Horse power

[A.Mortezania]

Dear Friends,

I have a question. When we see a catalogues of compressor in every evaporator and condenser temperature it has a different power input in Watt or Horse power or any other kind of power. I can understand it what is it and why it increases or decrease in different situation.

When we see some catalogues, For example company mentioned Model X compressor as for example 2HP or for example 10 HP (HP = Horse Power).
When compressor has different power input in different situations, What is the meaning of 2HP or 10HP here ?

Why for example Bitzer says compressor 6G-40.2 means 40 horse power ? As I explained above this compressor has different power input in different situation. What is the meaning of 40 horse power here ?

Sincerely yours.

[Rob White]

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Horsepower is a measure of the amount of work an engine can perform. Several different definitions exist for the term. Car aficionados are likely to be aware of the distinction between standard horsepower (HP) and brake horsepower (BHP), which is the measure of a motor’s power without any of the losses incurred by running auxiliary engine components. Most of the time, when we talk about horsepower in a more abstract sense, we are talking about a unit of power equivalent to 550 foot-pounds per second, or 745.7 watts.

All compressors have a motor component that is rated in horsepower or more recently Watts and kilowatt. A compressor motor’s job is simply to drive the cylinders or rotary screw that compress refrigerant. The process by which this occurs is complex. As a result, the relationship between the amount of horsepower a motor has and the amount of work a compressor can do is not always straightforward.

So each compressor is driven by an electric motor and that is measured in HP or kW
Rob

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[A.Mortezania]

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Horsepower is a measure of the amount of work an engine can perform. Several different definitions exist for the term. Car aficionados are likely to be aware of the distinction between standard horsepower (HP) and brake horsepower (BHP), which is the measure of a motor’s power without any of the losses incurred by running auxiliary engine components. Most of the time, when we talk about horsepower in a more abstract sense, we are talking about a unit of power equivalent to 550 foot-pounds per second, or 745.7 watts.

All compressors have a motor component that is rated in horsepower or more recently Watts and kilowatt. A compressor motor’s job is simply to drive the cylinders or rotary screw that compress refrigerant. The process by which this occurs is complex. As a result, the relationship between the amount of horsepower a motor has and the amount of work a compressor can do is not always straightforward.

So each compressor is driven by an electric motor and that is measured in HP or kW
Rob

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Dear Rob,
Thanks for your reply.

I will be thankful if you read definition below and say your opinion.

For example while we have a 5HP electromotor (or compressor) it means if we want stop shaft of this motor in every situation we must apply 5HP power (Or 5 * 0.745 KW).

But this 5HP electromotor will take different range of ampere form network in different situation.

Is this explanation true ?

Sincerely yours.

[Brian_UK]

The amperage that a motor consumes varies with the load placed upon it.

The example 5HP electromotor will not use 5HP if the load is only 3HP.

[A.Mortezania]

The amperage that a motor consumes varies with the load placed upon it.

The example 5HP electromotor will not use 5HP if the load is only 3HP.

Yes, Amperage is different and depends on situation, I can understand it clearly.

Just meaning of this small sentence is important for me “What is meaning of for example 5HP electromotor when we buy it” ?

If you check catalogue of compressors, Between Carlyle (Carrier) and most of companies in Europe there is important difference.

Carrier introduce their compressor by compressor CFM, For example 06EM299 (means 99 CFM compressor displacement) but Bitzer or DWM (Emerson) introduce their compressors via Horse power, For example DWM : DLSG-401 (4HP) or Bitzer : 4H-25.2 (25 HP).

Maybe I’m fool, But still it is not clear for me, What is the meaning of for example 5HP electromotor.
I have thought meaning is for stopping shaft of electromotor we must apply 5 HP power but you didn’t confirm that.

Sincerely yours.

[Brian_UK]

A 5HP electromotor can, when supplied with the correct voltage and amperage, provide motive effort equivalent to 5HP.

[narkom]

http://www.refrigeration-engineer.com/forums/showthread.php?463-Nominal-HP
http://hvac-talk.com/vbb/showthread.php?178206-Compressor-tonnage-horsepower
http://hvac-talk.com/vbb/showthread.php?69901-One-ton-equal-One-HP

[Segei]

5 HP means how "strong" is electrical motor (not compressor). If you need 6 HP motor, 5 HP (not strong enough)will be overloaded and overload should trip or motor will burn out.
Definitely, to provide required cooling everything starts from CFM. Knowing CFM of compressor and operating cycle, companies can calculate HP of the motor. Some company give CFM, others calculate and give you motor HP.

[A.Mortezania]

5 HP means how "strong" is electrical motor (not compressor). If you need 6 HP motor, 5 HP (not strong enough)will be overloaded and overload should trip or motor will burn out.
Definitely, to provide required cooling everything starts from CFM. Knowing CFM of compressor and operating cycle, companies can calculate HP of the motor. Some company give CFM, others calculate and give you motor HP.

Dear Segei,
Thanks for your reply.
You say : 5 HP means how "strong" is electrical motor. Exactly my question is it. OK, 5 HP means how big is electrical part. But what does it mean by HP ? for example why they do not tell electrical motor is size 5, They say electrical motor 5 HP.
Definitely mention electrical part by horse power has an important meaning and I want to make it clear for myself.

They tell electrical part for example is 5 HP, But this electrical part use different power input at different situation. What is the meaning of 5 horse power here ?

Also when you buy a car, Company says this car has for example 720 horse power motor. But this 720 HP motor of car uses different amount of gas in different situation.

I think we can find a relation between this two definition to reach to meaning.

Sincerely yours.

[NH3LVR]

Lets try to put this one to bed.
The HP of an electric motor is based on it's capacity to do work.
If it is a 5HP motor you will not stop it if you try to get 7HP out of it. It will be overloaded however and fail at some point in time due to heat.
Under most circumstances you will be using less than 5HP. However you may meet or exceed this under high head conditions or high suction pressure. (Just as your auto engine does not put out maximum HP cruising down the highway)
If you look at a open compressor (not a hermetic or semi-hermetic) the motor will come with a name plate with amp draw, rpm and often a "service factor" rating. This gives you a percentage of full load current (100%+)that you can use safely. For example if you have a 100HP motor with a 1.15 service factor you can safely use 115HP.

In the case of a hermetic or semi-hermetic the motor inside is not visible. Perhaps the manufacturer sticks to the conventional terminology, perhaps not.

[Brian_UK]

I find it difficult to follow your reason for not wanting electric motors to be classified the way that they have been for almost 120 years.

Why are you unable to ask for a 5HP motor, is speaking the letters HP or saying horse power to difficult that you want to say only 5?

Please explain your need to only say 5 as I am losing the will to live over this matter.

[Segei]

HP is a unit. It can be 5 HP, 5 kW, 5 MW... 1 HP=0.7457 kW. 5 HP is the maximum power of this motor. If required power 2 HP, 3 HP, 5 HP, this motor will handle the load. If required power 6 HP, 7 HP, overload of this motor will trip or motor burn out.

[A.Mortezania]

HP is a unit. It can be 5 HP, 5 kW, 5 MW... 1 HP=0.7457 kW. 5 HP is the maximum power of this motor. If required power 2 HP, 3 HP, 5 HP, this motor will handle the load. If required power 6 HP, 7 HP, overload of this motor will trip or motor burn out.

Dear Segei,

OK, Now is clear.