Dfvet106
22kw Generator wont run 5 ton AC unit

I have a 22kw Generac Generator (Serial No.3002658451) running on propane
and a 1 year old 15 SEER REEM 5 ton AC unit (152 LRA and RLA-23A) (Model No. RP1460AJ1NA) (Serial No. W491624844)
and the Outside unit will not turn over when the generator is running.

I have confirmed that the GAS is NOT the issue after 2 visits by the gas contractor. (A regulator has been added directly adjacent to the generator and it is set to 12in)
My AC guy installed a SUTTCO SPT 6 Hard Start unit.
My AC guy thought that if I was still having issues he could install a Sure Start SS1B16-32SN which he has installed on AC units when they are having issues working with solar units.

The generator guy recommended I call a second AC company (who they always use). The Second AC company said that I should install a Rheem hard start (5K-A1) and NOT install the Sure Start because in their experience that has always worked on Rheem units.

The generator guy agreed with the second AC company and said he has never heard of a Sure Start working.

I called Ziller Electric and they thought the industry was moving away from hard starts and moving toward soft starts. And they said that if the sure start was compatible that is what they recommended.

I really need some advise because I have already paid for 3 different certified generator specialists to visit at 50 bucks a pop.
Two gas guy visits and all of the recommended changes that the generator guys recommended and now I have to decide to spend 190 on a rheem hard start to replace the hard start I already had installed OR pay 460 to have the Sure Start installed.

Please HELP.
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Peddler
A hard start kit will make it harder to start rather than easier.  The soft start kit will make it easier to start but you should not need it, I suspect there is something else wrong.  We use 16KW units on 5 ton ACs all the time and there is no reason to need any kit for a 22KW.  You need to see if the magnetic contactor on the outdoor AC unit is pulling in or not if it is try amp probing the unit to see the actual amp draw.  Check for voltage drop at the unit also.  I have seen many of the more complex AC systems that don't like the Sine Wave of a generator and won't even try to start hence make sure the contactor is pulling in and the unit is trying to start.  If the AC is hooked up to the load shed then you have to wait for that circuit to close.  On the gas I hope you have 12" of water column not 12 PSI.  A hard start kit is for an AC unit that is failing and is not designed to lower the current inrush which the soft start unit is.
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Dfvet106
So when the generator guy was here he tested the amperage when the AC unit was starting at the transfer switch and he said that the actual amperage that the AC unit produced when it tried to start up should have been easily accommodated by the generator therefore the issue must be an AC unit issue ...... (Is the probing test that you are talking about needing to be done at the ac unit or would the one that the generator guy did at the transfer switch suffice?)
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grsthegreat
The Sure Start unit has worked on units that dont want to work on a generator in my past experience. I agree the hard start will not work, and make matters worse. The hard start they put on my own AC caused compressor to fail a few months later. I did not know the ac guy installed it till it was too late. The sure start need to run thru a few cycles before it works best.
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78buckshot
Have any of the techs tried to start it by manually pushing the contactor? I tend to agree with Peddler with unsteady frequency output from the generator being the culprit. Also it would be a good idea to check the compressor run capacitor, the compressor is probably a scroll and will typically start on utility power with a bad capacitor but will run hot and noisy, the generator frequency might not start it if the cap is bad. Discontinue the hard start capacitor and go back through all of the wiring.
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Geoff Z
I spoke with the OP. If memory serves he has a 153LRA. Which is substantial even for a 22kW running on propane. It should start by the numbers without issue. Provided there is not a substantial amount of other loads in operation simultaneously. 
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MacL
I'd test the AC amp draw on utility power.  You can use the min/max on amps and not use autorange and capture the LRA.

If your meter can test caps test the caps, and it's possible that your thermostat is malfunctioning and calling for the electric heat at the same time as the condenser.

Make sure your orifice on the generator is set to LP, turned clockwise and sunk down in the bore.

