HVAC compressor circuit breaker trips. Change breaker from 30 to 35 amps safe?

[TSPORT]

Hi all. This is an HVAC electrical question. I'm dual-posting in the Electrical section to solicit input from the electrician pros as well.
We had our complete HVAC system replaced last year. Twice in the past month the 30 amp breaker for the A/C compressor has tripped.
Never happened before with current system or prior system. The house was built in 1997 and the breakers are original. The breaker is on a dedicated circuit for the outside compressor unit. I called the HVAC company. They came out and checked things over. The tech seemed knowledgeable. He said everything looks OK with the HVAC system but that the compressor is rated for a 35 amps. He said the 30 amp breaker is old and recommended I replace the breaker with a 35 amp breaker and said the wiring is 10 awg and it's fine.
Is it safe to replace the 30 amp breaker w/ a 35 amp breaker in this situation?
If not, is it possible the 30 amp breaker is "wearing out" causing it to trip prematurely and should be replaced?

Thanks!

 

[Fitter30]

Change the breaker. Minimum circuit amps is 19.6. Your wire size is 10 gauge is rated at 30 amp. To use a 35 amp breaker would need 8 gauge. Electronic thermostat? In set up there will a compressor timer delay for 5 minutes that might toggled on.

 

[Sponsor]

 

[bigb56]

Per NEC 440 for motors and hermetic compressors the branch circuit OCPD can be sized larger than the ampacity of the conductor to allow for startup current (inrush). In the absence of nameplate info there is a chart in the NEC, but in this case we have the nameplate info which allows a maximum breaker size of 35 amps and a minimum circuit ampacity of 19.8 amps which allows a minimum of #12 AWG (copper). IOW the manufacturer intends for you to use a 35 amp breaker and it meets code. Wire size would be determined by installer by circuit length to minimize voltage drop with #12 being the minimum allowable.

 

[TSPORT]

Change the breaker. Minimum circuit amps is 19.6. Your wire size is 10 gauge is rated at 30 amp. To use a 35 amp breaker would need 8 gauge. Electronic thermostat? In set up there will a compressor timer delay for 5 minutes that might toggled on.

Thank you. It does have an electronic thermostat (Ecobee). I'll check the settings to see it has a timer delay feature.

 

[wwhitney]

Change the breaker. Minimum circuit amps is 19.6. Your wire size is 10 gauge is rated at 30 amp. To use a 35 amp breaker would need 8 gauge.

Not correct. This application allows a 20A ampacity wire to be protected at 35A. No need for #8, in fact #12 would be OK.

Cheers, Wayne

 

[RetiredInGueydan]

Hi all. This is an HVAC electrical question. I'm dual-posting in the Electrical section to solicit input from the electrician pros as well.
We had our complete HVAC system replaced last year. Twice in the past month the 30 amp breaker for the A/C compressor has tripped.
Never happened before with current system or prior system. The house was built in 1997 and the breakers are original. The breaker is on a dedicated circuit for the outside compressor unit. I called the HVAC company. They came out and checked things over. The tech seemed knowledgeable. He said everything looks OK with the HVAC system but that the compressor is rated for a 35 amps. He said the 30 amp breaker is old and recommended I replace the breaker with a 35 amp breaker and said the wiring is 10 awg and it's fine.
Is it safe to replace the 30 amp breaker w/ a 35 amp breaker in this situation?
If not, is it possible the 30 amp breaker is "wearing out" causing it to trip prematurely and should be replaced?

Thanks!

View attachment 105926
View attachment 105927

View attachment 105928

While a 35A breaker will prevent unnecessary trips, an OEM start kit should be used on every unit in the Carrier family to prevent hard starts.

 

[Fitter30]

Not correct. This application allows a 20A ampacity wire to be protected at 35A. No need for #8, in fact #12 would be OK.

Cheers, Wayne

Per NEC 440 for motors and hermetic compressors the branch circuit OCPD can be sized larger than the ampacity of the conductor to allow for startup current (inrush). In the absence of nameplate info there is a chart in the NEC, but in this case we have the nameplate info which allows a maximum breaker size of 35 amps and a minimum circuit ampacity of 19.8 amps which allows a minimum of #12 AWG (copper). IOW the manufacturer intends for you to use a 35 amp breaker and it meets code. Wire size would be determined by installer by circuit length to minimize voltage drop with #12 being the minimum allowable.

