RTAA low evap ref. temp. hair falling out!

[supertek65]

hey graham!!!!!!!!!!!!!!!!!!!!!!!

hows it goin??????????????????

hey graham, can u explain this

No head pressure = no suction pressure = no oil movement = no chiller ..Done

[milkyway]

what part dont you understand???

The vfd compared to fan cycle controls on cond fan motors

[jayguy]

The vfd compared to fan cycle controls on cond fan motors

head pressure controls turn the fan on and off based on a single pressure...in this case head pressure.

the vfd's turn the fans on and off based on the pressure differential between the saturated condensing pressure and the saturated evaporator pressure.

all txv's (mechanical or electronic) are rated by differential pressure (and a few other things). txv's move their rated tonnage based on this differential pressure. no differential pressure and there isn't any refrigerant movement.

if the saturated evaporator pressure drops and the saturated condensing pressure stays the same (because the pressure switches only switch based on a single pressure), then the txv tonnage rating goes up and you can move more refrigerant.

but what happens when the evaporator load goes up? the saturated evaporator pressure goes up, but the saturated condensing pressure stays the same (because of the pressure switches). due to this issue, the tonnage goes down and you can trip due to a heavy load.

by using the differential pressure, you have several advantages.
1. maintains txv tonnage at all evaporator loads and condenser loads.
2. when the saturated evaporator pressure is low AND the outdoor air temp is low (causing the pressure switch to turn OFF some fans), the vfd's would actually turn ON some fans in order to lower the head pressure and gain efficiency (assuming the differential is high enough)

[supertek65]

hey jay
did you get my email?

[Screwit]

Hey mlkwal1,

Follow the attached link to trane.com literature search and under the helical rotary liquid chillers section download the clear language diaplay troubleshooting bulletin. Page 20-21 details the VSF fan control for the RTAA 70-125 chillers which should help you to understand.


http://www.trane.com/Commercial/Uplo...-svd03a-en.pdf

[supertek65]

screwit
is that your namne or attitude???

LOL!!!!!!!!!!!!!!!!!!

or are you a screw chiller guy????

just wonderin????????????

Hey mlkwal1,

Follow the attached link to trane.com literature search and under the helical rotary liquid chillers section download the clear language diaplay troubleshooting bulletin. Page 20-21 details the VSF fan control for the RTAA 70-125 chillers which should help you to understand.


http://www.trane.com/Commercial/Uplo...-svd03a-en.pdf

[Screwit]

Supertech 65, hope my attitude does not come across that way - it is certainly not intended - been involved predominately with screw chillers for the last 20 years so thought the name was appropriate.

[supertek65]

LOL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

absolutely not, i am sure you have a great attitude!!!!!!!!!!!!!

i was just wondering if you had some other reason for the name???

frank

Supertech 65, hope my attitude does not come across that way - it is certainly not intended - been involved predominately with screw chillers for the last 20 years so thought the name was appropriate.

[cooolguy]

I've never worked on an RTAA without fan inverters. I understand this is a factory option. Is it possible to add the inverters in the field? And what all is involved?

yes, this is possible done that on a few units.

[milkyway]

thanks jay