134a

[roosel]

I am an inexperienced tech and have never worked with 134a. Today I was asked to check out a rooftop unit with 134a. what are the normal operating pressures for 134a? I know r-22 is around 70 to 75 on the low side and around 225 on the high side.

[jpsmith1cm]

A rooftop AC unit with R134a as a refrigerant?

[roosel]

I'm guessing it was for a cooler? it is on a resturaunt.

[Burnedout]

chiller?

[roosel]

I don't know. my boss told me to connect my guages and tell him the pressures. he wanted me to do this because he saw the suction line was frosted. I am sorry i could not be more specific.

[roosel]

when I asked him what they should be he told me that it depends on the size of the unit. I am beginning to think I know more about HVAC than he does. either way I am beginning to doubt him. and will surely have more questions in the future.

[jpsmith1cm]

So, what were the pressures?

Now this is making a bit more sense...


Did you take any measurements beyond pressures?

[ryan1088]

Wow?? Help us help you. Model? What it is? Pictures? Anything?!

[carmon]

134a my least favorite refrigerant....... I hate it...........

[roosel]

I apologize for the lack of details. this is my first post. I believe it was close to 2 tons. Again I apologize in advance for my poor memory. the label was worn and I almost mistook it for a 22 unit like the one next to it. I believe the pressures were like 25 psi on the low and 150? on the high. My boss told me to charge it so I did. just enough to melt the frost on down the line but it melted slowly. he told me that was good. but I didn't feel in my gut that he knew.

[carmon]

well ..... I assume he new something....

[beenthere]

I think you mean the condenser was on the roof.

Learn to ignore the pressure readings as a way to check charge. And learn to read and use saturation temps.

[timebuilder]

I apologize for the lack of details. this is my first post. I believe it was close to 2 tons. Again I apologize in advance for my poor memory. the label was worn and I almost mistook it for a 22 unit like the one next to it. I believe the pressures were like 25 psi on the low and 150? on the high. My boss told me to charge it so I did. just enough to melt the frost on down the line but it melted slowly. he told me that was good. but I didn't feel in my gut that he knew.

Here's what you do.

Get your post count up to 15 and apply for Pro membership. Once you have it, there is a large educational area here on the site where you can learn more.

[Nuclrchiller]

I think you mean the condenser was on the roof.

Learn to ignore the pressure readings as a way to check charge. And learn to read and use saturation temps.

That method of thinking in terms of temps instead of pressures was taught to me over 27 years ago by a now-retired boss and mentor. It has served me well on many types of equipment, both high pressure and low pressure. He would say "temps don't change, just pressure". That was before new refrigerants and high efficiency equipment, but the I believe his statement is still valid.