bikerboy108
Hi everyone installed a 16 kw generator and had it hooked up green lite is on and panel says ready to go.. Electrician went thru all the tests everything worked 2 questions
   1. have it set to exercise once every two weeks.. I am in NJ good choice or is once a week better?

    2, The start up draw on the one AC unit was determined too much for the 16kw I installed and rather than install a smart start on the compressor decided since power loss in summer is almost non existent I decided it was easirer for now to lock out AC unit If stand by ( generator) power goes on..  reading up on it was easier to not go up in attic to the air handler and just go from Transfer switch to thermostat wire in compressor ... So did I do this correctly?? Ran two wire thermostat wire from AC1 in Transfer Switch and ran it to compressor unit where I wire nutted it to where thermostat wire from house came in ???? See pics
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78buckshot
I can't see the wiring well enough at your ac condenser but it looks like you did not interrupt the thermostat signal. What size is the ac system? Did your electrician wire the transfer switch as a 'whole house' transfer?, if so then you did not lock out the ac, you have it on 'load shed'.
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bikerboy108
What is Load Shed ??   yes transfer switch is a whole house transfer switch ... we ran the "Brown" 2 wire therm wire from the transfer switch over to the compressor and wire nutted it to the "curly white" therm wire that comes from the house thermostat that controls the AC ...  

So is the connection to the transfer switch in the wrong spot?? Below in Italics was what I was trying to do???

If it is easier to run the wire outdoors to the condenser. Pull the disconnect to the unit to kill the 240 power source. Look for the high voltage contactor. It should have low voltage control wires to a 24v coil. Identify which is the 24v hot and disconnect it. Connect this wire to one from the nexus smart switch. Connect the other wire from the smart switch back to the contactor. All you want to do it put the switch of the nexus in series with the control wires.


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78buckshot
Load shed allows the ac to run if the generator can handle the load, so if the rest of the house is not using much energy then the ac can run, if the generator is near capacity and the ac tries to start the controller will sense a drop in engine speed and won't allow the ac to run. If you can separate the yellow control wires a little more and send a new picture I might be able to give more info. Leave the wiring as is in the transfer switch.
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bikerboy108
whole reason was the LRA on AC was 169 and 16kw generac couldn't handle that so easiest way I was told is either smart control.. or just eliminate it.. Hope these pics help    white therm wire from house ..brown from transfer switc
ac6.jpg  AC7.jpg     AC10.jpg 
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bikerboy108
I think the 16kw can only take 130 LRA ??? Not sure

If it is easier to run the wire outdoors to the condenser. Pull the disconnect to the unit to kill the 240 power source. Look for the high voltage contactor. It should have low voltage control wires to a 24v coil. Identify which is the 24v hot and disconnect it. Connect this wire to one from the nexus smart switch. Connect the other wire from the smart switch back to the contactor. All you want to do it put the switch of the nexus in series with the control wires.
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Birken Vogt
If you absolutely do not want the AC to run you could slave a contact on the side of the transfer switch mechanism instead of the computer controlled load shed you are using.

The 16kw has a bit of an oversized engine though so it might be able to start this large AC anyway.  I would try it out in the summer as-is and see how it does before changing to the slave contact method.
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Geoff Z
I think the load is simply too big. Should consider either a Sure Start on it or take it off the generator. There might even be a chance the generator could start it with no other load connected. However imho setting the system up for nuisance issues. For each time the SACM activates it must see a frequency drop to do so. Keep in mind everything else being simultaneously powered by the generator will be subject to that same frequency drop. Not good. There already is an auxiliary contact on the side of the transfer mechanism. Wire the switch leg to the run relay through that NC contact and done.
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78buckshot
Thanks for the wiring picture, you have it wired correctly for load shed however I would not run the ac on generator due to the tonnage - appears to be a 5 ton system, so either a SMM or do as Birken Vogt says and use a limit switch on the transfer mechanism.
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UPS
bikerboy108 wrote:
whole reason was the LRA on AC was 169 and 16kw generac couldn't handle that so easiest way I was told is either smart control.. or just eliminate it.. Hope these pics help    white therm wire from house ..brown from transfer switch


