Carrier 30HX head pressure

[MegaJunk]

Do these air cooled Carrier 30HX series screws typically run head pressures above what a more unitary guy would consider normal?

I'm looking at a condensing temp of 142 deg on a 95 deg design day at full load. This is a 142TR 30HXA146RZE561KA machine matched to a nominal 176 Ton 09AZV142VE-5 condenser. Had the onsite tech check the condenser split (its clean) & it was pushing 40 deg. Every high side temp seems to be high & my mind goes towards non condensables but the OEM tech told the bld engineer it's perfectly normal just leave it be.

[superheatrman]

This may be a good place to start...
http://xpedio.carrier.com/idc/groups/public/documents/techlit/30g,h-9t.pdf

[servicetrane]

pressures are very high, check with manyfold pressure to check the calibration of water temperature transductor.que cooling tower have? filter is clean water entering the condenser?

[Dallas Duster]

Well with the very little information you have provided it's hard to say what it could be at this time. Any thoughts to it being overcharged? What's a normal temperature for a normal summer where you are?

[MegaJunk]

She's on an air cooled condenser....

[MegaJunk]

My main question is if this level of head pressure is, by some oddity, normal for this machine? I really don't think so but I've been wrong a time or two.

Your replies are appreciated!

[Dallas Duster]

My main question is if this level of head pressure is, by some oddity, normal for this machine? I really don't think so but I've been wrong a time or two.

Your replies are appreciated!


I might respond more if you gave more information , it's a tuff trade I know but that's life.

[klove]

If you're looking for correct responses, post all of your readings taken at a stable point of operation, especially those that have a direct correlation to high side pressure. If you suspect non-condensibles, pump the circuit(s) down and check for them. Your condenser temp is high, especially considering that your nominal chiller tonnage is right at 25% smaller than your condenser rating, but you're not giving folks much to base an opinion on.

[MegaJunk]

It's a bit of a battle for me to get out to look at it since Carrier wrote it up as all is well. But, your reply was what I was looking for. Thanks

[MegaJunk]

Here's some basic info on the B circuit. We were at 86 deg OA and operating the compressor at full load with all condenser fans at 100%.

Discharge Pressure 178 psig
Discharge Temp 149 deg
Discharge Superheat 63 deg
Condensing Temp 121 deg
Liquid Line @ EXV 110 deg
Liquid Line Subcooling 11 deg
Condenser Split 24 deg

Return water temp 49 deg
Supply water temp 43 deg

I'm wondering why the condensing temp runs at the high end of the limits when the matched condenser is oversized to begin with. My experiance tells me the head pressure should be 150-160 on an 86 deg day especially with all fans going.

[klove]

Have you done the things that have already been suggested?

[MegaJunk]

Sorry, TYPO discharge superheat 28 deg.

[MegaJunk]

I am being told by others that there is no problem.

[klove]

Well then, go with what "others" say. They may or may not be correct. But either use what you're given that you've asked for, or don't ask. No one wants their time wasted, and if all you're looking for is a laundry list of "Things that cause high head pressure", you can get that out of any decent refrigeration textbook.

[Dallas Duster]

Things look pretty good to me but I would want to know EXV position.

[MegaJunk]

Well then, go with what "others" say. They may or may not be correct. But either use what you're given that you've asked for, or don't ask. No one wants their time wasted, and if all you're looking for is a laundry list of "Things that cause high head pressure", you can get that out of any decent refrigeration textbook.


I ask because I know somthing is not correct and it's outside of typical issues. I ask on this site since a few of you probably regularly work on these particular units and would know if they run higher heads.

Found the problem it's was nothing on the servicable side. Just so happened to be buried in the equipment design & application data.....