Compressor Pressures at High Ambient Air

[Andreas11]

If you have the following A/C system requirement:

Continuous operation at 130F Outside Air, 80F Dry Bulb/67F Wet Bulb Indoor Air

What can you expect your evaporating and condensing temperatures to be?
I am guessing about 160F condensing and 50F evaporating.

How would an initial surge of hot ambient air affect the evaporating temperature? In other words, if you started with your return air temp at 130F, would the evaporating temperature be high and how quickly would it come under control?

How much higher would a blocked filter drive the condensing and evaporating temperatures at this high ambient condition?

- Andreas

[Gary]

If you have the following A/C system requirement:

Continuous operation at 130F Outside Air, 80F Dry Bulb/67F Wet Bulb Indoor Air

What can you expect your evaporating and condensing temperatures to be?
I am guessing about 160F condensing and 50F evaporating.

How would an initial surge of hot ambient air affect the evaporating temperature? In other words, if you started with your return air temp at 130F, would the evaporating temperature be high and how quickly would it come under control?

How much higher would a blocked filter drive the condensing and evaporating temperatures at this high ambient condition?

- Andreas

The evaporating and condensing temperatures are dependent upon relative coil sizing and surface area, as well as temperature and volume of airflow.

Why do you ask?

[Andreas11]

We make air conditioning systems for locomotives. The system is contained in one box, like a large scale window A/C unit. We are trying to get a rough idea of the compressor amp draw at that high ambient air condition, 130F, to size our electronics. I am trying to make the connection from the high air temperature to the compressor suction and discharge pressures. There is also the concern of the blocked filter and how this would drive up compressor pressures. In addition, we wonder what would happen initially if the locomotive cab is also at 130F.

[Gary]

I assume you are referring to a blocked refrigerant filter/drier, not a blocked air filter?

[Andreas11]

dirty condenser filter is what I meant

[Gary]

That's still not clear. Are we talking about an air filter or a refrigerant filter? (Yes, there is such a thing as a condenser air filter)

[Andreas11]

condenser air filter

[Gary]

Condensing temperature runs 20-35F over ambient, depending upon condenser size and airflow. Any blockage of airflow, such as a blocked condenser air filter, will add to this.

The low side pressure can be limited by MOP charge in the TXV and/or a CPR valve.

You might want to reconsider switching to R410A. At those temperatures, the pressures are going to be horrendous. You will need heavy duty everything.

[declan simmonds]

Hello all
do you think that using R134A for that application is way off also just thinking ? if not why not ? thanks

[paul_h]

r134a wouldn't be bad, there's a reason why they use it in cars, high ambients and load, and the fact that you don't need a low evap temp for a/c.
wait: who even mentioned the refrigerant, I re-read the post and the OP didn't even mention it.

[declan simmonds]

thanks paul does that mean i get a brownie points im sure other with say im wrong

[declan simmonds]

hello all i know he didnt mention the type of gas but gary said you would be better of using r410a for that application but i was thinking r134a would be better for that application as you said we use it in cars high temps and heat loads
cheers
declan ps im bored in madrid with no work

[Andreas11]

Thanks for the information, especially to Gary. The refrigerant is 134a.

[Gary]

r134a wouldn't be bad, there's a reason why they use it in cars, high ambients and load, and the fact that you don't need a low evap temp for a/c.
wait: who even mentioned the refrigerant, I re-read the post and the OP didn't even mention it.

The OP discussed switching refrigerants from R134a to R410A in another thread. I would strongly advise against using R410A in this application.

[nairb02]

plz help me i dont know how to post in forums.. im a newbie here so please help me. i have lots of questions to ask thats why i want to know how to post in forums.

[nike123]

plz help me i dont know how to post in forums.. im a newbie here so please help me. i have lots of questions to ask thats why i want to know how to post in forums.
And, you are just posted, as you see.
Go to forum relevant to your subject:
http://www.refrigeration-engineer.com/forums/index.php
And hit New Thread button on top of opened page.

[paul_h]

Read this forum.
http://www.refrigeration-engineer.com/forums/forumdisplay.php?f=25

And specifically this post I wrote about basic navigation

http://www.refrigeration-engineer.com/forums/showpost.php?p=94877&postcount=2