Are you sure the white wire where you made the new connection is directly from the thermostat?  Generally the thermostat is wired to the air handler with 3 to 5 wire cable so it can control the blower fan and also the heat if a combined system.  A 2 wire cable then runs from the air handler to the compressor contactor.  If what is being locked out here is only the compressor, then if it is warm enough for the thermostat to be calling for cooling, the blower fan will run continuously.
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bikerboy108
UPS wrote:


Are you sure the white wire where you made the new connection is directly from the thermostat?  Generally the thermostat is wired to the air handler with 3 to 5 wire cable so it can control the blower fan and also the heat if a combined system.  A 2 wire cable then runs from the air handler to the compressor contactor.  If what is being locked out here is only the compressor, then if it is warm enough for the thermostat to be calling for cooling, the blower fan will run continuously.


 You are probably right white wire comes from air handler


Geoff Z wrote:
I think the load is simply too big. Should consider either a Sure Start on it or take it off the generator. There might even be a chance the generator could start it with no other load connected. However imho setting the system up for nuisance issues. For each time the SACM activates it must see a frequency drop to do so. Keep in mind everything else being simultaneously powered by the generator will be subject to that same frequency drop. Not good. There already is an auxiliary contact on the side of the transfer mechanism. Wire the switch leg to the run relay through that NC contact and done.
Geoff Z wrote:
I think the load is simply too big. Should consider either a Sure Start on it or take it off the generator. There might even be a chance the generator could start it with no other load connected. However imho setting the system up for nuisance issues. For each time the SACM activates it must see a frequency drop to do so. Keep in mind everything else being simultaneously powered by the generator will be subject to that same frequency drop. Not good. There already is an auxiliary contact on the side of the transfer mechanism. Wire the switch leg to the run relay through that NC contact and done.


There already is an auxiliary contact on the side of the transfer mechanism. Wire the switch leg to the run relay through that NC contact and done

Geoff
#1  I answered UPS Above does that affect you answer?
#2  Your answer is greek to me will my electrician understand that?
     
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Geoff Z
Sorry I should have been more clear. The two wires you have terminated on the SACM will simply be removed from there and terminated on the auxiliary contact. That contact will be normally closed (NC) while on utility power allowing the A/C to run. On generator power that contact will open disabling the A/C.
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Geoff Z
I also meant to confirm that you are correct that the 16kw is rated for 130LRA. Once we begin to introduce other loads on the generator that 130LRA capability begins to diminish. The more other load on the generator the less LRA motor start is available. If you decide to try and start it in the summer revisit this thread and let us know how it goes. I would be really interested to hear the result.
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78buckshot
From the model info on the condenser plate it looks like a 5 ton ac system, the 16kw will struggle to start it if it can do it at all, my 15kw labors to start my 3 ton if I take all of the other loads off - I don't have a soft start.
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murphy
78buckshot wrote:
From the model info on the condenser plate it looks like a 5 ton ac system, the 16kw will struggle to start it if it can do it at all, my 15kw labors to start my 3 ton if I take all of the other loads off - I don't have a soft start.


