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bernard
01-04-2004, 09:29 PM
When setting up switches is there is there a method for working out the settings including differential. At present I normally set up H.P. at 300 LP at 10. should this alter depending on the gas.

Regards to the wise ones.

Bernard

Latte
01-04-2004, 09:46 PM
HP/LP Settings should be different depending on gas.

Take R12/R409(FX56) Head pressure should be about 120psi therefore when the system was pressure/strength tested is was probably put upto 150psi max. A HP switch set at 350 would be useless because the system whould blow well before then. Also if these gases were used in a low temp application (Unlikely i know) but the system would stop because the suction pressure would be if anything in a vac.

R404 Head pressure should be about 240psi running so an HP at 350psi would be higher than i would put it (Prob 325 at most)

R22 runs about 190-200 so 350psi also well excessive.

Let us know what kind of equipment and gases you are woking on and i am sure someone will post the OFFICIAL HP Guidelines.


Regards

Raymond

bernard
01-04-2004, 09:53 PM
Raymond

Thankyou for your reply:

The one I am most concerned about is R407c.But what you say makes sence there must be a guide or % to set these switches above the hp running pressure.

Thankyou

Bernard

Latte
01-04-2004, 10:05 PM
Sorry Bernard,
Got me on that one, never used the stuff yet & my HRP sliderule doesnt show it. If anyone has a list of HP switch settings or wants to put one together i would like to see it

regards

Raymond

Brian_UK
01-04-2004, 10:12 PM
One way of deciding on the settings is to work out the condensing temperature at maximum design ambient then add a small overshoot allowance.

The differential should be quite wide to reduce compressor cycling; remember everytime the compressor starts it pumps a bit of oil out, if it doesn't run for long enough then the oil doesn't return.

End result - dry compressor - bang :eek:

If there is a continual head pressure problem then it should be investigated and rectified.

Latte
01-04-2004, 10:16 PM
Hello Brian,
Maximum design ambient, now there is a subject that could take up a lot of space within the forum.

Anyone out there know the head pressures of R407 & R410 & what the HPCO's should be.

Regards

Raymond

chemi-cool
01-04-2004, 10:18 PM
hi raymond,

there is no such thing,

what you said before is right for the uk.

over here, R22 works around 250 and more in the summer.
so the settings will be different.

I guess the setting depend on the working conditions.

chemi

Argus
01-04-2004, 10:30 PM
The nearest thing to chapter and verse in the UK is BS EN 378, Part 2.
Look at section 5, tables 1 & 2. It give a methodology for determining the maximum allowable pressure (Ps) for the refrigerant of your choice.

This standard is harmonised to the PED and would, I suspect, qualify as Standard Engineering Practice for equipment below Category 1. (Outside the scope of the PED.

Pressure limiting devices are set at < 0.9 Ps if you have a relief valve or <1 Ps without.

Differential is not defined.

You can obtain a copy from BSI or main public libraries should have sets. BSI should give you a list of Libraries that carry complete sets (usually on Microfilm).

Hope this helps.
________
Mercury Monarch picture (http://www.ford-wiki.com/wiki/Mercury_Monarch)

Peter_1
02-04-2004, 06:14 AM
For me it's simple: HP is there to protect the compressor. So max allowabale pressure found on the nameplate and subtract 1 bar safety for it, which will be mostly 24 bar. Dff mostly not settable.
LP: Cut in at somewhat lower then normal operating pressures en diff set so that machine stops before atmospheric pressure.
Otherwise, the 1 st day it becomes warm - like last days- all the same calls:'Hey, my compressor is going on-off real fast"
The problem becomes even bigger especially with a resettable HP. If it's a freezer, you can't be fast enough then to repair.

iceman007
02-04-2004, 02:15 PM
Absolute maximum setting of 90% mwp, but should be set with safety of plant as priority. Head pressures will vary dependent on ambient temp as well as gas type.
BS EN378 I believe defines maximum working pressure at different saturation points for the gas in use. I believe it is at a temp of 32 degrees on the low side, and for the high side, 55 degrees for an air cooled condenser and 43 degrees in the case of water cooled condensers. Saying that we usually check manufacturers data and go from there.

As Peter says we usually set LP so that it will cut just above atmospheric pressure, for instance if the system has to be pumped down etc as well as to protect the compressor.