Carefully extract the fuel selector pin and make sure the grommets aren't torn and blocking any holes.
State your problem, not your diagnosis.
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sggoat
Peddler wrote:
A hard start kit will make it harder to start rather than easier.  The soft start kit will make it easier to start but you should not need it, I suspect there is something else wrong.  We use 16KW units on 5 ton ACs all the time and there is no reason to need any kit for a 22KW.  You need to see if the magnetic contactor on the outdoor AC unit is pulling in or not if it is try amp probing the unit to see the actual amp draw.  Check for voltage drop at the unit also.  I have seen many of the more complex AC systems that don't like the Sine Wave of a generator and won't even try to start hence make sure the contactor is pulling in and the unit is trying to start.  If the AC is hooked up to the load shed then you have to wait for that circuit to close.  On the gas I hope you have 12" of water column not 12 PSI.  A hard start kit is for an AC unit that is failing and is not designed to lower the current inrush which the soft start unit is.

Believe peddler is correct in the assessment-may be assoc with the mfg(rheem) I have one of those(2nd one--my mistake in replacing in kind) , and they have a prob with the air handler startup too soon and the lousy overloads in the compressor--My 20KW is now set to start two minutes after power loss--gives the A/C comp a little time to cool before restart. Before this adj. the unit would dump the O/L and sit there until the thing cooled down enough to let the comp restart(if I was home when the interruption happened, a good hosing down of the compressor with water would allow restart right away). Since the time delay extension, (the A/C compressor o/ls were replaced--once they operate, they are more subject to operating prematurely)--have had no issues since. --hope info helps---
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MacL
You did not say whether you had any load shedding modules connected or not.  

If that is what is happening; that your load module is responding too quickly to the drop in frequency caused by the LRAs, you may be able to increase the permitted overload time.  Or,  if you have very little electric load in the house (gas furnace, gas hot water) to bypass the load module and not use it, and then you'd have to mindful of not overloading the generator a little more.

If there are no thermostat wires connected to the module inside the switch, it is not being used and I would shut it down further by removing the 0 ground wire off its terminal.  However the newest models with the SACM modules even if you don't connect an ac to it, it cannot be shut down.

I shut them down if unused because they can still malfunction and cause a no transfer problem, and they unnecessarily consume voltage on the 12 volt transfer circuit.  If it's not an asset, it's a liability.  Shutting them down also should protect them from damage from age (internal heating) and perhaps it will still be working in 5 years when you decide to load shed an ac because now you've added a pool.

If a load module trips due to frequency drop, it should come back on in 5 minutes.  So if you're load module clicks right after your ac tries to start and the green lights go out, that is what is keeping your ac from starting.  After the 5 minutes pass the #1 light comes on and then each of the others at 30 second intervals after that.

The module that comes inside the switch, you can put your thermostat wires on AC2 and leave AC1 unused and allow a couple more seconds before it opens the circuit.  And the modules that mount on the bricks behind the ac, they have a knob inside you could try setting to 2 instead of 1 (if more than one module adjust them all up 1.  You wouldn't want two modules on the same number. Those types of modules could be bypassed and shut down as well if you feel that you don't need load shedding.
State your problem, not your diagnosis.
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Dfvet106
MACL - This is what the inside of the transfer switch looks like if that answers any of your questions MacL. I do not believe I have any load shed modules attached. Also I am sure that the generator is set to LP because that was one of the things that was wrong in the beginning.

SSGoat - My AC automatically does not start until 6 minutes until after the generator has started and then tries to start every 6 minutes after that.
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Geoff Z
The terminals with the orange legend is your load shed module. It is currently not being used.
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RJRENTON
sggoat wrote:

Believe peddler is correct in the assessment-may be assoc with the mfg(rheem) I have one of those(2nd one--my mistake in replacing in kind) , and they have a prob with the air handler startup too soon and the lousy overloads in the compressor--My 20KW is now set to start two minutes after power loss--gives the A/C comp a little time to cool before restart. Before this adj. the unit would dump the O/L and sit there until the thing cooled down enough to let the comp restart(if I was home when the interruption happened, a good hosing down of the compressor with water would allow restart right away). Since the time delay extension, (the A/C compressor o/ls were replaced--once they operate, they are more subject to operating prematurely)--have had no issues since. --hope info helps---