Have the capacitors in your compressor cabinet been tested recently?  The last one I changed had dropped from 45 mfd to 0.7 mfd.  That greatly increases the starting current.  My old 7 kW generator could easily start my 3 ton compressor after I installed a soft start unit.  It reduced the starting current from 79 amps to 45 amps.
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Geoff Z
With soft start the generator would have no problem at all. It would take the starting current to somewhere between 70-80 amps. We too awhile back got a call from a first time customer. 8kw on nat gas trying to start 83LRA. The compressor would stall the generator. Her installer walked away from it and she called us. Soft start took it down to 38 amps. Generator started it no problem.
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78buckshot
Hi murphy, Yes I have checked the run cap in my condensing unit, it's a simple single stage scroll R-22. I'm not concerned too much as we have only lost power once in 8 years where I had to bypass my zone panel and run the ac. I'm an HVAC tech also( I think you are) and we replace dozens and dozens of run capacitors each summer for our customers due to voltage spikes. I've seen our utility line in as low as 204 and as high as 259 all in the same day in different locations in our county. I probably would not have an automatic generator other than for the fact that my wife's parents lived with us for a couple of years and needed power for medical reasons and of course to run the well.
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ZZZRSC
Sorry for all the revisions.
If there are only 2 low voltage (18-20 ga.) wires running to your condensing unit, then you could not go wrong with a pair of wires from the Xfer switch in series with either yellow, low voltage, wire coming into the unit.  If you had more low voltage wires, such as in a heat pump, then, yes, you could go wrong.  That is one big, old, A/C unit, at least 5 tons, maybe more, shame you didn't get a photo of the whole nameplate.  The other thing is that this will leave the indoor fan unit running during a call for cooling and that will usually be circulating air through the return, or supply, duct in the attic, which can be very hot.  You can either add a 6 inch layer of insulation on the ductwork, or switch the thermostat off manually during a power outage, to kill the fan motor. 
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ZZZRSC
While there is no doubt that voltage spikes, more than four starts per hour, high ambient temperatures, and other reasons can shorten the life of a capacitor, the biggest factor by far, was the abundance of poor quality capacitors that flooded the market from China starting about 16 years ago.  My company keeps detailed records of every job we service and when a capacitor fails more than once in a 5 year period, we investigate the cause.  We found there was none.  We even had the utility company put a $20,000 power quality monitor on a nursing home we were have problems with. In 3 months there was nothing wrong with the power.  We finally concluded the capacitors were at fault.  When we tried to find US made capacitors, we only found one company.  The advertise as such, and charge at least double of the imported ones.  This was not an issue since the imported ones are usually less than $20 each for larger ones, smaller ones were $3. We never saw the problem again, and its been 5 years now.  Search the web and you will see dozens of companies that found the same result.
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bikerboy108

Geoff Z wrote:
Sorry I should have been more clear. The two wires you have terminated on the SACM will simply be removed from there and terminated on the auxiliary contact. That contact will be normally closed (NC) while on utility power allowing the A/C to run. On generator power that contact will open disabling the A/C.


Sorry been away for a while..But Generator installed inspected, exercises once a week, hooked up to wi-fi ALL GOOD thanks for the help.. So for now having other projects lined up I just want to eliminate the AC from going on.. May do the soft start before summer but electric issues usually winter not summer.. Someone said soft start a little complicated to install?? cost ?? Is that the case??

But back to current issue .Geoff Z so take the 2 wires off of AC 1 and connect them to the 2 spade connections on right side as shown Sound right... I should be able to do that on my own
Does it matter which wire to either spade connector..
So AC will work when power is from Utility and will not start if Utility power out and  Generac on...
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Geoff Z
You are correct. It is not polarity conscious so doesn't matter which wire on which spade. Just make sure as it sits in utility position there is continuity between the two spades. I believe that is how it should be set up. When contactor goes to generator position you should loose continuity between the two spades and drop out the a/c compressor. 
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bikerboy108
Geoff Z wrote:
You are correct. It is not polarity conscious so doesn't matter which wire on which spade. Just make sure as it sits in utility position there is continuity between the two spades. I believe that is how it should be set up. When contactor goes to generator position you should loose continuity between the two spades and drop out the a/c compressor. 

Geoff went to remove the wires and connect them to spade contacts the ones I had were Too big... do these run in sizes?? They seem small... Would you have the number or size?? Thanks
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78buckshot
3/16 inch sta-kon
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bikerboy108
78buckshot wrote:
3/16 inch sta-kon


thanks
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DanS26
bikerboy....install the soft start...it is not that difficult.  Your customer will be pleased...especially when the power goes out in 100* weather after a sever thunderstorm this summer.
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