Regards
James

Latte
27-04-2004, 08:20 PM
Hi all,
Just a quick list of approxomate pressures in response to Bernards original post. Obviously these are approx & ambients could change.If i have worked these out wrong can someone let me know

Regards

Raymond

Gas Type, HP, LP@0coil, LP@-10 Coil, LP@-30 Coil.
R12, 118, 30, 17, 1" vac.
R134, 125, 28, 14 , 1" vac/
R22, 190, 58, 36, 9.,
R502, 215, 67, 36, 14.
FX10, 220, 68, 44 , 13,
FX56 125, 27, 15 , 1" vac,
R404 230 , 72 , 48, 14,
R407 220, 50, 32 , 13,
R410 320 , 100, 68, 24,
R507 240, 76 , 48 , 16,

rbartlett
28-04-2004, 05:58 AM
those hp settings will have you going back resetting units all summer

cheers

richard

Jasper
28-04-2004, 07:34 AM
This is the information in BS EN 378

Latte
28-04-2004, 05:30 PM
Hi All,
I meant to say these are approx RUNNING Pressures if the system is OK, Condenser Clean Ect. THESE ARE NOT settings for hp/lp switches

Regards

Raymond

Dan
29-04-2004, 12:02 AM
I am thinking of a refrigeration system, here. One condition that I would pay attention to is to make sure the high pressure control is set at least 25 psig below the pressure relief valve of the system, for what I would hope is an obvious reason. :) I would guess that a 407C system would have a 425 psig relief valve on it, so I would set it no higher than 400 psig and no lower than 375 psig which is about 135 Deg F bubble point. Anything lower and you run the risk of tripping out during transient high load conditions such as after defrost on a hot day.

As far as the low pressure control setting goes, I am assuming you are talking about a pump down situation. If that is the case, you would use one setting for low temperature and a different setting for medium temperature.

Forgetting about pressures, I would set a low pressure control for a -20 deg F evaporator no higher than 10 deg F below the design evaporator temperature and no lower than 5 deg F below the design temperature. With 407C 2 psig would be a good setting which corresponds to a dew point of -30 deg F.

For medium temperature, +20 deg F application I would set the cutout at 25 to 28 psig (7 to 10 deg F). No point in pumping down a compressor lower than necessary.

Differential settings are best done per the application. Again, for pumpdown situations, you want to mitigate the short cycles. If you pump deeper than necessary, you will probably desire a higher cut-in pressure (or larger differential) than if you pump down the practical minimum amount. I would convert the air temperature into an evaporator pressure and make sure I don't have the cut-in pressure below my warmest acceptable air temperature. Let's say, maybe 40 deg F (65 psig) for medium temperature and 10 deg F (27 psig) for a freezer.

frank
29-04-2004, 09:18 PM
Nice Post Dan - we all should look at temperatures more than pressures as this is what we are trying to achieve - temperature control. :o

By the way - I must say that your photo does not look anything like the picture in my mind of you after reading your posts for so long. (A bit of a compliment ;) )

Frank

Coolie
20-10-2004, 05:44 PM
Hello Brian,
Maximum design ambient, now there is a subject that could take up a lot of space within the forum.

Anyone out there know the head pressures of R407 & R410 & what the HPCO's should be.

Regards

Raymond
R407c -- Suction should be around 3 bar and discharge around 15 bar.
NOt sure about R410, but I know it's a lot higher

Gary
22-10-2004, 05:12 PM
Nice Post Dan - we all should look at temperatures more than pressures as this is what we are trying to achieve - temperature control. :o

Frank

Exactly so. Determine the proper temperature at which to trip the control, then get out the P/T chart and find the corresponding pressure for whatever refrigerant you are using.

I generally recommend tripping a HP control at about 135-140F/57-60C. Look at your P/T chart to find what pressure that corresponds to for any refrigerant.

Refrigeration is about temperatures, not pressures. When you learn to think in terms of temperatures, you can work with any refrigerant. A new refrigerant only requires a new P/T chart.

Back when only a few refrigerants were in common use, I told people to paint over the pressure scales on their gauges, so they would be forced to use the temperature scales. Temperature is what really matters.

