily on compressor start, then the Mini-PCS would just dump the whole load and initiate a restart delay of 2 minutes. Then I would disables the Mini-PCS and A/C ran OK.


BTW - A/C runs fine on shore power.

I had the exact same problem with my coach AC. I saw large current spikes when the compressor kicked in. Ran fine on shore power, but kept tripping out on the generator. It actually tripped the genset breaker once as well.

I bought the Easy Start unit, but havenít installed it as yet. Will be following this closely.

The AC will run off the generator if I turn on the inverter. Lew installed a hybrid inverter with my upgrade. The batteries will provide that extra kick the compressor apparently needs now.
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Old 06-13-2019, 04:47 PM   #23
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MIKE - Been reading this and scratching my head also. But the behaviour does seem to point to the Mini PCS relay and/or contacts. Indulge me here and tell me if this makes sense:

1. From Mini-PCS install pdf:
"Normal operation, A/C contacts are closed and 0 ohms present. When Mini-PCS sheds, Relay contacts open and 100K resistance exists between two wires"

2. If you have some issue with your relay contacts, i.e. not completing a "shorted wire = 0 ohms", then you may have xx-k ohm resistance between contacts even when closed.

3. At the higher 30A power, you still have enough juice margin to overcome xx-k ohms resistance that the A/C does not shed.

4. But at the lower 20A gen which we agree is right at the limit of tripping, that small resistance between the relay contacts is enough to trip it since the A/C is asking for more juice that it's not getting. As the gen supplies more current, the Mini-PCS senses the impending overload and sheds before the gen breaker trips.

5. And since the shed order for the Mini is Appliance, Compressor, Fan - then the compressor sheds but the fan keeps to run still.

Does this make sense? Though mine is setup different since I am using the Midi, I do not have a separate compressor vs. fan shed, they are shared shed.
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Old 06-13-2019, 09:40 PM   #24
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MIKE - Been reading this and scratching my head also. But the behaviour does seem to point to the Mini PCS relay and/or contacts. Indulge me here and tell me if this makes sense:

1. From Mini-PCS install pdf:
"Normal operation, A/C contacts are closed and 0 ohms present. When Mini-PCS sheds, Relay contacts open and 100K resistance exists between two wires"

2. If you have some issue with your relay contacts, i.e. not completing a "shorted wire = 0 ohms", then you may have xx-k ohm resistance between contacts even when closed.

3. At the higher 30A power, you still have enough juice margin to overcome xx-k ohms resistance that the A/C does not shed.

4. But at the lower 20A gen which we agree is right at the limit of tripping, that small resistance between the relay contacts is enough to trip it since the A/C is asking for more juice that it's not getting. As the gen supplies more current, the Mini-PCS senses the impending overload and sheds before the gen breaker trips.

5. And since the shed order for the Mini is Appliance, Compressor, Fan - then the compressor sheds but the fan keeps to run still.

Does this make sense? Though mine is setup different since I am using the Midi, I do not have a separate compressor vs. fan shed, they are shared shed.
ALEX - you are making good sense. The installation manual I have does not mention what you discussed about relays. In fact it does not match my installation - it is for a unit that supports 50A service.

Could you post a copy of the PCS Installation manual you have?

The Mini-PCS diagram you posted does not match what I got from Precision Circuits Inc. for the Airstream installations with Dometic Comfort Control Digital Thermostat. I'm attaching the one that matches my installation. In that digarm below you will see that the PCS relays only control power to the Coffee Maker and Microwave. The load shedding for the A/C and Water Heater are done by the electronic control board through the load shed features built into the A/C and WH. The PCS load shed is only for the A/C compressor, not the fan.

Before I installed the EasyStart the PCS would just shut down the whole electrical system when the A/C compressor started as it pulled over 40A momentarily on start.

Now with EasyStart installed the compressor start load is about 14A. On shore power everything works fine, with a much smoother compressor start-up. But on generator the compressor load is shed shortly after starting as the run current climbs toward 20A. There is definitely something different going on inside the PCS when on generator.

