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Discussion Starter · #1 · (Edited)
I have a new Carrier 5 ton A/C unit that was installed in Oct 2021. The unit was manufactured in Jul 2021. My old 17 year old Ruud unit had a hard start kit because we have a 24kw whole house backup generator. I mentioned this to the installer and he replied the new Carrier has a hard start kit built in so I said ok. I noticed recently when the generator was running and each time the A/C unit started up ... the surge on the generator seem to be unusually strong or intense.

Can someone confirm if the newer Carrier 5 ton units do come with a built in hard start kit or was the installer incorrect??? Thanks

I should mention that I am waiting on a response from the Customer Service Dept. of the HVAC Contractor that installed the unit to answer this question ... long lines though!!!

Building Architecture Grass Wall Gas
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Most new units do not come with hard-starts built in.
Hard start is normally not needed with a scroll compressor (most new ones are scrolls) except for if directed by the manufacturer in certain applications (long line length, for example)

For a generator application, would be wise to add one though, especially with the unit being 5 ton.

It's easy to check - open electrical compartment with power off ( don't touch anything) and look for an extra capacitor and relay.
 

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Discussion Starter · #3 ·
Most new units do not come with hard-starts built in.
Hard start is normally not needed with a scroll compressor (most new ones are scrolls) except for if directed by the manufacturer in certain applications (long line length, for example)

For a generator application, would be wise to add one though, especially with the unit being 5 ton.

It's easy to check - open electrical compartment with power off ( don't touch anything) and look for an extra capacitor and relay.
Thanks for the reply ... For what they charged me I will have them come back out and put one on. Just didn't sound like something the manufacturer would build in without advertising it!!
 

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Thanks for the reply ... For what they charged me I will have them come back out and put one on. Just didn't sound like something the manufacturer would build in without advertising it!!
It's not something I would like to see on the regular, that is for sure! OEM might have a similar stance that they bring in bigger current to the start winding, and if something hangs up, can take out a compressor. Personally never seen it on HVAC, but most certainly in other applications.
 

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I notice that our new Carrier unit is very loud when starting compared to our previous 40 year old unit. Is that normal? Fairly loud "bowww!" sound.
 

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Discussion Starter · #6 ·
It's not something I would like to see on the regular, that is for sure! OEM might have a similar stance that they bring in bigger current to the start winding, and if something hangs up, can take out a compressor. Personally never seen it on HVAC, but most certainly in other applications.
Thanks for the reply.
 

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I would say that the problem is with the generator not the AC. Most generators do not produce all the electricity and amp at an idle. So your gen needs to pick the load while ramping up and getting into the rpm range where it is producing voltage and current for this motor load.
Your ac will draw approximately 150 amps for a few cycles, (6 times running current) while the generator tops out at 100 amps. You bet the compressor is going to scream.
Sorry a hard start kit will only prolong the agony of the compressor until it fails. Hard start kits are the cheap way to raise the voltage so a compressor will turn faster and get out of the start cycle into run.
You need to configure the gen to idle much higher so it is closer to where it produces power.
The generator is finite power, limited, where the POCO is infinite, unlimited.

Does your generator have voltage and HZ controls? or are they rpm driven? Have they been checked recently?
Have you checked the output of the generator with a load bank?
Are you using natural gas for a fuel? NG has less Btu's than diesel or gas so that means you generator produces less kw. Unless of course it was rated for NG.
 

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Njuneer
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I would say that the problem is with the generator not the AC. Most generators do not produce all the electricity and amp at an idle. So your gen needs to pick the load while ramping up and getting into the rpm range where it is producing voltage and current for this motor load.
Your ac will draw approximately 150 amps for a few cycles, (6 times running current) while the generator tops out at 100 amps. You bet the compressor is going to scream.
Sorry a hard start kit will only prolong the agony of the compressor until it fails. Hard start kits are the cheap way to raise the voltage so a compressor will turn faster and get out of the start cycle into run.
You need to configure the gen to idle much higher so it is closer to where it produces power.
The generator is finite power, limited, where the POCO is infinite, unlimited.

Does your generator have voltage and HZ controls? or are they rpm driven? Have they been checked recently?
Have you checked the output of the generator with a load bank?
Are you using natural gas for a fuel? NG has less Btu's than diesel or gas so that means you generator produces less kw. Unless of course it was rated for NG.
Not here to argue and make points but I guess that is what I might do here. A 24kw generator is far from a throw away screamer genny. Likely a qualified rig that runs at 1800rpm, in the sweet spot of torque. As well, amps x volts don't equal watts! That is when you factor PF. But a good generator is certainly built to handle heavy inrush and likely has a rating for it, which is much higher than the rated KW rating.

OP, what this inrush ability is more than anything, is angular momentum or the inertia of the rotating mass of the generator head and engine. One if the simplest ways to stabilize loads is either run an idler motor on the line, or add flywheel weight. I won't go into this much because it dives off topic to places no one cares about, but it does work. This is not guess work, it is well proved out in EE text books.

But I do agree with SW that when a generator is smacked with a load, it simple cannot respond instantly! For this reason mass helps! It cannot mask all the BS with fakely rated gennies, but when looking at real ones, we can find ways to solve the problem.
 

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I don't know, but that air conditioner is TOO CLOSE to the gas meter (and also the refrigerant piping is ugly). Code says that condensing unit is supposed to be 3 feet away from any gas regulator vents. A work-a-round could be to install piping into those gas regulator vent holes and pipe them so that they're 3 feet away. Or move the condensing unit over another 3 feet. Or leave it how it is with the understanding that if your house explodes some day, your insurance claim will likely be denied.

Has this install been inspected by the city?
 

