L.R. vs R.L. Amps?

[Allan Yates]

I have a water source heat pump, and I am calculating what size
of generator would be required to run at least part of it. It is
a dual compressor unit, but I don't understand electrical rating
plate. Part of it says:

Compressor R.L. Amps 9.4 + 13.0
Compressor L.R. Amps 64 + 81
Branch Circuit Sel. Current 26.0
Max. Breaker Amps 40

I have a 40 amp breaker installed. I was assuming that one compressor
used 9.4A and the second compressor used 13A. However the third item on
the list appears to indicate that the total current is 26A, which would
infer that the compressors used 13A each.

Thus I have two questions, how should the above information be interpreted
to give the current draw for each compressor? And what does R.L. and L.R.
mean?

Thanks,

Allan.
aya...@nortel.ca

[Neil H.]

Allan,

R.L. stands for Rated Load, this is somewhat equivalent to the Full Load
rating of a motor (FLA). Compressors are given RLA values since they
are often used at less than the full load rating of the compressor
motor.

L.R. stands for Locked Rotor. This is the amount of current that you
can expect the compressor to draw if the drive motor rotor were locked.
This also provides a reference for the current required to start the
motor.

I'm strictly guessing here, but it *appears* that one compressor draws
9.4A (when the compressor is operating at ARI standard conditions) and
64 A at start up, while the second draws 13 A and 81 A. The Branch
Circuit Selection Current was probably determined by multiplying the
largest compressor RLA by 1.25 and adding the RLA of the smaller
compressor. That is 13 * 1.25 + 9.4 which rounds up to 26 A. This is
coincidentally the same as 2 * the 13 A compressor.

Neil

--
My Email address is Spamouflaged.
Please remove "Spamnot." from my Email address when replying.

[rto...@removethis.oanet.com]

On 18 Jan 1998 04:23:29 GMT, aya...@bnr.ca (Allan Yates) wrote:

>
>I have a water source heat pump, and I am calculating what size
>of generator would be required to run at least part of it. It is
>a dual compressor unit, but I don't understand electrical rating
>plate. Part of it says:
>
> Compressor R.L. Amps 9.4 + 13.0
> Compressor L.R. Amps 64 + 81
> Branch Circuit Sel. Current 26.0
> Max. Breaker Amps 40
>
>I have a 40 amp breaker installed. I was assuming that one compressor
>used 9.4A and the second compressor used 13A. However the third item on
>the list appears to indicate that the total current is 26A, which would
>infer that the compressors used 13A each.
>
>Thus I have two questions, how should the above information be interpreted
>to give the current draw for each compressor? And what does R.L. and L.R.
>mean?
>
>Thanks, Allan. aya...@nortel.ca

LR means "locked rotor" which, in turn, means the current that would
flow if the rotor was locked and could not turn. It is an indication
of the momentary starting current that occurs every time the
compressor starts. It is important that the breaker does not trip out
when this current flows momentarily but that it does if it flows for a
second or more.

[Robert Olcott]

On 18 Jan 1998 04:23:29 GMT, aya...@bnr.ca (Allan Yates) wrote:

>
>I have a water source heat pump, and I am calculating what size
>of generator would be required to run at least part of it. It is
>a dual compressor unit, but I don't understand electrical rating
>plate. Part of it says:
>
> Compressor R.L. Amps 9.4 + 13.0
> Compressor L.R. Amps 64 + 81
> Branch Circuit Sel. Current 26.0
> Max. Breaker Amps 40
>
>I have a 40 amp breaker installed. I was assuming that one compressor
>used 9.4A and the second compressor used 13A. However the third item on
>the list appears to indicate that the total current is 26A, which would
>infer that the compressors used 13A each.
>
>Thus I have two questions, how should the above information be interpreted
>to give the current draw for each compressor? And what does R.L. and L.R.
>mean?
>
>
>Thanks,
>
>Allan.
>aya...@nortel.ca

Allen,
According to my 'lil technical pocket handbook the R.L. is
refering to RLA or Running Load Amps which is the same as FLA or
Full Load Amps. LR or more precisely is LRA which is Lock Rotor
Amps. This is approximately 6 X the former. Why I can't say. When
I read a data plate I look for the RLA or FLA and multiply that by
the voltage and power factor of 1.73 (only if it is 3 phase). This
gives an estimate of the wattage used. Other factors are
efficiency and percent load. The best way to determine actual
wattage is to measure the amps and volts with a meter and then
multilply. This, times hours of operation will give you watt hours
which when you devide by 1000 will yield Kwh.
The second part of your question of 26 amps may be 9.4
compressor 1 + 13 for compressor 2 and 3.6 amps for accessories
such as controls, sump heaters, fans or what ever makes up that
portion of the system.
The 40 amp breaker rating is a safety device which needs
to be high enough to prevent unneccessary tripping but not so high
as to allow overheating and combustion of conductors to and within
the units. There are national electrical codes that specify the
proper ratings for cicuit breakers and repsective electric loads.
I am sure that some others can come up with the more
technical reasons for the different ratings and the rational
behind them. I can only hazard a guess that these are different
methods of measuring not unlike measuring combustion engines as
brake horspower vs. say, shaft horsepower. Hope this helps,
Bob Olcott
Olcott Energy Management