Gary
22-10-2004, 05:32 PM
Hi all,
Just a quick list of approxomate pressures in response to Bernards original post. Obviously these are approx & ambients could change.If i have worked these out wrong can someone let me know

Regards

Raymond

Gas Type, HP, LP@0coil, LP@-10 Coil, LP@-30 Coil.
R12, 118, 30, 17, 1" vac.
R134, 125, 28, 14 , 1" vac/
R22, 190, 58, 36, 9.,
R502, 215, 67, 36, 14.
FX10, 220, 68, 44 , 13,
FX56 125, 27, 15 , 1" vac,
R404 230 , 72 , 48, 14,
R407 220, 50, 32 , 13,
R410 320 , 100, 68, 24,
R507 240, 76 , 48 , 16,

Translate all of these pressures into temperatures, and you will find that all systems run at roughly the same temperatures, regardless of refrigerant. You can memorize a few temperatures or a very long list of pressures. Temperatures make the job much easier.

rbartlett
22-10-2004, 06:00 PM
Refrigeration is about temperatures, not pressures. When you learn to think in terms of temperatures, you can work with any refrigerant. A new refrigerant only requires a new P/T chart.

Back when only a few refrigerants were in common use, I told people to paint over the pressure scales on their gauges, so they would be forced to use the temperature scales. Temperature is what really matters.[/QUOTE]





temperature alone is as irrelevant as pressure in isolation. it seems slightly patronising - to me at least- when some say

' forget the pressure tell me the temperature'

it's nonsense you cannot diagnose by temperature alone..

if i said the suction pipe is 12 deg's c what's wrong?
could you tell me??????

i rather doubt it..

no you would give me a list of alternatives much the same if i said 'the pressures 34psig whats the matter?'

rant over back to the wine..;-))

cheers

richard

Gary
22-10-2004, 06:17 PM
temperature alone is as irrelevant as pressure in isolation. it seems slightly patronising - to me at least- when some say

' forget the pressure tell me the temperature'

it's nonsense you cannot diagnose by temperature alone..

if i said the suction pipe is 12 deg's c what's wrong?
could you tell me??????

i rather doubt it..

no you would give me a list of alternatives much the same if i said 'the pressures 34psig whats the matter?'

rant over back to the wine..;-))

cheers

richard

I totally agree. There is no temperature or pressure that, by itself, tells me anything important about the system. It is temperature differences that tell us everything we need to know. TD's, dT's, subcooling, superheat, approaches. All of these involve subtracting one temperature from another temperature. Working with pressures adds an unnecessary layer of confusion, since we must then convert them to temperatures.

So, instead of saying, "Forget the pressure, tell me the temperature", let's say, "Forget the pressures, tell me the temperatures".

And if you want me to figure out everything that's wrong with the system, then tell me ALL of the temperatures. Unless you really want to go back next week to find the other problem(s) that you missed the first time around.

Peter Mitchell
22-10-2004, 07:13 PM
well said Rbartlets I know if I work only in temprature or pressure then you are not able to understand what a system is doing.
if the liquid line was hot you would quickley check the condensor for dirt or faulty fans and you would be able to fix the problem 99% of the time, not to bad
if the liquid was cold then without gauges you know nothing except it aint working and you need a lucky guess
I am drinking a rather nice rioja at mo

Gary
22-10-2004, 07:38 PM
Perhaps I'm not stating this clearly enough, so let's rephrase this one more time:

Forget the pressures, tell me the saturation temperatures which those pressures correspond to on a P/T chart.

Gary
22-10-2004, 07:47 PM
well said Rbartlets I know if I work only in temprature or pressure then you are not able to understand what a system is doing.
if the liquid line was hot you would quickley check the condensor for dirt or faulty fans and you would be able to fix the problem 99% of the time, not to bad
if the liquid was cold then without gauges you know nothing except it aint working and you need a lucky guess
I am drinking a rather nice rioja at mo

Whether you realize it or not, you are defining hot/cold liquid line in context to ambient temperature. Your definition of "hot" or "cold" depends on how hot or cold the ambient is. You are considering two temperatures, not one.

If someone told you their liquid line temp was 110F/43C, would you say they had an airflow problem? What if that liquid line were surrounded by 110F/43C ambient air?

BTW, condenser delta-T (air out temp minus air in temp) is a much more accurate indicator of condenser airflow problems.

frank
22-10-2004, 07:55 PM
it's nonsense you cannot diagnose by temperature alone..

if i said the suction pipe is 12 deg's c what's wrong?
could you tell me??????

I disagree Richard

If you had your gauges connected and you read a pressure then you would still have to do a temp/pressure conversion to get the overall picture. Don't forget that we are trying to control temps. How do you determine superheat? - temp/ pressure relationship. How do you determine sub-cool? - temp/pressure relationship.

