Momentary 110V AC power trips.

[Jeremy Parrett]

I have installed a new Coleman Airxcell 24000btu basement dual compressor a/c unit. The old one was only 4 years old. Its installation   was well documented on this website.  The unit failed due to a badly designed cold air duct that caused blower flutter and very poor air flow. After R&Ring this unit in 2012 to replace one evap. blower and pc board two weeks ago the unit failed again. This time it was the same blower. 
 Good Sam ESP eventually agreed to fund this replacement as well.  Signature RV in Stuart.FL did the work.  By inverting the squirrel cage so the cold air ducted out the top of the unit we were able to design a very efficient curve  to join the original Beaver vertical duct, without cutting into the cage several times ( previous install) which severely compromised its integrity and performance.
 Altogether this installation was near perfect and the unit functions really well.
  OK......so now when the a/c powers up either on 110V ac 50 amp from power cord or with generator running we experience a   very brief power trip.  The TV switches off and all clocks etc need resetting.  The a/c unit keeps running though.
  I am wondering if the weak link might be the "Transfer switch"    I would appreciate any responses and ideas.

    Thanks,  Jeremy.  2000 Beaver Marquis Amethyst  . 2004 F250SD King Ranch with Blue OX 10,000lb tow .

[Fred Brooks]

               Hi Jeremy,

        From your discription, it sounds like both compressors are engaging at the same time. I am not sure how airexcell engineered the system but as a technician I would think they should engage 1 compressor and then momentary delay to come on line and then engage the second compressor. The reason I say this is because almost all RV air conditioners draw momentarily 54 amps to start the compressor. This is "momentary" and not long enough to trip a circuit breaker. However if there was a 108 amp momentary spike to the shore system, I would think that all peripheral electrical would experience a loss enough to reset. 
          Hope this helps, Fred

[Edward Buker]

Jeremy,

I think Fred has a good idea on the root cause of the "trip" but you may also be right. The circuit that holds the transfer switch in an on state, looks at voltage to make the decision. It may be that voltage drops enough so that it is momentarily losing contact by design. If you were in the bay, when the air kicks on, you could see if you could hear the relay click. Small chance this could be an overly sensitive transfer switch circuit if you find the compressors are coming on one at a time.

The other possibility is that the transfer switch keeps contact but the coach voltage drops low enough where the sensitive electronics cut out regardless. Only cure is to lighten the load of the air units coming on together. The other thing to look at, is there a delay circuit to keep the compressor from coming back on for several minutes once it kicks off. That would also create a severe load until the pressure has time to equalize some between the high and the low side. The delay and prevention of a two compressor start up are things that should be built into the control systems of the unit.

Later Ed

[Steve Huber Co-Admin]

Jeremy,
Did they change out the thermostat when that installed the new AC unit? It controls the delay of the 2nd compressor. If they put in a new T'stat or rewired the old one, they may have defeated the delay circuit and you would experience what Fred described. You can check this by monitoring AC current 2 on the CMP panel. Set the desired temp on the T'stat to 3 or more degrees colder than ambient and select Air Cond. If the AC Current 2 on the CMP jumps to 10 amps or so immediately at AC turn on, the delay is not working. If that is the case, I can maybe assist in getting it wired correctly.
Steve

[Edward Buker]

Jeremy,

It is possible in the wiring of the new unit that they did not get a compressor on each leg? If one was running and a second kicked on it would be a deep voltage drop. The other thought that came to mind is the TV and the microwave, if that is the clock you were referring to, are on the inverter circuit. The inverter has a relay also and that could go to bypass momentarily trying to switch in the inverter with a voltage drop if you leave that on. Might turn the inverter option off and see if that has any affect. Some surge guard protection devices can be sensitive to voltage drops also.

This is a new unit and all we know is the old one did not cause this issue but the new one does. If you can get a measure of starting current and running current on each compressor that would be helpful. If for instance the gas charge is too high in one of the compressor cooling units, it can cause excessive load on start up. Basically you need to know if the current demand of each compressor is in spec and operating properly before you rule in other possibilities and spend money on them. A good starting check would be, do both compressors draw the same current on your coach monitor panel on start up (may be hard to see) and during operation.

Fred's thought that both compressors might be coming on together is the best candidate but these are other issues you might consider if the 2nd compressor delay is working.