[EJS]

rto...@removethis.oanet.com wrote:
>
> On 18 Jan 1998 04:23:29 GMT, aya...@bnr.ca (Allan Yates) wrote:
>
> >
> >I have a water source heat pump, and I am calculating what size
> >of generator would be required to run at least part of it. It is
> >a dual compressor unit, but I don't understand electrical rating
> >plate. Part of it says:
> >
> > Compressor R.L. Amps 9.4 + 13.0
> > Compressor L.R. Amps 64 + 81
> > Branch Circuit Sel. Current 26.0
> > Max. Breaker Amps 40
> >
> >I have a 40 amp breaker installed. I was assuming that one compressor
> >used 9.4A and the second compressor used 13A. However the third item on
> >the list appears to indicate that the total current is 26A, which would
> >infer that the compressors used 13A each.
> >
> >Thus I have two questions, how should the above information be interpreted
> >to give the current draw for each compressor? And what does R.L. and L.R.
> >mean?
> >
> >Thanks, Allan. aya...@nortel.ca
>

> LR means "locked rotor" which, in turn, means the current that would
> flow if the rotor was locked and could not turn. It is an indication
> of the momentary starting current that occurs every time the
> compressor starts. It is important that the breaker does not trip out
> when this current flows momentarily but that it does if it flows for a
> second or more.

Jeez, my feeling is that the R.L. is Run Load amps and the two different
amp ratings are for two applied volage potentials., such as 208 single
phase or 240 single phase and further info is probably found elsewhere
on the unit. Two compressors huh?
Just for info and rule of thumb (dangerous, my thumb has a bandaid on
it) L.R. or locked rotor is generally 5 to 6 times higher than R.L.A.

[Gerry O'Brien]

EJS wrote in message <34C43C...@monad.net>...

>rto...@removethis.oanet.com wrote:
>>
>> On 18 Jan 1998 04:23:29 GMT, aya...@bnr.ca (Allan Yates) wrote:
>>
>> >
>> >I have a water source heat pump, and I am calculating what size
>> >of generator would be required to run at least part of it. It is
>> >a dual compressor unit, but I don't understand electrical rating
>> >plate. Part of it says:
>> >
>> > Compressor R.L. Amps 9.4 + 13.0
>> > Compressor L.R. Amps 64 + 81
>> > Branch Circuit Sel. Current 26.0
>> > Max. Breaker Amps 40
>> >
>> >I have a 40 amp breaker installed. I was assuming that one compressor
>> >used 9.4A and the second compressor used 13A. However the third item
on
>> >the list appears to indicate that the total current is 26A, which would
>> >infer that the compressors used 13A each.
>> >
>> >Thus I have two questions, how should the above information be
interpreted
>> >to give the current draw for each compressor? And what does R.L. and
L.R.
>> >mean?

The L.R. stands for Locked Rotor Amperage and is what the system draws when
the compressor first starts. Locke Rotor means when the rotor of the
electrical motor running the the compressor is at a stand still and must
start. It is higher and will always be higher but does not indicate
anything to be used in power calculations

The R.L. is the compressor Running Load Amperage. It is the amperage that
is drawn while the compressor is running under normal full load. This is
the figure to be used for power calculations.

As far as a generator goes, make sure that it will stand the surge that
will be generated when the unit starts.

Gerry

[JERRY ATTRICK]

Allan Yates wrote:

> I have a water source heat pump, and I am calculating what size
> of generator would be required to run at least part of it. It is
> a dual compressor unit, but I don't understand electrical rating
> plate. Part of it says:
>
> Compressor R.L. Amps 9.4 + 13.0
> Compressor L.R. Amps 64 + 81
> Branch Circuit Sel. Current 26.0
> Max. Breaker Amps 40
>
> I have a 40 amp breaker installed. I was assuming that one compressor
> used 9.4A and the second compressor used 13A. However the third item on
> the list appears to indicate that the total current is 26A, which would
> infer that the compressors used 13A each.
>
> Thus I have two questions, how should the above information be interpreted
> to give the current draw for each compressor? And what does R.L. and L.R.
> mean?
>

> Thanks,
>
> Allan.
> aya...@nortel.ca

LR stands for locked rotor current, which would be the amount of current a
motor would draw if you prevented it from turning. This is provided because a
disconnect must be capable of interrupting this amount of current. I forget
what RL stands for but I think it's Rated Load amps, an indication of what the
motor normally draws. I have never seen Branch Circuit Sel. before (minimum
wire size or branch ampacity is more familiar). You may find non motor loads
being added into that number. You also need to know something about how big a
motor the generator can start. Starting current for a motor is much higher
when starting then when running. As I recall I went by horsepower on this,
but it's been awhile since I put the generator in the truck. I think the
exhaust fumes have taken their toll on my mind, making me wonder if I should
have had it done professionally (I know my next one will be).