It's no good approaching an R22 system on an A/|C application and saying " I'm looking for a back pressure of 55psig" you need to now what temps you are getting on the system.

Temps alone don't give the overall picture but they do give a better insight of how thesystem is working against how it should against just looking at the pressures.

If you had a system on A/C on R22 with a gauge pressure of 55psig - what does that mean? Unless you do a press/temp relationship comparison then it doesn't mean anything.

Point made?

Peter Mitchell
22-10-2004, 07:56 PM
hot or cold is not a refrence to ambient but is a refrence to body temprature when you touch somthing it will feel hot to you and hot to me if all thing are equall
The wine is really kicking in
If you were realy wanting to push the boat out there is infact no such thing as cold just not as hot

rbartlett
22-10-2004, 08:05 PM
I disagree Richard

If you had your gauges connected and you read a pressure then you would still have to do a temp/pressure conversion to get the overall picture. Don't forget that we are trying to control temps. How do you determine superheat? - temp/ pressure relationship. How do you determine sub-cool? - temp/pressure relationship.

It's no good approaching an R22 system on an A/|C application and saying " I'm looking for a back pressure of 55psig" you need to now what temps you are getting on the system.

Temps alone don't give the overall picture but they do give a better insight of how thesystem is working against how it should against just looking at the pressures.

If you had a system on A/C on R22 with a gauge pressure of 55psig - what does that mean? Unless you do a press/temp relationship comparison then it doesn't mean anything.

Point made?



err point not made at all

i said you cannot work from temperature alone, you agree then tell me you disagree whilst going on about temp/pressure..

what is your point exactly??


cheers

richard

Gary
22-10-2004, 08:10 PM
Sorry, guys. I've been editing while you were posting, so read it all again... LOL

It's mid afternoon here, so I haven't started on the liebfraumilch yet. I'll catch up later. :)

rbartlett
22-10-2004, 08:13 PM
Sorry, guys. I've been editing while you were posting, so read it all again... LOL

It's mid afternoon here, so I haven't started on the liebfraumilch yet. I'll catch up later. :)


well don't hang around you've got a lot of catching up to do *hic*

cheers

richard

frank
22-10-2004, 08:31 PM
Richard

Just trying to make the point that you should not just look at pressues - everything is related (temp/pressure). Obviously my Leibfraumilch has kicked in :D

Peter Mitchell
22-10-2004, 08:36 PM
my piont is that if you only use say temprature then you will be able to fix some problems but not all
If you had a system that had air in it then just looking at the temprature you would not be able to find this problem you might think it needed more gas

Gary
22-10-2004, 08:41 PM
my piont is that if you only use say temprature then you will be able to fix some problems but not all
If you had a system that had air in it then just looking at the temprature you would not be able to find this problem you might think it needed more gas

If the system had air in it, then the difference between the saturated condensing temperature and the ambient temperature would be excessive.

If you know all of the temperatures, including the saturation temperatures, then you can find all of the problems.

Peter Mitchell
22-10-2004, 09:02 PM
Would you not get the simmilar readings if the unit was grossly over charged. I aggree with your statment but stick on gauges and the high discharge pressure with less than ambient tempratures at discharge of condencer
Maybe all you need is to get two readings whether pressure or temprature as thay are directly related
superheat can be measured by temp in versus temp out or pressure out versus temprature out how fancy would the gauges have to be for pressure in versus pressure out?
Too much wine I think

Gary
22-10-2004, 09:26 PM
Would you not get the simmilar readings if the unit was grossly over charged. I aggree with your statment but stick on gauges and the high discharge pressure with less than ambient tempratures at discharge of condencer


In order to do this you would need to know what 'high discharge pressure' means for every refrigerant on the market.

OR

You could know what 'high saturated condensing temperature' means. Then you can work with any refrigerant for which you have a P/T chart.

Your choices are: Memorize a long list of pressures, or memorize a single temperature.