Regarding the hard start kit being installed,  what TYPE is is?  There were two types available...one used a PTC (positive temperature coefficient) thermistor whose resistance rapidly increased taking the start capacitor out of the circuit.  The second type is using a pontential relay whose normally closed contact combined in series with a relatively high value start capacitor (say 108 mfd @ 370 VAC) in parallel with the motor run capacitor will give the compressor an extra kick (higher starting torque with out increasing the LRA draw).   Also consider the  motor run capacitor may is a little weak.    I'm not sure about the Rheem condenser but something that has a high SEER rating MAY ALREADY have a an ECM or Electronically Communicated Motor driving a scroll compressor,  which has no valves unlike a piston compressor.   An ECM motor is a special device that uses a derived pulse width generated sine  wave to allow for variable compressor speed resulting in variable cooling capacity.   Often used in conjunction with an ECM motor is a similar control for the air handler/furnace blower.   The ECM motor also referred to as a brushless DC motor...which usually has a permanent magnet rotor assembly.   Putting a hard start kit on an ECM motor Will possibly damage it, the control components or both.   Usually a scroll compressor, because it has no valves, will not hold pressure on shut down unless there is a liquid line lock off valve controlled by the thermostat or condenser's contactor.     Just my opinion of course. 
Bob Renton

 
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BillM

My Lennox 5 Ton M/N 13ACXN060-230-21 was installed in late June.  The HVAC contractor installs hard starts on all of them, by practice.  My 22kW generator took the load of the 5 ton with the house using power normally without issue.  In my particular case, the hard start module failed the same day so I ran without anything, again, testing the generator taking the load, even testing it while the electric car was taking 32amps as well.  No issues.  The manufacturer of the Hard Start wrote me a check for $500 for the inconvenience of the hard start failing, so I bought a Soft Start from Ziller and installed it.  The generator still takes the load of the AC without issue.  I've tested for 10 hours with the A/C on a near 90 degree day running for half the time with many starts due to 3 zones in the house on the 1 unit.  My Lennox has an RLA of 26.4 and an LRA of 125.

In my opinion, your generator should run that AC unit fine.  If that AC is drawing the correct current, your 22kW should be fine.  It's easy enough with the right meter to see what your AC unit is drawing on start.

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Geoff Z
BillM you should be somewhere around 50LRA with the Soft Start installed. Your 22kW won't even notice that. OP is at 153LRA however the 22kW should start that no problem. I was told years back by tech that air cooled units should have their full rated LRA motor start capability loaded up to 40% of other loads simultaneously. Beyond 40% other load in use the LRA capability begins to diminish. However I have never done testing myself to confirm that. I believe your scenario is a good example if you started the 5 ton without Soft Start with 32 amps running simultaneously.  
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BillM
Geoff Z wrote:
BillM you should be somewhere around 50LRA with the Soft Start installed. Your 22kW won't even notice that. OP is at 153LRA however the 22kW should start that no problem. I was told years back by tech that air cooled units should have their full rated LRA motor start capability loaded up to 40% of other loads simultaneously. Beyond 40% other load in use the LRA capability begins to diminish. However I have never done testing myself to confirm that. I believe your scenario is a good example if you started the 5 ton without Soft Start with 32 amps running simultaneously.  


Yes, I did.  I ran for almost a month naked, no hard or soft start installed.  At the time, I was working through a problem in a different thread here.  It was trying to figure out why the lockout mode of an SMM basically does absolutely nothing.  It was later determined via a tech bulletin that I was not aware of that the 'lockout' switch on the SMM has no real effect and that the SMM is basically only going to shed the load, my Level 2 EVSE/car charger, if the generator is overloaded.  It was exactly that scenario I was trying to test.  I had the car taking a confirmed 32 amps, ran my double ovens in broil mode, turned on a lot of lights and was figuring the AC Compressor would put me over.  It did not.  I tested it many times over a course of a week.  
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Peddler
I have seen a 22 KW hold a 104 amp load (10 amp over the rated output) for a prolonged period of time.  That is why we don't use load shedding devices except to get around code authorities.  You have to overload the generator excessively in order for the shedding devices to work.  There is absolutely no reason for this unit can't run a 5 ton AC without any starting devices.
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Cobranut
Peddler wrote:
I have seen a 22 KW hold a 104 amp load (10 amp over the rated output) for a prolonged period of time.  That is why we don't use load shedding devices except to get around code authorities.  You have to overload the generator excessively in order for the shedding devices to work.  There is absolutely no reason for this unit can't run a 5 ton AC without any starting devices.