The A/C ran OK on generator when my Interstate was new. Over time, starting about two years ago the PCS would not let the generator run the A/C. My work around for the few times I needed to run A/C on gernator was to shut down the PCS by turning off all 120VAC breakers except the A/C. The PCS generator limit is 20A. The generator circuit breaker is 21A so I must be running on the edge as I can run A/C on generator with PCS disabled.

The A/C compressor run current has increased as the A/C got older. Not sure yet if I can fix this.
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Old 06-13-2019, 10:43 PM   #25
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MIKE - a couple of things:

1. Since the A/C runs fine on shore power AND does not trip the 20A breaker, even if we factor in the increased current draw because the compressor is getting old, I personally think the A/C is still within tolerance specs of what is expected of the unit as they get older. I mean, that's about true for any compressor (rv or residential), right?

2. So, I agree with what you mentioned on the other thread. If this were my unit, I would chase the PCS, specifically the relay part, coz that's where all the determining factor occurs between those contacts as to how much voltage gets dropped between the contacts. If the contacts are total short (0 ohms) when connected and >100k ohms when open, then the relay is doing it's job and not dropping voltage (acting like a resistive load even when closed) causing increased current flow leading to a load shed.

3. Regarding posting my Install Manual - it is not relevant anymore since you posted your actual setup diagram. PCS has I think close to 10 different versions on the Mini, just depending on 30A or 50A, dual A/C or single and number of appliances. The most they handle is 4 out of 5 loads at any given time, as they only use 4 relays. The 5th relay slot is taken up by the gen counter and +/- battery terminals. But they all pretty much do the same thing. It only differs in the shed order that they implement based on specific rv manufacturer request.

4. Based on your diagram, the A/C shed lines for Relay #3 are pin 2 (COM) & pin 6 (NO=Normally Open). I would ohm out between Pins 2 & 6 when shorted and open. If it's anything other than 0 at short and >100k at open, then relay is the problem.

5. Also, based on your diagram, they are not shedding the A/C fan at all, just the compressor. Kinda makes sense since they already used up all 4 relays and the fan only draws 2A at most. I think their rationale is once you have shed Coffeemaker, then Micro, then A/C- then what's the point in shedding a 2A fan, right?

6. Actually your PCS (and mine) are both 30A units. 50A is ignored. The 50A units will have the 50A green led in the display's Service column. The other way to tell is the 50A units will shed generator loads at 44A and not close to 20A (as the 20A do). If your unit had been mistakenly installed with the 50A PCS, then you would have the opposite problem. - i.e it would pop your breaker and would never shed anything.

7. Is your W/H on during this entire time? Just asking since that is the last load specified in your shed list. If that is drawing unusual higher current than normal, that will obviously affect the loads shedded upstream of it as you bump into the 20A limit.
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Old 06-15-2019, 05:37 PM   #26
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ALEX - my WH was off. I posted the results of my final test in the other thread about A/C on generator:
http://www.airforums.com/forums/f240...ml#post2252755

I'll have to dig deeper to see if Mini-PCS is working properly. I did also test other load shedding by the Mini-PCS. On generator I turned on the WH - it displayed a 12A load. Then I turned on the Microwave, which adds about 15A. The PCS immediately shed the WH as designed and left the Microwave running.
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Old 06-15-2019, 11:06 PM   #27
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ALEX - my WH was off. I posted the results of my final test in the other thread about A/C on generator:
http://www.airforums.com/forums/f240...ml#post2252755

I'll have to dig deeper to see if Mini-PCS is working properly. I did also test other load shedding by the Mini-PCS. On generator I turned on the WH - it displayed a 12A load. Then I turned on the Microwave, which adds about 15A. The PCS immediately shed the WH as designed and left the Microwave running.
MIKE - I just read your post on the other thread. WHEW, certainly threw a lot of us in circles. The new symptoms with Easy Start was as what you, me, and others were thinking - just a red herring to mess us up. Regardless, it still made me/us conclude the cause was same - the Mini PCS. I could not pull up prices on Mini or Midi (mine). But if its cheap enough, prob. easier to just R&R with a brand new set Mini or Midi rather than chasing it around? I am kinda lazy that way. My Midi on Gen mode does not shed A/C even with some extra loads like Float charging, small tv, fridge. So long as I stay away from microwave & Bulk charge.