BTW, it is not possible for the condenser leaving air temperature to be less than ambient (condenser entering air) temperature.

rbartlett
22-10-2004, 09:38 PM
nice story but irrelevant

we are talking about diagnostics by temperature in relation to refrigerants not the cooling characteristics -or otherwise- of water

cheers

richard

Gary
22-10-2004, 09:58 PM
nice story but irrelevant

we are talking about diagnostics by temperature in relation to refrigerants not the cooling characteristics -or otherwise- of water

cheers

richard

It isn't the pressure of the (OFN, water, refrigerant, whatever) flowing inside of the coil that cools the air flowing outside of the coil, it is the temperature of the (OFN, water, refrigerant, whatever) flowing inside of the coil that cools the air flowing outside of the coil.

It's about temperature, not pressure.

rbartlett
22-10-2004, 10:18 PM
and this is a PRESSURE enthalpy diagram

cheers

richard

Gary
22-10-2004, 10:31 PM
Thinking I may start on that bottle early tonight... LOL

Peter_1
22-10-2004, 10:36 PM
I said it already in other posts, I rarely use a thermometer and I know my job and can repair quick and good most problems.
The battery for my temperature meter was out when I needed it some time ago, well.. it took me months before I needed it again and I realised I still had no new battery for it.

Why translate pressures always in temperatures and why for christ sake you have to do this to set a pressure switch? On the gauges of a pressure switch are only pressures indicated, no temperatures at all, so why translate it again to pressures? I don't see it. It all has to do how you learned it. I think I skileld myself with pressure gauges while Gary did it with a thermometer. The new generation is doing it with a laptop or a handheld unit.
Is my method therefore not as good as Gary's TECH method? I doubt it.

I set pressure switches to the max allowable pressure the manufacturer gives me, mostly 26 bar for the HP versus LP just above atmospheric pressure (not for a scroll of course) What is wrong with that? It never gave me problems and no one could ever convince me that this is wrong.

A high pressure switch is a safety device to protect the compressor going above the max allowable design pressure, given by the manufacturer. So I only do what they recommend me without translating it to temperatures which i find is real b..s.

It's like other posters said (Frank I think): you need both, pressures and temperatures.

Peter Mitchell
22-10-2004, 10:40 PM
sorry I did not mean the air temprature through the coil but the liquid temprature leaving the coil going to the system

Gary
22-10-2004, 10:48 PM
I set pressure switches to the max allowable pressure the manufacturer gives me, mostly 26 bar for the HP

That isn't near high enough for R410A, and is much too high for R12.

You may not be doing things the wrong way, but you are doing things the hard way.

Gary
22-10-2004, 10:59 PM
LP just above atmospheric pressure (not for a scroll of course) What is wrong with that? It never gave me problems and no one could ever convince me that this is wrong.


What if the LP control is being used to control the temperature in a cooler or a freezer?

Gary
22-10-2004, 11:21 PM
Why is this a difficult concept? I know that the HP control should trip at about 135-140F/57-60C saturated condensing temperature. A glance at my pressure/temperature chart tells me what the pressure setting should be for every refrigerant. Is it somehow easier to remember what the pressure setting should be for each and every refrigerant?

Dan
23-10-2004, 12:49 AM
Hi Peter. My oh my what a path this discussion has taken. :)

I set pressure switches to the max allowable pressure the manufacturer gives me, mostly 26 bar for the HP versus LP just above atmospheric pressure (not for a scroll of course) What is wrong with that? It never gave me problems and no one could ever convince me that this is wrong.

What is maximum allowable pressure? If the equipment has a pressure relief valve, then I would say that is the maximum allowable pressure, and I would be sure to set the control safely below it's setting.


A high pressure switch is a safety device to protect the compressor going above the max allowable design pressure, given by the manufacturer. So I only do what they recommend me without translating it to temperatures which i find is real b..s.


Pressure safety controls, of course, are unrelated to saturation properties. Perhaps the dilemma that has helped this discussion to turn into so much fun is that we are thinking that the high pressure control (simply a safety device) and the low pressure control (not so simply a safety device) are completely different animals even when using the same bellows and switches.


LP just above atmospheric pressure (not for a scroll of course) What is wrong with that? It never gave me problems and no one could ever convince me that this is wrong.
I have long held the same opinion, although I have no idea why you are separating scrolls from the mix. Copeland CSS classes teach that this is not a good idea to arbitrarily pump down to just above atmosphere. I remember more that the reasons made sense to me than I do the reasons.

Oil foaming on medium temperature applications during the pumpdown event, when it is unnecessary, perhaps?