Doesn't the evolution controller on those shut down the genset if it is overloaded for more than a few seconds? 
The one time my 30kw shutdown on overload I was working in my shop, right beside the unit, and could clearly hear the turbo pitch rise and fall in response to changing loads, but the rpm never changed audibly at all until the controller shut it off.
I'm guessing that a load shed module would do nothing at all in my case. 
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RJRENTON
Geoff Z wrote:
BillM you should be somewhere around 50LRA with the Soft Start installed. Your 22kW won't even notice that. OP is at 153LRA however the 22kW should start that no problem. I was told years back by tech that air cooled units should have their full rated LRA motor start capability loaded up to 40% of other loads simultaneously. Beyond 40% other load in use the LRA capability begins to diminish. However I have never done testing myself to confirm that. I believe your scenario is a good example if you started the 5 ton without Soft Start with 32 amps running simultaneously.  


Perhaps you can define what you mean by "soft start".  Most people's interpretation is either an inductive reactance device that limits inrush current (starting torque) or LRA OR something similar.  The current generation controller use a AC to DC power converter and a DC to AC pulse width modulated inverter using Insulated Gate Bipolar Transistors to recreate a variable amplititude/frequency to control the motor's inrush current and speed.   One must realize what is the connected load and how its being controlled....old methods (hard start kits) may or may not be applicable.  In addition, perhaps the motor's LR's KVA code should taken into account.   Inrush current is difficult to determine, unless you are using one of the new FLUKE's devices capable of measuring and recording the event.    Just my opinion of course. 
BOB RENTON 
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Peddler
I have to assume that the EVO controller watches Hz just like the other load sed devices.  It ran for a long while at over 100 amps but it held 60 Hz.  If there is a current measuring device built in it must be set pretty high.
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Cobranut
Peddler wrote:
I have to assume that the EVO controller watches Hz just like the other load sed devices.  It ran for a long while at over 100 amps but it held 60 Hz.  If there is a current measuring device built in it must be set pretty high.


Mine can display output current on the controller, and it has CT's on each leg near the MCB.  When it shut down, there was no audible drop in rpm at all.  Perhaps this is different on the air cooled units.
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Peddler
In looking at the schematic I guess at least some of these have CTs so maybe they can monitor load but if so it must have a set point above the rated output.
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restosud
i raised this current transformer on some aircooled units but never got a reply from anyone in the know.
2013 20kw evolution aircooled has the ct's
2016 22kw evolution aircooled doesn't have them.
how can it possibly know what the output is?
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Cobranut
restosud wrote:
i raised this current transformer on some aircooled units but never got a reply from anyone in the know.
2013 20kw evolution aircooled has the ct's
2016 22kw evolution aircooled doesn't have them.
how can it possibly know what the output is?


Without a way to measure the current, it can't know the output. It can only monitor rpm, and if rpm drops, it assumes the unit is overloaded. 
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Geoff Z
RJRENTON wrote:


Perhaps you can define what you mean by "soft start".  Most people's interpretation is either an inductive reactance device that limits inrush current (starting torque) or LRA OR something similar.  The current generation controller use a AC to DC power converter and a DC to AC pulse width modulated inverter using Insulated Gate Bipolar Transistors to recreate a variable amplititude/frequency to control the motor's inrush current and speed.   One must realize what is the connected load and how its being controlled....old methods (hard start kits) may or may not be applicable.  In addition, perhaps the motor's LR's KVA code should taken into account.   Inrush current is difficult to determine, unless you are using one of the new FLUKE's devices capable of measuring and recording the event.    Just my opinion of course. 
BOB RENTON 


I should say Sure Start sorry for confusion. We call it Sure Start Soft Start. 

This is the unit we carry:
https://www.zillerelectric.com/products/sure-start-soft-start-single-phase-unit-handles-16-32-fla-230vac?_pos=4083&_sid=cad29f488&_ss=r
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BillM
I installed the Sure Start Soft Start thingy and the startup sound of my 5 ton was less pronounced.  I did not test amp load before or after, but did notice it started softer.  
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