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I don't know, but that air conditioner is TOO CLOSE to the gas meter (and also the refrigerant piping is ugly). Code says that condensing unit is supposed to be 3 feet away from any gas regulator vents. A work-a-round could be to install piping into those gas regulator vent holes and pipe them so that they're 3 feet away. Or move the condensing unit over another 3 feet. Or leave it how it is with the understanding that if your house explodes some day, your insurance claim will likely be denied.

Has this install been inspected by the city?
Just needs an extension on the regulator vent. Was certainly in the manual if the AC so they have no excuse on why it's so close.
 

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Discussion Starter · #11 ·
I would say that the problem is with the generator not the AC. Most generators do not produce all the electricity and amp at an idle. So your gen needs to pick the load while ramping up and getting into the rpm range where it is producing voltage and current for this motor load.
Your ac will draw approximately 150 amps for a few cycles, (6 times running current) while the generator tops out at 100 amps. You bet the compressor is going to scream.
Sorry a hard start kit will only prolong the agony of the compressor until it fails. Hard start kits are the cheap way to raise the voltage so a compressor will turn faster and get out of the start cycle into run.
You need to configure the gen to idle much higher so it is closer to where it produces power.
The generator is finite power, limited, where the POCO is infinite, unlimited.

Does your generator have voltage and HZ controls? or are they rpm driven? Have they been checked recently?
Have you checked the output of the generator with a load bank?
Are you using natural gas for a fuel? NG has less Btu's than diesel or gas so that means you generator produces less kw. Unless of course it was rated for NG.
I understand your comments but the 24kw generator as configured is enough power for the sized of the house and HVAC system. The older RUUD unit had a hard start kit on it and created an acceptable amount of "scream" from generator on startup. I just noticed that the "scream" from the generator with the new Carrier on startup appears to be more intense. This is what led to the original question which was are manufacturers including the hard start kits on the newer a/c units. Apparently the installer misunderstood my question due to a language barrier because Customer Support for the HVAC company that did the installed just confirmed he should have installed the hard start kit and will get someone out to correct it. Thanks.
 

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Discussion Starter · #12 ·
I don't know, but that air conditioner is TOO CLOSE to the gas meter (and also the refrigerant piping is ugly). Code says that condensing unit is supposed to be 3 feet away from any gas regulator vents. A work-a-round could be to install piping into those gas regulator vent holes and pipe them so that they're 3 feet away. Or move the condensing unit over another 3 feet. Or leave it how it is with the understanding that if your house explodes some day, your insurance claim will likely be denied.

Has this install been inspected by the city?
House was built in 1985 and that's where everything was originally installed. The new unit was installed in the same location. The gas company had to install an larger meter and additional regulators, etc. I will get them to add the extension. Thanks
 

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...
Your ac will draw approximately 150 amps for a few cycles, (6 times running current) while the generator tops out at 100 amps. You bet the compressor is going to scream.
Sorry a hard start kit will only prolong the agony of the compressor until it fails. Hard start kits are the cheap way to raise the voltage so a compressor will turn faster and get out of the start cycle into run.

...
Are you using natural gas for a fuel? NG has less Btu's than diesel or gas so that means you generator produces less kw. Unless of course it was rated for NG.
No, that isn't how hard starts work. They offset the phase angle more for much more torque, at the cost of power factor. You drop the start capacitor back out so that your start windings aren't drawing too much current, the PF is within spec, and because the hard start capacitor can't handle prolonged use. The additional torque allows it to get up to speed much quicker, reducing the inrush substantially. It doesn't increase the voltage.

6× is a rule of thumb, not actual inrush current. The actual inrush is just a bit below the LRA rating of the compressor. (current is only limited by the winding and supply wire resistance.)

The lower energy density of natural gas isn't really why an engine of the same size pushes less power on NG compared to gasoline. It's because it wasn't engineered for the lower density, so it's stoichiometric ratio is way off and isn't burning very efficiently. Carburetor aren't needed with gaseous fuels, so those 3 in one converter kits are rather inefficient. At 24kw, I'm going to assume that they have a dedicated stand by generator, designed for natural gas, or whatever fuel they are using, and not a conversion.
PS. Dedicated NG generators are generally all highly turbocharged to get around the lower density and achieve the same amount of power in the given displacement.

OP: as user said, turn off the power, and open the electrical cover on the ac. It's only 3 screws, don't take it any more. Take a picture and post it. Replace the cover and turn the power back on. By convention it won't have a hard start kit, and they will need the exact one carrier wants as scroll compressors are more difficult to size for. What's the model number?
 

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Which regulator vent needs the extension and how long should it be??? Thanks
Both of them. 3ft away from the electrical parts of the ac, not just the metal parts. I modified your picture, assuming no windows in the area. Gas company should have done it on the meter upgrade but those companies are getting more strict about this stuff so it's not likely they will do something these days. You can get all the parts from any local big box home improvement store, it'll be standard pipe threads.

Looks like the gas company upgraded your service to a higher pressure service. I assume for the generator.

 

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Discussion Starter · #16 ·
Both of them. 3ft away from the electrical parts of the ac, not just the metal parts. I modified your picture, assuming no windows in the area. Gas company should have done it on the meter upgrade but those companies are getting more strict about this stuff so it's not likely they will do something these days. You can get all the parts from any local big box home improvement store, it'll be standard pipe threads.

Looks like the gas company upgraded your service to a higher pressure service. I assume for the generator.

Ok, thanks for the reply and that's what I assumed you were referring to but wanted to make sure on both regulators. Yes, they upgraded the gas meter to a larger one for the generator. No windows on that side of the house The generator is actually on the complete opposite side of the house to the right of our detached garage. Electric meter service is on the back of the garage. Had to run that gas line under soffit all the way over there around the back of the house and garage.
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