The location of the solenoid valve becomes relevant. If you are pumping down a refrigerator with a liquid line solenoid valve located on the compressor unit that is 200 feet away from the refrigerator, the deeper the low pressure control setting, the more frequent the additional short cycles will insert themselves, and temperature control and medium temperature defrosts could become a problem.

A last point, even with low temp stuff, why not take advantage of every psig that a Deg F can provide? R22 low temp ice cream applications force you to hover with a cut out very close to atmospheric temperatures. Other refrigerants permit you to raise the cut out well above atmospheric pressures. Why not take advantage of that? Pressure controls will drift over time, why play it so close to the edge when it is unnecessary?

Fun thread, gents!

Gary
23-10-2004, 04:47 AM
What is maximum allowable pressure? If the equipment has a pressure relief valve, then I would say that is the maximum allowable pressure, and I would be sure to set the control safely below it's setting.

In most cases, it would take a fire to reach the relief valve setting. Setting the HP just below the relief valve setting could allow prolonged running at very high pressures, at least causing unnecessary wear and tear, poor performance, and high energy costs, and at worst damaging the compressor.

Does setting it too high cause problems? No, it just ensures that it will never trip. It might as well not be there. It is useless.

Peter_1
23-10-2004, 07:49 AM
That isn't near high enough for R410A, and is much too high for R12.

You may not be doing things the wrong way, but you are doing things the hard way.

I know, compressors for R410A can be set much higher because the manufacturer releases them for a higher pressure.Mitsubishi states testing 5 minutes on 41 bar (4.15 MPa)!!
My statement was for the 'old gasses'.

Peter_1
23-10-2004, 07:52 AM
What if the LP control is being used to control the temperature in a cooler or a freezer?
So.....What do you mean with this? It still works, at least with the machines I installed the last 20 years.

Peter_1
23-10-2004, 07:55 AM
I have long held the same opinion, although I have no idea why you are separating scrolls from the mix. !
I was thinking more on all those who try to work with a pump-down with scrolls, especially on freezers. Almost impossible and not allowed by the manufacturer due to the pressure differential which will be too high while pumping down.

Gary
23-10-2004, 01:59 PM
So.....What do you mean with this? It still works, at least with the machines I installed the last 20 years.

You seem to be assuming that all LP controls are used for pumpdown systems. I have encountered a great many coolers and freezers which have no temperature control, no solenoid valve, and no pumpdown. The temperature in the cooler or freezer is controlled by cycling the LP control. This is what I was referring to.

Gary
23-10-2004, 02:28 PM
It always amazes me that people will insist on doing things the hard way, even becoming defensive about it, for no other reason than it is the traditional way to do it. I find it even more amazing that the schools continue to teach the hard way, for the same reason.

People who look at their gauges, then convert those pressures to temperatures, have a huge troubleshooting advantage over those who only see the pressures.

They know what saturated temperatures are typical/acceptable/unacceptable for a given set of conditions. They need only glance at a pressure/temperature chart to know what typical/acceptable/unacceptable pressures are for any refrigerant under current conditions.

Those who think in terms of pressures are lost when they encounter a refrigerant they are not familiar with. They have no idea what pressures are typical/acceptable/unacceptable for current conditions.

Gary
23-10-2004, 03:01 PM
Hi all,
Just a quick list of approxomate pressures in response to Bernards original post. Obviously these are approx & ambients could change.If i have worked these out wrong can someone let me know

Regards

Raymond

Gas Type, HP, LP@0coil, LP@-10 Coil, LP@-30 Coil.
R12, 118, 30, 17, 1" vac.
R134, 125, 28, 14 , 1" vac/
R22, 190, 58, 36, 9.,
R502, 215, 67, 36, 14.
FX10, 220, 68, 44 , 13,
FX56 125, 27, 15 , 1" vac,
R404 230 , 72 , 48, 14,
R407 220, 50, 32 , 13,
R410 320 , 100, 68, 24,
R507 240, 76 , 48 , 16,

Saturated temperature version of the same list:

Gas Type, HP, LP@32F/0C Coil, LP@14F/-10C Coil, LP@-22F/-30C Coil
R-whatever, 99F/38C, 32F/0C, 14F/-10C, -22F/-30C

leonmartinharms
13-06-2010, 10:06 PM
1.you take the max avarage ambient for the region,say 35 deg.
2.take condensor td,say 15k.
3.add 5psi for safety
add 1,2 and 3 =35+15+5=55 degrees. this temp should match the pressure on hp gauge.
That applies to all gasses