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ewart
19-06-2006, 12:12 AM
I have problems to determine compressor horse power especially on commercial and domestic refrigerator please help me to know the correct procedure.

Toolman
19-06-2006, 01:00 PM
I have problems to determine compressor horse power especially on commercial and domestic refrigerator please help me to know the correct procedure.

Horsepower is so inaccurate , wattage or Kilowatts is much more accurate . You should be able to find tech data on the WWW on how to calculate wattage . There is an easy way fro Air-Condtioning a basic rule is 150 watts per square metre ( Sorry I only know metric ) EG : 5 mtrs x 4 mtrs =20 sq mtrs x 150 watt = 3000 watts or 3 KW .
:D

US Iceman
19-06-2006, 01:56 PM
Hi ewart,

To solve for the horsepower in an accurate fashion you need several pieces of data.

For single phase motors use this method:

(volts x amps x motor efficiency x power factor) divided by 746

For three phase motors use this method:

(volts x amps x motor efficiency x power factor x 1.73) divided by 746

The motor efficiency and power factor are somewhat unknown unless you can obtain the motor efficiency from the manufacturer, and the power factor (for the electrical distribution) from the electric utility.

Since you may have to guess at these two variables you still may not get an entirely accurate answer. However, it might provide an idea of what you have.

Another method is to use a rule-of-thumb. For three phase motors on 460 volts the amperage will be approximately 1.5 amps per horsepower.

For three phase motors on 230 volts the amperage will be approximately 3.0 amps per horsepower.

If my memory is correct you can use this for single phase motors. You might want to check this out since it's been a LONG time for me to have worked on these small systems.

For single phase motors on 230 volts the amperage will be approximately 6 amps per horsepower.

For single phase motors on 115 volts the amperage will be approximately 12 amps per horsepower.

malik55
19-06-2006, 05:07 PM
No simple answer,
To find exact compressor's H.P you have to check manufacturers data for a certain compressor and its application, All other methods are not so accurate, Some model numbers may tells power for it but those are nominal powers, for AirCond applications take one H.P per Ton but again that is only rule of thumb.

S.K.VARDE
20-06-2006, 03:48 PM
Swept volume at defined rpm, volumetric efficiency, operating temperature range of the system, specific volume and then the enthalpy difference may help you to find you out the SHP of the compressor.

you may refer any basic text book to calculate the same.

I think, now you can do it.

ewart
21-06-2006, 02:33 AM
Thank you gentle men for these info. i will see how best i can use them at the same time i will post info on a refrig. and compressor for you to calculate.
Thanks

The_AV8R
22-07-2009, 05:31 PM
So would compressor power consumption simply be desired heating output / (compressor efficiency+cycle efficiency)?

Say I want a 1.75 kW heating output, and my compressor is rated at 80% efficiency, am I looking for a compressor that produces about 2.19 kW (3 hp)?

lana
27-07-2009, 04:21 AM
Hi everybody,

It has been a very long time .... I have been very very busy.

Horse power is a unit for electric power. Most people confuse this with cooling or heating power. International unit system use Watt for every form of power, including heating, cooling and electricity.
The confusion comes from this : you can not convert cooling Watt into HP. Because the first one is heat power and the second is electrical.
Now consider this : there is a compressor which has cooling capacity of 10000Watts at (-20C/50C) and its power consumption is 6000Watts at the same conditions. You only can convert the 6000watts into HP.
On the other hand refrigeration compressors consumes different electrical power at different operating conditions therefore, there are different Horse powers at each condition. When a compressor is called 10HP, this is a nominal HP and it dose not tell us very much.
1 HP = 736 Watt ..... ELECTRICAL power only

Cheers

D.D.KORANNE
27-07-2009, 09:59 AM
Probably compressor manufacturer will select the highest evap temp & highest condensing temp to arrive at the power consummption & select a nminal rated motor which by & large will suit all the applications under the envelope

marc5180
27-07-2009, 05:39 PM
Welcome back Lana, it's good to see you posting on the forums again:).