SUB Cooling adjustment

[riderman]

Mark, Yes you are correct! I read mis-information from another source. Thanks eveyone for the responces. As you know, it is hard to find correct information sometimes. Thanks again, I ment no offence to anybody, so I hope no one took any.

[riderman]

Have to remember that your tag says regular guest so we that don't know you assume homeowner with a set of gauges and a few tools.[/QUOTE]


It's all good. I work for Uncle sam on this equipment and have several EPA certs and such. I sometimes ask too detailed info in the oipen forum and rightfully get cautioned and was suprised at getting a little flack for what I thought was a simplified no detailesd question. I see yall's point.

[dijit]

I read the instructions before I adjust the TXV, but seems to me the opening or closing of the valve changes both the SH and the SC.
I believe you should adjust for the SH first then fill till proper SC.
luck dan

It will affect both but a TXV is designed to control superheat and not subcooling. The bulb and external or internal equalizer work in combination to sense and control superheat, the effect on subcooling is a passive one only. Use it for what it was designed for and your life will be easier.

Mark Beiser's post is the correct way to do it, but if you want to skin your cat differently, have fun.

[riderman]

Just wondering here...If the SC and SH spec is 7-9 degrees and I'm sitting at 11-12 degrees, what is the consequence? I'll fix it, but it seems a lot of systems require around 10 degrees anyway.

[timtanguay]

They call it a superheat spring for a reason on txvs...adjusting the slring adjusts the sh.

Lack of sc can also be from a dirty condenser.

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[git-r-dun]

Just wondering here...If the SC and SH spec is 7-9 degrees and I'm sitting at 11-12 degrees, what is the consequence? I'll fix it, but it seems a lot of systems require around 10 degrees anyway.

To answer your question, none. Understanding the operation and flow of refrigerant is important and there is a misconception it appears of what a TXV does. Although TXVs aren't utilized as a capacity control device, in essence that's what they do (to a certain degree and within limits). They control flow of refrigerant based on SH set point (not SC). By modulating the opening of the orifice (in oppose to a one size fixed orifice) refrigerant flow through the evaporator will vary. Under high demand/ high heat load, your SC will drop ( maybe even below these rule of thumbs or factory recommendations) as system SH setpoint is trying to be maintained. On the contrary, when there is a low load ( for whatever reason) TXV is going to reduce flow causing SC to be above rule of thumbs as refrigerant will stack in the condenser. This could even result into driving your head pressure up as, just like a restriction, you have less available space in the condenser to reject heat. I would still be very curious for someone to give a play by play on adjusting TXVs to accomplish SC first and then charge system to achieve SH. I guarantee you'll be readjusting that TXV.

[JWB]

The purpose of measuring sc is to ensure we have a solid column of liquid for the TEV/TXV. So we are measuring the degrees below saturation point for the given refrigerant, with this we ASSUME that there is liquid for the valve. Since the valve is in the evap, a lot can happen on the way from the condenser to the evap. Temp rise in an attic installed lineset, of a rooftop lineset, kinked lines etc.

The fact that Goodman's valves are adjustable surprises a lot of folks I work with.

I have learned a lot from this site. How to fight with ya'll has never been my goal.