General Question...

[mlamars]

Are the amps higher when the superheat is low or high?

[pecmsg]

Are the amps higher when the superheat is low or high?

W H A T !

[pecmsg]

I don’t see where SH will affect when Evap amperage!

[mlamars]

Its a question that was asked in class today and I just needed some clarification

[pecmsg]

I guessed that:
Look up Emerson Compressor Performance Curves.

[pageyjim]

Are the amps higher when the superheat is low or high?

The compressor will generally draw more amperage when the system is overcharged than when it is undercharged. If you understand superheat then you have your answer and reason why.

It's a good example of how looking at the whole system and understanding how one part impacts another. Stay in the habit of looking at the whole system and not making a diagnosis on limited data. It will make you a better tech in the long run.

[shellkamp]

The compressor will draw more amperage when the system is overcharged than when it is undercharged. If you understand superheat then you have your answer and reason why.

It's a good example of how looking at the whole system and understanding how one part impacts another. Stay in the habit of looking at the whole system and not making a diagnosis on limited data. It will make you a better tech in the long run.

That's not a completely accurate statement.

Sent from my Moto Z (2) using Tapatalk

[idontgetit]

Are the amps higher when the superheat is low or high?

What a FUN question!!!

the answer is not so perfectly clear for it has varied answers.

To answer it correctly, a lot of variables have to be established as that relationship is NOT exactly linear in nature.

Assume fixed speed comp with no capacity control's aka it will ride the load then there are fewer possible answers. if your actually interested in thinking about and learning, read on, if it is only a test answer you seek it won't be much help.

so to keep it simple change the realities a little.

compressor =1 cubic foot per stroke, 1 stroke per minute, the amount in mass of refrigerant it moves will have MANY factors but the main ones will be pressure and temp as they will have the most affect.

remember the system is always under absolute pressure so psig has to be upped by approximately 15 psi so if we see 100 high, and 10 low we actually have 115 over 25, this actually makes a huge difference as 100\10= is a comp ratio of 10, but 115\25 is 4.6 pressure ratio.

Higher pressure = greater density = more mass.
Higher temperature = lower density = lower mass

The compressor in this discussion is DUMB, it is going to pump whatever comes back to it.

If at the 10\100 pressures discussed we have 0 superheat and 1 pound of refrigerant per cubic foot then at 0 deg SH your comp is going to have a mass flow rate of 1 lb per minute, if you add heat load but no change in pressures (theoretical, not how it really works) then you will reduce the density of the vapor entering the compressor. If the refrigerant properties are such that 10 degrees of SH @ 25 PSIA would be 1/2 lb per cubic foot, those 10 degrees would result in a new mass flow rate of 1/2 lb per minute aka it is doing a lot less work, aka less amperage.

Now if it is the same system with a TEV that will respond to the load increase, it is going to open and allow more refrigerant to flow into the compressor and lower the superheat, however more refrigerant = more mass and changed pressure ratio aka more work, aka more amperage.

The compressor pumps BTU's in the form of heat laden refrigerant, it will respond to the increased load accordingly. Edit: SH is only A PART of it, the pressure has a huge roll as well. While there are other factors, the pressure and temperature of the return vapor are number 1 and 2 when it comes to how much work the compressor is going to do, aka horsepower, aka amps x volts and the volts ain't changing on this one.

This is indeed a really fun question and believe it or not, a long long time ago there was a theory one could adjust the charge on a fixed bore device system by the compressor amperage and ambient conditions of the coils.

A CPR is a protection for the compressor when the loads may be significantly above normal conditions, it is actually adjusted to the compressor's rated load amperage specifications, a whole nother ball of wax.

Good luck in your schooling, if you are very curious and explore questions like this in detail, you will indeed go far

[Poodle Head Mikey]

Based solely on your question's presented information (and assuming SSH <g>) I would say:

higher amps with lower SSH.

The compressor is doing more work, isn't it?

PHM
-------

Are the amps higher when the superheat is low or high?

[Adlerberts-Protege]

More liquid = more amps = dead compressor.

[servicefitter]

Good low sh would raise amps just before the amps go real low and the compressor gets quiet.

[SVTCharlie]

The compressor will generally draw more amperage when the system is overcharged than when it is undercharged. If you understand superheat then you have your answer and reason why.

It's a good example of how looking at the whole system and understanding how one part impacts another. Stay in the habit of looking at the whole system and not making a diagnosis on limited data. It will make you a better tech in the long run.

Finally someone posts a good answer that addresses the OP's post without ripping him or looking down upon him.

[pecmsg]

Finally someone posts a good answer that addresses the OP's post without ripping him or looking down upon him.

How can we answer with this Vague Question?

Are the amps higher when the superheat is low or high?

[ammoniadog]

Based solely on your question's presented information (and assuming SSH <g>) I would say:

higher amps with lower SSH.

The compressor is doing more work, isn't it?

PHM
-------

It might be doing more work at that exact moment in time, but overall it will be doing less work because it can reach setpoint sooner and shut itself off.

Then when it's not running the superheat AND amp draw will both be zero.

Low superheat for the win!

[GoCougs]

This thread is making my head hurt


Sent from my iPhone using Tapatalk