Later Ed

[Jeremy Parrett]

hello all and thanks for some interesting ideas.
 I watch the CMP Panel as the unit comes on line.  No amperage draw on line 1 and 17 then 14 amps on line 2 so only one compressor is starting initially. 
  Therefore I am wondering if it is the main 110 V AC  breaker at fault.  This  suggested by Signature RV, Stuart. FL  who installed the unit. 
  The thermostat is the one installed in 2011 .  It seems to work fine and allows the second compressor to run after a few minutes delay if I set the temp more than 2 degrees lower than room temp.
  Switching off the Zantrex Freedom Inverter replicates the issue .Perhaps the momentary voltage drop is causing the Inverter to drop off.
  Now, are there settings  I can change on this newly installed unit (Alliance Coach August 2013 ) ?
 The previous Coleman Airxcell unit did not cause this voltage drop but then it never worked very well either. 
 

[Edward Buker]

Jeremy,

The 17 going to 14 sounds about right. Check when the second one comes on and see if it the same. With the breaker itself not kicking off I would doubt that it is defective. You can get a weak one but it usually kicks off. One thing you can do is go to the main breaker panel and pull the main breaker and each of the two breakers that the air unit is on as well as the one that feeds the inverter (should be 30amps) and reseat them a few times to renew the contacts that go to the buss.

Later Ed

[Jeremy Parrett]

Ed,
  I have cycled the main , 2 air con, and inverter breakers.
 I also enabled 'ac charge' on the  Freedom Inverter panel.  What is that "function" ?
Whatever I have done seems to have solved the problem . The  Coleman Airxcell unit came on line again nothing tripped !!!
    Will keep you posted and thanks for your help.
   Jane and I are really looking forward to   the Napa Noel and then  Quartzsite in January  .
       Best wishes,    Jeremy

[Edward Buker]

Jeremy,

Any contact resistance can add load. When I said pull and reseat the breakers that was to eliminate any extra contact resistance. When you flip breaker on and off you can also reduce contact resistance by mechanically making and breaking contacts. You may have improved things or you may have gotten lucky having higher voltage at the power feed at the time and this problem may be marginal....time will tell. As far as the AC Charge setting, I have not seen that one. There is a setting for AC Low which tells the inverter what incoming voltage I should transfer over to inverter mode. You may want to play with that setting to see if it helps. You may find a voltage where it may help your problem. Say the TV is sensitive to 100V and shutting down at 100V, if the inverter was fast enough it could switch over at say 105V and prevent this. If the inverter was slow and causing a break in power and that was killing the TV, making that setting lower like 90V, could possibly keep the power from breaking during a switch over. Have to try that setting both ways to see if it has an affect.

Hopefully your cure will last...

Later Ed

[Jeremy Parrett]

Hi Ed,
   The Coleman Airxcell HVAC has run for 24 hours without tripping anything . Until I can find the Instruction Manual for the Freedom Inverter I am going to leave  all  alone !!
     Many thanks for your help.
            Jeremy

[Fred Brooks]

        Hi Jeremy,

   If you can take a picture of the xantrex remote panel and post it, I have the owners manual if you want it. I can also share what I believe is the charge button you refer to. Regards, Fred

[Jeremy Parrett]

Hello Fred,
I found the Xantrex Feedom manual.  Wow....u need to be a scientist to fully understand it,  but I will read it and check to see if they settings are correct.
We are still having momentary outages when 110v AC trips before inverter licks in. I think this is normal
Also we have occasional blips when both generator and inverter are running .

[Fred Brooks]

                Hi Jeremy, If its any consolation, I,ve heard that comment before about the manual. Here is what I share with my customers. If you read the manual all at once it puts you technical information overload. It was obviously written by an engineer that knows what he is talking about but can can't convey stuff in laymans terms. I've found if you read only one section and then play with the remote it makes sense. If not comfortable wait a day and try again.
        Another consideration is the internal transfer relays that automatically engage when shore power is lost or disengaged. I,m not sure what that threshold voltage would be let me check my repair manuals.
     Glad to hear it is running and cooling. I cross my fingers every time I turn on my SMC original air.
            Regards Fred

[Jerry Emert]

On the attached functional diagram of a typical inverter.  Notice that the AC power for the air conditioners actually goes to the air conditioners before the inverter from the main power panel.  Also notice that one leg of the AC goes to the inverter to change the state of the relay in the inverter.  That changing of state does 2 things.  It activates the relay to close contacts to route the AC to the inverter charger and it goes to hold the relay in the “activated state.”  Only one leg does the “work” in the relay to activate it and hold it activated.  If the AC leg that “does the work” is being loaded excessively by the AC unit on that line it could cause your symptoms by momentarily allowing that “holding” current to decrease to a point that it can no longer hold the relay in the activated state.  These symptoms could also be caused by the relay in the inverter not operating up to specs.  Having said all of this, remember this is a typical inverter and may be slightly different in yours.  This was exactly like the Xantrex in my coach. 
Good luck. I hope this helps.
Jerry