Start a compressor when it's 100° inside and out till house catches the load that 19.6 min amps will be higher.
Scroll compressors start unloaded most like Carries takes three revolution before refrigerant is to full compression.

https://www.google.com/url?q=https://www.shareddocs.com/hvac/docs/1001/Public/0E/04-581089-01.pdf&sa=U&ved=2ahUKEwjHrcDM9aaPAxUcjYkEHeBXEgoQFnoECAEQAw&usg=AOvVaw1JhTuECeGTDyPOcu6aZiU0

 

[RetiredInGueydan]

Start a compressor when it's 100° inside and out till house catches the load that 19.6 min amps will be higher.
Scroll compressors start unloaded most like Carries takes three revolution before refrigerant is to full compression.

https://www.google.com/url?q=https://www.shareddocs.com/hvac/docs/1001/Public/0E/04-581089-01.pdf&sa=U&ved=2ahUKEwjHrcDM9aaPAxUcjYkEHeBXEgoQFnoECAEQAw&usg=AOvVaw1JhTuECeGTDyPOcu6aZiU0

Hence the need for a start kit, among other reasons.

 

[Slomoola]

KILL or OPEN the disconnect or breaker. Measure for AC voltage present. Kill ALL power.

Open up the compressor winding power wires. Look for one of the 3 legs shorting out or low Ohms.

Make sure ALL connections are tight. Use an AC clamp amp meter and test the running draw across the three phases.

Couple be a worn out contactor or loose fill in the blank. Something drawing excessive amps tripping a 30 amp breaker.

 

[Slomoola]

Did this just happen OR was it from day one when the system was new?

 

[Slomoola]

Seeing 15.4 run load amps on compressor tag. Half of a 30 amp breaker. Something is wrong. Putting a 35 amp breaker in should be your last effort. Fix the problem first before throwing parts at it.

Possible leg off the compressor shorting or close to a short.

 

[TSPORT]

Hence the need for a start kit, among other reasons.

I'm thinking about the hard start kit. The compressor is loud when first starting. Thanks for the input.

 

[TSPORT]

Did this just happen OR was it from day one when the system was new?

It only happened twice last summer and it was very hot out when it did occur. The entire system is just over a year old. I replaced the breaker about a month ago w/ the 35amp one. I'll see how it goes next summer. AC probably won't be needed until next June.

 

[Slomoola]

That compressor has a 92 amp locked rotor rating. Meaning she pulls 92 amps of in-rush current trying to turn the compressor over from a dead stop. The guy saying go down to 12ga wire should be ignored.

 

[wwhitney]

The guy saying go down to 12ga wire should be ignored.

The same label from which you got the 92A LRA also says "minimum circuit amps 19.8A". That is the ampacity required for the wiring. #12 Cu has a 60C ampacity of 20A, so #12 Cu in any wiring method would be sufficient.

In fact, the 75C ampacity of #14 Cu is 20A, so if you using a 75C wiring method, #14 Cu would suffice. Although depending on your interpretation of NEC 350.10(4) and 356.10(9), that would usually preclude the use of LFNC and LFMC, as those wiring methods are only rated for 60C in a wet location.

Cheers, Wayne

 

[bigb56]

That compressor has a 92 amp locked rotor rating. Meaning she pulls 92 amps of in-rush current trying to turn the compressor over from a dead stop. The guy saying go down to 12ga wire should be ignored.

Really? What size should be used, #3 copper? #2? Please link the reference/ chart that shows how to size conductors for inrush currents.

 

[Slomoola]

I do not size the wire for the running ampacity only. Usually double or triple that figure depending on tonnage. Why? Compressor is the largest amp draw in the outdoor unit. She will turn over easier and quieter with a larger ga copper whip. Makes the compressor last longer. Use lamp cord if you like. Not at my house.

 

[bigb56]

I do not size the wire for the running ampacity only. Usually double or triple that figure depending on tonnage. Why? Compressor is the largest amp draw in the outdoor unit. She will turn over easier and quieter with a larger ga copper whip. Makes the compressor last longer. Use lamp cord if you like. Not at my house.

Well I guess there's no harm in that besides putting you at a bidding disadvantage but I pretty much exhausted the web trying to find any evidence that oversized conductors will extend motor life and came up empty handed. All the experts, including Mike Holt, seem to agree that it is not necessary. On the other hand, everyone agrees that a hard start/soft start kit increases longevity.

 

[Slomoola]

What I've read about hard starts is you have more available current to turn the compressor over from a dead stop, allegedly, over time, will burn the compressor windings out. Mine with the 5-2-1 hard start sure fires faster and easier "audibly", at my house.

Again for the above reason, you are not to install a hard start until your compressor gets lazy starting up or not at all.

Knowing that, I've had my 5-2-1 on for say 5+ years now. Compressor is the last of the then new R-22 systems in time. Still cools like a champ.

 

[Slomoola]

Well I guess there's no harm in that besides putting you at a bidding disadvantage but I pretty much exhausted the web trying to find any evidence that oversized conductors will extend motor life and came up empty handed. All the experts, including Mike Holt, seem to agree that it is not necessary. On the other hand, everyone agrees that a hard start/soft start kit increases longevity.

Adding in 100 degree temps, need larger gauge copper to lessen the voltage drop on the in-rush current. Solar energy the same deal. Several factors need visited to upsize the wire. Cheap insurance over time.