Lra is NOT startup amps.

 

Well, according to this website: hvacrinfo.com/definitions.htm#lra

LRA= LRA - Locked Rotor Amps: It's the current you can expect under starting conditions when you apply full voltage. It occurs instantly during start up.

Can you please elaborate on your statement!?

 

Well, according to this web site hvacrinfo.com/definitions.htm#lra

LRA= LRA - Locked Rotor Amps: It's the current you can expect under starting conditions when you apply full voltage. It occurs instantly during start up.

Can you please elaborate on your statement!?

 

Lra is locked rotor amps. Max amp draw with rotor locked or held in place. You
May or may not reach lra for a millisecond(s) during start up.
Fla is full load amps that the motor is able to run at with out overloading or overheating
Rla is rated load amps as applied in a specific application per design. Typically lower than fla, but could be the same

Copeland has sb’s specifying contactor rating requirements and approved vendors

 

Rla is rated load amps as applied in a specific application per design. Typically lower than fla, but could be the same

Understood,
So FLA == RLA (Rated Load Amps)
RLA=<FLA!! I think you mean Running Load Amperes, Here?!! Rated Load Amps is higher than Running Load Amps, am I right!?

Thanks,

 

Equipment mfgs im’s and nameplates list the needed information

 

Good Lord! That's the longest way around sizing a relay I've ever seen! Like ehsx said, the data should be on the compressor tag, they always list LRA and sometimes FLA. Match this data up with the relay on the board you've got. They sometimes list max FLA and LRA ratings too. If your not sure then wire the relay to control a 20amp contactor coil then you know it will handle the current.

 

the data should be on the compressor tag, they always list LRA and sometimes FLA. Match this data up with the relay on the board you've got. They sometimes list max FLA and LRA ratings too. If your not sure then wire the relay to control a 20amp contactor coil then you know it will handle the current.

This compressor is from a Chinese manufacturer 'DONPER' and they provide nothing in their compressor's tag !! TBH, even their datasheets aren't very "descriptive".

 

this is how you size your relay/contactor/motor starter or even VFD


there is NO OTHER WAY, this is the industry standard by the compressor manuf to meet UL requirements


you go to the manuf of compressor and find the motor in the compressor MAXIMUM OPERATING CURRENT (MOC)

compressor no longer have rla or fla on the


MOC/1.56

that is it

copeland, bitzer all publish there MOC data

 

this is how you size your relay/contactor/motor starter or even VFD


there is NO OTHER WAY, this is the industry standard by the compressor manuf to meet UL requirements


you go to the manuf of compressor and find the motor in the compressor MAXIMUM OPERATING CURRENT (MOC)

compressor no longer have rla or fla on the


MOC/1.56

that is it

copeland, bitzer all publish there MOC data

Shouldn't it be MCC/1.56 wor wire and breaker selection and MCC/1.4 for contactor selection?
MCC, not MOC.

Difference between RLA, MOC, LRA and MCC.:
https://emersonclimate.custhelp.com/app/answers/detail/a_id/5342

 

I talked with both engineers at emerson and bitzer on this

they both mean the same thing, they told me, just different convention for authorities they serve, europe or North america

as long as you can find the value of MAX amp draw, you can use it for part selection

IE, I use bitzer MOC, and copeland MCC for VFD selection

 

IE, I use bitzer MOC, and copeland MCC for VFD selection

MCC >> MOC.
Does this mean that VFD's sized based on MCC are sized better (safer)?

 

Also if i remember

contactor is 1.56

conductor is 1.4

 

Opposite. Contactor = MCC/1.4

 

copy and paste from bitzer

"Technical Data

(6G-30.2Y)
Technical Data
Displacement (1450 RPM 50Hz) 126,8 m³/h
Displacement (1750 RPM 60Hz) 153,0 m³/h
No. of cylinder x bore x stroke 6 x 75 mm x 55 mm
Weight 228 kg
Max. pressure (LP/HP) 19 / 28 bar
Connection suction line 54 mm - 2 1/8''
Connection discharge line 35 mm - 1 3/8''
Connection cooling water R 3/4''
Oil type R134a/R407C/R404A/R507A/R407A/R407F tc<55°C: BSE32 | tc>55°C: BSE55 (Option)
Oil type R22 (R12/R502) B5.2 (Standard)
Oil type R290/R1270 SHC226E (Standard)
Motor data
Motor voltage (more on request) 575V PW-3-60Hz
Max operating current 40.0 A
Starting current (Rotor locked) 103.0 A Y / 167.0 A YY
Max. Power input 39,5 kW
Extent of delivery (Standard)"

 

sized bigger.

 

Wow, a lot of stuff going on in this thread, and a bunch of mis-information.

I'll give you one simple answer to one of your questions. On average, LRA will be 5-7 times greater than FLA, so I just use 6 times greater and it worked out well for a long time. But I live in a 60 Hz world, I would imagine it would take more amps to start in a 50 Hz world, just a guess.

 

Wow, a lot of stuff going on in this thread, and a bunch of mis-information.

What misinformation are you referring to?

 

UL gets the 1.56 from the NEC i believe,

Manufactures use the 1.4 as a Safety Factor!

Mike

 

TBH guys I just got even more confused, this is what I got from your replies:

• LRA is locked rotor amps is Max amp draw with rotor locked or held in place and it may or may not reach LRA for a millisecond(s) during start up.

• FLA is full load amps that the motor is able to run at without overloading or overheating while RLA is rated load amps as applied in a specific application per design. Typically, lower than FLA, but could be the same !!!!!
I thought that Rated Load Amps is a red-point not a target, the overload protection will open if compressor is pulling RLA or over while Running Load Amps is current drawn during normal operation of compressor !!?

• So now i need to go to the manuf of compressor and find the motor in the compressor MAXIMUM OPERATING CURRENT (MOC) and /or MCC and then use below ration to get current drawn by compressor in all sort of applications!!!
MOC/1.56 or MCC/1.4 (contactor is 1.56, conductor is 1.4)

• see attached overload protector characteristics; it says "Max.T.C Amp.(25℃ )= 6.0 A" maybe i can use this to choose my relay since this is the max current that the overload protector will allow to be drawn by compressor before opening !!? am i right!?

 

I consider rla to be a maximum load. Therefore I always make sure the compressor is drawing less than rla when operating under NORMAL conditions.
That way there is a little leeway for things like dirty condenser coils or high ambient conditions.
And a quick rule of thumb is lra ÷6 = rla. That formula isn't exact but it gets you really close.

 

is there a UL marking on the data plate?

 

No, it doesn't.
but it has RoHS, VDE, CCC tho.

 

then you have to use your own judgment

if it has no UL markings, who knows

its an appliance