Glad at least it's back to your normal SOP.
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Old 06-21-2019, 05:24 AM   #28
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To my knowledge my PCS has never come into play. I simply remember not to run one power-hungry thing (WH, AC, or microwave) when also running another. But I do have a question regarding the PCS. I thought it simply cut power to one (or more) of the power hungry things in some priority order. But these posts seem to suggest that it cuts power to the compressor part of the AC, but not the fan. How can that be? Doesn't power to both the compressor and fan come in ('downstream' of the PCS) on the same wire? Seems to me that it would be the Easy Start, not the PCS, that is cutting power to compressor but not the fan.

PS: I assume that the PCS circuit labeled 'coffee maker' is simply the plug above the galley - correct?
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Old 06-21-2019, 07:48 AM   #29
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But these posts seem to suggest that it cuts power to the compressor part of the AC, but not the fan. How can that be? Doesn't power to both the compressor and fan come in ('downstream' of the PCS) on the same wire? Seems to me that it would be the Easy Start, not the PCS, that is cutting power to compressor but not the fan.

PS: I assume that the PCS circuit labeled 'coffee maker' is simply the plug above the galley - correct?

TITUS - On my PCS, power is cut to both compressor & fan, it does not distinguish between the two. But certain prior versions of the MINI PCS (wired appropriately with the right Dometic A/C adapters) have the ability to cut-off compressor & leave the fan running. My PCS seems to only have the A/C and microwave on shed list. But come to think of it, since I do not have the MINI with LED version (I have the MIDI with the LCD display rolling list), I think I only see the shed list based on what is existing 'live' appliances,. if/when I power them up then the rolling list will reflect their presence. I gotta confirm this next time and power up everything. Glad you brought it up.
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Old 06-24-2019, 02:48 PM   #30
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MIKE - It is 102 here at 3,200 ft asl and my batts are BULK charging. I can happily report even on 20A dedicated breaker at daughter's hous, PCS sheds the A/C. So gen or not, especially if its this hot, (as you said) that's all we got

Sheds as steady state current starts staying at the 19A mark
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Old 06-25-2019, 10:00 AM   #31
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MIKE - It is 102 here at 3,200 ft asl and my batts are BULK charging. I can happily report even on 20A dedicated breaker at daughter's hous, PCS sheds the A/C. So gen or not, especially if its this hot, (as you said) that's all we got

Sheds as steady state current starts staying at the 19A mark
ALEX - thanks for the data point. That 102 is HOT! Today I'm enjoying the view from our 4th floor penthouse at a nice beach resort on Providenciales island in the Turks & Caicos. It is a very comfortable 85 with a nice breeze. Had a nice swim after breakfast on the beach. Life is good!
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Old 06-25-2019, 10:28 AM   #32
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ALEX - thanks for the data point. That 102 is HOT! Today I'm enjoying the view from our 4th floor penthouse at a nice beach resort on Providenciales island in the Turks & Caicos. It is a very comfortable 85 with a nice breeze. Had a nice swim after breakfast on the beach. Life is good!
MIKE - And it's only the beginning of summer here. Your 85 with nice breeze - that's definitely the Good Life! I won't see that here anymore until October's Indian Summer
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Old 09-30-2019, 08:52 PM   #33
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I am totally new to the AI family. I still have not figured-out how to run all the appliances and AC. Do I need to buy an Easy Start and worry about mini/midi PCS stuff? I have the 2108 AI Grand Tour. Do those issues still apply?
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Old 10-01-2019, 01:49 PM   #34
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I am totally new to the AI family. I still have not figured-out how to run all the appliances and AC. Do I need to buy an Easy Start and worry about mini/midi PCS stuff? I have the 2108 AI Grand Tour. Do those issues still apply?
WELCOME!!

You should not have to do anything with your new Interstate. Just start the generator and then run the A/C to see how it works. I understand the 2018 Interstates have an LP only on-demand water heater so it wont be a factor when you run the generator.
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