superheat cause increased head pressuse?

[bluecool]

Does evaporator superheat cause a increase in condenser head pressure? Nowhere in my entry level hvac text book have I seen this question being answered outright.

[tibs]

more details, low sh, high Sh.

why did you ask ? real trouble or ...

[Ron223]

Does evaporator superheat cause a increase in condenser head pressure? Nowhere in my entry level hvac text book have I seen this question being answered outright.

Keep in mind that at the point your reading your head pressure your refrigerant is typically subcooled. The superheated gas is actually picking up even more heat passing through the compressor. Both in mechanical heat and the heat of recompression. Making it essential that we have proper air flow through the outdoor coil to change states and subcool the hot gas to a liquid prior to the metering device.

[craig1]

high evaporator superheat will result in lower head pressures.

as you add charge to bring down the superheat, you will start absorbing more heat in the evaporator. This increase the temperature of the condenser, which increases the head pressure.

[bluecool]

more details, low sh, high Sh.

why did you ask ? real trouble or ...

I just thought it was odd that my text book from trade school didn't answer the question. Does superheat at any level from anywhere cause head pressure to increase? I suppose from the lack of responces its a boring question.

[bluecool]

high evaporator superheat will result in lower head pressures.

as you add charge to bring down the superheat, you will start absorbing more heat in the evaporator. This increase the temperature of the condenser, which increases the head pressure.

system charge is normal. does superheat from anywhere capable of raising head?

[Ron223]

system charge is normal. does superheat from anywhere capable of raising head?

Superheat alone typically shouldn't to significantly but a high load will. Generally speaking SH is just the condition of the refrigerant.

[bluecool]

Superheat alone typically shouldn't to significantly but a high load will. Generally speaking SH is just the condition of the refrigerant.

Does shouldn't to significantly mean: it doesn't?

[mgenius33]

What is your definition of superheat?

[Ron223]

Does shouldn't to significantly mean: it doesn't?

Your asking for a definitive answer to something with many variables. I'll venture to say that with normal load conditions, proper charge and airflow, no. If it did contribute the pressure increase would be minimal because you have to keep in mind that the purpose of the outdoor unit (in cooling) is to reject heat. Do you have a good understanding of the three states of refrigerant? And the refrigeerant cycle? I'm not making any assumptions as to what you do or don't know but if not this would greatly help you understand what your asking. And is this just a general question or are you actually trying to troubleshoot a job? Of so whats the rest of the conditions?

[ar_hvac_man]

high evaporator superheat will result in lower head pressures.

as you add charge to bring down the superheat, you will start absorbing more heat in the evaporator. This increase the temperature of the condenser, which increases the head pressure.

That is assuming the charge is low.

[bluecool]

Your asking for a definitive answer to something with many variables. I'll venture to say that with normal load conditions, proper charge and airflow, no. If it did contribute the pressure increase would be minimal because you have to keep in mind that the purpose of the outdoor unit (in cooling) is to reject heat. Do you have a good understanding of the three states of refrigerant? And the refrigeerant cycle? I'm not making any assumptions as to what you do or don't know but if not this would greatly help you understand what your asking. And is this just a general question or are you actually trying to troubleshoot a job? Of so whats the rest of the conditions?

not troubleshooting, thought I might learn something especially if someone answered yes. Although, didn't know a refrig. could reach a solid

[ar_hvac_man]

Readings during a hot pull down or heavy load would show high superheat and higher head pressure.

[Ron223]

not troubleshooting, thought I might learn something especially if someone answered yes. Although, didn't know a refrig. could reach a solid

What do you mean by a "solid"?

[bluecool]

Readings during a hot pull down or heavy load would show high superheat and higher head pressure.

are you saying that superheat creates higher head press?

[ar_hvac_man]

Someone mentioned the three states of refrigerant. :whistle:

[hvacrmedic]

No.

[ar_hvac_man]

are you saying that superheat creates higher head press?

no.

[Ron223]

Someone mentioned the three states of refrigerant. :whistle:

Correct, I did. (And this may be your point) To the OP if you don't know the three states of refrigerant, you really must learn and understand them (and the refrigerant cycle). Not only would you then understand the answer your seeking, but its also essential if your going to attempt to diagnose a non-electrical system fault. Without that understanding your not able to grasp what is happening inside that line set, let alone begin to process the corrective actions required.

[craig1]

What do you mean by a "solid"?

I think he was confusing your 3 states comment with the 3 states of matter: solid, liquid, gas. as opposed to the 3 states of refrigerant: superheated, subcooled, and saturated.

[mark beiser]

High evaporator load can cause high superheat and high head pressure, but in that scenario high superheat is one of the symptoms of the high evaporator load, not a cause of the high head pressure.

The refrigeration cycle is a dynamic system, you have to look at what is going on in the whole cycle, rather than focusing on one or 2 measurements.

[timebuilder]

You should bring this up in class, maybe with some of the responses here.

[Saturatedpsi]

system charge is normal. does superheat from anywhere capable of raising head?

Two things will make head pressure go high: too much refrigerant or not enough condenser air. The two things that affect superheat are coil loading and airflow. If there's anything close to a direct relationship between head pressure and superheat, it would be with a fixed orifice system where the head pressure affects the rate of liquid flow, which will affect superheat. But even then, it's head pressure affecting superheat and not vice-versa.

[mark beiser]

Two things will make head pressure go high: too much refrigerant or not enough condenser air.

So will high evaporator load.

[Saturatedpsi]

So will high evaporator load.

Yes, and for that matter so will high ambients. ;) bluecool's question, as worded, can't be sufficiently clarified because it has no meaning. It's essentially asking if a measured value at one place will create a symptom somewhere else, which is suggesting a "cause and effect" relationship between superheat and head pressure; which is not a valid premise. :limb:

[bornriding]

Yya'll can correct me, if I stray in the wrong direction here....but

Superheat is SENSIBLE heat added to the refrigerant from inside the evap until the compressor.

This 'heat is then also increased by the compressor, before sending the heat & the refrigerant to the evaporator.

This sensible heat must be rejected by the 1st part of the condenser, before the change of state can occur.

So though any change in the high side pressure would be minimal & for the most part unperceptable, the high side IS affected by the amount of superheat.

Richard

[Saturatedpsi]

Superheat is SENSIBLE heat added to the refrigerant from inside the evap until the compressor.

So though any change in the high side pressure would be minimal & for the most part unperceptable, the high side IS affected by the amount of superheat.

Richard

The condenser rejects the total quantity of heat picked up in the evaporator and generated in the compressor, be it latent or sensible. And if something causes the superheat to change, the head pressure might change, and depending on how much the superheat changes, the change in head pressure won't necessarily be "minimal & for the most part unperceptible".

But the numbers (head, suction, superheat & subcooling) change due to changes in air flow volume, refrigerant flow and heat content of the air volume. But a change in a number isn't what makes a change in another number. Read Mark Biser's comments a few posts above this one.